AU2003235057B1 - A Truss Bracket - Google Patents

Description

A TRUSS BRACKET FIELD OF THE INVENTION This invention is directed to a truss bracket to attach a roof truss to a wall.

BACKGROUND ART During severe windstorm events, large uplift forces are generated on the roofs of houses. Therefore, it is now a legal requirement in many regions to have the roof truss properly secured to the wall.

One type of house uses a timber wall frame and the roof truss is secured to the top of the timber wall frame and typically to the upper horizontal wall beam. Steel threaded rods extend from the top wall beam and into the concrete floor slab.

Another type of house uses a concrete wall and the roof truss needs to be secured to the top of the concrete wall. The concrete wall is typically made of concrete blocks (known in Australia as Besser blocks).

These blocks are hollow and concrete can be poured down the blocks to form a masonry wall.

There are various known arrangements by which the roof truss can be attached to a masonry wall but each suffer from disadvantages being lack of adjustability, the relatively large number of parts required, lack of proper anchoring, and the rather longer assembly and securing time required to fix the roof truss to the masonry wall.

Typically, the uppermost course of concrete blocks is provided with a channel to allow reinforcement rods (also known as bond beam reinforcement) to be laid horizontally in the upper course of blocks. Figure 2 illustrates a typical known concrete block having this channel. This upper course of blocks is known as a masonry lintel.

One very well-known truss attachment system uses a steel plate (known as a cleat). The cleat is substantially rectangular and typically has a length of 200 millimetres, a width of 50 millimetres and a thickness of five millimetres. The cleat is provided with an opening at the lower end to allow the cleat to be threaded on to one of the reinforcement rods. Concrete is 2 then poured into the uppermost course of concrete blocks and about the reinforcement to anchor the cleat into the top of the masonry wall. At this stage, the top of the cleat projects from the top of the wall and this is illustrated in figure 1 which shows this type of conventional arrangement. The upper part of the cleat is also provided with a large hole to accommodate a bolt.

A roof truss is then placed against the steel cleat, and a hole needs to be drilled through the roof truss, this hole needing to be carefully aligned with the hole in the upper part of the cleat. A bolt is then pushed through the aligned holes and a nut is attached to anchor the roof truss to the wall. One disadvantage with this arrangement is the time taken to secure the cleat into the wall, the rather large number of tools that are required which will include a drill, the need to carefully drill a hole through the truss to align with the hole in the cleat, a spanner, and need to tighten the nut (it being appreciated that a typical house will have many roof trusses each of which will need to be secured). Another disadvantage is that each truss needs to be temporarily held in place during the attachment process. A further disadvantage with the cleat arrangement is that the "hold down value" is different between different regions. Therefore, if a larger hold down value is required, a larger bolt is used which now requires a different hole to be drilled through the truss. It is also known to attach an over strap to the cleat. The over strap is attached at one end to the bolt, extends over the top of the truss and is attached to the same bolt at the other side of the truss. This is not entirely satisfactory as the truss is still held in place by one anchor point being the cleat anchored into the masonry wall.

Another type of attachment arrangement which is not very common and not particularly popular is to use a threaded rod on either side of the truss. The bottom of the threaded rod is embedded in the concrete of the masonry wall and a timber top plate is placed on top of the bond beam.

Therefore, there would be an advantage if it were possible to provide a roof truss bracket particularly suited to a masonry wall (although not necessarily limited thereto), and which can attach a roof truss in a manner which uses less tools and which is less labour-intensive.

It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

OBJECT OF THE INVENTION It is an object of the invention to provide a roof truss bracket which may at least partially overcome some of the above-mentioned disadvantages or provide the consumer with a useful or commercial choice.

In one form, the invention resides in a roof truss bracket, the bracket comprising a substantially U-shaped member which comprises a bottom wall, a first upstanding sidewall and a second upstanding sidewall, each said sidewall being provided with an opening to allow a reinforcing rod to extend through each said sidewall, one sidewall in use extending along one side of the truss and the other sidewall in use extending along the other side of the truss, each sidewall being long enough to allow it to be bent over the top of the truss and down the other sidewall of the truss, each sidewall adapted to be nailed to the truss.

An advantage of the system is that the bracket can secure a roof truss using a hammer and nails only (or a nail gun) and therefore does not require a hole to be drilled through the truss and a nut and bolt to secure the truss. Also, each sidewall can be secured to the masonry wall to provide two anchor points instead of a single anchor point as is the case with the cleat system.

The bracket typically comprises a metal strap and the strap will typically be galvanised or otherwise made corrosion resistant. However, the strap need not be made of metal and may also be made of other strong materials such as plastic composite materials, metal composite materials and the like.

The bracket will typically be substantially U-shaped although no specific limitation is meant thereby. For instance, the bracket could conceivably be V shaped or have other shapes provided that a reinforcement rod can extend through each sidewall to secure the bracket to the masonry wall. It is also envisaged that the bracket may comprise a pair of separate sidewalls which need not be connected to each other at their lower ends and each sidewall can be attached to the reinforcement rod and embedded into the masonry wall. It is also envisaged that the bracket may be H shaped.

However, it is convenient for the bracket to be formed of a single strap of metal bent into a substantial U-shape.

Each sidewall will have a length, a width and a thickness to suit the purpose. For a typical roof truss attached to a masonry wall, it is considered convenient for each sidewall to have a length of between 200-800 millimetres and preferably between 300-500 millimetres, with a typical example being a length of about 410 millimetres. Each sidewall may have a width of between 10-200 millimetres and preferably between 20-100 millimetres, with a typical example having a width of about 50 millimetres.

The thickness of the material can be between 0.5-10 millimetres with a typical example having a thickness of between 1-3 millimetres.

The spacing between each sidewall may vary to suit but the spacing will typically be about the same or larger than the thickness of the roof truss. A typical spacing will be between 20-200 millimetres and a typical example will be approximately 40 millimetres. If the sidewalls are interconnected by a bottom wall, the dimensions of the bottom wall will typically be between 20-200 millimetres long with a typical example being approximately 40 millimetres, between 10-200 millimetres wide with a typical example being the same width as the sidewall, and a thickness of between 1millimetres with a typical example being the same thickness as each sidewall.

Each sidewall is provided with an opening to allow a reinforcement rod to extend through the sidewall. The opening will typically be circular and will have a diameter sufficient to allow the reinforcement rod to pass through the opening. As the reinforcement rod will typically have a diameter of about 15 millimetres, the opening will have a diameter of 15-20 millimetres with a typical example being 18 millimetres. More than one opening may be provided if considered necessary.

The opening will typically be in a lower part of the sidewall such that this part of the sidewall will be anchored in the concrete. The opening may therefore be positioned between 10-50 millimetres above the lower edge of the sidewall with a typical position having the centre of the opening approximately 30 millimetres from the bottom of the sidewall.

Each sidewall can be bent over the top of the truss to extend over at least the top and preferably some of the opposed sidewall of the truss.

To enable each sidewall to do this without overlapping each other, each sidewall may have a cutout portion or a portion of reduced width to enable the two sidewalls to extend over the truss in a side-by-side relationship as opposed to a totally overlapping relationship. This can provide greater strength to the bracket hold down ability. Thus, the top portion of each sidewall and typically the top 100-200 millimetres of the sidewall will have a reduced width or cutout portion. It is preferred that this cutout portion reduces the normal width of the sidewall by between 40-60%.

Each sidewall is typically provided with nail openings to allow each sidewall to be nailed to the truss. Typically, openings are provided entirely through each sidewall. However, it is also envisaged that each sidewall may be provided with depressions to act as guides for nails. It is also envisaged that each sidewall may not be provided with openings and that a nail can be simply punched through the sidewall. However, the advantage of providing openings or guides is that this ensures that the nails are spaced apart and that sufficient nails are used to provide an acceptable tie down.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will be described with reference to the following illustrations in which: Figure 1. Illustrates a known type down arrangement using a cleat.

Figure 2. Illustrates a plan view of the bracket according to an embodiment of the invention.

Figure 3. Illustrates a side view of the bracket of Figure 2.

Figure 4. Illustrates a view of the bracket by itself.

BEST MODE Referring to the drawings and initially to figure 1, there is illustrated a known system. In this known system, a steel plate (known as a cleat) 10 has one end embedded in the uppermost course 11 of a masonry wall. A timber truss 12 is then positioned against the cleat and must be temporarily held in place while a hole is drilled through the timber truss to coincide with a hole in cleat 10. A bolt 13 is then pushed through the aligned holes and a nut 14 is fastened to the bolt and rotated to tightly clamp truss 12 to cleat Referring now to figures 2-4 there is illustrated a roof truss bracket according to an embodiment only of the invention. Referring initially to figure 4, truss bracket 15 is substantially U-shaped and has a bottom wall 16, a first upstanding sidewall 17 and a second upstanding sidewall 18. The bracket is made from a single strip of galvanised steel which is bent to shape.

In this particular embodiment, the bracket has a thickness of between 1-3 millimetres. Bottom wall 16 has a length of 40 millimetres and a width of millimetres. Each sidewall 17, 18 is substantially identical (although a mirror image of each other), and each sidewall has a length of 410 millimetres and a width of 50 millimetres in a lower part of the sidewall. In the bottom region of the sidewall is an opening 19 which has a diameter of 18 millimetres and which allows a reinforcement rod 20 (see figure two and figure three) to pass through each hole 19 to secure the bracket to the reinforcement rod 20 at two positions.

The upper part of each sidewall 17, 18 has a cutout 21 which extends along the top 150 millimetres of each sidewall and which effectively halves the width of the sidewall at this part. The cutouts are on opposed sides of each sidewall as illustrated in figure 4. Each sidewall is provided with a plurality of nail openings 22.

In use, the bracket is shaped as illustrated in figure 4 and is threaded over reinforcing rod 20. A truss 12 can then be placed such that sidewalls 17, 18 extend up each side of the truss 12. Each sidewall 17, 18 can then be bent over the top and down the other sidewall of the truss, this being illustrated in figure 2 and figure 3. Each sidewall can then be nailed to the truss. Each sidewall 17, 18 can extend over the truss in a side-by-side relationship (best illustrated in figure 2) due to the cutout portion in each sidewall.

The particular bracket arrangement has many advantages.

Firstly, the bracket is lightweight. The trusses can be attached to a masonry wall more quickly than by previous methods. The hold down can be completed while the crane (which lifts the trusses onto the roof) is on-site.

The bracket can be attached to the truss using a hammer and nails or can be attached using a nail gun. A complete loop strap strapping is provided over the top of the truss. The truss is not weakened by having a large hole drilled through it (which is required with the prior art cleat attachment method). The hold down value can be increased by using a greater number of nails. The bracket can be provided with various different thicknesses with the thicker the bracket the higher the hold down value will be. For small lightweight trusses only a few nails are required. The bracket arms can be opened up to cater for all thicknesses of trusses.

Throughout the specification and the claims (if present), unless the context requires otherwise, the term "comprise", or variations such as "comprises" or "comprising", will be understood to apply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers.

It should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Claims (13)

1. A roof truss bracket, the bracket comprising a substantially U- shaped member which comprises a bottom wall, a first upstanding sidewall and a second upstanding sidewall, each said sidewall being provided with an opening to allow a reinforcing rod to extend through each said sidewall, one sidewall in use extending along one side of the truss and the other sidewall in use extending along the other side of the truss, each sidewall being long enough to allow it to be bent over the top of the truss and down the other sidewall of the truss, each sidewall adapted to be nailed to the truss.

2. The bracket as claimed in claim 1, wherein the bracket comprises a metal strap.

3. The bracket as claimed in any one of the preceding claims, wherein each sidewall has a length of between 200-800 millimetres.

4. The bracket as claimed in any one of the preceding claims, wherein each sidewall has a width of between 10-200 millimetres.

The bracket as claimed in any one of the preceding claims, wherein the U-shaped member has a thickness of between 0.5-10 millimetres.

6. The bracket as claimed in any one of the preceding claims, wherein the spacing between each sidewall is between 20-200 millimetres.

7. The bracket as claimed in any one of the preceding claims, wherein each sidewall is provided with a single circular opening to enable a reinforcement rod to pass through each sidewall.

8. The bracket as claimed in any one of the preceding claims, wherein the opening in each sidewall is between 10-50 millimetres above a lower edge of the sidewall.

9. The bracket as claimed in any one of the preceding claims, wherein each sidewall is provided with a plurality of nail openings.

The bracket as claimed in any one of the preceding claims, wherein each sidewall is provided with a cutout portion adjacent an upper portion of each sidewall.

11. The bracket as claimed in claim 10, wherein the cutout portion has a length of between 50-300 millimetres. 9

12. The bracket as claimed in claim 10 or claim 11, wherein the cutout portion reduces the width of the sidewall by about one half.

13. A bracket substantially as hereinbefore described with reference to figures 2-4. Dated this 18 th day of August 2003 Joseph GEDOUN and Anna-Leisa Maureen GEDOUN By their Patent Attorneys CULLEN CO.