Field of invention

The present invention relates to a roof assembly and in particular to a built-up roof assembly for external use on low-slope or flat roofs.

Background art

Built-up roof assemblies are widely used in commercial and residential buildings to provide waterproofing and heat insulation on flat or low-slope roofs. Compared to conventional roofing materials such as slate, tile and shingles, a built-up roof assembly provides a continuous sealed surface. This is advantageous for flat and low-slope roofs where water run-off is less effective than sloped roofs.

Conventional built-up roofing systems are composed of alternate layers of asphalt or bitumen and reinforced fabric ply sheets layered on top of the deck surface of the roof. This layered structure ensures that the roof assembly is watertight, preventing water leaking through into the building below. One or more layers of a rigid thermal insulation material such as polyisocyanurate is often incorporated into the structure to improve heat retention. The system is often topped with a layer of gravel or other aggregate material to act as a ballast and prevent UV radiation damaging the membrane structure.

The materials used in conventional built-up roof systems have several disadvantages. Hot bitumen can release hazardous fumes and vapours during installation. Furthermore, bitumen and polyisocyanurate are combustible, with the latter giving off highly toxic by products such as hydrogen cyanide gas when burned.

Developers are increasingly making use of flat roofs as usable space, particularly in residential developments. Built-up roof systems are therefore often installed on flat or low- slope roofs underneath an external terrace or deck assessable from within the building. Some buildings such as blocks of flats may have a stepped structure with many low-slope roofs under external terraces.

Creating a usable external space on a roof increases the need for non-combustible or at least fire-retardant roof materials. Falling embers from barbeques or firepits on the terrace or discarded cigarettes could ignite a conventional bitumen and fabric roof. In stepped or tiered buildings, a fire on a built-up roof could more easily spread to adjacent apartments and upper floors. Even if a fire remained contained, the spread of highly toxic fumes from the combustible materials could pose a health hazard to those on upper floors.

The creation and management of sustainable drainage systems (SuDS) is increasingly important in building design to help prevent water pollution and flooding in urban areas. “Flat” roofs are usually built with a gradual slope (as low as 1 in 100) to prevent water remaining on the roof and damaging the structure. However, in periods of heavy rainfall, building regulations in certain areas may require that the building temporarily retains some water before controllably releasing the water into the sewers. This helps to regulate the volume of water passing into sewer systems during heavy rainfall to minimise the risk of flooding. The water may also be treated to remove pollutants. In major developments in suburban or rural locations, water retention and treatment may be achieved by directing rainwater runoff into a retention pond. Pollutants may be removed through sedimentation and the pond can be landscaped to be aesthetically pleasing and create a habitat for wildlife. In built-up urban locations, space may be limited and exposed retention ponds may not be possible. Geocellular systems have a modular or honeycomb type structure formed from plastic which creates a void suitable for collecting and storing rainwater runoff. These systems can be buried underneath roads, car parks or play areas adjacent developments and can manage soakaway or store water.

In particularly dense urban areas buried geocellular systems may not be feasible due to a lack of suitable ground sites. In this case a blue roof may be used to provide temporary storage and slow release of rainwater after a storm. Existing blue roof systems are similar to buried geocellular systems, typically consisting of a plastic (polypropylene or similar) modular honeycomb structure which creates a void for the storage of water. The size of the system can be adapted to suit the amount of water to be detained, and in some cases a blue roof system can incorporate a “green” or “living” roof system as part of the rainwater management strategy. However, the use of a combustible plastic honeycomb structure can significantly affect the fire performance and rating of a built-up roof system by potentially providing fuel and a source of oxygen to a fire.

Summary of the Invention

The present invention seeks to provide a roof assembly for a flat or low-slope roof which will not burn when subjected to a sustained source of ignition such as a fire burning within the building below. The roof assembly is suitable for use on any building with a flat or low-slope roof, including buildings constructed by conventional methods including flats office buildings, factories, warehouses and public buildings, modular buildings which are prefabricated or constructed offsite, and semi-permanent or portable buildings. The roof assembly of the present invention does not make use of bitumen or combustible fabric ply layers. The layered structure of the present roof assembly has a vapour control layer placed immediately above the roof deck and a waterproofing layer placed above an insulation layer. Each of the vapour control layer and the waterproofing layer has at least one fire- retardant component which results in the layer being essentially non-combustible by preventing the layer from igniting or burning when exposed to fire. The insulation layer may comprise a main insulation layer and a secondary insulation layer, or may comprise a single insulation layer with no primary or secondary insulation layer. The insulation layer (or both the primary and secondary insulation layers) include a non-combustible coating layer. In certain embodiments the roof assembly also has a water detention system installed above the waterproofing layer. A secondary roof system may also be present for the cultivation of plants on a “green” or “living” roof. The water detention system and a drainage and water retention layer of the secondary roof system are non-combustible.

In the context of the present invention the term “non-combustible ” should be interpreted as a material which will not readily ignite or combust when exposed to an ignition source which would be reasonably expected in the context of a residential building, and will not substantially contribute combustible fuel to an established building fire. Such “non combustible” materials fulfil the requirements of the Euroclass A1 fire rating as outlined in Official Journal of the European Communities L 050, 23/02/2000 P. 0014 - 0018. To meet the Euroclass A1 rating, when a cylindrical test specimen of a material is inserted into a vertical tube furnace at a temperature of around 750 °C (as specified by EN ISO 1182) the temperature change in the furnace should be equal to or less than 30 °C, the mass change of the sample during the test should be less than or equal to 50 % and no sustained flaming of the sample should be observed during the test. In addition to this the gross calorific potential of the material should be less than or equal to 2.0 MJ kg ¹ or 1.4 MJ m ² when measured in accordance with the EN ISO 1716 test procedure. Materials may fulfil the requirements of the Euroclass A1 fire rating by being inherently non-combustible or may be composite materials which contain one or more inherently combustible constituent components but also have fire retardant additives to make them non-combustible.

The present invention also seeks to provide a durable roof assembly with long-lasting waterproofing and thermal insulation. The vapour control layer of the present invention protects moisture from rising through the deck surface of the building from within the building. This protects the insulation material from becoming damp which could reduce its effectiveness and helps to prevent “bubbling” on the roof surface. The insulation material of the main and/or secondary insulation layers is also at least partially covered by a coating layer. This helps prevent or substantially limit moisture passing into the insulation material (which would reduce its effectiveness as a thermal insulator). Above the insulation material, a durable waterproofing layer is applied to a continuous surface of the insulation layer provided by the coating layer to ensure complete coverage and prevent rainwater leakage into the insulation material from above. The waterproofing layer may be applied directly to the coating layer. Alternatively, a rigid support structure such as a metal sheet, panel, shell or frame may be applied between the continuous surface and the waterproofing layer.

Reference in this specification to a “continuous surface” encompasses any surface which does not allow fluid to pass through. For example, the surface of a metal plate or a non- porous coating would be a “continuous surface” in the context of this invention, but a metal mesh or an incomplete or porous coating would not.

Certain embodiments of the present invention also seek to provide a roof assembly suitable for managing and draining rainwater in line with building regulations. In certain embodiments, the insulation layer provides a sloped upwards facing surface over which the waterproofing layer is applied to create a sloped roof. In alternative embodiments, a secondary insulation layer provides a sloped upwards facing surface over which the waterproofing layer is applied to create a sloped roof to enable water to run off to drainage channels and to prevent water sitting on the waterproofing layer. The slope of the roof may be between 1 in 40 and 1 in 100. In particular embodiments, the roof assembly also includes a water detention system designed to control the runoff of rainwater from the building, particularly during periods of heavy rainfall.

Viewed from a first aspect the present invention provides a roof assembly for a roof of a building, comprising a vapour control layer positioned or positionable on a surface of a roof; an insulation layer positioned or positionable on the vapour control layer, the insulation layer comprising an insulation material and a coating layer, wherein the coating layer extends over at least an upper surface of the insulation material to provide a continuous surface over an upper face of the insulation layer; a waterproofing layer positioned or positionable on the continuous surface, wherein the vapour control layer, the insulation layer and the waterproofing layer comprise exclusively non-combustible materials.

Reference in this specification to “positioned on” or “positionable on” may mean positioned/positionable directly on, i.e. contacting and with no intermediate layers; or may mean positioned/positionable indirectly on, i.e. with one or more intermediate layers or air- filled gaps between the features.

The surface of a roof may be any flat or substantially flat external surface of a building capable of supporting weight. For example, the surface may be a concrete, reinforced concrete or steel deck surface. The roof may have direct access from within the building, for example the building may be “stepped” with access to roofs at different levels. Alternatively the roof may have no direct access from within the building and may be accessible only by ladders or other external means.

By utilising non-combustible materials for the vapour control layer and the waterproofing layer, the roof assembly is protected from any fire passing up from within the building below or down onto the roof surface from above. This is particularly advantageous when the roof is used as a terrace which may have barbeques, firepits, chimeneas or other sources of hot embers positioned above it. The fire-retardant material may be a naturally non-combustible material or may be an ordinarily combustible material with a fire- retardant component added to make it non-combustible. In the context of the present invention the term “fire-retardant component” should be interpreted as a component of a material which has been added to the material to prevent or substantially reduce combustion of the material such that the material meets the requirements of the Euroclass A1 fire rating. This may be achieved either through physical processes, chemical reactions or a combination of physical and chemical processes. Commonly used fire-retardant additives include aluminium and magnesium hydroxides, borates, organohalogen compounds, various hydrates and organophosphorus compounds. The vapour control layer may comprise a polymer based coating material with one or more fire-retardant components and may have a glass or mineral fibre matting encompassed by the coating material. The glass or mineral fibre matting gives the vapour control layer structural rigidity. The polymer based coating material may comprise a cross-linked polymer formed by an exothermic curing process.

The insulation material and the coating layer are also non-combustible. This advantageously means that no part of the roof assembly will combust or contribute to a fire. The insulation material may be a mineral or glass wool insulation material. Mineral or glass wool is advantageous as it is non-combustible, readily available and widely used as a building material. The coating layer may be a polymer based coating material with one or more fire-retardant components added. The coating layer may be applied only to an upper surface of the insulation material or may completely surround and encase the insulation material. Alternatively the coating layer may be a metal foil such as an aluminium foil. The coating layer may comprise both a metal foil coating surrounding the insulation material and a polymer based coating material surrounding the metal foil.

The insulation layer may have a composite structure which comprises a primary insulation material with a structural capping board positioned over a top face of the primary insulation material, and a coating layer which surrounds and completely encases the primary insulation material and the structural capping board. The primary insulation material may be a mineral or glass wool. The structural capping board may be composed of concrete. The coating layer may consist of a metal foil such as an aluminium foil which surrounds the primary insulation material and structural capping board, and a polymer based coating material which surrounds the metal foil.

This composite structure, where the insulation material and structural capping board is completely encased in a coating layer is advantageous as it enables the insulation layer to be assembled off-site so that the insulation material is encased in a coating layer before being positioned on the building. This prevents the insulation material absorbing water during assembly. If the insulation material is wet when the waterproofing layer is applied then the trapped moisture could expand at higher temperatures and cause bubbling or cracking (outgassing) to the waterproofing layer.

The structural capping board advantageously provides additional structural rigidity to the insulation layer. Mineral or glass wool insulation material is typically compressible. Applying pressure to the waterproofing layer may cause the insulation layer to compress unevenly, which could weaken the waterproofing layer or cause it to crack. In particular, applying pressure to a particular point on the waterproof layer (point loading) may compress the insulation material at that point, causing the waterproofing layer to flex and crack. The structural capping board diffuses point loading. The structural capping board may be between 5 mm and 15 mm thick. Preferably the structural capping board is between 7 mm and 10 mm thick. Particularly preferably the structural capping board is about 8 mm thick.

The composite structure of the insulation layer may further comprise a core of vacuum packed mineral or glass wool insulation material. The insulation material of the core may be encased and vacuum packed in a metal foil shell such as an aluminium foil shell. The core may be completely surrounded and encased by the primary insulation material or may be in contact with both the primary insulation material and the structural capping board.

Non-combustible mineral and glass wool insulation materials typically require additional depth to achieve the same insulative properties compared to conventional combustible insulation materials such as polyisocyanurate. Vacuum packing mineral or glass wool can enhance the insulative properties of the material for a given thickness. The roof assembly can therefore have a reduced thickness or depth whilst retaining a high U-value, without requiring combustible materials.

The insulation layer may be substantially wedge-shaped, such that the upper surface of the insulation material and the continuous surface have a slope relative to the surface of the roof. This arrangement of insulation is often referred to as a “cut-to-falls” insulation. All or a portion of the insulation material may have a wedge-shaped profile, a lower face being substantially horizontal adjacent the vapour control layer and the upper face angled relative to the lower face and the vapour control layer. The arrangement and angle of slopes on the continuous surface can be adjusted to suit drainage requirements of the roof. There may be, for example, one gradual slope over the whole of the continuous surface to allow rainwater to drain to one side of the assembly. Alternatively, two slopes may meet at a low point in the middle of the continuous surface to form a drainage channel. The slope preferably has a gradient of between 1 in 40 and 1 in 100.

The insulation layer may comprise a main insulation layer positioned or positionable on the vapour control layer and comprising a primary insulation material; and a secondary insulation layer positioned or positionable on the main insulation layer and comprising a secondary insulation material, wherein the coating layer extends over at least an upper surface of the secondary insulation material to provide the continuous surface over the upper face of the insulation layer.

At least a portion of the upper face of the secondary insulation material may be angled relative to the main insulation layer to define at least one slope on the continuous surface. For example, all or a portion of the secondary insulation material may have a wedge- shaped profile, a lower face being substantially horizontal adjacent the main insulation layer and the upper face angled relative to the lower face and the main insulation layer.

The insulation material is preferably completely coated and encased by the coating layer. Each of the primary and secondary insulation materials are preferably completely coated and encased by the coating layer. This prevents or substantially limits moisture entering and becoming trapped in the insulation material, which would reduce its effectiveness. The primary and secondary insulation materials may be the same material or a different material. Preferably the primary and secondary insulation materials each comprise a mineral or glass wool insulation material.

The insulation layer may further comprise a rigid support body, wherein the rigid support body has a continuous portion positioned or positionable between the continuous surface and the waterproofing layer. The rigid support body may be a generally planar sheet or panel and may be made of a metal such as steel or aluminium. The rigid support body may further comprise one or more protrusions extending from the continuous portion towards the vapour control layer. The protrusions may be rods or spikes which extend into the insulation layer to anchor the rigid support body. Alternatively the protrusions may extend around the secondary insulation layer or individual sections of secondary insulation material to form an external shell or frame which fully or partially surrounds and encases or encapsulates the secondary insulation layer. The rigid support body provides an alternative surface to which the waterproofing layer can be applied. An external frame may have a combination of a continuous rigid or flexible structure and a rigid or flexible mesh, webbing or cage-like structure which partially covers the secondary insulation layer. The rigid support structure protects the waterproofing layer against movement and board ghosting which may lead to cracking and leaks.

The insulation layer may comprise multiple individual sections of insulation material each positioned or positionable on the vapour control layer. The main insulation layer may comprise multiple individual sections of primary insulation material each positioned or positionable on the vapour control layer. The secondary insulation layer may comprise multiple individual sections of secondary insulation material each positioned or positionable on the main insulation layer. This is advantageous particularly for larger roofs, as the insulation layers can be more easily moved into position during installation. Each individual section may be individually completely coated and encased by a coating layer.

Each individual section of secondary insulation material may have a rigid support structure such as an external shell or frame, the external shell or frame at least partially surrounding the individual section and having a continuous surface extending over a top surface of the individual section, wherein the waterproofing layer is positioned or positionable on each of the continuous surfaces. Where the slope is not constant over the entire secondary insulation layer, splitting the secondary insulation layer into individual sections allows each section to be pre-prepared with the required angle on its top surface. During installation the individual sections can be arranged on the main insulation layer to achieve the desired slope profile. Adjacent individual sections of insulation material are preferably joined at their upper faces by a foil adhesive tape. The foil tape acts as a sealant to seal the gap between adjacent individual sections of insulation material and creates a bond-break within the system to combat structural movement (e.g. as a new building moves and settles) that may cause failure to the waterproofing layer. The foil tape preferably comprises an aluminium foil tape and non-combustible adhesive.

Where insulation material is positioned or intended to be positioned against a vertical surface (such as a wall) then the roof assembly preferably comprises a metal angle fillet positioned between the top surface of the insulation layer and the vertical surface. The waterproofing layer can then be applied to the insulation layer and the angle fillet. The angle fillet removes the substantially 90 degree directional change in the waterproofing layer at the junction between the top surface of the insulation layer and the vertical surface. This reduces the risk of waterproofing layer failure at that junction. Preferably the metal angle fillet is composed of aluminium.

The roof assembly may further comprise a water detention system positioned or positionable above the waterproofing layer, the water detention system comprising an inlet suitable for receiving water from a rainwater collection surface; a void suitable for storing a volume of water; and an outlet fluidly connected to the void, wherein the outlet has a flow regulator to controllably release the volume of water from the void; wherein the water detention system comprises exclusively non-combustible materials. For example, the water detention system may be formed from steel or aluminium.

The water detention system may comprise a base with surrounding walls extending upwards from the base to give a tray-like structure where the base and walls define a void. The base may be positioned directly on the waterproofing layer or the water detention system may be raised above the waterproofing layer on one or more legs. Alternatively the base may comprise the waterproofing layer itself. The void may contain one or more structural features such as beams to strengthen the water detention system. The height of the walls may be tailored to the specific requirements of the building such as anticipated rainfall and local water detention requirements. For example in areas with a high frequency of heavy or prolonged rainfall events, the walls may be taller to allow a greater volume of water to be temporarily detained.

The inlet may be an open upper face of the tray -like structure to allow rainwater to fall directly into the void. Alternatively or additionally the void may be fed by an inlet pipe to collect water which fell elsewhere on the building. The inlet and/or outlet may be connected to a further water detention system elsewhere on the building. The flow of water between interconnected water detention systems may be controlled passively (for example by gravity) or actively (for example by electronic valves and a control system) to manipulate the rate of runoff from the building and ensure rainwater weight is evenly distributed.

The flow regulator may be a passive flow regulator such as a restriction plate with small holes to allow water to flow through at a reduced rate. Alternatively the flow regulator may be a valve system which may be controlled manually or automatically to adjust the flow of water as required. A filter system such as a bed of gravel may be positioned upstream of the flow regulator to prevent debris such as leaves within the water detention system blocking the flow.

The water detention system may further comprise an overflow outlet which is capable of diverting water from the void into a drainage pipe when the void contains more than a pre determined volume of water. In periods of exceptionally heavy and prolonged rainfall or if the flow regulator becomes blocked, the overflow outlet prevents the water detention system collecting too much water and becoming too heavy to be safely supported by the roof of the building.

The roof assembly may further comprise a secondary roof system positioned or positionable above the waterproofing layer, the secondary roof system comprising a drainage and water retention layer comprising a sheet of non-combustible material having a series of troughs arranged over a top face; a non-combustible fibrous material positioned or positionable within the troughs; and a plant matter growing medium positioned or positionable above the drainage and water retention layer. The secondary roof system is a system designed for the cultivation of plants to create a “green roof’.

The secondary roof system may be placed directly above the waterproofing layer or may be placed above a water detention system. The secondary roof system may cover a part of or all the waterproofing layer or water detention system.

The drainage and water retention layer may be made from a metal such as steel or aluminium. The troughs may be arranged in rows across the sheet. The troughs may be elongate, square-shaped or circular. The depth of the troughs may be between 2 cm and 20 cm depending on the amount of retained water required for plant growth. The troughs may be filled with a ballast material such as gravel in addition to the non-combustible fibrous material. The non-combustible fibrous material may be a mineral or glass wool growing support medium. This provides ballast to the secondary roof system whilst also providing a medium to retain organic material and provide space for root growth.

The plant matter growing medium may be any porous material capable of retaining moisture and organic matter whilst having low density. This plant matter growing medium may have a fibrous structure such as a woven hessian material or a mineral or glass wool material. The fibrous structure helps to retain organic matter such as soil and provides grounding for plant roots.

The roof assembly may further comprise a non-combustible flooring system positioned or positionable above the waterproofing layer. This enables the roof area to be used as a terrace, for example as an outdoor recreation area. The flooring system may be positioned directly above the waterproofing layer or may be placed above the water detention system or the secondary roof system. The flooring system may comprise a plurality of tiles arranged on a support frame. Each tile may be a ceramic or porcelain substrate within an aluminium or steel tray. The support frame may be made from a metal such as steel or aluminium. The tiles may be elongate. The flooring system may extend over all or only a part of the waterproofing layer, water detention system or secondary roof system. There may be gaps provided between adjacent tiles to allow rainwater to pass through the flooring system into the secondary roof system, the water detention system or onto the waterproofing layer.

The roofing assembly may further comprise a non-combustible ballast material positioned or positionable on at least a portion of the waterproofing layer. For example, gravel may be spread over the waterproofing layer. This is particularly advantageous for systems without a water detention system, secondary roof system or flooring system placed above the waterproofing layer. This material acts as ballast for the roof assembly. The ballast material also protects the waterproofing layer against UV damage from direct sunlight.

The roofing assembly may further comprise a back-up drainage pipe connected to the vapour control layer. This allows water to be drained from the vapour control layer in the event that a leak develops in the waterproofing layer and water passes through the insulation layers and onto the vapour control layer. Where the assembly includes a water detention system, the back-up drainage pipe provides an alternative drain in the event of failure to the water detention system.

Viewed from another aspect this invention provides a building comprising a roof assembly as hereinbefore defined, wherein the vapour control layer is positioned on a surface of a roof of the building; the insulation layer is positioned on the vapour control layer; and the waterproofing layer is positioned on the continuous surface of the insulation layer.

Viewed from a further aspect this invention provides a kit of parts for a roof assembly, comprising a vapour control layer comprising a non-combustible material; an insulation layer positionable on the vapour control layer, the insulation layer comprising a non combustible insulation material and a non-combustible coating layer, wherein the coating layer extends over at least an upper surface of the insulation material to provide a continuous surface over an upper face of the insulation layer; and a non-combustible waterproofing layer comprising positionable on the continuous surface.

The insulation layer may comprise a main insulation layer positionable on the vapour control layer and comprising a primary insulation material; and a secondary insulation layer positionable on the main insulation layer and comprising a secondary insulation material, wherein the coating layer extends over at least an upper face of the secondary insulation material to provide the continuous surface over the upper face of the insulation layer.

The insulation layer may be substantially wedge-shaped. Where the insulation layer comprises both primary and secondary insulation layers, the secondary insulation layer may be substantially wedge-shaped.

Preferably the insulation material is completely coated and encased by the coating layer. Where the insulation layer comprises both primary and secondary insulation layers, each of the primary and secondary insulation materials are preferably completely coated and encased by the coating layer.

The kit of parts may further comprise a rigid support body positionable on the continuous surface of the insulation layer, wherein the rigid support body has a continuous portion positionable between the continuous surface and the waterproofing layer.

The insulation layer may comprise multiple individual sections of insulation material each positionable on the vapour control layer. The primary insulation layer may comprise multiple individual sections of primary insulation material each positionable on the vapour control layer. The secondary insulation layer may comprise multiple individual sections of secondary insulation material each positionable on the main insulation layer. Each individual section may be individually completely coated and encased by a coating layer. Each individual section of secondary insulation material may have a rigid support structure such as an external shell or frame at least partially surrounding the individual section, wherein each external frame or shell comprises a continuous surface extending over a top surface of the individual section.

The kit of parts may further comprise a water detention system positionable above the waterproofing layer, the water detention system comprising an inlet suitable for receiving water from a rainwater collection surface; a void suitable for storing a volume of water; an outlet fluidly connected to the void, wherein the outlet has a flow regulator to controllably release the volume of water from the void; wherein the water detention system comprises exclusively non-combustible materials.

The water detention system may further comprise an overflow outlet.

The kit of parts may further comprise a secondary roof system positionable above the waterproofing layer or the water detention system, the secondary roof system comprising a drainage and water retention layer comprising a sheet of non-combustible material having a series of troughs arranged over a top face; a non-combustible fibrous material positionable within the troughs; and a plant matter growing medium positionable above the drainage and water retention layer.

The kit of parts may further comprise a non-combustible flooring system positionable above the waterproofing layer.

The kit of parts may further comprise a non-combustible ballast material positionable on at least a portion of the waterproofing layer.

Viewed from yet another aspect the present invention provides a method of construction for a roof assembly, comprising applying a non-combustible vapour control layer to a surface of a roof; applying an insulation layer above the vapour control layer, wherein the insulation layer has a non-combustible insulation material and a non-combustible coating layer provided at least at an upper face of the insulation material to provide a continuous surface; and applying a non-combustible waterproofing layer on the continuous surface.

The vapour control layer and/or the waterproofing layer may be applied respectively to the surface of the roof or the upwards facing surface of the secondary insulation layer as one or more liquid coatings by roller and/or spraying. The vapour control layer may be applied by placing a glass fibre matting material onto the surface of the roof and then applying the one or more liquid coatings to the glass fibre matting material. The liquid coatings may be dispersions of one or more components in a solvent. The solvent may be water or another organic liquid which evaporates after application. A water-based liquid is advantageous as it releases fewer harmful fumes on drying. However other organic solvents may offer faster drying times due to higher volatility. The liquid coatings may comprise a polymer material (for example a flexible methacrylate (FMMA) or Styrene-Ethylene-Butylene-Styrene (SEBS)) which undergoes an exothermic curing process to form the vapour control layer or and/or the waterproofing layer. The exothermic curing process may be a spontaneous process in the presence of air or may require addition of a hardener. Alternatively the vapour control layer and/or the waterproofing layer may be applied as a pre-formed sheet.

The method may further comprise positioning a water detention system above the waterproofing layer.

The method may further comprise positioning a secondary roof system above the waterproofing layer or above the water detention system.

The method may further comprise positioning a non-combustible flooring system above the waterproofing layer, above the water detention system or above the secondary roof system.

The method may further comprise further comprising positioning a non-combustible ballast material on at least a portion of the waterproofing layer.

Brief description of drawings

A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

Figure 1 is an exploded view of part of a roof assembly according to the present invention. Figure 2 is a cross-sectional view of another roof assembly according to the present invention.

Figure 3 is a simplified cross-sectional view of a roof assembly including a water detention system. Figure 4 is a simplified cross-sectional view of a roof assembly including a water detention system and a secondary roof system.

Figure 5 is a simplified cross-sectional view of a roof assembly including a water detention system and a terrace floor.

Figure 6 shows a partially assembled roof assembly according to the present invention.

Figure 7 shows a partially assembled roof assembly including a water detention system.

Figure 8 shows a partially assembled roof assembly including a water detention system and a secondary roof system.

Figure 9 shows a partially assembled roof assembly including a water detention system and a terrace floor.

Figure 10 shows a partially assembled roof assembly including a water detention system and a paved floor.

Figure 11 is a cross-sectional view of another roof assembly according to the present invention.

Figure 12 is a cross-sectional view of another roof assembly according to the present invention.

Figure 13 is a different cross-sectional view of the roof assembly of Figure 11 with a sloped roof configuration.

Figure 14 is a different cross-sectional view of the roof assembly of Figure 12 with a sloped roof configuration.

Detailed description of preferred embodiment of the invention

Referring initially to Figures 1 and 6, Figure 1 shows a simplified exploded view of part of a roof assembly 1. Figure 6 shows a partially assembled roof assembly 1. The roof assembly 1 is intended to be positioned directly on a deck surface 2 which is an upwards facing external surface of a building and is made from concrete. The deck surface 2 is capable of supporting weight.

A lowermost component of the roof assembly 1 is a vapour control layer 3. The vapour control layer 3 is placed over and in contact with the deck surface 2. The vapour control layer 3 restricts the flow of moisture. This helps to prevent condensation occurring within the roof assembly 1 as moist warm air from within the building cools as it passes upwards through the roof assembly 1. In this particular embodiment the vapour control layer 3 is an FMMA based membrane with an aluminium hydroxide fire retardant additive, formed around a glass fibre matting material. The vapour control layer 3 is applied to the deck surface 2 by placing the glass fibre matting material on the deck surface 2. A liquid spray comprising FMMA and aluminium hydroxide is then applied to the deck surface 2 and the matting material. The FMMA then undergoes a spontaneous exothermic curing process to form the vapour control layer 3 around the matting material. By applying the vapour control layer 3 as a spray, the thickness of the vapour control layer 3 can be adjusted as necessary to achieve the desired vapour resistance. Applying as a spray also ensures an even and complete coverage compared to a pre-formed sheet of material. The glass fibre matting material provides structural support to the vapour control layer 3.

Above the vapour control layer 3 is a main insulation layer 4. The main insulation layer 4 has a primary insulation material 5 which is a mineral or glass wool insulation material. The primary insulation material 5 provides thermal and acoustic insulation, preventing excessive heat loss through the roof assembly as well as reducing the noise of rainfall or from an accessible terrace above the roof assembly passing into the building below. The mineral or glass wool of the primary insulation material 5 is non-combustible. In the embodiments of Figures 1 and 6, the primary insulation material 5 is completely coated in a coating layer 13. The coating layer is a flexible methylmethacrylate polymer based coating with an aluminium hydroxide additive to make the coating layer 13 non combustible.

As shown in Figures 2 and 6, the main insulation layer 4 is made up of several pieces of primary insulation material 5. Each individual piece of the main insulation layer 4 is completely coated with a coating layer 13.

In this particular embodiment, a secondary insulation layer 6 is placed over the first insulation layer 4. The secondary insulation layer 6 has less vertical depth (is thinner) than the first insulation layer 4. The secondary insulation layer 6 has a secondary insulation material 7 which is the same mineral wool insulation material as the primary insulation material 5. The secondary insulation material 7 is therefore also non-combustible. The secondary insulation material 7 is also completely coated in a flexible methylmethacrylate polymer based coating layer 14. As shown in Figure 2, the secondary insulation layer 6 is made up of several individual pieces of secondary insulation material 7, each individually coated with coating layer 14, to ensure complete coverage of the main insulation layer 4, the vapour control layer 3 and the deck surface 2.

As best shown in Figure 6, each individual piece of secondary insulation material 7 also has an external shell 8 disposed over an upper face 9 of the secondary insulation material 7. The external shell 8 is a rigid aluminium shell and has a continuous surface 10 extending over the upper face 9 of the secondary insulation material 7. This creates a rigid, non- porous upper surface. The external shell 8 is non-combustible.

As shown in Figures 1, 2 and 6, the main insulation layer 4 is thicker than the secondary insulation layer 6. By placing the main insulation layer 4 underneath the secondary insulation layer 6, the metal external shell 8 cannot form a cold bridge between the upper and lower edges of the insulation. The external shell 8 therefore creates a non-combustible a non-porous rigid upper surface to allow application of a waterproofing layer, without impacting on the effectiveness of the insulation.

As shown in Figure 6, gaps in the continuous surface 10 between individual pieces of the secondary insulation layer 6 are sealed using a sealing fillet 15.

A waterproofing layer 11 is applied to the continuous surface 10. The waterproofing layer is designed to prevent any rainwater passing through into the insulation material. The rigid and non-porous upper surface provided by the external shell 8 protects the waterproofing layer against movement and damage such as cracking. This prolongs the life of the waterproofing layer and prevents leaks of water into the insulation material. Similar to the vapour control layer 3, the waterproofing layer 11 consists of a FMMA based polymer coating 17 applied over and around a glass fibre matting 16. The coating 17 is applied as a liquid spray to the continuous surface 10 and matting 16. The FMMA based polymer coating contains aluminium hydroxide as a fire-retardant additive to make the waterproofmg layer 11 non-combustible. The FMMA undergoes a spontaneous exothermic curing process after application to create a dry, waterproof surface. The use of an exothermic curing liquid applied coating limits the environmental impact or health hazards of the application process compared to the use of organic solvent based coatings.

As best shown in Figure 2, the secondary insulation layer 6 is tapered so that the continuous surface 10 has is inclined relative to the main insulation layer 4 and the deck surface 2. The incline has a slope of 1 in 60 (Figure 2 is not shown to scale). The waterproofing layer 11 on the continuous surface 10 therefore has a similar incline. This allows any water on the continuous surface 10 to run off into a drainage system (not shown). This prevents damage to the waterproofing layer 11 as a result of water collecting and forming pools on the waterproofing layer 11. Pooled water may gradually damage the waterproofing surface through chemical leaching and freeze/thaw cycles. The slight incline therefore prolongs the life of the waterproofing layer.

Referring now to Figures 3 and 7, an alternative roof assembly 20 is shown. The alternative roof assembly 20 is also positioned on a deck surface 2 of a roof. The vapour control layer 3 and the main insulation layer 4 are the same as in roof assembly 1. As with roof assembly 1, the primary insulation material 5 and secondary insulation material 7 are a mineral wool insulation material and are coated in an FMMA based polymer coating which has an aluminium hydroxide fire retardant additive. The external shell 8 is a rigid aluminium shell which provides a continuous surface 10. The secondary insulation layer 6 has individual sections of secondary insulation material 7 each encased in an external shell 8

Above the waterproofing layer 11 is a water detention system 21. There is no requirement for the secondary insulation layer 6 to be tapered in this particular embodiment, as the water detention system 21 is intended to provide rainwater storage on the roof assembly 20. The water detention system 21 has a base 24 which abuts the waterproofing layer 24. A series of walls 22 are welded to and extend vertically from the base 24. The base 24 and the walls 22 together define a void 23 suitable for storing a volume of water. The void contains support structures 19 to enable placement of additional roof elements on and above the water detention system. The base 24 and the walls 22 are formed of steel.

Within a section of the base 24 is a flow regulator 26. The flow regulator 26 is designed to allow water from within the void 23 to flow at a controlled rate from the void 23 to an outlet pipe 25. The flow regulator 26 is a metal sheet with an array of apertures to allow a restricted flow of water. A gravel filter 45 prevents foreign objects from blocking the apertures.

With reference again to Figure 6, the outlet pipe 25 passes through the insulation layers, waterproofing and vapour control layers of the roof assembly 20 and the deck surface 2 of the building through a primary outlet 18 connected to a drainage pipe (not shown). Additional insulation material 28 is placed around the outlet pipe 25 to limit heat loss through the outlet pipe 25.

The outlet pipe 25 is also connected to the void 23 via an overflow pipe 27. The overflow pipe 27 passes through the metal sheet of the flow regulator 26 and extends upwards into the void 23 to a predetermined height above the base 24. The height of the overflow pipe 27 above the base 24 is determined according to the anticipated average rainfall onto the roof assembly 20, the local requirements for sustainable drainage systems (SuDS) and the strength of the deck surface 2 and the roof of the building. The overflow pipe 27 has a large diameter compared to the diameter of the apertures on the flow regulator 26. During periods of heavy rain, the void 23 of the water detention system 21 will fill up, as water will enter through the top of the void 23 at a faster rate than water drains through the flow regulator 26. When the level of water in the void 23 reaches the height of the overflow pipe 27, water will flow through the overflow pipe 27 and into the outlet pipe 25. This prevents the water level rising above the height of the overflow pipe 27. The weight of water within the water detention system 21 is thereby prevented from increasing above a safe maximum for the roof.

Referring now to Figures 4 and 8, yet another roof assembly 30 is shown. Roof assembly 30 has all the features of roof assembly 20 and additionally has a secondary roof system 31. The secondary roof system 31 is a “living” or “green” roof system designed for the cultivation of plants 37 such as sedums and rockfoils. The secondary roofing system 31 is positioned above the water detention system 21.

The secondary roofing system 31 has a drainage and water retention layer 32 which is a steel platform with a series of troughs 33 arranged in rows. The troughs 33 contain a fibrous mineral wool material 38. Between the troughs 33 are peak areas 34. The peak areas 34 and troughs 33 contain openings 35 which enable water to drain from the drainage and water retention layer 32 into the void 23 of the water detention system 21. Rainwater falling on the secondary roofing system 31 will soak the fibrous mineral wool material 38, then overflow into the water detention system 21. This ensures that enough rainwater is retained within the secondary roofing system 31 to enable the cultivation of plants 37.

A growth medium 36 is placed above the drainage and water retention layer 32. The growth medium 36 is a porous woven hessian fabric material with a built-in anti-root inhibitor. The structure of the growth medium 36 helps retain moisture and organic matter such as soil, as well as providing a grounding for plant roots. In this particular embodiment the growth medium 36 is approximately 100 mm thick, although the thickness of the growth medium 36 can be adjusted to allow for different sized plants. Certain portions of the drainage and water retention layer 32 are not covered by the growth medium 36. In the embodiment of Figure 4, flagstones 39 are placed on the drainage and water retention layer 32 to act as a ballast material for roof assembly 30 and to provide a walkway.

Referring now to Figures 5 and 9, a further roof assembly 50 is shown. The roof assembly 50 is also positioned on a deck surface 2 of a roof. The vapour control layer 3 and the main insulation layer 4 are the same as in roof assembly 1. The secondary insulation layer 6 has a secondary insulation material 7 encased with an external shell 8 with a continuous surface 10 over an upper face of the secondary insulation material 7. As with roof assembly 1, the primary insulation material 5 and secondary insulation material 7 are a mineral wool insulation material, and the external shell 8 is a rigid aluminium shell. The secondary insulation layer 6 has individual sections of secondary insulation material 7 each encased in an external shell 8. As shown in Figure 5 the continuous surface 10 is inclined downwards towards a minimum point (the incline is exaggerated in Figure 5). The roof assembly 50 also includes a water detention system 21. The water detention system 21 has a base 24 which aligns with and abuts the inclined continuous surface 10, and walls 22 which define a void 23 suitable for storing water. The void 23 contains structural features 19 to enable further roofing elements to be positioned above the water detention system 21 (for simplicity the structural features are not shown in Figure 5). A flow regulator 26 controls the rate of water flow between the void 23 and an outlet pipe 25. The flow regulator is positioned at the minimum point of the continuous surface 10 and the base 24. This ensures that the water detention system 21 does not retain a significant volume of water longer than required as a result of water pooling within the void 23. The water detention system 21 of the roof assembly 50 is also equipped with an overflow pipe 27 to prevent the weight of water in the water detention system 21 becoming too high. In this particular embodiment, the top of the overflow pipe 27 is around 150 mm above the base 24.

Above the water detention system 21 is a non-combustible flooring system 40. The non combustible flooring system 40 has a support frame 42 arranged over the water detention system 21. The support frame 42 is composed of aluminium and is designed to support an array of tiles 41. In this embodiment each tile is a porcelain substrate contained within an aluminium tray. The tiles 41 are attached to the support frame 42 to define a terrace surface 43 sufficient for use as a load bearing surface. Rainwater falling onto the terrace surface 43 can pass through gaps 44 between adjacent tiles 41 into the water detention system 21.

Referring now to Figure 11, a cross-section of an alternative roof assembly 60 is shown. Although not shown in Figure 11, the roof assembly 60 is compatible with a water detention system 21, a secondary roof system 31 and/or a non-combustible flooring system 40 as described.

The roof assembly 60 has a vapour control layer 61 which is composed of the same material and functions in the same way to the vapour control layer 3. The vapour control layer 61 is positioned on and in contact with the deck surface 2. The deck surface 2 is a concrete deck surface capable of supporting weight and is around 200 mm thick. Above the vapour control layer 61 is a main insulation layer 62. The main insulation layer 62 has a composite structure consisting of a primary insulation material 63, an insulation core 64, a concrete structural capping board 65, and a coating layer 66. The coating layer 66 consists of an aluminium foil shell 67 which seals and contains the insulation materials 63, 64 and the structural capping board 65, and an FMMA based polymer coating 68 applied to the aluminium foil shell 67. The polymer coating 68 has an aluminium hydroxide fire retardant additive. The insulation core 64 is a block of mineral or glass wool insulation material which is vacuum packed within an aluminium foil shell. The insulation core 64 is surrounded by the primary insulation material 63. The structural capping board 65, the aluminium foil shell 67 and the polymer coating 68 together provide a non-porous rigid upper surface 69 to allow application of a waterproofing layer, without impacting on the effectiveness of the insulation. The complete encasement of the main insulation layer 62 in a coating layer 66 enables the main insulation layer 62 to be prefabricated as modular units and then simply arranged on the vapour control layer as required on site. The number, size and shape of the modular units can be adapted as required to suit the size and shape of the deck surface 2.

Above the main insulation layer 62 is a waterproofing layer 70. The waterproofing layer 70 is designed to prevent any rainwater passing through into the insulation layer 62. The rigid and non-porous upper surface 69 protects the waterproofing layer 70 against movement and damage such as cracking. This prolongs the life of the waterproofing layer 70 and prevents water leaking into the insulation layer 62. Similar to the vapour control layer 61 and the waterproofing layer 11, the waterproofing layer 70 consists of a FMMA based polymer coating applied over and around a glass fibre matting. The coating is applied as a liquid spray to the matting which is laid on the rigid upper surface 69. The FMMA based polymer coating contains aluminium hydroxide as a fire-retardant additive to make the waterproofing layer 70 non-combustible. The FMMA undergoes a spontaneous exothermic curing process after application to create a dry, waterproof surface. The use of an exothermic curing liquid applied coating limits the environmental impact or health hazards of the application process compared to the use of organic solvent based coatings. Referring now to Figure 12, a cross-section of another alternative roof assembly 80 is shown. The roof assembly 80 is similar to the roof assembly 60 and (although not shown) is compatible with a water detention system 21, a secondary roof system 31 and/or a non combustible flooring system 40 as described.

The roof assembly 80 has a vapour control layer 81 which is composed of the same material and functions in the same way to the vapour control layer 3. The vapour control layer 81 is positioned on and in contact with the deck surface 2. The deck surface 2 is a concrete deck surface capable of supporting weight and is around 200 mm thick.

Above the vapour control layer 81 is a main insulation layer 82. The main insulation layer 82 has a composite structure consisting of a primary insulation material 83, a concrete structural capping board 85, and a coating layer 86. In this particular embodiment there is no distinct insulation core. The main insulation layer 82 is therefore simpler (and has a lower production cost), although the insulative properties for a given depth are lower. The coating layer 86 consists of an aluminium foil shell 87 which seals and contains the insulation material 83 and the structural capping board 85, and an FMMA based polymer coating 88 applied to the aluminium foil shell 87. The polymer coating 88 has an aluminium hydroxide fire retardant additive. The structural capping board 85, the aluminium foil shell 87 and the polymer coating 88 together provide a non-porous rigid upper surface 89 to allow application of a waterproofing layer, without impacting on the effectiveness of the insulation. The complete encasement of the main insulation layer 82 in a coating layer 86 enables the main insulation layer 82 to be prefabricated as modular units and then simply arranged on the vapour control layer as required on site. The number, size and shape of the modular units can be adapted as required to suit the size and shape of the deck surface 2.

Above the main insulation layer 82 is a waterproofing layer 90 which is like the waterproofing layer 70 as hereinbefore described.

As illustrated by Figures 12 and 13 respectively, the main insulation layers 62, 82 of roof assemblies 60 and 80 can be configured to be tapered or wedge-shaped so that the upper surface 69, 89 is inclined relative to the deck surface 2. This is achieved by positioning a tapered block of mineral or glass wool insulation material 71, 91 above the primary insulation material 63, 83. The waterproofing layer 70, 90 therefore has a similar incline. This allows any water on the waterproofing layer to run off into a drainage system (not shown), thus preventing water collecting and forming pools on the waterproofing layer. This reduces damage to the waterproofing layer through chemical leaching and freeze/thaw cycles and prolongs the life of the waterproofing layer.

As shown in Figure 12, in this particular embodiment the primary insulation material 63 has a wedge-shaped cross-section, with the insulation core 64 embedded completely within the primary insulation material 63 and tapered block 71 such that it is not in contact with the structural capping board 65. The structural capping board 65 is inclined relative to the deck surface 2.