GB2027477A - Joist hanger - Google Patents

Abstract

A joist support comprising an isosceles triangular shaped sheet metal member which is divided by a pair of cuts 11 and 12 extending obliquely generally towards each other from respective points 15, 16 on opposite equal length edges 13 and 14 of the triangular member. A pair of folds 25, 26 are made from the ends of the cuts 11 and 12 and extending away from the line joining the points 15 and 16, the folded up portions of metal forming wings 19 and 20 which are disposed parallel to each other and perpendicular to the base. The joist is set on the base between these wings, to which it is secured by nailing and the end of the joist is positioned approximately at the line 17 joining the points 15 and 16, which coincides with the face of the masonry in which the joist support is being secured. The only connection between the joist support and the masonry is between adjacent courses of masonry and hence the support can be positioned anywhere along a wall structure for the optimum spacing of joists, without the cutting of bricks or blocks forming the masonry. The broadest part of the base coincides with the position of maximum loading, along the line 17 coinciding with the face of the wall. The joist support base is stiffened by a tapering rib 28. A tongue 23 is pressed out of the base to form a stop 29 which abuts against the masonry. The apex 30 us turned down and with the hole 24 forms a key for mortar. Nail holes 21 are provided in the wings 19, 20. <IMAGE>

Description

SPECIFICATION Joist hanger This invention relates to joist supports.

Joist supports or hangers are frequently used in buildings to support joists which are usually of wood, where they meet external and internal walls of a building. Although joists can be built directly into courses of masonry, this practice is undesirable in some respects, particularly as it may give rise to fire risk.

Previously proposed joist hangers have been made of pressed steel and have comprised a main part of generally "lazy-Z" shape, the top horizontal bearing portion being inserted between courses of masonry and the lower horizontal portion providing a base on which the joint is held. Side straps have been provided to retain the joints centrally in position and to rigidify the lazy-Z shaped main part. The side straps have been welded in position.

This construction has disadvantages. For example, the welding on the side straps has involved an extra manufacturing operation and the welds have to be very carefully made if they are not to cause structural weakness.

The upright portion of the lazy-Z main part has effectively spaced the end of the joist (and hence the load supported) away from the wall, which tends to increase the moment exerted on the hanger and hence tends to loosen it.

The main part of the hanger has had a width equal to that of the joist which is relatively narrow considering the load to be supported. There has been a tendency for the concentrated load of the joist to cause the masonry to crumble along the edge of the bearing portion of the hanger which in turn aggravates any tendency for the bearing portion to pull out.

A range of sizes has had to be provided to accommodate the various depths of joist in current use, each size requiring separate press tools for forming the metal and welding jigs.

It is an object of the invention to provide a joist support which overcomes or reduces some or all of these disadvantages. It is a further object of the invention to provide a method of making such a joist support.

According to the first aspect, the invention provides a joist support consisting of a single sheet metal member comprising a base and a pair of wings extending in the same sense away from the base and in planes generally parallel to each other and perpendicular to the base, the sheet metal member being divided to afford the base and wings by a pair of cuts extending obliquely generally towards each other from respective points on opposed edges of the sheet metal member at equal acute angles to a line joining said points, the wings comprising portions of metal on the side of the respective cuts remote from said line bent out of the general plane of the base.

One or more stiffening formations may extend along the base. The or each formation may comprise a rib pressed out of the general plane of the base and the or each rib may extend away from the base in the same sense as the wings.

A stop may be provided on the base at a position disposed along said line. The stop may comprise a portion of the base which is pressed out of the plane of the base.

The base may additionally be provided with keying formations.

According to the second aspect, the invention provides a method of making a joist support comprising taking a sheet metal blank, forming a pair of cuts in the blank, said cuts extending obliquely generally towards each other from respective points on opposed edges of the blank at equal acute angles to a line joining said points, the metal being formed to afford a base and a pair of wings, said wings comprising portions of metal on the side of the respective cuts remote from said line and being bent generally perpendicularly away from the base in the same sense and in planes parallel to each other, the base being formed with one or more stiffening formations extending therealong.

The method may include a preliminary step of taking a sheet of metal and blanking out therefrom a plurality of said sheet metal blanks. The blanks are preferably so shaped as to occupy in combination, the entire area of the sheet metal.

The method may additionally include the step of forming one or more stiffening formations comprising ribs extending along the base. Preferably, the or each rib is formed so as to extend out of the plane of the base in the same sense as the wings. A lug may additionally be pressed out of the metal of the base to afford a stop on said line.

An embodiment of the invention will now be described in more detail by way of example only, reference being made to the accompanying drawings in which: Figure 1 is a plan view of a sheet metal blank Figure 2 is a plan view of a joist support Figure 3 is a side elevational view of the joist support of Fig. 2 Figure 4 is an end elevational view of the joist support.

Referring firstly to Fig. 1 of the drawings, this shows a blank generally indicated at 10 from which a joist support is to be made. The blank is heavy guage sheet metal such as galvanized steel for example. It will be seen that the blank 10 is of triangular form and comprises half a square so that a plurality of such blanks can be cut from a rectangular sheet of metal without any metal wastage.

The blank is provided with a pair of cuts 11 and 12 which extend inwardly from a pair of opposed edges 1 3 and 14 respectively of the triangular blank. The two cuts 1 1 and 12 extend obliquely generally towards each other from the points 15 5 and 16 on the respective edges 13 and 14. Considering an imaginary line indicated in dotted outline at 1 7 in the drawings, and extending across the blank between the points 1 5 and 16, it will be seen that each of the cuts extends from one of the points 15 or 16 at an equal acute angle to the line 17.

The blank is thus divided off into a base 18 and a pair of portions which will later form wings 19 and 20 to be referred to subsequently.

While the blank is in the flat form shown in Fig. 1 a plurality of holes 21 are punched or drilled in the wing portions 19 and 20. A Ushaped cut 22 is formed in the base 18, surrounding a tongue 23 of metal. One or more additional holes is also formed in the base at 24 for example.

The blank shown in Fig. 1 is formed to the shape illustrated in Figs. 2, 3 and 4 by one or more pressing operations performed in generally known manner. It will be seen that the wings 1 9 and 20 are pressed out of the general plane of the base so as to extend in the same sense generally at right angles away from the base. The wings are bent along parallel lines 25 and 26 so as to extend upwardly in parallel planes. These wings provide lateral location for a joist 27 which is indicated in chain dotted outline in Fig. 4.

A tapering upstanding rib 28 is formed in the base, extending from end to end thereof, the rib being directed upwardly in the same direction as the wings. This rib is for stiffening purposes and could be replaced by any other suitable stiffening formations. The tongue 23 is pressed downwardly in a direction away from the wings so as to provide a stop 29 best seen in Fig. 3 of the drawings. The apex 30 of the triangular blank is turned downwardly and forms, with the additional hole 24, a mechanical key enabling this portion of the base to be embedded in mortar between adjacent courses of masonry.

In order to secure a joist to a wall under construction, the portion of the base between the apex 30 and the line 1 7 is embedded in the mortar between courses of masonry, with the stop 29 abutting the masonry. It will therefore be appreciated that the widest portion of the base, along the line 17, coincides with the free edge of the masonry and the remaining portion of the joist support extends outwardly therefrom. Succeeding courses of masonry are added so that the base of the support is firmly cantilevered.

A joist is brought into position between the wings 1 9 and 20. It will be seen that'the forward corners 31of the wings abut the ma sonry which again serves to locate the joist support correctly. The joist is placed in position abutting the masonry and between the wings 19 and 20. It is secured by means of naits passing through holes 21. It will be seen that there is no restriction on the height of the joist which can be used so that only one size of joist support needs to be provided for use with a whole range of joist depths, provided that the joists have the conventional width which is approximately 50 millimetres.

The tapering upstanding rib 28 provides the main bearing area of the base which supports the joist. When the joist is fully loaded, there is a tendency for the rib 28 to embed itself in the wood of the joist and to crush the fibres somewhat in the central region. However, the tendency for the fibres to crush is resisted by the portions of the joist lying between the rib and the wing on each side of the base.

It will be seen that the portion of the joist support embedded in the masonry is of fairly substantial area and has its widest portion at the masonry edge. When the support is loaded by the joist, there is a downward force exerted which tends to bend the base but this is resisted because the widest portion of the base which is the most difficult to bend is disposed at the position where the bending would tend to take place. The less heavily stressed portions of the base are of correspondingly lesser width and embedded further into the masonry. The joist can be placed directly against the masonry and hence the load acts very close to the line 17, which minimises the turning moment exerted.

In conventional building practice, the spacing of joists is not related to the size of the bricks or blocks forming the masonry wall but rather to the span of floor boards which can be carried without distortion and creaking.

This often means that the joists are not spaced an integral number of bricks or blocks apart and hence, if the joists are embedded directly into the masonry the bricks or blocks need to be cut. The joist support described above is capable of being placed at any position along a course of masonry so that the optimum joist spacing can be used.

It will be seen from Fig. 4 that the joist base is located at a specific position relative to the courses of masonry. In a conventional joist hanger, the portion of the hanger embedded in the masonry is spaced well above the portion which supports the under side of the joist. Thus, if the masonry courses are truly horizontal but the joist is twisted or warped through its depth, which is frequently the case, the underside of a conventionally supported joist may be considerably out of the horizontal plane. This is not the case with the joist support described above. However, it can be much more important for the underside of the joist to be truly~horizontal than for the upper side, where the joist supports a ceiling from above and a floor on its upper side.The floor boards, being relatively robust, need not be very precisely supported but the tolerances which can be coped with by a conventional plaster board ceiling are very slight and hence any warping of the joist makes it difficult or impossible to secure the plaster board in place neatly, leaving an unsatisfactory ceiling surface.

Although the joist hanger described and illustrated is made from a triangular blank, it could be made from other shapes of blank although these are preferably such that the blanks can be cut from sheet metal without wastage. For example, the blanks could be rectangular or of broad generally V-shape.

It is sometimes the practice for joist hangers or supports to be secured to the joists and then offered up to the wall to be secured in place. The joist support of the present invention can be used in this manner but it is advantageous to make one minor change which is that the tongue 23 is bent upwardly in the same direction as the wings and serves to locate the free end of the joist at the line 1 7 so that the correct amount of the base is then inserted into the masonry.

In the foregoing description, we have referred to the joist support as being made of metal, for example galvanised mild steel.

However, it is envisaged that other structural materials might be suitable, for example, a fibre reinforced plastics material having suitable load bearing and life characteristics.

In general, the spacing of the wings 1 9 and 20 will be determined by the width of the joist and it will be appreciated that a range of sizes may be provided to accommodate joists of different widths, simply by increasing the size of the blank.

Claims (14)

1. A joist support consisting of a single sheet metal member comprising a base and a pair of wings extending in the same sense away from the base and in planes generally parallel to each other and perpendicular to the base, the sheet metal member being divided to afford the base and wings by a pair of cuts extending obliquely generally towards each other from respective points on opposed edges of the sheet metal member at equal acute angles to a line joining said points, the wings comprising portions of metal on the side of the respective cuts remote from the said line bent out of the general plane of the base.

2. A joist support according to claim 1 wherein one or more stiffening formations extend along the base.

3. A joist support according to claim 2 wherein the or each stiffening formation comprises a rib pressed out of the general plane of the base.

4. A joist support according to claim 3 wherein the or each rib extends away from the base in the same sense as the wings.

5. A joist support according to any preceding claim wherein a stop is provided on the base at a position disposed along said line.

6. A joist support according to claim 5 and comprising a portion of the base which is pressed out of the plane of the base.

7. A joist support according to any preceding claim wherein the base is additionally provided with keying formations.

8. A joist support according to any preceding claim wherein said single sheet metal member is initially of isosceles triangle form.

9. A method of making a joist support comprising taking a sheet metal blank, forming a pair of cuts in the blank, said cuts extending obliquely generally towards each other from respective points on opposed edges of the blank at equal acute angles to a line joining said points, the metal being formed to afford a base and a pair of wings, said wings comprising portions of metal on the side of the respective cuts remote from said line and being bent generally perpendicularly away from the base in the same sense and in planes parallel to each other.

10. A method according to claim 9 and additionally including the step of forming one or more stiffening formations comprising ribs extending along the base.

11. A method according to claim 10 wherein the or each rib is formed so as to extend out of the plane of the base in the same sense as the wings.

1 2. A method according to any one of claims 9 to 11 wherein a lug is additionally pressed out of the metal of the base to afford a stop on said line.

1 3. A method according to any one of claims 9 to 1 2 and including a preliminary step of taking a sheet of metal and blanking out therefrom a plurality of said sheet metal blanks.

14. A method according to claim 1 3 wherein said blanks are shaped to occupy, in combination, the entire area of the sheet metal.

1 5. A method according to claim 14 wherein said blanks are of isosceles triangle shape.

1 6. A joist support substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 7. A method of making a joist support according to claim 9 and substantially as hereinbefore described.