GB2423533A

GB2423533A - Foundation base

Info

Publication number: GB2423533A
Application number: GB0503829A
Authority: GB
Inventors: Clive Nightingale
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-02-24
Filing date: 2005-02-24
Publication date: 2006-08-30
Anticipated expiration: 2025-02-24
Also published as: GB0503829D0; GB2423533B

Abstract

A foundation base 1 for an extension to an existing structure comprises a concrete slab 3, shutter means 4 and one or more fixing bolts 5, in which the concrete slab is disposed against the existing structure in use, in which the shutter means 4 encloses at least one side portion of the concrete slab 3, and in which the one or more fixing bolts 5 attach the shutter means 4 to the existing structure through the concrete slab 3. By anchoring it to the existing structure, the strength of the concrete slab is increased.

Description

Foundation Base This invention relates to a foundation base, for use

particularly but not exclusively as a foundation base for a conservatory.

Conservatory extensions do not commonly require regulatory approval, and as a result they are often weak and badly constructed. This can lead to failures as a result of settlement and rotation. The problems occur because of poor building practice, but also because of inherent weakness in the methods used.

In particular, the concrete foundation slab is often simply created in an excavated space, and no further supporting structures are used to increase the strength of the slab, or to anchor it to the existing structure.

The present invention is intended to overcome some of the above problems.

Therefore, according to a first aspect of the present invention a foundation base for an extension to an existing structure comprises a concrete slab, shutter means and one or more fixing bolts, in which the concrete slab is disposed against an existing structure in use, in which the shutter means encloses at least one side portion of the concrete slab, and in which the one or more fixing bolts attach the shutter means to the existing structure through the concrete slab.

(It will be appreciated that the concrete slab is formed on site with wet cement, and therefore the above invention is only achieved once the foundation has been laid and the concrete is set. The invention is described herein by reference to the completed foundation base for clarity, however the invention also includes a method of constructing the foundation base, and a kit of parts for doing so, which are described below.) In a preferred construction the concrete slab can be formed with a number of straight sides, a first of which is opposite to the existing structure. The shutter means can enclose said first side, and each other side not disposed against the existing structure. A plurality of fixing bolts can be provided and one or more fixing bolts can attach the shutter means disposed against the first side of the concrete slab to the existing structure, and one or more fixing bolts can attach together shutter means which are opposite to each other.

Preferably the concrete slab can comprise a main substantially horizontal body section, and a downwardly extending skirt section provided at the sides not disposed against the existing structure. The skirt section can be provided with a toe section extending laterally outwardly from a bottom end of the skirt section. The shutter means can extend around the skirt section and the toe section. (Obviously, when the wet concrete is laid the shutter means can mould the shape of the skirt section and the toe section.) Thus, the shutter means can comprise an elongate sheet of metal which is bent lengthwise through substantially 90 degrees along a first axis, and is bent lengthwise through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis. Thus the shutter means can comprise a first portion, a second portion normal to the first, and a third portion normal to the second. In the completed foundation base the first portion can be disposed against an outer face of the skirt section, the second portion can be disposed against an upper surface of the toe section and the third portion can be disposed against an outer face of the toe section.

In one arrangement the shutter means can be a single length of metal which surrounds all the sides of the concrete slab not disposed against the existing structure.

However, in another embodiment the shutter means can comprise a number of separate straight elongate sheets of metal, each of which are disposed against one side of the concrete slab not disposed against the existing structure. This way the shutter means can be constructed in long strips and cut to fit, either during manufacture or on site. The separate pieces can be bolted together at their ends with

suitable brackets.

The first portion of the shutter means can be provided with a number of bolt apertures through which the fixing bolts pass. Further, the shutter means can be provided with a lip extending at 90 degrees from the end of the third portion. In one arrangement the lip can extend inwardly, and in an alternative embodiment the lip can extend outwardly.

In a preferred construction a first structural support mesh can be provided in the concrete slab. The first structural support mesh can be bent through substantially degrees along a first axis, and bent through substantially 90 degrees in the opposite direction along a second axis, which second axis can be spaced apart from, and be parallel to the first axis. Thus the first structural support mesh can comprise a first portion, a second portion normal to the first, and a third portion normal to the second. The first portion can be disposed in the body section of the concrete slab, the second portion can be disposed in the skirt section, and the third portion can extend into the toe section.

Preferably the first portion of the first structural support mesh can be carried by the fixing bolts.

A second structural support mesh can be provided in the concrete slab. It can comprise a level mesh substantially corresponding in shape with the plan dimensions of the body section of the concrete slab, and it can be disposed above the fixing bolts.

The first structural support mesh, the second structural support mesh and the fixing bolts can be wired together as appropriate to ensure correct positioning in use.

In addition vertical spacers can be provided to support the fixing bolts at points along their length such that the fixing bolts are kept level. The spacers can comprise a post with a foot at the bottom and a three way connector at the top. The tree-way connector can comprise three sleeves arranged perpendicular to one another through three dimensions. A first sleeve can be vertically mounted to the post, and two further sleeves can carry the horizontally arranged bolts at a point where they cross over.

In one embodiment a plurality of apertures can be provided in the second portion of the shutter means, through which the concrete slab can be viewed.

In addition a plurality of shutter pins can be provided, which comprise a pin with a lip at one end. The shutter pins can be driven into the ground until the lip is disposed against the second portion of the shutter means, thereby to secure the shutter means to the ground. (In embodiments where the lip extends outwardly, apertures can be provided in the lip to accommodate the pins.) As mentioned above, the invention also includes a method of constructing a foundation base as described above.

Therefore, according to a second aspect of the present invention a method of constructing a foundation base for an extension to an existing structure, using a kit of parts comprising concrete mixture, shutter means, one or more fixing bolts, a first structural support mesh and a second structural support mesh, in which the shutter means comprises one or more elongate sheets of metal which are bent lengthwise through substantially 90 degrees along a first axis, and bent lengthwise through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that each sheet comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the first portion of the shutter means is provided with one or more bolt apertures through which the fixing bolts pass, in which one or more apertures are provided in the second portion of the shutter means through which the concrete slab can be viewed, in which the first structural support mesh is bent through substantially 90 degrees along a first axis, and is bent through substantially degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that the first structural support mesh comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the second structural support mesh comprises a level mesh substantially corresponding in shape with the proposed plan shape of the foundation base, comprises the following steps: 1. Excavating and preparing a first trench adjacent to the existing structure to receive the foundation base, 2. Excavating and preparing a deeper second trench around portions of the perimeter of the first trench which are not adjacent the existing structure, 3. Arranging at least one shutter means in the second trench such that it is opposite to the existing structure, and such that an end of the first portion of the shutter means is level with the proposed height of the foundation base, and the first and third portions of the shutter means are substantially vertical, 4. Passing one or more fixing bolts through said one or more apertures in the first portion of the shutter means and affixing them to the existing structure.

5. Simultaneously with step 4, arranging the first structural support mesh such that it is supported by the fixing bolts and such that the first portion is disposed in the first trench, the second portion is disposed in the second trench, and the third portion extends under the second portion of said at least one shutter means, 6. Arranging the second structural support mesh in the first trench above the fixing bolts, 7. Pouring wet concrete into the first trench and the area of the second trench enclosed by the shutter means, and continuing to do so until wet concrete is visible through the one or more apertures in the second portion of the shutter means, filling the space underneath said second portion.

It will be appreciated that the above described method includes the minimum steps required to achieve the first aspect of the invention, in that it only includes fixing one shutter means to the existing structure.

Therefore, in a preferred method two further steps are included. After step 3, shutter means are arranged throughout the length of the second trench, and after step 4, one or more fixing bolts are passed through shutter means in the second trench which are opposite to one another thereby fixing them together.

The above methods cover arrangements in which the shutter means is a single unit, and portions of it are being fixed together, and in which the shutter means is a number of separate pieces, which are being fixed together.

In addition, the invention includes a kit of parts for constructing a foundation slab as described above.

Therefore, according to a third aspect of the present invention a kit of parts for constructing a foundation base for an extension to an existing structure, comprises shutter means, one or more fixing bolts, a first structural support mesh and a second structural support mesh, in which the shutter means comprises one or more elongate sheets of metal which are bent lengthwise through substantially 90 degrees along a first axis, and bent lengthwise through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that each sheet comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the first portion of the shutter means is provided with a number of bolt apertures through which one or more fixing bolts pass in use and affix the shutter means to the existing structure, in which the first structural support mesh is bent through substantially 90 degrees along a first axis, and is bent through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that the first structural support mesh comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the second structural support mesh comprises a level mesh substantially corresponding in shape with the proposed plan shape of the foundation base.

The invention can be performed in various ways, but two embodiments will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a cross-sectional side view of a part of a foundation base according to first aspect of the present invention; Figure 2 is a plan view of the foundation base as shown in Figure 1 in a partconstructed condition; Figure 3 is a plan view of the foundation base as shown in Figure 1 in a constructed condition; and Figure 4 is a plan view of a second foundation base according to the first aspect of the present invention.

As shown in the Figures, a foundation base 1 for an extension to an existing structure (part of which 2 is shown in Figure 2) comprises a concrete slab 3, shutter means 4 and one or more fixing bolts 5, in which the concrete slab 3 is disposed against an existing structure (2) in use, in which the shutter means 4 encloses at least one side portion (6) of the concrete slab 3, and in which the one or more fixing bolts 5 attach the shutter means 4 to the existing structure 2 through the concrete slab 3.

As stated above, the present invention is described in terms of the completed foundation base for ease of understanding, and that is what is shown in Figures 1, 3 and 4. However, it will be appreciated from the following that the concrete slab is formed on site with wet cement, and that the invention also includes a method of constructing the foundation base, and a kit of parts for doing so.

Referring to Figure 3, foundation base 1 is formed with six straight sides, one of which abuts the existing structure 2, and the other five of which do not. (It will be appreciated that foundation base I is one of many different shapes which could be created, and which could abut more than one wall of an existing structure 2.) A first side 6 is directly opposite to the existing structure 2, two sides 7 and 8 are perpendicular to one another and two further sides 9 and 10 are opposite to one another.

The concrete slab 3 comprises a main substantially horizontal body section 11, and a downwardly extending skirt section 12 (visible in Figure 1) provided at the sides 6, 7, 8, 9 and 10 not disposed against the existing structure 2. The skirt section 12 is provided with a toe section 13 (also visible in Figure 1) extending laterally outwardly from its lower end.

The shutter means 4 comprises a number of separate straight elongate sheets of metal 14, 15, 16, 17 and 18 which are disposed against the sides 6, 7, 8, 9 and 10 respectively. The separate sheets are bolted together at their ends with vertical brackets 32 and horizontal brackets 33.

Referring to Figure 2, two fixing bolts 19 and 20 attach the sheet 14 (which in the completed foundation base 1 shown in Figure 3 is disposed against the first side 6 of the concrete slab 3) to the existing structure 2. Two fixing bolts 21 and 22 attach the sheets 17 and 18 together, and fixing bolt 23 attaches the sheets 15 and 16 together. In the completed foundation base 1 shown in Figure 3, all the fixing bolts 19, 20, 21, 22 and 23 are immersed in concrete.

As shown in Figure 1, the shutter means 4 comprises sheets of metal which are bent lengthwise through 90 degrees along a first axis 24, and bent lengthwise through 90 degrees in the opposite direction along a second axis 25. The two axes 24 and 25 are parallel. Thus the shutter means 4 comprises a first portion 26, a second portion 27 normal to the first 26, and a third portion 28 normal to the second 27.

Therefore, in the completed foundation base I the shutter means 4 extends around the skirt section 12 and the toe section 13. (Obviously, when the wet concrete is laid the shutter means 4 moulds the shape of the skirt section 12 and the toe section 13.) The first portion 26 is disposed against an outer face 29 of the skirt section 12, the second portion 27 is disposed against an upper surface 30 of the toe section 13 and the third portion 28 is disposed against an outer face 31 of the toe section 13.

The first portion 26 is provided with a number of bolt apertures 34 through which the fixing bolts 5 pass. Further, the shutter means 4 are provided with a lip 35 extending inwardly at 90 degrees from the end of the third portion 28.

A first structural support mesh 36 is provided in the concrete slab 3. As with the shutter means 4, the first structural support mesh comprises a number of components cut to fit the foundation, with one straight piece for each side, as is clear from Figure 2.

Referring to Figure 1 the pieces of first structural support mesh 36 are bent through substantially 90 degrees along a first axis 37, and bent through substantially degrees in the opposite direction along a second axis 38, which second axis 38 is spaced apart from, and parallel to the first axis 37. Thus the first structural support mesh 36 comprises a first portion 39, a second portion 40 normal to the first 39, and a third portion 41 normal to the second 40. The first portion 39 is disposed in the body section 11 of the concrete slab 3, the second portion 40 is disposed in the skirt section 12, and the third portion 41 extends into the toe section 13. The first portion 39 is carried by the fixing bolts 5.

A second structural support mesh 42 is provided in the concrete slab 3. As shown in Figure 2 the second structural support mesh 42 comprises a level mesh substantially corresponding in shape with the plan shape of the body section 11. It is clearly slightly smaller than that shape so it can fit therein. The second structural support mesh 42 is disposed in the body section 11 above the fixing bolts 5.

A plurality of apertures 43 are provided in the second portion 27 of the shutter means 4, through which the concrete slab 3 can be viewed. The purpose of these apertures 43 is explained below.

Vertical spacers 44 are provided which support the fixing bolts 5 at points along their length such that the fixing bolts 5 are kept level. The spacers 44 comprise a post 45 with a foot 46 the bottom and a three way connector 47 the top. The tree- way connector 47 comprises three sleeves 48, 49 and 50 arranged perpendicular to one another through three dimensions. The first sleeve 48 is vertically adjustably mounted to the post 45, the second sleeve 49 is mounted to the first sleeve 48, and the third sleeve 50 is mounted below the second sleeve 49. Clearly, the spacers 44 are disposed at locations where the fixing bolts 5 cross-over (as is clear from Figure 2). Figure 1 shows the spacer 44 at the point were fixing bolts 19 and 23 cross-over.

A plurality of shutter pins 51 are provided, which comprise a pin with a lip 52 provided at one end. The shutter pins 51 are driven into the ground 53 with the lip 52 disposed against the second portion 27 of the shutter means 4, thereby to secure the shutter means 4 to the ground 53.

The foundation base I further comprises known underlying materials including a layer of 100mm to 150mm M.OT. Type 1 material 54 compacted with a wackerjplate, a layer of 50mm dense polystyrene insulation 55, and a covering layer of 1200g visqueen 56, which is wrapped around the shutter means 4 at the end of construction as described below.

In use the foundation base 1 is constructed as follows.

A first trench 57 is excavated adjacent to the existing structure 2, to receive the body portion 11 of the concrete slab 3. A second trench 58 deeper than the first 57, is excavated around the perimeter of the first trench 57.

The lower layers 54, 55 and 56 are laid once the ground under the trenches jC Ri') 57 and 58 has been checked for suitability. The visqueenjayer 56 is initially larger than as shown in Figure 1, as it is used to cover the setting concrete during construction, then cut and fitted as shown in Figure 1.

The shutter means 4 are cut to the correct lengths for the particular construction, either during manufacture or on site. They are arranged as appropriate in the second trench 58 with the upper end 59 of the first portion 26 level with the proposed height of the foundation base 1, and with the first and third portions 26 and 28 vertical.

The fixing bolts 5 are also cut to the correct lengths for the particular construction, either during manufacture or on site. Once the shutter means 4 are in place, fixing bolts 19 and 20 are passed through the apertures 34 in the first portion 26 of shutter means sheet 14, and affixed to the existing structure 2 in a suitable manner, as shown in Figure 2.

Fixing bolts 21 and 22 are passed through sheets 17 and 18, affixing them together, and fixing bolt 23 is passed through sheets 15 and 16 affixing them together. The ends of the bolts 5 are secured with suitable nuts 60.

Spacers 44 are arranged along the fixing bolts 5 and positioned at the cross- over points. In the embodiment shown the overlying fixing bolts 21, 22, and 23 are positioned 45mm below the top 59 of the shutter means 4.

At the same time as positioning the fixing bolts 5 as described above, the pieces of first structural support mesh 36 are arranged in position, being supported by the fixing bolts 5. The fixing bolts must be threaded through the pieces of first structural support mesh 36.

When this is done, the pieces of first structural support mesh 36 are positioned with the first portion 39 on top of the fixing bolts 5 in the first trench 57, the second portion hanging down into the second trench 58, and with the third portion 41 extending under the second portion 27 of the shutter means 4.

The second structural support mesh 42 is then placed on top of the fixing bolts 5 in the first trench 57.

The pieces of first structural support mesh 36, and the second structural support mesh 42 are wired together, and to the fixing bolts 5, as appropriate to fix their positions. In particular, the second portion 40 of the first structural support mesh 36 is arranged 200mm from the second portion 26 of the shutter means 4.

The shutter pins 51 are driven into the ground 53 until the lip 52 is disposed against the second portion 27 of the shutter means 4.

Once all the above steps are complete, the foundation base is as represented in Figure 2. In that arrangement the shutter means 4 forms a secure mould to receive wet concrete, and the first and second structural support meshes 36 and 42 are correctly positioned for the concrete to be poured around them.

The concrete is then mixed as appropriate and poured into the first trench 57, and the area of the second trench 58 enclosed by the shutter means 4. This is continued until the concrete has formed the toe sections 13. This is confirmed by viewing the wet concrete through the apertures 43, and/or continuing to pour until wet concrete comes out of the apertures 43.

The concrete is levelled off using the top 59 of the shutter means 4 as a tamping rail, and any concrete expelled through the apertures 43 is removed.

The visqueen 56 is wrapped around the shutter means 4 and onto the setting concrete, which is allowed to set over time. After three days or so the visquee56 is cut and positioned as shown in Figure 1 to form a damp course.

Once complete the foundation base I serves to support a new structure. In particular, the shape of the shutter means 4 provides a lower base for an exterior wall 61 (shown in hashed lines in Figure 1) and a higher base of an interior wall 62 (also shown in hashed lines in Figure 1). Once these are constructed the second trench 58 can be filled in to ground level, as indicated by hashed line 63 in Figure 1.

The second aspect of the present invention provides a method for constructing a foundation base for an existing structure using a kit of parts. The above description provides support for the second aspect of the present invention.

The third aspect of the present invention provides a kit of parts for constructing a foundation base for an extension to an existing structure. The above described components provide support for the third aspect of the present invention.

The above described embodiment can be altered without departing from the spirit of the invention. For example, in one alternative construction shown in Figure 4 the shutter means comprises one large component 64 bent to fit into the second trench, and some of the fixing bolts attach portions of it together. In all other respects the embodiment shown in Figure 4 is identical to that shown in Figure 3. In another alternative embodiment (not shown) the first structural support mesh is formed from one large component bent to fit into the first and second trenches.

In addition, it will be appreciated that the above described embodiment relates to just one shape of foundation base with six sides. In alternative embodiments (not shown) foundation bases are provided with different numbers of sides, and even with curved or shaped sides. In such embodiments the supporting components are shaped as appropriate. In other alternative embodiments (not shown) the foundation base is laid adjacent two or more walls of an existing structure. In such embodiments the fixing bolts fix two or more sheets of shutter means, or portions of a single shutter means, to the existing structure, and may or may not affix sheets, or portions, of shutter means to each other.

Thus a novel foundation base is provided which can be readily constructed without any of the pitfalls of known systems. In addition, a foundation base is provided which is intrinsically strong due to the formation of the fixing bolts, and the integral structural support meshes.

Claims

Claims 1. A foundation base for an extension to an existing structure

comprises a concrete slab, shutter means and one or more fixing bolts, in which the concrete slab is disposed against an existing structure in use, in which the shutter means encloses at least one side portion of the concrete slab, and in which the one or more fixing bolts attach the shutter means to the existing structure through the concrete slab.
2. A foundation base as claimed in Claim 1 in which the concrete slab is formed with a number of straight sides, a first of which is opposite to the existing structure, in which the shutter means are disposed against each side not disposed against the existing structure, in which a plurality of fixing bolts are provided, in which one or more fixing bolts attach the shutter means disposed against the first side of the concrete slab to the existing structure, and in which one or more fixing bolts attach together shutter means which are opposite to each other, through the concrete slab.
3. A foundation base as claimed in Claim 2 in which the concrete slab comprises a main substantially horizontal body section, and a downwardly extending skirt section provided at the sides not disposed against the existing structure.
4. A foundation base as claimed in Claim 3 in which the skirt section is provided with a toe section extending laterally outwardly from a bottom end of the skirt section.
5. A foundation base as claimed in Claim 4 in which the shutter means extends around the skirt section and the toe section.
6. A foundation base as claimed in Claim 5 in which the shutter means comprises an elongate sheet of metal which is bent lengthwise through substantially degrees along a first axis, and is bent lengthwise through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that the shutter means comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the first portion is disposed against an outer face of the skirt section, the second portion is disposed against an upper surface of the toe section and the third portion is disposed against an outer face of the toe section.
7. A foundation base as claimed in Claim 6 in which the shutter means comprises a number of separate straight elongate sheets of metal, each of which are disposed against one side of the concrete slab not disposed against the existing structure.
8. A foundation base as claimed in Claim 6 in which the shutter means comprises a single elongate sheet of metal disposed against the sides of the concrete slab not disposed against the existing structure
9. A foundation base as claimed in Claim 7 or 8 in which the first portion of the shutter means is provided with a number of bolt apertures through which the fixing bolts pass.
10. A foundation base as claimed in Claim 9 in which the shutter means are provided with a lip extending inwardly at 90 degrees from the end of the third portion.
11. A foundation base as claimed in Claim 9 in which the shutter means are provided with a lip extending outwardly at 90 degrees from the end of the third portion.
12. A foundation base as claimed in Claim 10 or 11 in which a first structural support mesh is provided in the concrete slab, in which the first structural support mesh is bent through substantially 90 degrees along a first axis, and is bent through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that the first structural support mesh comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the first portion is disposed in the body section of the concrete slab, in which the second portion is disposed in the skirt section, and in which the third portion extends into the toe section.
13. A foundation base as claimed in Claim 12 in which the first portion of the first structural support mesh is carried by the fixing bolts.
14. A foundation base as claimed in Claim 13 in which a second structural support mesh is provided in the concrete slab, in which the second structural support mesh comprises a level mesh substantially corresponding in shape with the plan shape of the body section, and in which the second structural support mesh is disposed in the body section above the fixing bolts.
15. A foundation base as claimed in Claim 14 in which a plurality of apertures are provided in the second portion of the shutter means, through which the concrete slab can be viewed.
16. A foundation base as claimed in Claim 15 in which vertical spacers are provided in the concrete slab, which spacers are adapted to support the fixing bolts at points along their length such that the fixing bolts are kept level.
17. A foundation base as claimed in Claim 16 in which the vertical spacers comprise a post with a foot at the bottom and a three way connector at the top, said the tree-way connector comprising three sleeves arranged perpendicular to one another through three dimensions, in which a first sleeve is vertically mounted to the post in use, and in which two further sleeves each carry a fixing bolt at a point where two fixing bolts perpendicular to one another cross over.
18. A foundation base as claimed in Claim 17 in which a plurality of shutter pins are provided, which shutter pins comprise a pin with a lip provided at one end, in which the shutter pins are driven into the ground with the lip disposed against the second portion of the shutter means, thereby to secure the shutter means to the ground.
19. A foundation base substantially as described herein and as shown in Figures 1, 3 and 4.
20. A method of constructing a foundation base for an extension to an existing structure, using a kit of parts comprising concrete mixture, shutter means, one or more fixing bolts, a first structural support mesh and a second structural support mesh, in which the shutter means comprises one or more elongate sheets of metal which are bent lengthwise through substantially 90 degrees along a first axis, and bent lengthwise through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that each sheet comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the first portion of the shutter means is provided with one or more bolt apertures through which the fixing bolts pass, in which one or more apertures are provided in the second portion of the shutter means, through which the concrete slab can be viewed, in which the first structural support mesh is bent through substantially 90 degrees along a first axis, and is bent through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that the first structural support mesh comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the second structural support mesh comprises a level mesh substantially corresponding in shape with the proposed plan shape of the foundation base, comprising the following steps: 1. Excavating and preparing a first trench adjacent to the existing structure to receive the foundation base, 2. Excavating and preparing a deeper second trench around portions of the perimeter of the first trench which is not adjacent the existing structure, 3. Arranging at least one shutter means in the second trench such that it is opposite to the existing structure, and such that an end of the first portion of the shutter means is level with the proposed height of the foundation base, and the first and third portions of the shutter means are substantially vertical, 4. Passing one or more fixing bolts through said one or more apertures in the first portion of the shutter means and affixing them to the existing structure.

5. Simultaneously with step 4, arranging the first structural support mesh such that it is supported by the fixing bolts and such that the first portion is disposed in the first trench, the second portion is disposed in the second trench, and the third portion extends under the second portion of said at least one shutter means, 6. Arranging the second structural support mesh in the first trench above the fixing bolts, 7. Pouring wet concrete into the first trench and the area of the second trench enclosed by the shutter means, and continuing to do so until wet concrete is visible through the one or more apertures in the second portion of the shutter means, filling the space underneath said second portion.
21. A method of constructing a foundation base according to Claim 20 in which after step 3 shutter means are arranged throughout the length of the second trench.
22. A method of constructing a foundation base according to Claim 21 in which after step 4 one or more fixing bolts are passed through shutter means in the second trench which are opposite to one another thereby fixing them together.
23. A method of constructing a foundation base substantially as described herein.
24. A kit of parts for constructing a foundation base for an extension to an existing structure, comprises shutter means, one or more fixing bolts, a first structural support mesh and a second structural support mesh, in which the shutter means comprises one or more elongate sheets of metal which are bent lengthwise through substantially 90 degrees along a first axis, and bent lengthwise through substantially degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that each sheet comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the first portion of the shutter means is provided with a number of bolt apertures through which one or more fixing bolts pass in use and affix the shutter means to the existing structure, in which the first structural support mesh is bent through substantially 90 degrees along a first axis, and is bent through substantially 90 degrees in the opposite direction along a second axis, which second axis is spaced apart from, and is parallel to the first axis, such that the first structural support mesh comprises a first portion, a second portion normal to the first, and a third portion normal to the second, in which the second structural support mesh comprises a level mesh substantially corresponding in shape with the proposed plan shape of the foundation base.
25. A kit of parts for constructing a foundation base substantially as described herein.