A METHOD OF FORMING A STRUCTURE

Field of the invention

This invention relates to a method of forming a structure and more particularly, although not exclusively, to a foundation construction suitable for forming a ring foundation of a house or a combined foundation and wall structure, but can also be used to assemble components of retaining walls, tilt slabs, water tanks and like constructions.

Background of the Invention

Conventionally concrete ring foundations for houses are poured in situ. Generally this involves digging a trench in which formers/boxing is constructed to receive the concrete and retain it during curing. A good deal of time and physical effort is thus required on-site to prepare the site (e.g. digging trenches), constructing the formers/boxing, pouring the concrete, waiting for the concrete to cure and then removing the formers/boxing.

As an alternative to such a system it is known to provide a foundation construction or system which includes preformed beams or wall sections that span between and bear on preformed bearing or footing blocks/pads. By using preformed componentry of this type a good deal of work is carried off- site which provides a number of advantages, one being the ability to carry out the preforming of the componentry in an environment which is not weather dependent. Also, better quality control and/or consistency of foundation construction can be achieved over the poured on-site foundations where quality can be an issue when workers are used who are of limited skills/experience or are careless, or have little regard for quality.

It is also known to employ a precast pile or post which is installed in the ground and onto the top of which the preformed beams/walls are placed and

fixed. Alternatively, it is known to place a pad or bearing member onto the top of the pile/post and onto which the preformed beam can be located and fixed.

In yet a further known system the preformed beam can be located in notches/recesses in a footing box. Cement/grout can then be poured into the footing box to complete the construction.

These known foundation systems using preformed components suffer from a significant drawback in that positioning, levelling and orientation of the preformed pad/bearing element or piles/post or footing box needs to be precise in order to ensure that the foundation is accurate and more particularly the top of the preformed beam is true and level. This can lead to a high level of on-site preparation work and/or skill of those positioning the bearing elements/pads into the correct orientation and level.

Summary of the Invention

It is an object of the present invention to provide a structure which employs the use of preformed components but does not suffer from the drawbacks identified above or which at least provides the public with a useful choice.

There is thus provided a method of forming a structure comprising the steps of: a. positioning preformed structural elements in desired positions with ends of the structural elements in a desired alignment; and b. forming a pile about the ends of the structural elements which extends down to a support base.

According to this method preformed structural elements (beams/wall elements etc.) are located on-site and supported in a required location,

orientation and level, so that adjacent elements are joined together and integrated into a pile formed at the join on-site.

Thus, unlike known prefabricated foundation systems, the present invention advantageously employs a combination of preformed components and on- site formation of a support element e.g. pile.

By not relying solely on preformed elements the present invention overcomes the problems associated with known preformed component type foundation systems. While the present invention requires some more on-site work in forming the foundation (because of the need to box and pour the pile and join between preformed beams/walls) the advantages outweigh the further on-site time and labour.

However, it is envisaged that this increased on-site time is more than offset by the fact that site preparation is less and can be carried out mechanically by machinery because ensuring the beams/wall elements are level and correctly orientated is not directly depended on the accurate determining of levels of trenches or surfaces in/on which the bearing pads are located or, indeed, accurate formation of trenches. Also, in the case of preformed piles/posts, the accurate driving/positioning of same to ensure the top surface is correctly and accurately located (and level) is not necessary.

Brief description of the drawings In the following more detailed description of the invention according to one preferred embodiment reference will be made to the accompanying drawings in which:-

Figure 1 is a side elevation view of a part of a ring foundation for a house, the foundation being made in accordance with the present invention,

Figure 2 is a perspective view of a part of the foundation assembly,

Figure 3 is a perspective illustration of a beam element made in accordance with the invention,

Figure 4 is an illustration of a beam element suspended by suspension devices to correctly position, orientate and hold a beam element at a required level on-site,

Figure 5 is a partial top plan view of modified forms of the beam elements located end to end in a foundation,

Figure 6 is a partial elevation view of the arrangement in Figure 5, and

Figure 7 is a side elevation view of structure in which piles join adjacent wall elements.

Detailed Description

The structure described is based on a set of pre-cast elements manufactured off-site, transported to the job site and then assembled in an order that gives the correct dimensions and layout of the given structure. The structure formed may be foundations or the foundations and walls of a building or retaining walls, tilt slabs, water tanks and like constructions. The structural elements may be suspended from above or supported underneath. The structural elements may be supported on a "table device" or by overhead

support devices designed to hold the elements in place while concrete is poured to form a pile located at the join between adjacent elements. Reinforcing rods of the elements may be tied, welded or otherwise joined together to ensure a mechanical connection of adjacent elements. A settable material, preferably concrete, is poured into a boxed aperture at the join and into the ground to form a pile. Thus the reinforcing is encapsulated and this not only completes the connection between elements but fills or forms a pile at the same time.

The join between elements may therefore sit on a pile. The size of the pile is determined either by soil testing and calculation based on the weight of the building/construction to be supported or by use of a penetrometer, which gives information required for the pile type.

The advantage of this construction is a saving in time and money as well as having a ring foundation that has a known loading capacity every time. Time savings are achieved by largely replacing man power with machine power. The process is largely non-weather dependent. A smooth finish on the foundation means less time cleaning up afterwards. Also, a known amount of concrete can be allowed for.

As shown in figures 1 to 6 a foundation structure is based on the use of preformed structural elements in the form of beams 10. These are moulded or cast, preferably off-site, and can be made to standard lengths. The elements 10 can then be combined to achieve the correct length and/or configuration of each part of the assembly.

It is envisaged that there may be a standard maximum length of beam elements 10, preferably about 1 .8 metres. However, beam elements 10 can be made to whatever length is necessary to correspond with distances

between piles as may be predetermined based on soil testing, weight of building, and other relevant factors in the design of the building and the configuration of the ring foundation.

The beam elements 10 could, if desired, be made of different depths to accommodate variations is topography of the site. However, it is believed that this will not be necessary as the beam elements 10 are suspended/supported on site and then subsequently supported by the piles. Hence any beam element which does not have the lower part thereof in soil can be backfilled/compacted into soil after a pile has been formed.

Each beam element 10 is preferably formed with reinforcing with at least some reinforcing 1 1 extending from each end 14. Typically the reinforcing will be in the form of steel rod.

In the event that the depth of the beam elements 10 varies, depending on requirements dictated by the design of the building foundations, standard dimensions of depth can be employed or the beam element can be cast according to specific requirements for a particular foundation.

The beam element 10 can be of a rectangular cross-section. In an alternative embodiment it can be in the form shown in Figure 3 where one or two (as shown) rebates 1 3 is/are formed in the upper surface 12. The rebate can be provided in order to accommodate a cladding system (exterior and interior) such as bricks, plaster on polystyrene system etc.

Referring now to Figure 1 , there is shown an elevation view of a typical section of a foundation where a plurality of beam elements 10 are located in an aligned configuration with adjacent ends 14 of the beam elements 10 being opposed and spaced apart. Figure 1 shows the ground contour G and

an excavated level L. As is shown in Figure 1 , the beam elements 10 are supported in the required orientation and with top surfaces 12 level. This can be achieved by locating the underside of the beam elements 10 on "table devices" T. In an alternative arrangement, as described later and shown in Figure 4, suspension devices can be used to hold the beam element in the correct position. Alternatively the beam elements 10 may simply be chocked up above ground using blocks of wood, bricks or other convenient materials. Whilst the structure will typically be formed on ground it could be formed above some other support base also.

The table device T can be formed by a length 28 of suitable material such as timber or steel. This extends transverse of the length of the beam element 10 to project either side of the beam element. As is shown in Figures 1 and 2 these lengths 28 are engaged on the underside of the beam element 10. Preferably there is one length 28 adjacent each end of the beam element 10.

Each end of length 28 has a threaded rod 29 engaged in a correspondingly threaded opening in the length 28. If necessary an additional thickness 30 of material can be fixed to the end of length 28 to provide sufficient length of threaded opening to provide stability of the rod 29 is a position normal to the plane of the length 28.

To the top of the rod 29 can be welded or otherwise fixed a hex nut or head. This enables the rod 29 to be rotated so that the length of rod 29 projecting beneath the length 28 to be adjusted.

The lower end of the rod 29 can be fitted with a pivot 31 which is engageable with a pressure pad 32 or fixed to the pressure pad. This pad 32 provides a good footprint area for the end of the rod 29. Thus in use the rods 29 can be adjusted in position to adjust the height and vertical orientation of

the beam element 10. The position of the end of the beam element 10 can also be adjusted by physically manoeuvring the beam element on the length 28. In this way the beam element 10 can be supported in an adjusted height, alignment and vertical disposition. The pivot coupling 31 enables the pressure pad or foot 32 to adjust to the contour of the ground.

A cavity C is excavated into the ground below each join J between the beam elements 10. In one form of the invention ballast material M can be located adjacent the edges of the excavated cavity C so as to stop overflow of concrete as will hereinafter be apparent. In another form blocks B or other form of partitioning/boxing element can be used.

At the join J the reinforcing 1 1 extending from the ends 14 of the adjacent beam elements 10 is joined. Preferably it is also joined to reinforcing 1 5 which extends down into the pile cavity C. The join can be by tying, welding or other means such as a sleeve 1 1 a (see Figure 6) can be slid over upturned ends 1 1 b of reinforcing 1 1 and the upper end of reinforcing 15. In this arrangement the reinforcing 15 can be tied/welded to one of the upturned ends 1 1 b.

A shutter S is applied at the join J to both sides of the beam elements 10 and hence span therebetween. This shutter is intended to contain poured concrete and will generally be planar. However, it can also be used to provide a shape to the exterior of the ring foundation. For example, while Figure 1 shows the beam elements 10 in an aligned configuration a pair of the elements 10 could be located at right angles i.e. at the corner of the foundation.

Alternatively, in more complex buildings, the elements 10 could be located at an angle other than 90° and in such a case the shuttering would need to be

formed to create the apex of the angle so that there is a smooth transition between the ends of the elements 10 when the concrete is poured as hereinafter described.

The block/boxing element B can span between the shutters S and be fixed thereto. Preferably they are releasably fixed to the shutters S. In one preferred form the blocks B can be lengths of timber which will be left in place after the pile has been formed.

With the beam elements 10 in place, levelled, and the reinforcing thereof , joined together (and joined with the pile reinforcing 1 5), a settable material can be poured once the shutters S and blocks/boxing elements B are positioned and retained in place. The settable material will typically be concrete and in some applications light weight concrete including pumice or polystyrene may be employed. The concrete is then poured through the join J to fill the cavity C. Thus the concrete fills the cavity C and then subsequently fills up to the top of the join J i.e. level with the upper surfaces 12 of the beam elements 10. Consequently, in one single pour the pile P is formed and the join J filled. The pile P is thus integrally formed as a unit with the join J between the beam elements 10. A series of piles P may be simultaneously formed in this manner to form an integrated structure.

Upon the concrete curing the shuttering S can be removed and then any backfilling that may be necessary or desirable around the foundation elements 10 and joins J can be carried out. It is envisaged that some degree of backfilling may take place once the beam elements 10 have been correctly position and joined, and the shuttering put in place prior to pouring of the concrete.

It will be appreciated by those skilled in the art that the setting up of the beam elements 10 in the correct location, orientation, and with the upper surfaces aligned and level as required for the foundation, can be carried out by different means. For example, when it is possible to accurately mechanically excavate a surface on which the beam elements can sit, additional means for suspending the beam elements in the correct position will not be required. As disclosed above, however, table devices T can be used to support the elements 10. Therefore, the contour/level of the excavated surface L is not critical. In yet a further technique a pair of suspension devices can be used to suspend each beam element 10.

As shown in Figure 4 the suspension device 20 can be in the form of a frame of an inverted U-shape with the lower end of each leg thereof being connected to a foot 22. The suspension device 20 can therefore straddle the beam elements 10 with the feet 22 sitting on the excavated level L or on pressure pads if the subsoil is such that a larger area foot is required.

Extending down from the cross-piece 23 is a suspension element which in the illustrated form can be a threaded rod which is adjustably engaged through a threaded opening in or carried by the cross-piece 23. The rod 24 is provided at its lower end with a hook or similar attachment 25 which can engage in a hook 26 cast into the beam element 10. The threaded suspension rod, therefore, provides a means of accurately adjusting the position of the beam elements so that it is at the correct height and the upper surface 12 is at the correct level.

The beam elements can remain suspended by the suspension devices until such time as the concrete has been poured and cured whereupon the suspension devices can be removed. In an alternative but less preferred arrangement backfilling/ballast can be placed beneath the suspended beam

elements once they have been correctly located whereupon the suspension devices can be removed leaving the beam elements suspended/supported by the ballast material/backfill.

It will be appreciated by those skilled in the art that the pile P, when formed, is of a dimension such that it provides a supporting surface for the underside of the ends 14 of the beam elements 10 as is illustrated in Figure 1 . Thus, in the completed foundation, the beams/wall elements 10 are supported by the piles P and joined together by the reinforcing encapsulated in the concrete. Because of the shuttering S the concrete poured into the join J will be flush with the vertical surfaces of the adjacent beam elements whereby a smooth continuous finish is applied to the wall of the foundation so that only minimal cleaning up is required after pouring of the concrete.

The method is open to modification as will be appreciated by those skilled in the art. For example, as shown in Figure 5 the ends of the beam elements 10 can be profiled to have a projecting portion 33. When two beam elements 10 are aligned end to end these opposing projecting portions 33 provide only a small gap 34 therebetween. Thus, only minimal shuttering spanning the gap 34 is required. In this way only a minimal join will be visible to the exterior side of the foundation. Also, as the shuttering only need span a small area a good flat surface as a transition between the ends of the beam elements 10 is achieved. Further it will be appreciated that expansion joints may be provided in or between structural elements.

Figure 7 shows an embodiment in which wall elements are used as the preformed structural elements instead of beams. Wall elements in the form of solid wall element 36, wall element 37 having a window opening 38 therein, and archway element 39 are shown by way of example. In this embodiment the same general method is used so that wall sections 36, 37 and 39 are

maintained in their desired positions by suitable support structures (which may include lateral supports), shutter boards (not shown) are placed bridging the joins between adjacent wall elements, and concrete is poured into the cavity so formed to form piles 35. A Preformed pillar 40 with reinforcing extending into a central cavity may be positioned between wall sections so that concrete may be poured through the cavity and into a pile cavity to form an integrated pillar and pile. In this manner the walls and foundations of a structure may be simultaneously formed. The structure may be a house, retaining wall, water tank or other similar structure.

The present invention thus provides a construction which employs preformed components and on-site poured piles which encapsulate the join of adjacent preformed components. The construction therefore provides savings of time and costs due to the advantageous use of off-site preforming the beam elements 10 and the on-site pouring in one operation of the pile and join between the preformed components.

As well as these savings the structure will have a known loading capacity every time and it will be able to predetermine the size of the piles required for the structure from calculations based on known parameters such as arising from soil testing and the weight of the proposed building. By having a system whereby the excavated level does not need to be accurately determined, the excavation can be largely carried out by machine power thereby replacing the cost and time of physical labour in excavating for the foundation.