Lintels are well known in the construction industry as supporting beams that span an opening in a wall, such as that of a window, door or fireplace. The principle is that by using a lintel over an opening in a wall, the weight above the opening is transferred to the wall either side of the opening, and the wall does not collapse around the opening.

Known lintels are made out of steel, concrete or timber and are made in numerous fixed standard sizes in order to suit various sizes of openings in various sizes of walls. Typically a distributor of lintels, e. g. a builders merchant, will stock about 60 or 70 different types of box cavity lintel for cavities varying from 50mm to 90mm. This amount of stock can occupy as much as 100,000 square feet of the distributor's yard. It is an object of the present invention to reduce the amount of lintels that a distributor must stock, and therefore the space occupied in the distributor's storage yard.

A box cavity lintel consists of opposed upper and lower walls and opposed side walls to form a box section, and two wings. One of the wings extends laterally away from each side of the box section. The box section is situated in the cavity of a cavity wall when in use, and the two wings are built into an inside and outside wall of the cavity wall respectively. In some known box cavity lintels, the top wall of the box section provides an inclined surface that slopes downwards towards the outside wall of the cavity wall in order that any mortar, or other debris,

that falls on the lintel is directed to slide, or move, to the outside wall and away from the inside wall. Such debris may fall on the lintel during construction of those parts of the wall that are above the lintel. Directing debris to one side of the cavity can help to prevent"cold bridging".

Cold bridging occurs when heat is transferred by conduction through any material that bridges the inside wall to the outside wall through the cavity, thereby creating cold spots, and subsequently increased condensation on the inside wall. Cold bridging can also occur through the lintel itself, if the lintel is made of a material that conducts heat.

A significant amount of money has been invested by the British government in trying to reduce the effects of cold bridging. Existing lintels are known to conduct heat, and it is an aim of some embodiments of the invention to provide a lintel that does not significantly conduct heat in order to reduce cold bridging.

A disadvantage of known steel lintels is that they have to be galvanised, and subsequently painted regularly in order that they are not eroded by the weather. This is a particular problem in coastal areas where weather conditions can be severe, and lintels have to be maintained by painting them on a very regular basis. A similar problem arises with the use of wooden lintels. It is an aim of some embodiments of the invention to provide a maintenance-free lintel.

A further disadvantage of known box cavity lintels is that they can be difficult to carry and are easily dropped. A box cavity lintel can be particularly slippery when a worker is wearing wet gloves and this can create a significant health and safety concern. It is an aim of some embodiments of the invention to provide a more user-friendly lintel, that can be more easily carried.

It will be appreciated that for at least some aspects of the invention, a part of the invention resides in the appreciation that the aforementioned problems exist and that they should be tackled. Hitherto people have either not appreciated the need, or just accepted the problems.

According to a first aspect of the invention, there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and a second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing laterally extends away from the second side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, wherein one of the wings includes at least one weakened region running in a longitudinal direction along the wing, wherein the weakened region provides a region of the wing that is more easily severed than regions of the wing to either side of the weakened region.

Either or both of the wings may comprise at least one weakened region.

The weakened region can be fractured, severed, or otherwise broken to allow the width of the lintel to be adjusted. This enables one type of lintel to be used with walls of different thicknesses, and can reduce the amount of stock that a distributor must keep. For example, a distributor may use about 2,000 square feet of his yard to stock a sufficient number of box cavity lintels according to the present invention that can be used with a variety of different walls. This is a significant reduction when compared with the 100,000 square feet of yard required for the lots of different sized box cavity lintels that are not adjustable.

In some embodiments, there is provided more than one weakened region in the wing. This enables the lintel to be used with a greater variety of different thickness walls.

A distributor may stock one lintel at a maximum width size, which will cover the largest of the various wall cavity widths. A user can fracture the weakened region when using the lintel for use with smaller than maximum width openings.

Preferably, the weakened region is arranged so that it can be fractured by hand, as this removes the need for tools to adjust the width of the lintel.

The weakened region may comprise a region of reduced thickness compared to the rest of the wing, alternatively, or additionally, the weakened region may comprise perforations and/or a region that is not reinforced.

The weakened region may run the entire length of the lintel.

Alternatively, the weakened region may be intermittent along the length of the lintel.

The lintel may be made out of reinforced plastic, as this material is not a significant conductor of heat and can help reduce the effects of cold bridging. The plastic lintel may be reinforced with glass fibre, carbon fibre or another material that increases the strength of the plastic lintel.

Further, the lintel can be reinforced with carbon matting or glass fibre matting. In some embodiments, some regions have carbon matting or glass fibre matting, and some regions do not have carbon matting or glass fibre matting.

A reinforced plastic lintel also provides the advantage that it is lightweight in comparison with steel, concrete and timber. This will make the lintel easier to carry and can improve the health and safety associated with a person lifting and carrying the lintel. Possibly, one person could carry a reinforced plastic lintel according to embodiments of the present invention by themselves, whereas known lintels are heavy and can typically require more than one person to carry them. A further advantage of having a lightweight lintel is that it may be less likely to be dropped and damaged when on site and/or in transit.

In other embodiments the entire lintel is reinforced with matting. The regions having carbon matting or glass fibre matting improve the strength of the lintel, and are preferably at regions of the lintel that experience high stress. The regions of the lintel that experience high stress may be at corners of the lintel. In embodiments where some regions of the lintel do not have matting, the cost and weight of the lintel is reduced when compared with a lintel entirely reinforced with matting.

The lintel may comprise a lip extending from a free-end of the wing, in a plane that is substantially perpendicular to the wing. The lip may be a generally upright wall, which is preferably located on the inside of an inside wall of a cavity wall when in use. The lip provides an inside surface that, in use, is substantially parallel to, and in contact with, the wall in which the lintel has been built. Having the inside surface parallel to, and in contact with, the wall increases the strength provided by the lintel, as the lintel is more firmly secured within the wall. Locating the lip on the inside of a wall, for example, when in use allows the lip to be obscured by plastering over it.

The box section may comprise an extension wall that extends upwardly from the box section, which enables more debris to fall onto the lintel

before cold bridging occurs. The box section may also comprise at least one hand-hold rib that projects from a wall of the box section, to enable a person to get a better grip on the lintel when carrying it. The at least one hand-hold rib may extend from a side wall of the box section.

The at least one rib can provide a finger grip for lifting and carrying the lintel. The rib/s allow a person to get a good grip on the lintel when carrying it, and this reduces the chances of the lintel slipping when compared with a lintel without hand-hold ribs. Providing a lintel that is easier to carry can reduce the chances of the lintel being dropped and damaged when the lintel is on site and/or in transit. It may also enable a single person to carry the box cavity lintel by themselves, whereas a known prior art box cavity lintel may require more than one person to carry it.

Preferably at least one rib extends from the first side wall of the box section and at least one rib extends from the second side wall of the box section. Two ribs may extend from the first side wall of the box section and two ribs may extend from the second side wall of the box section.

Alternatively, three ribs may extend from the first side wall of the box section, and two ribs may extend from the second side wall of the box section.

The wing, or wings, that include the at least one weakened region may comprise a plurality of snap-off portions disposed at increasing distances from the box section, and each snap-off portion is joined to its adjacent snap-off portion by a weakened region. A plastic lintel according to some embodiments of the present invention particularly facilitates having one or more snap-off portions.

Preferably, a wing of the box cavity lintel further comprises at least one mortar channel running in a longitudinal direction along the wing, wherein the mortar channel, in use, keys the lintel to the wall in which it is built.

A mortar channel firmly secures the lintel within the wall and can provide a lintel with improved overall strength when it is fitted within a wall.

The mortar channel can be a region of the wing that is of reduced thickness to accommodate mortar of the cavity wall when the lintel is in use. Alternatively, the mortar channel can be a region of the wing that is of increased thickness that more firmly secures the lintel within the mortar of the wall when in use. In further still embodiments, the mortar channel may be a region of the wing that deviates from the plane of the wing and then returns to the plane of the wing. The region of the wing that is not in the plane of the wing may be of the same thickness as the rest of the wing, and may further key the lintel to the wall.

In some embodiments, any weakened region that is not broken when the lintel is to be fitted into a wall can act as a mortar channel in order to improve the keying of the lintel into the wall.

The at least one mortar channel may be located within a bottom surface of a wing. Alternatively, or additionally, at least one mortar channel may be located within a top surface of a wing. Either, or both, of the first and second wings may include at least one mortar channel.

Preferably, the mortar channel extends along the length of the lintel. In alternative embodiments, the mortar channel may be intermittent along the length of the lintel.

Preferably, the lintel further comprises a region of a wall of the lintel that decreases in thickness at an increasing distance from a join between two walls of the lintel.

Having a wall of tapered thickness can provide improved strength in regions of the wall that are thickened. Some regions are not thickened to avoid the lintel consisting of unnecessary material and being unnecessarily heavy in regions of the lintel that do not require improved strength.

The regions of increased thickness may comprise a region of reinforcement of the lintel.

The wings of the lintel may decrease in thickness at an increasing distance from the box section of the lintel. The side walls of the box section may decrease in thickness at an increasing distance from the bottom wall of the box section. Further, the bottom wall of the box section may decrease in thickness at an increasing distance from the side walls of the box section.

Preferably, the angle between the top wall of the box section and the two side walls of the box section is greater than ninety degrees.

Having an angle of greater than ninety degrees between the top wall and the two side walls of the box section produces a top wall that slopes downward towards each side wall of the lintel. This causes any debris that falls onto the top of the lintel to slide to either side of the lintel and can help prevent cold bridging.

The top wall of the box section may be curved in cross-section. The top wall of the box section may provide a top surface that is a semi-circle in

cross-section. Alternatively, the cross-section of a top surface of the top wall of the box section may be a portion of a curve that is not a complete semi-circle.

In some embodiments, the top wall of the box section may comprise a first and a second portion, wherein the first portion of the top wall is joined to the first side wall of the box section and the second portion of the top wall is joined to the second side wall of the box section, wherein the first and second portions of the top wall are joined together at a point that is further from the bottom wall of the box section than the ends of the first and second portions that are joined to the first and second side walls respectively.

According to a second aspect of the invention, there is provided a method of manufacturing a lintel according to the first aspect of the invention, the method comprising using a continuous extrusion or pultrusion method to produce the lintel through a die mould.

The lintel may be a plastic lintel. Manufacturing a plastic lintel according to the present invention can provide cheaper manufacturing costs when compared to known steel, concrete and timber lintels. The continuous extrusion or pultrusion process can enable lintels to be manufactured constantly, for example 24 hours a day, 7 days a week.

Known prior art lintels are made discretely one at a time. Embodiments of the present invention allow a greater number of lintels to be manufactured in a shorter time, and in a more efficient manner.

According to another aspect of the invention, there is provided a box cavity lintel made at least partly of fibre-reinforced plastic.

Preferably, a region of the lintel is made out of the fibre-reinforced plastic to reduce the amount of heat that can travel through the lintel by conduction. All, or substantially all, of the lintel may be made out of fibre-reinforced plastic.

Preferably the fibres are made out of a material that is a poor conductor of heat. The fibres may be glass fibres or carbon fibres.

The amount of fibre present in the total volume of reinforced plastic may vary depending on the application of the lintel. Some applications may require a strong lintel and can contain a high percentage of fibre. Other applications may not require as much strength and may contain a low percentage of fibre.

A fibre-reinforced plastic lintel has the advantage that it does not significantly conduct heat, and therefore reduces the effects of cold bridging.

The lintel can be made from thermoplastic or thermoset resins, or composites including glass fill or engineering plastics, or composite materials.

In prior art attempts to manufacture a lintel out of plastic, the load bearing capacity and construction strength has been a problem when compared with steel, timber or concrete lintels. However, the lintel according to some embodiments of the present invention provides sufficient strength through the use of fibre-reinforced plastic, as well as preventing cold bridging.

Preferably the lintel comprises regions of matting. The matting may be a matrix, network, sheet matrix or other configuration that provides a

region of the lintel of increased strength. The matting may be carbon matting or glass fibre matting, and preferably the regions of carbon matting or glass fibre matting are located at points of the lintel of high stress, such as at bends or corners of the lintel.

According to another aspect of the invention there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing extends laterally away from the second side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, the box cavity lintel further comprising a lip extending from the region of a free-end of one of the wings in a plane that is generally in the same direction as the side walls.

The lip, in combination with the wing from which it extends, and the side wall of the box section from which the wing extends, defines a channel.

Brickw ork of a cavity wall can be built in the channel and the lip increases the strength provided by the lintel, as the lintel is more firmly secured within the wall.

The lip may extend from a free-end of the first wing, and/or a lip may extend from a free-end of the second wing.

According to another aspect of the invention there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and a second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first

side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing laterally extends away from the second side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, the box cavity lintel further comprising an extension wall that extends upwardly from the box section.

Having an extension wall effectively increases the height of the box section. This means that more debris must fall onto the lintel before a "cold bridge"is formed between an inside and outside wall of a cavity wall, when compared with lintels without an extension wall. The extension wall serves as a screen, screening the brickwork above the top wall of the box section from debris resting on the top wall. The extension wall may also increase the overall strength of the lintel.

Preferably the extension wall extends upwardly from the top wall of the box section at a region substantially adjacent the first side wall of the box section.

Preferably the, or another, extension wall extends upwardly from the top wall of the box section at a region substantially adjacent the second side wall of the box section.

According to another aspect of the invention there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and a second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing laterally extends away from the second side

wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, the box cavity lintel further comprising at least one hand-hold rib that extends from a wall of the box section.

The at least one rib provides a finger grip for lifting and carrying the lintel. The rib/s allow a person to get a good grip on the lintel when carrying it, and this reduces the chances of the lintel slipping when compared with a lintel without hand-hold ribs according to the present invention.

The at least one rib may extend any distance from the box section in order to enable a person carrying the lintel to get a better purchase on the lintel. The at least one rib may extend anything between 0.5mm and 5 mm from the box section. More preferably, the at least one rib may extend between 0. 5 mm and 3mm from the box section, and more preferably still the at least one rib may extend 2 mm from the box section.

Preferably at least one rib extends from the first side wall of the box section and at least one rib extends from the second side wall of the box section. Two ribs may extend from the first side wall of the box section and two ribs may extend from the second side wall of the box section.

Alternatively, three ribs may extend from the first side wall of the box section, and two ribs may extend from the second side wall of the box section.

Providing a lintel that is easier to carry can reduce the chances of the lintel being dropped and damaged when the lintel is on site or in transit.

According to another aspect of the invention, there is provided a lintel comprising a wing arranged to be built into a wall when in use, wherein the wing includes at least one weakened region running in a longitudinal direction along the wing, wherein the weakened region provides a region of the wing that is more easily severed than regions of the wing to either side of the weakened region.

According to another aspect of the invention, there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and a second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing laterally extends away from the second side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, wherein a wing of the box cavity lintel further comprises at least one mortar channel running in a longitudinal direction along the wing, wherein the mortar channel, in use, keys the lintel to the wall in which it is built.

It will be appreciated that mortar can include any material that is located between bricks/blocks in a wall that is used to hold the bricks/blocks together to form the wall.

The mortar channel can be a region of the wing that is of reduced thickness to accommodate mortar of the cavity wall when the lintel is in use. Alternatively, the mortar channel can be a region of the wing that is of increased thickness that more firmly secures the lintel within the mortar of the wall when in use. In further still embodiments, the mortar channel may be a region of the wing that deviates from the plane of the

wing and then returns to the plane of the wing. The region of the wing that is not in the plane of the wing may be of the same thickness as the rest of the wing, and may further key the lintel to the wall.

A mortar channel firmly secures the lintel within the wall and can provide a lintel with improved overall strength when it is fitted within a wall when in use.

The at least one mortar channel may be located within a bottom surface of a wing. Alternatively, or additionally, at least one mortar channel may be located within a top surface of a wing. Either, or both, of the first and second wings may include at least one mortar channel.

Preferably, the mortar channel extends along the length of the lintel. In alternative embodiments, the mortar channel may be intermittent along the length of the lintel.

Having a mortar channel located within a wing is particularly applicable to lintels made out of fibre reinforced plastic. The manufacturing processes used to make a fibre reinforced plastic lintel having at least one mortar channel can easily accommodate the different cross-sectional profile provided by a lintel having a mortar channel. Examples of such manufacturing processes include extrusion and pultrusion processes.

According to another aspect of the invention there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and a second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing laterally extends away from the second side

wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, wherein a region of a wall of the lintel decreases in thickness at an increasing distance from a join between two walls of the lintel.

Having a wall of tapered thickness can provide improved strength in regions of the wall that are thickened. Some regions are not thickened to avoid the lintel consisting of unnecessary material and being unnecessarily heavy in regions of the lintel that do not require improved strength.

The regions of increased thickness may comprise a region of reinforcement of the lintel. In embodiments where the lintel is made out of fibre reinforced plastic, preferably glass fibre reinforced plastic, the regions of increased thickness may comprise regions that are reinforced with matting, preferably glass fibre matting.

Preferably, the wings of the box section decrease in thickness at an increasing distance from the box section of the lintel. The side walls of the box section may decrease in thickness at an increasing distance from the bottom wall of the box section. Further, the bottom wall of the box section may decrease in thickness at an increasing distance from the side walls of the box section.

According to another aspect of the invention there is provided a box cavity lintel comprising a box section, a first wing and a second wing, the box section comprising a first and a second side wall, a top wall and a bottom wall, wherein the first wing extends laterally away from the first side wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an inside wall of a cavity wall when in use, and the second wing laterally extends away from the second side

wall of the box section at a region substantially adjacent the bottom wall and is arranged to be built into an outside wall of a cavity wall when in use, wherein the angle between the top wall of the box section and the two side walls of the box section is greater than ninety degrees.

Having an angle of greater than ninety degrees between the top wall and the two side walls of the box section produces a top wall that slopes downward towards each side wall of the lintel. This causes any debris that falls onto the top of the lintel to slide to either side of the lintel.

This can help prevent cold bridging as the lintel causes any debris to settle unevenly on top of the box section, and creates a gap in the debris at the highest point of the top wall of the box section. A cold bridge will only occur when the debris resting on top of the top wall bridges the highest point of the top wall of the box section.

A greater amount of debris is required to fall onto a box cavity lintel according to this embodiment of the invention, when compared with prior art lintels.

The top wall of the box section may be curved in cross-section. The top wall of the box section may provide a top surface that is a semi-circle in cross-section. Alternatively, the cross-section of a top surface of the top wall of the box section may be a portion of a curve that is not a complete semi-circle.

In some embodiments, the top wall of the box section may comprise a first and a second portion, wherein the first portion of the top wall is joined to the first side wall of the box section and the second portion of the top wall is joined to the second side wall of the box section, wherein the first and second portions of the top wall are joined together at a point that is further from the bottom wall of the box section than the ends of the

first and second portions that are joined to the first and second side walls respectively.

The first and second portions of the top wall may be flat walls.

Alternatively, the first and second portions of the top wall may be curved walls. In some embodiments, the first and second portions may be joined together in a region that is substantially half way between the first and second side walls. Alternatively, the first and second portions may be joined together in a region that is closer to one of the first and second side walls.

According to another aspect of the invention there is provided a method of manufacturing a lintel according to any of the earlier aspects of the invention, the method comprising using a continuous extrusion or pultrusion method to produce the lintel through a die mould.

According to another aspect of the invention there is provided a method of fitting a box cavity lintel into a cavity wall, the box cavity lintel comprising a box section and two wings extending laterally from opposing walls of the box section, the method comprising the steps of: adjusting the width of the box cavity lintel by severing at least one of the wings at a weakened region running in a longitudinal direction along the wing, wherein the weakened region provides a region of the wing that is more easily severed than regions of the wing to either side of the weakened region; and building the box cavity lintel into the cavity wall.

It will be appreciated that any of the features discussed with reference to an aspect of the invention may also be relevant to other aspects of the invention.

It will also be appreciated that many of the aspects of the invention and their associated features are equally applicable to lintels that are not box cavity lintels. For example, aspects of the invention may be applicable to box lintels, double skin lintels, internal wall lintels or any other known lintels. A box lintel is similar to a box cavity lintel. A box lintel consists of only one wing arranged to be built into an inside wall of a cavity wall and a box section arranged to be built into an outside wall of a cavity wall.

The invention will now be further described by way of example with reference to the accompanying drawings, of which:- Figure la shows a schematic cross-sectional view of a box cavity lintel according to an embodiment of the present invention; Figure lb shows a perspective view of the lintel of Figure la ; Figure le shows schematically the lintel of Figure la in use in a cavity wall; Figure 2 shows schematically alternative embodiments of a wing of a lintel according to the present invention; Figure 3 shows a schematic cross-sectional view of a box cavity lintel according to an embodiment of the present invention; Figure 4 shows a schematic cross-sectional view of a box cavity lintel according to another embodiment of the present invention; Figure 5a shows a schematic cross-sectional view of a box cavity lintel according to a further embodiment of the present invention;

Figure 5b shows a perspective view of the lintel of Figure 5a; Figure 5c shows a schematic cross-sectional view of a box cavity lintel according to a further embodiment of the present invention ; Figure 6a shows schematically the amount of debris required to fall onto a prior art lintel to form a cold bridge; Figure 6b shows schematically the amount of debris required to fall onto a lintel according to an embodiment of the present invention to form a cold bridge; Figure 7 shows schematically a cross-sectional view of a lintel according to an embodiment of the present invention; Figure 8a shows schematically a cross-sectional view of a lintel according to an embodiment of the present invention; and Figure 8b shows schematically a cross-sectional view of a lintel according to an embodiment of the present invention.

Figure la shows a schematic cross-sectional view of a building lintel 10 according to an embodiment of the present invention and Figure lb shows a perspective view of the same lintel 10. The lintel 10 is a box cavity lintel comprising a box section 26, first wing 18 and second wing 22.

The box section 26 is defined by first side wall 12, second side wall 16, bottom wall 20 and top wall 14. The first wing, or flange, 18 extends laterally away from the first side wall 12 of the box section 26, and the second wing, or flange 22 extends laterally away from the second side wall 16 of the box section.

Second wing 22 comprises two parallel weakened regions 24a, 24b of reduced thickness that run the length of second wing 22 and are arranged to form"snap-off"portions 28a, 28b of the wing 22. The weakened regions 24a, 24b enable the length of the wing 22, and therefore the width of the lintel 10, to be easily varied. The box section 26 of the lintel 10 can be manufactured to a minimum cavity size, for example 2 inches (about 5 cm), so that the box section 26 can fit into the smallest, and therefore also any larger, width cavity. Having a lintel 10 of variable width enables the same type of lintel to be used with cavity walls of different thicknesses, which can reduce the amount of stock a distributor must keep.

The lintel 10 can be considered as a"multi-width-span building lintel", as it is capable of spanning walls of a multitude of widths. That is, it can be used to span various cavity wall thicknesses and widths.

To use the lintel 10 shown in Figure 1, a user will first determine the width of the cavity wall in which he wants to build the lintel 10. The user can then compare the width of the cavity wall to the dimensions of the lintel 10, and decide which weakened region 24a, 24b, if any, should be broken to reduce the width of the lintel 10 by the width of snap-off portions 28a, 28b, so that the lintel 10 is of a suitable width for the cavity wall. In some embodiments it will be possible to exactly match the width of the lintel 10 with the width of the cavity wall. In other embodiments, where an exact match between the width of the lintel 10 and the width of the cavity wall is not available, the width of the lintel 10 can be adjusted so that it is narrower than the cavity wall and does not project out of either side of the cavity wall when in use. In other embodiments it may be advantageous for the lintel 10 to project out of one, or both, sides of the cavity wall.

In this embodiment, the user will hold the wing 22 of the lintel 10 with one hand either side of the weakened region 24a, 24b that he has determined needs breaking. The user then flexes the wing 22 until the weakened region 24a, 24b stress fractures. In other embodiments, the user may support the lintel 10 on some bricks or in a vice, and use both hands to flex and fracture the weakened region 24a, 24b. In some embodiments, the weakened region/s 24a, 24b that are not desired to be fractured can be held in a vice to prevent them from also breaking.

In other embodiments the weakened region can be arranged to be cut, sawn, ground, chiselled, or otherwise fractured by any other suitable method. Including using hand-tools, possibly powered hand tools, and any other tools that a builder may have.

It will be appreciated that the second wing 22 can have any number of weakened regions 24 to make the lintel usable with a number of walls of different widths. The weakened regions can be located in either, or both, of first wing 18 and second wing 22, and any of the weakened regions can be selected to be broken based on the dimensions of the cavity wall.

In some embodiments it may be beneficial to break a weakened region in each wing 18,22 in order for the box section 26 to occupy a desired position within the cavity.

As shown in Figure 1c, first wing 18 is arranged to be built into the brickwork of an inside wall 30 of a cavity wall, and second wing 22 is arranged to be built into the brickwork of an outside wall 32 of the cavity wall. The box section 26 is arranged to be located inside the cavity 34 of the cavity wall.

In the embodiment shown in Figure lc, second wing 22 has been snapped- off at weakened region 24b in order that the lintel fits within the brickwork of the inner wall 30 and the brickwork of the outer wall 32 without projecting out of the cavity wall on either side. The snapped-off portion 28 of second wing 22 is shown in dotted lines. The other weakened region 24a is located within the brickwork 32 of the outer wall and does not reduce the effective strength of the lintel 10.

The lintel 10 is made out of glass reinforced plastic. Having a plastic lintel is an advantage as it does not conduct heat between the inside and outside walls, and helps reduce cold bridging. Glass reinforced plastic can provide sufficient strength and load bearing capacity in order to meet the required standards.

Further advantages of a plastic lintel include its lightweight, cheaper manufacturing costs, maintenance-free-that is it does not require galvanising or painting regularly, and it can be produced in a continuous process by extrusion or pultrusion.

The lintel can be made from a plastic material or a composite material or a thermo set glass filled material.

Figures 2a to 2d show schematically plan views of a wing 22 having a weakened region according to alternative embodiments of the present invention.

Figure 2a shows an embodiment where the weakened region is provided by perforations 70. The perforations 70 are a series of holes through the entire thickness of the wing 22.

Figure 2b shows an embodiment where the weakened region is provided by a region 74 without reinforcement. Regions with reinforcement 72 are located either side of the region 74 without reinforcement. This means that the region 74 without reinforcement is weak relative to the reinforced regions 72 either side of the region 74.

Figure 2c shows an embodiment where the weakened region is provided by spaced bridges 76 between a first portion 75 and a second portion 77 of the wing 22.

Figure 2d shows an embodiment where the weakened region is provided by regions 78 of reduced thickness compared with the rest of the wing.

In this embodiment the regions of reduced thickness do not run the entire length of the wing. The ratio of the length of the reduced thickness regions 78 compared with the gaps between the reduced thickness regions 78 can be selected as any suitable ratio. The ratio should provide sufficient strength when the weakened region is not broken, yet still be capable of being fractured when so desired.

It will be appreciated that the thickness of the wing could be reduced by providing an indention in the top surface of the wing, in the bottom surface of the wing, or in both the top and bottom surface of the wing. In embodiments where the top and bottom surfaces of a wing include indentations, the indentations may be at the same distance from the end of the wing. In other embodiments the indentation in the top surface of the wing may be offset from the indentation in the bottom surface of the wing. Having the indentations offset from one another may provide a better break when the weakened region is broken.

Alternatively, the weakened region could be provided by any way of creating a frangible region in the wing 22.

In some embodiments the weakened region may not run for the entire length of the lintel. There may be un-weakened regions spaced between the weakened regions. This can provide improved strength whilst still enabling the width of the lintel to be adjusted.

Figure 3 shows an embodiment of the invention where the strength of a plastic lintel 10'is further improved by providing matting 80, for example carbon matting or glass fibre matting, at points of high stress of the lintel 10'. In this embodiment, the points of high stress of the lintel 10'have been identified as regions in the vicinity of bends of the lintel 10'. In other embodiments, additional, or alternative, points of high stress can be identified. In other embodiments still, the entire lintel 10' can be reinforced with mating 80.

Figure 4 shows a cross-sectional view of an alternative embodiment of a building lintel 110 according to the present invention. The lintel 110 is similar to the embodiment shown in Figure 1, and similar elements have been given the same reference numbers in the 100 series.

In this embodiment there are four weakened regions 124 in each of first and second wings 118,122 to enable the width of the lintel 110 to be adjusted by fracturing either or both of the wings 118,122 at one of the weakened regions 124. The first and second wings 118, 122 also comprise two mortar channels 150 on the underside of each wing 118, 122. The mortar channels 150 accommodate mortar within the brickwork of the wall when the lintel is in use, and help secure the lintel 10 within the wall.

Figure 5a shows a cross-sectional view of an alternative embodiment of a building lintel 210 according to the present invention and Figure 5b shows

a perspective view of the lintel 210. The lintel 210 comprises a box section 226, first wing 218 and second wing 222. The box section 226 is bound by first side wall 212, second side wall 216, bottom wall 220 and sloping wall 214 at the top of the box section 226. The box section 226 comprises an extension wall 242 extending from the sloping wall 214 at the top of the box section 226. The box section 226 also comprises a number of ribs 244 on its side walls 212,216.

The sloping wall 214 of the box section 226 is arranged to divert any mortar or other debris that falls onto the lintel 210 to one side of the lintel 210 in order to reduce the chances of"cold bridging". Cold bridging occurs when heat is transferred by conduction through any material that bridges the inside wall to the outside wall through the cavity, thereby creating cold spots, and subsequently increased condensation, on the inside wall.

The first wing 218 extends laterally away from the first side wall 212 of the box section 226, and the second wing 222 extends laterally away from the second side wall 216 of the box section 226. Lip 240 extends laterally from the free-end of first wing 218 and is in a plane that is substantially perpendicular to wing 218. In this embodiment, the lip 240 extends in a generally upward direction. In other embodiments the lip extends in a generally downward direction, and in further embodiments still, the lip extends both upwardly and downwardly to make a"T" junction at the end of the wing.

The lip 240 part-defines a channel 246 in which the brickwork of a wall can be built. This provides the lintel 210 with increased strength because the lintel is more firmly secured within the wall. In this embodiment, the channel 246 is provided by lip 240, first wing 218 and first side wall 212.

The channel 246 can accommodate brickwork of the inner wall of a cavity

wall. The channel 246 is located around the inner wall of a cavity wall for cosmetic reasons, as typically the inside of the inner wall will be plastered over, and the plaster will obscure the lip 240.

It will be appreciated that in other embodiments the lip 240 may be located at the free-end of the second wing 222 that is to be located in the outer wall of a cavity wall when in use, instead of at the free-end of the first wing 218 to be located in the inner wall when in use. In other embodiments, both wings 218,222 can have a lip 240.

The second wing 222 comprises a weakened region 224 to enable the length of second wing 222 to be shortened by fracturing the second wing 222 at the weakened region 224. That is, in this embodiment one wing has a lip 240 and the other wing has a weakened region to enable adjustment of the width of the lintel 110.

In some embodiments there can be a region of increased thickness located next to the weakened region 224 in order to provide a good break when the wing is broken at its weakened region.

The extension wall 242 effectively increases the height of the box section 226. This means that more debris must fall onto the lintel 210 before a "cold bridge"is formed between an inside and outside wall of a cavity wall, when compared with lintels without an extension wall 242.

Ribs 244 extend from the side walls 212,216 of the box section 226 to provide finger grips for lifting and carrying the lintel 210. The ribs 244 allow a person to get a good grip on the lintel 210 when carrying it, and this reduces the chances of the lintel 210 slipping when compared with a lintel 210 without ribs 244. This is particularly useful when the lintel 210 is wet.

In this embodiment the ribs 244 are continuous along the length of the 210. In other embodiments the ribs 244 can be intermittent along the length of the lintel 210.

Figure 5c shows schematically an alternative embodiment of a lintel 210' according to the present invention. This embodiment of a lintel 210'is similar to the embodiment of a lintel 210 shown in Figure 5, and the discussion of the elements of lintel 210'that are the same as those illustrated by the lintel 210 in Figure 5a will not be repeated here.

Lintel 210'includes three ribs 244'on the first side wall 212'of the box section 226', and two ribs 244'on the second side wall 216'of the box section 226'.

Figure 6a illustrates schematically a prior art lintel 302 without an extension wall, and Figure 6b illustrates schematically a lintel 310 according to the present invention with an extension wall 342. Figures 6a and 6b show the relative amounts of debris 336 that must fall onto the top wall of the box section of a box cavity lintel before cold bridging occurs between an inside wall 330 and an outside wall 332 of a cavity wall. It can be seen that the lintel 310 according to the present invention requires three times as much debris to create a cold bridge when compared with the prior art lintel 302.

Figure 7 shows schematically a box cavity lintel 410 according to an embodiment of the present invention built into an inside wall 430 and an outside wall 432 of a cavity wall. The lintel 410 has an upturned lip 440 at the end of wing 418 to enable the lintel 410 to be firmly secured within the cavity wall, and provide improved strength. In this embodiment, the

lip 440 has been concealed with plaster 450, so that it does not detract from the appearance of the wall.

Figure 8a shows schematically an alternative embodiment of a box cavity lintel 510 according to the present invention. Lintel 510 is located in use between an inside wall 530 and an outside wall 532 of a cavity wall. The top wall 514 of the box section of the lintel 510 is curved so that debris 536 that falls onto the top of the lintel 510 slides to either the inside wall 530 or outside wall 532 and does not contact the debris on the other wall 530,532 and form a cold bridge between the inside wall 530 and outside wall 532. A cold bridge only forms when sufficient debris 536 falls onto the lintel to join the gap between the debris 536 on either side of the lintel. The amount of debris required to fall on the lintel 510 to create a cold bridge is more than the amount of debris 536 required to form a cold bridge over prior art lintels with a flat sloping top wall.

The top wall 514 may be a semi-circle in cross-section. Alternatively, any other curve that causes debris 536 to move to one side of the lintel 510 or the other may be used.

Figure 8b shows schematically an alternative embodiment of a box cavity lintel 610 according to the present invention. The embodiment is similar to that shown in Figure 8a, and similar elements have been given the same reference numbers in the 600 series.

In this embodiment the top wall of the box section consists of a first portion 614a and a second portion 614b. The first portion 614a is joined to the top of the first side wall 612 of the box section, and the second portion 614b is joined to the top of the second side wall 616 of the box section. The first portion 614a and second portion 614b join together at a point that is further from the bottom wall 620 of the box section than the

ends of the first and second portions 614a, 614b that are joined to the side walls 612,616. This creates a peak where the first and second portions 614a, 614b join so that any debris 636 that falls onto the lintel 610 to the left of the peak slides towards the inside wall 630, and any debris 636 that falls to the right of the peak slides towards the outside wall 632. The debris 636 is therefore separated to either side of the lintel 610 until sufficient debris 636 falls onto the lintel to cover the peak created by the join between the first and second portions 614a, 614b of the top wall.

In this embodiment the join between the first and second portions 614a, 614b of the top wall is half way between the first and second side walls 612,616 of the box section of the lintel, and the first and second portions 614a, 614b are inclined at the same angle to the horizontal. In other embodiments, the join between the first and second portions 614a, 614b of the side wall may be offset to one side, and/or the first and second portions 614a, 614b of the top wall may be inclined at different angles to the horizontal.

It will be appreciated that a lintel according to some embodiments of the invention can enable one lintel to be used with a variety of walls having different dimensions. The lintel can be manufactured at a maximum width size, which will cover the largest of the various wall cavity widths and can have it's width adjusted to fit into any walls that are narrower than the maximum width. Similarly, the box section of a cavity lintel can be manufactured at a minimum cavity width size so that it is capable of fitting within the smallest possible cavity, and also within a larger cavity with a gap between the box section and an inside of one of the walls within which the lintel is built.

A builder can stock one type of lintel according to embodiments of the present invention for use with a variety of walls. When he desires to use

the lintel he can measure the wall into which the lintel is to be built, and identify a weakened region in a wing that, when broken, would allow the lintel to fit within the wall without overhanging, and sticking out of either side of the wall. The builder can then break the wing of the lintel at the weakened region that he has identified, and build the lintel into the wall as normal.