GB2476646A

GB2476646A - Joist end seal with reduced extent bottom wall

Info

Publication number: GB2476646A
Application number: GB0922574A
Authority: GB
Inventors: Kenneth Stanley Targett
Original assignee: CAPIT BUILDING PRODUCTS Ltd
Current assignee: CAPIT BUILDING PRODUCTS Ltd
Priority date: 2009-12-29
Filing date: 2009-12-29
Publication date: 2011-07-06
Anticipated expiration: 2029-12-29
Also published as: GB0922574D0; GB2476646B

Abstract

A joist seal (50) is fitted to an end of a joist (14) that is built into a brickwork wall (20). The joist seal has: a rear wall portion (12) covering an end face of the joist; a pair of side wall portions (22) projecting from the rear wall portion and extending along the sides of the end of the joist; a bottom wall portion (68) projecting from the rear wall portion and sandwiched between the underneath of the joist and the blockwork (18) of the wall beneath the joist; and an arrangement (62) sealing the side wall portions to the blockwork wall to either side of the joist. The bottom wall portion projects from the rear wall portion to a substantially lesser extent (K) than the side wall portions, so that it can make an impression in the blockwork below and so that the underside of the joist, shown at the top in figure 4 can directly contact the block work below over a substantial portion of the thickness of the wall. Keying can be provided on sidewalls of the end cap.

Description

TITLE

Joist end seal

DESCRIPTION

This invention relates to joist end seals.

When an end of a joist is to be built into a blockwork wall of a building in the traditional way, the wall is built up to the level of the underside of the joist. The end of the joist is then laid directly on a block of the wall, and then the wall is built up with blocks and mortar around the end of the joist. There is therefore frictional contact of the underside of the end of the joist with the block below the joist and frictional and/or adhesive contact between the mortar of the wall and the sides and top of the end of the joist. This frictional and/or adhesive contact desirably resists movement of the joist longitudinally with respect to the wall.

In the case where the joist is a traditional sawn timber joist, the timber may shrink and split, and the mortar may shrink, thus causing gaps through which air can leak and also reducing the frictional and/or adhesive contact between the mortar and the sides and top of the end of the joist. However, the frictional contact between the underside of the end of the joist and the block below is maintained.

In recent years, engineered joists have become popular, an example of which is in the form of an I-beam having top and bottom flanges of timber or LVL (laminated veneer lumber) which are held together spaced apart by a web of, for example, OSB (oriented strand board) or structural fibreboard. In another example of an engineered joist, the top and bottom flanges are held together spaced apart by a series of sheet metal or wooden spacers rather than by a web.

Most composite joists suffer from substantially less shrinkage in cross-section that timber joists, and composite joists do not normally split. Shrinkage of mortar tends to cause generally vertically extending cracks due to shrinkage of the mortar in the horizontal direction; shrinkage of the mortar in the vertical direction predominantly causes the wall to settle. Therefore, with engineered joists, shrinkage of the mortar can reduce the frictional and/or adhesive contact between the mortar and the sides of the end of the joist and causing gaps to the sides of the joist through which air can leak. Shrinkage of the mortar may also cause a lesser reduction in the frictional and/or adhesive contact between the mortar and the top of the end of the joist. Again, the frictional contact between the underside of the end of the joist and the block below is maintained.

There is a desire to seal the end of the joist to the wall, otherwise air leakage though the wall will reduce the thermal and acoustic insulation properties of the wall.

A joist seal 10 as shown schematically in Figure 1 of the accompanying drawings is based on the joist seal shown in patent document GB2392928A (Simpson Strong-Tie International, Inc.). The joist seal 10 is moulded from plastics material and has: a rear wall 12 which covers the end of the joist 14; a bottom wall 16 which projects forwardly from the rear wall 12 and which rests on a block 18 of the blockwork wall 20 and on which the underside of the end of the joist 14 rests; a pair of side walls 22 which project forwardly from the rear wall 12 along the sides of the end of the joist 14; a top wall 24 which projects forwardly from the rear wall 12 above the top of the end of the joist 14; and an out-turned flange 26 connected to the front edges of the bottom, side and top walls 16,22,24 for overlapping the front face of the blockwork wall 20 once the wall 20 is built up around the end of the joist 14. The joist seal 10 is therefore a five-sided box with a flanged opening. Provided that the bottom, side and top walls 16,22,24 and the flange 26 can seal to the blockwork wall 20, the joist seal prevents air leakage through the wall 20.

It will be appreciated that the joist seal 10 of Figure 1 substantially eliminates any frictional and/or adhesive contact between the blockwork wall 20 and the sides and top of the end of the joist 14. Also, the frictional contact between the blockwork wall 20 and the bottom of the end of the joist 14 is substantially reduced because the coefficient of friction between the joist 14 and the plastics material of the joist seal 10 is substantially less than the coefficient of friction between the joist 14 and a block 18. There is therefore a concern that this substantial reduction in the frictional and/or adhesive force, compared with building the end of the joist 14 directly into the blockwork wall 20, may require the use of additional joist restraint straps fixed between the joist 14 and the wall 20, resulting in increased material and labour costs.

This problem with the joist seal 10 of Figure 1 is alleviated to a substantial extent by the joist seal 30 which is shown schematically in Figure 2 of the accompanying drawings and which is based on the joist seal described in detail in patent document GB2426987A (Vaughan and Hennen). Like the joist seal 10 of Figure 1, the joist seal 30 of Figure 2 has rear, side and top walls 12,22,24. However, the joist seal 30 is devoid of a bottom wall so that the underside of the end of the joist 14 rests directly on and has frictional contact with the block 18 below. Also, the side and top walls 22,24 project from the rear wall 12 only part-way through the thickness of the blockwork wall 20, 50 that, ignoring any shrinkage of the mortar, there is some frictional and/or adhesive contact between the mortar and the sides and top of the joist 14 that are exposed to the mortar. Furthermore, the joist seal 30 has out-turned flanges 32,34 projecting from the front edges of its side and top walls 22,24 which are arranged to be embedded in the mortar part-way through the thickness of the blockwork wall 20, so as to provide an effective seal between the side and top walls 22,24 and the mortar. When used with an I-beam joist 14, the voids between the upper and lower flanges 36,38 of the joist 14 are typically filled, at the end of the joist 14, with filler blocks 40 before the wall 18 is built up around the end of the joist 14.

Alternatively, the voids may be filled with mortar within the thickness of the wall 18. However, with such a large volume of mortar, problems are often encountered with mortar drop (i.e. the mortar falling out of the voids before it has set).

With the seal 30 of Figure 2, the bottom edges of its rear and side walls 12,22 directly contact the block 18 below the end of the joist 14. In the event that air can enter the joist seal 30, for example due to gaps appearing in the mortar particularly to the sides of the joist, or because the voids between the upper and lower flanges 36,38 of an I-beam joist 14 have not been completely filled, there is a concern that the lower edge of the rear wall 12 of the joist seal 30 will not provide a particularly effective seal with the block 18 below, so that air can pass to the very end of the joist 14 and then escape beneath the lower edge of the rear wall 12 to the other side of the blockwork wall 20.

An aim of the present invention, or at least of specific embodiments of it, is to address this latter concern whilst still providing the advantages described above of the joist seal 30 of Figure 2 compared to the joist seal 10 of Figure 1.

In accordance with a first aspect of the present invention, there is provided a joist seal for fitting to an end of a joist that is to be built into a blockwork wall. Similarly to the joist seal of Figure 1, the joist seal of the invention has: a rear wall portion for covering an end face of the joist; a pair of side wall portions projecting from the rear wall portion and for extending along the sides of the end of the joist; a bottom wall portion projecting from the rear wall portion for being sandwiched between the underneath of the joist and the blockwork of the wall beneath the joist; and side sealing means for sealing the side wall portions to the blockwork wall to either side of the joist. The joist seal of the invention is characterised in that the bottom wall portion projects from the rear wall portion to a substantially lesser extent than the side wall portions.

In accordance with a second aspect of the invention, there is provided a building having: a blockwork wall; and a joist having an end fitted with a joist seal according to the first aspect of the invention built into the wall. The rear wall portion covers the end face of the joist; the side wall portions extend along the sides of the end of the joist; the bottom wall portion is sandwiched between the underneath of the joist and the blockwork of the wall beneath the joist; and the side sealing means seals the side wall portions to the blockwork wall to either side of the joist.

The bottom wall portion of the joist seal may be easily compressible so that it allows the bottom of the end of the joist directly to contact the blockwork of the wall over substantially the whole of the remainder of the thickness of the blockwork wall so that the underside of the joist can frictionally grip the blockwork. However, the material from which building blocks are made typically crumbles when exposed to very high pressures. Also the timber or LVL from which joist are typically made deforms to some extent when exposed to very high pressures.

Therefore with a suitably small bottom wall portion of the joist seal, the blockwork of the wall and/or the bottom of the joist will typically naturally deform in the region of the bottom wall portion of the joist seal so that the bottom of the end of the joist directly contacts the blockwork of the wall over substantially the whole of the remainder of the thickness of the blockwork wall so that the underside of the joist can frictionally grip the blockwork.

Preferably, the bottom wall portion projects from the rear wall portion by no more than mm, and more preferably by no more than 15 mm.

The wall preferably has a thickness of 100 mm or more. The bottom wall portion preferably projects from the rear wall portion by no more than 25 % of the thickness of the wall, and more preferably by no more than 15% of the thickness of the wall.

The bottom wall portion of the joist seal and the bottom of the joist preferably directly contact a block of the blockwork wall beneath the end of the joist without any substantial amount of mortar between that block and the bottom wall portion of the joist seal and the bottom of the joist.

Preferably, the bottom wall portion has a wall thickness of no more than 1.5 mm, and more preferably no more than 1.0 mm.

The joist seal may be formed from any suitable material, but is preferably formed from sheet metal.

Similarly to the joist seal 30 of Figure 2, the joist seal of the invention may further include: a top wall portion projecting from the rear wall portion for extending above the top of the end of the joist; and top sealing means for sealing the top wall portion to the blockwork wall above the joist.

In an example of the joist seal 30 of Figure 2 which has been placed on the market and is intended for use with a blockwork wall 20 having a thickness A of 100 mm or more, the joist seal 30 is moulded from polypropylene, and the length B from front to back of the joist seal 30 is 67.5 mm. When the joist seal 30 is properly fitted to a blockwork wall 20 having a thickness A of 100 mm, there is a space C between the rear face of the rear wall 12 of the joist seal 30 and the rear face of the blockwork wall 20 of between 3.5 mm and 7.5 mm. The mortar is therefore in contact with the top surface of the upper flange 36 only through a small part of the thickness of the wall 20 in the region 42 denoted by diamond hatching in Figure 2. With the figures given above, it will be appreciated that the length D of this region 42 is only about 25 to 29 mm. Beyond the region 42, the top surface of the upper flange 36 of the joist 14 is either in contact with the underside of the top wall 24 of the joist seal 30 which, being of polypropylene, is relatively slippery, or is spaced below the top wall 24 of the joist seal 30. There is a concern that the resulting reduction in the frictional and/or adhesive force, compared to a joist 14 which is directly built into a wall 20 may require the use of additional joist restraint straps fixed between the joist 14 and the wall 20, resulting in increased material and labour costs.

In order to address this concern, in one embodiment of the invention, the extent of the top wall portion and top sealing means in the direction which, in use, is the longitudinal direction of the joist is no more than 50 mm. The joist seal therefore allows the mortar of the wall to contact and grip the top of the joist over a greater distance, in the thickness direction of the wall, than in the example described with reference to Figure 2 above. Preferably, said extent of the top wall portion and top sealing means is from 40 mm to 50 mm, or from 30 mm to 40 mm, or from 20 mm to 30 mm, or less than 20 mm. The top sealing means may include an out-turned flange projecting from the top wall portion for being embedded in mortar of the blockwork wall above the joist. Additionally or alternatively, the top sealing means may include surface formations on the top wall portion for being keyed to mortar of the blockwork wall above the joist.

Alternatively, in another embodiment of the invention, the joist seal is devoid of any substantial top wall portion extending from the rear wall portion and for extending over the top of the end of the joist so that, in use, mortar of the blockwork wall can directly contact the top face of the joist over substantially the whole extent of the end of the joist within the thickness of the blockwork wall.

The side sealing means may include out-turned flanges projecting from the side wall portions for being embedded in mortar of the blockwork wall to the sides of the joist.

Alternatively or additionally, the side sealing means includes surface formations on the side wall portions for being keyed to mortar of the blockwork wall to the sides of the joist.

Specific embodiments of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of an end portion of an I-beam joist resting on a partly-built blockwork wall and fitted with a joist seal as taught by patent document GB2392928A; Figure 2 is an isometric view of an end portion of an I-beam joist resting on a partly-built blockwork wall and fitted with a joist seal as taught by patent document GB2426987A; Figure 3 is an isometric view of a joist seal of a first embodiment of the invention; Figure 4 is similar to Figure 3, but showing the joist seal upside down; Figure 5 is a sectioned plan view of the joist seal of Figures 3 and 4, on a larger scale; Figure 6 shows a sheet metal blank for forming the joist seal of Figures 3 to 5, after it has been stamped and pressed, but before folding; Figure 7 shows, on a smaller scale than Figures 3 and 4, the joist seal of Figures 3 to 5 fitted to an end of a joist on a wall, before the wall has been built up around the end of the joist; Figure 8 is a horizontal section, on a larger scale than Figures 3 and 4, through the joist, joist seal and wall after the wall has been built up around the end of the joist; Figure 9 is a corresponding vertical section through the joist, joist seal and wall; and Figure 10 is similar to Figure 7, but showing a second embodiment of the joist seal.

Referring to Figures 3 to 7, the joist seal 50 of the first embodiment of the invention is for use with an I-beam joist 14 having a height E of 240 mm and a width F of 60 mm (an example of which is the SteicoJoist 5J60/240) which is to be built in to a blockwork wall 18 having a thickness A of 100 mm.

The joist seal 50 is formed from galvanised mild-steel sheet having a thickness of between 0.7 mm and 1 mm. The joist seal 50 has a rear wall 12 having an internal width G which is slightly greater than the width F of the joist 28. Projecting forwardly from the rear wall 14 are a pair of side walls 22 each having an internal width H of about 105 mm. The internal height J of the rear wall 12 and side walls 22 is a few millimetres greater than the height E of the joist 14, for example 242 mm. Each side wall 22 is formed from an outer layer 52 projecting from the rear wall 12 to a front edge 54, where the steel sheet is folded back on itself to form an inner layer 56 extending back to the rear wall 12. Over most of its area, the outer layer 52 is formed with an array of raised areas 58 each of which is punched with a hole 60 so that the inner and outer layers 52,56 together provide an array of re-entrant craters 62.

However, towards the rear of the outer layer 52, a band 64 of the outer layer 52 is left plain.

Adjacent its front corners, each inner layer 56 is punched with a hole 66, aligned with one of the crater holes 60. Although not shown in the drawings, in the relaxed state of the joist seal 50, the side walls 22 may converge slightly in the direction away from the rear wall 12.

A bottom wall 68 projects forwardly from the lower edge of the rear wall 12 through a distance K of about 10 mm. A top wall 70 projects forwardly from the top edge of the rear wall 12 through a distance L of about 20 mm, and a top flange 72 then projects upwardly from the front edge of the top wall 70 through a distance M of about 10 mm.

Referring in particular to Figure 7, the joist seal 50 is fitted to the end of the joist 14 by inserting the end of the joist 14 between the side walls 22 and sliding the joist seal 50 into position so that the end face of the joist 14 engages the front face of the rear wall 12 of the joist seal 50 and so that the top face of the bottom wall 68 of the joist seal 50 engages the underside of the joist 14. The top wall 70 of the joist seal 50 therefore projects forwardly over the top edge of the joist. If the side walls 22 of the joist seal 50 naturally converge, they will grip the sides of the flanges 36,38 of the joist 14 to hold the joist seal 50 in position. However, if desired, nails may be driven through the four holes 66 in the inner layers 52 of the side walls 22 (having first passed through the corresponding crater holes 60 in the outer layer of the side walls 22) into the sides of the joist flanges 36,38. In this case, the nails are preferably not driven fully home. The end of the joist 14 is then positioned on the wall 20 so that the joist seal 50 does not overhang the rear face of the wall 20, but also so that at least 90 mm of the end of the joist is bearing on the wall. The blocks 18 of the wall 20 are made of a material that crumbles when high pressures are applied to it. The weight of the joist alone may be sufficient for the short bottom wall 68 of the joist seal 50 to dent the block 18 on which the joist 14 is resting, but if not, the upper flange 36 of the joist 14 may be given a sharp blow with a hammer or mallet so that the bottom wall 68 of the joist seal 50 forms an impression in the block 18, and through the remainder of the thickness of the wall 20, the underside of the joist 14 comes into contact with the block 18.

The wall 20 is then built up around the end of the joist 28 in the conventional maimer with further 215 x 440 x 100 mm blocks 74 and mortar 76, including a chopped, up-ended, coursing block 78 above the joist 14.

Referring in particular to Figures 7 and 8, it will be appreciated that, due the front edges 54 of the side walls 22 projecting beyond the front face of the wall 20, there is no need to use filler blocks 40 in the joist voids in order to prevent an excessive amount of mortar being required and in order to prevent mortar dump. However, some form of filler is still preferably used in order to prevent air circulating in the joist voids within the thickness of the wall 20 thus reducing the thermal resistance of the wall.

Referring in particular to Figure 8 of the drawings, it will be seen that, when the wall is built up around the end of the joist 14, the mortar 76 of the wall 20 keys to the craters 62 in the side walls 22 of the joist seal 50. Therefore, when the mortar 76 shrinks in the horizontal direction away from the sides of the joist 14, it will tend to pull the cratered portions of the side walls 22 away from the sides of the joist 14, but an effective seal between the mortar 76 and the side walls 22 will be maintained. Flexing of the plain bands 64 of the side walls 22 will permit such movement of the cratered portions of the side walls 22.

As can be seen from Figure 9, the top flange 72 of the joist seal 50 becomes embedded in the mortar 76, and the mortar 76 contacts and adheres to the upper face of the top flange 36 of the joist 14 in a region 42 extending over a distance D of about 75 mm to 80 mm in the thickness direction of the wall 22. This compares with a distance D of only 25 to 29 mm in the prior art example described with reference to Figure 2. Also, as shown in Figure 9, the bottom wall 68 of the joist seal 50 has made a depression in the block 18 beneath so that the bottom face of the joist 14 contacts the block 18 over a distance N of about 85 mm to 90 mm in the thickness direction of the wall 22.

Referring now to Figure 10, the joist seal 80 of the second embodiment of the invention is similar to the joist seal 50 described above, except that the side walls 22 are narrower in the thickness direction of the wall 20 so that the front edges 54 of the side walls 22 do not project beyond the front face of the wall 20. In this case, filler blocks 40 are fitted in the joist voids in order to prevent an excessive amount of mortar being required and in order to prevent mortar dump.

It will be appreciated that many modifications and developments may be made to the embodiments of the invention described above. For example, rather than being stamped, pressed and folded from sheet metal, the joist seals 50,80 may be moulded from plastics material, and in this case the thin bottom wall 68 may be an integral part of the moulding or may be formed by a metal insert in the moulding. Surface formations other than the craters 62 may be provided on the side walls 22 to enable the mortar 76 to key to the side walls 22. Also, side flanges, similar to the side flanges 32 described with reference to Figure 2, may be formed on the side walls 22 of the joist seals 50,80 of the embodiments of the invention in addition to, or instead of, the craters 62. Instead of, or in addition to, being formed with a top flange 72, the top wall 70 may be formed with surface formations, for example similar to the craters 62, for keying to the mortar 76 above the joist 14. Alternatively, the top wall 70 may be omitted.

It should be noted that the embodiments of the invention have been described above purely by way of example and that many modifications and developments may be made thereto within the scope of the present invention.

Claims

-10 -CLAIMS(The reference numerals in the claims are not intended to limit the scope of the claims.) 1. A joist seal (50;70) for fitting to an end of a joist (14) that is to be built into a blockwork wall (20), the joist seal having: a rear wall portion (12) for covering an end face of the joist; a pair of side wall portions (22) projecting from the rear wall portion and for extending along the sides of the end of the joist; a bottom wall portion (68) projecting from the rear wall portion for being sandwiched between the underneath of the joist and the blockwork (18) of the wall beneath the joist; and side sealing means (62) for sealing the side wall portions to the blockwork wall to either side of the joist; characterised in that: the bottom wall portion projects from the rear wall portion to a substantially lesser extent (K) than the side wall portions.
2. A joist seal as claimed in claim 1, wherein: the bottom wall portion projects from the rear wall portion by no more than 25 mm.
3. A joist seal as claimed in claim 1, wherein: the bottom wall portion projects from the rear wall portion by no more than 15 mm.
4. A joist seal as claimed in any preceding claim, wherein: the bottom wall portion has a wall thickness of no more than 1.5 mm.
5. A joist seal as claimed in any of claims 1 to 3, wherein: the bottom wall portion has a wall thickness of no more than 1.0 mm.
6. A joist seal as claimed in any preceding claim, wherein: -11 -the joist seal is formed from sheet metal.
7. A joist seal as claimed in any preceding claim, further including: a top wall portion (70) projecting from the rear wall portion for extending above the top of the end of the joist; and top sealing means (72) for sealing the top wall portion to the blockwork wall above the joist.
8. A joist seal as claimed in claim 7, wherein: the extent (L) of the top wall portion and top sealing means in the direction which, in use, is the longitudinal direction of the joist is no more than 50 mm.
9. A joist seal as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is from 40 mm to 50 mm.
10. A joist seal as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is from 30 mm to 40 mm.
11. A joist seal as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is from 20 mm to 30 mm.
12. A joist seal as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is less than 20 mm.
13. A joist seal as claimed in any of claims 7 to 12, wherein: the top sealing means includes an out-turned flange (72) projecting from the top wall portion for being embedded in mortar of the blockwork wall above the joist.
14. A joist seal as claimed in any of claims 7 to 12, wherein: -12 -the top sealing means includes surface formations on the top wall portion for being keyed to mortar of the blockwork wall above the joist.15. A joist seal as claimed in any of claims 1 to 6, wherein: the joist seal is devoid of any substantial top wall portion projecting from the rear wall portion and for extending over the top of the end of the joist so that, in use, mortar of the blockwork wall can directly contact the top face of the joist over substantially the whole extent of the end of the joist within the thickness of the blockwork wall.
15. A joist seal as claimed in any preceding claim, wherein: the side sealing means includes out-turned flanges projecting from the side wall portions for being embedded in mortar of the blockwork wall to the sides of the joist.
16. A joist seal as claimed in any preceding claim, wherein: the side sealing means includes surface formations (62) on the side wall portions for being keyed to mortar of the blockwork wall to the sides of the joist.
17. A joist seal substantially as described with reference to Figures 3 to 7 of the drawings.
18. A building having: a blockwork wall (20); and a joist (14) having an end fitted with a joist seal (50;80) as claimed in any preceding claim built into the wall; wherein: the rear wall portion covers the end face of the joist; the side wall portions extend along the sides of the end of the joist; the bottom wall portion is sandwiched between the underneath of the joist and the blockwork of the wall beneath the joist; and the side sealing means seals the side wall portions to the blockwork wall to either side of the joist.

-13 -
19. A building as claimed in claim 18, wherein: the blockwork (18) of the wall and/or the bottom of the joist are deformed in the region of the bottom wall portion of the joist seal so that the bottom of the end of the joist directly contacts the blockwork of the wall over substantially the whole of the remainder of the thickness of the blockwork wall.
20. A building as claimed in claim 19, wherein: the bottom wall portion of the joist seal and the bottom of the joist directly contact a block of the blockwork wall beneath the end of the joist without any substantial amount of mortar between that block and the bottom wall portion of the joist seal and the bottom of the joist.
21. A building as claimed in any of claims 18 to 20, wherein: the wall has a thickness of 100 mm or more.
22. A building as claimed in any of claims 18 to 21, wherein: the bottom wall portion projects from the rear wall portion by no more than 25 % of the thickness of the wall.
23. A building as claimed in any of claims 18 to 21, wherein: the bottom wall portion projects from the rear wall portion by no more than 15% of the thickness of the wall.
24. A building as claimed in any of claims 18 to 23 when directly or indirectly dependent on claim 7, wherein: the extent of the top wall portion and top sealing means in the longitudinal direction of the joist is no more than 50% of the thickness of the wall.
25. A building as claimed in claim 24, wherein: -14 -said extent of the top wall portion and top sealing means is from 40% to 50% of the wall thickness.
26. A building as claimed in claim 24, wherein: said extent of the top wall portion and top sealing means is from 30% to 40% of the wall thickness.
27. A building as claimed in claim 24, wherein: said extent of the top wall portion and top sealing means is from 20% to 30% of the wall thickness.
28. A building as claimed in claim 24, wherein: said extent of the top wall portion and top sealing means is less than 20% of the wall thickness.
29. A building substantially as described with reference to Figures 3 to 13 of the drawings.Amendments to the claims have been filed as followsCLAIMS(The reference numerals in the claims are not intended to limit the scope of the claims.) 1. A building having: a blockwork wall (20); a joist (14) having an end built into the wall; and a joist seal (50;70) fitted to the end of the joist (14), the joist seal having: a rear wall portion (12) covering an end face of the joist; a pair of side wall portions (22) projecting from the rear wall portion and extending along the sides of the end of the joist a bottom wall portion (68) projecting from the rear wall portion and sandwiched between the underneath of the joist and the blockwork (18) of the wall beneath the joist; and side sealing means (62) sealing the side wall portions to the blockwork wall to either side of the joist; characterised in that: the bottom wall portion projects from the rear wall portion to a substantially lesser extent (K) than the side wall portions.2. A building as claimed in claim 1, wherein: the bottom wall portion projects from the rear wall portion by no more than 25 mm.3. A building as claimed in claim 1, wherein: the bottom wall portion projects from the rear wall portion by no more than 15 mm.4. A building as claimed in any preceding claim, wherein: the bottom wall portion has a wall thickness of no more than 1.5 mm.5. A building as claimed in any of claims 1 to 3, wherein: the bottom wall portion has a wall thickness of no more than 1.0 mm.6. A building as claimed in any preceding claim, wherein: the joist seal is formed from sheet metal.7. A building as claimed in any preceding claim, wherein the joist seal further includes: a top wall portion (70) projecting from the rear wall portion and extending above the top of the end of the joist; and top sealing means (72) sealing the top wall portion to the blockwork wall above the joist.8. A building as claimed in claim 7, wherein: the extent (L) of the top wall portion and top sealing means in the direction which, in use, is the longitudinal direction of the joist is no more than 50 mm. r9. A building as claimed in claim 7, wherein: U) said extent of the top wall portion and top sealing means is from 40 mm to 50 mm. (0O 10. A building as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is from 30 mm to 40 mm.11. A building as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is from 20 mm to 30 mm.12. A building as claimed in claim 7, wherein: said extent of the top wall portion and top sealing means is less than 20 mm.13. A building as claimed in any of claims 7 to 12, wherein: the top sealing means includes an out-turned flange (72) projecting from the top wall portion and embedded in mortar of the blockwork wall above the joist.14. A building as claimed in any of claims 7 to 12, wherein: the top sealing means includes surface formations on the top wall portion and keyed to mortar of the blockwork wall above the joist.15. A building as claimed in any of claims 1 to 6, wherein: the joist seal is devoid of any substantial top wall portion projecting from the rear wall portion and and extending over the top of the end of the joist so that mortar of the blockwork wall directly contacts the top face of the joist over substantially the whole extent of the end of the joist within the thickness of the blockwork wall.16. A building as claimed in any preceding claim, wherein: the side sealing means includes out-turned flanges projecting from the side wall portions and embedded in mortar of the blockwork wall to the sides of the joist.LI) 17. A building as claimed in any preceding claim, wherein: Q the side sealing means includes surface formations (62) on the side wall portions and (Q keyed to mortar of the blockwork wall to the sides of the joist.18. A building as claimed in any preceding claim, wherein: the blockwork (18) of the wall and/or the bottom of the joist is/are recessed in the region of the bottom wall portion of the joist seal so that the bottom of the end of the joist directly contacts the blockwork of the wall over substantially the whole of the remainder of the thickness of the blockwork wall.19. A building as claimed in claim 18, wherein: the bottom wall portion of the joist seal and the bottom of the joist directly contact a block of the blockwork wall beneath the end of the joist without any substantial amount of mortar between that block and the bottom wall portion of the joist seal and the bottom of the joist.20. A building as claimed in any preceding claim, wherein: the wall has a thickness of 100 mm or more.21. A building as claimed in any preceding claim, wherein: the bottom wall portion projects from the rear wall portion by no more than 25 % of the thickness of the wall.22. A building as claimed in any preceding claim, wherein: the bottom wall portion projects from the rear wall portion by no more than 15 % of the thickness of the wall.23. A building as claimed in any of claims 7 to 14, or any of claims 16 to 22 when directly or indirectly dependent on claim 7, wherein: the extent of the top wall portion and top sealing means in the longitudinal direction of LI) the joist is no more than 50% of the thickness of the wall. (0Q 24. A building as claimed in claim 23, wherein: said extent of the top wall portion and top sealing means is from 40% to 50% of the wall thickness.25. A building as claimed in claim 23, wherein: said extent of the top wall portion and top sealing means is from 30% to 40% of the wall thickness.26. A building as claimed in claim 23, wherein: said extent of the top wall portion and top sealing means is from 20% to 30% of the wall thickness.27. A building as claimed in claim 23, wherein: said extent of the top wall portion and top sealing means is less than 20% of the wall thickness.28. A building substantially as described with reference to Figures 3 to 13 of the drawings. L() (0