EP1816271A2

EP1816271A2 - Improvements in or relating to joists and floor panels containing same

Info

Publication number: EP1816271A2
Application number: EP07250300A
Authority: EP
Inventors: Roger Smith
Original assignee: Howarth Timber Engineering Ltd
Current assignee: Howarth Timber Engineering Ltd
Priority date: 2006-02-02
Filing date: 2007-01-25
Publication date: 2007-08-08
Also published as: EP1816271A3; US20070193194A1

Abstract

Width enlargement means is described, which is adapted to be attached to a joist end to adapt the latter for use with a joist hanger having a joist receiving socket with diverging side cheeks therein. When attached, the cross section shape of the end of the joist becomes trapezoidal so as to form a wedge. The inclined faces engage the diverging side cheeks of the socket thereby to provide lateral support for the joist end when fitted in the joist receiving socket. One form of enlargement means for a conventional rectangular cross section joist comprises triangular cross section fillets, which are adapted to be fitted to the opposite faces of the end of a the joist. Alternatively it may comprise a wedge shaped member having a central slot into which the end of the joist is fitted. Where the joist has an I-beam cross section, fillets are secured to opposite faces of the central web of the I-beam, or the end of the latter is fitted into a slot in a slotted wedge. Alternatively at least one metal structure is adapted to be fitted to one end of the joist, and the outer faces of the metal structure or structures are spaced by a greater distance in the region of the upper edge of the I-beam section than they are in the region of the lower edge thereof. Where the joist has an I-beam cross section the metal structure(s) may be attached to the web or the upper or lower rails, or all three. However formed the included angle between the inclined faces of the enlargement means whether formed by fillets or a wedge shaped member, or one or more metal structures, is substantially the same as, but not greater, than that between the diverging cheeks of the joist hanger socket in which the joist is to be received in use.

Description

Field of Invention

This invention concerns joists which are employed in pre-fabricated floor panels and in particular to locating and supporting the ends of such joists. It is to be understood that a floor panel between floors of a building can also be thought of as a ceiling panel when viewed from below and the expression floor panel employed herein is intended to cover both.

Background to the invention

It is known to construct floor and ceiling panels off-site and deliver them to where they are required ready to be lifted into position, typically by a crane. Each panel is comprised of a plurality of parallel spaced apart joists below and secured to a decking sheet of wood such as plywood or chipboard or the like. The latter typically includes lifting eyes by which the assembly can be craned into place in a building under construction.
Since the load bearing components of the panel are the joists, it is necessary for at least the ends of the joists to rest on load bearing walls or into the sockets of joist hangers attached to walls or timber beams.
This method of assembly of the floors and ceilings of a building is especially popular in the case of so-called timber framed buildings, where the load bearing walls are constructed from timber panels which are secured at their ends to form corners or longer runs of walls. Furthermore it is customary for the buildings to be pre-assembled where the wall and floor panels are constructed. In this way it is possible to determine the positions of the joists relative to ring beam timbers or upper edges of wall panels or intermediate beams on which they are to be supported, and the joist hangers can be secured to the relevant timbers while the floor panels are in position. The floor panels can then be lifted clear of the supporting joist hangers and the pre-assembled building parts dismantled to allow them to be shipped to where the building is to be permanently constructed.
Since the joist hangers have been positioned exactly where the joists are to be located relative to the rest of the structure, the assembly of floor panels to beams and walls is greatly simplified. The nails or screws used to secure the ends of the joists to the cheeks of the hangers can be inserted after the panel has been lowered into position, since the ends of the joists will be fully supported by the hangers even though they are not secured to the cheeks of the hangers.
Whilst this method of assembly works well in theory, difficulties can arise in practice especially if there is any appreciable cross wind and/or there are insufficient personnel to position the panels precisely relative to the joist hangers, to enable each panel to drop into the sockets formed by the hangers.
It has been proposed to provide a modified joist hanger (hereinafter referred to as a hanger of the type described) which comprises two side cheeks defining an open-topped channel in which in use a joist end is located, and a bridge section which joins the lower ends of the two cheeks on which the underside of the joist will rest, in which the two side cheeks diverge from the bridge to facilitate entry thereinto by a joist.
By providing diverging cheeks in the hangers to facilitate the introduction of the joists into the sockets, conventional joists will only be gripped between the cheeks at the bottom of each socket. Whilst this may be acceptable it is preferable for each joist end to be held captive over the full depth of the joist.
The present invention seeks to provide means by which the ends of conventional joist can be modified to enable it to be used with hangers modified as aforesaid.

Summary of Invention

According to a first aspect of the present invention width enlargement means is provided adapted to be attached to a joist end to adapt the latter for use with a joist hanger having diverging side cheeks in a joist receiving socket therein, whereby the width enlargement means causes at least part of the cross section of the end of the joist to become trapezoidal so as to form a wedge, the inclined faces of which in use engage the diverging side cheeks of the socket thereby to provide support for the joist end when fitted in the joist receiving socket of the hanger.
Conventionally, joists are normally formed with a rectangular cross-section or an I-shaped cross-section. Width enlargement means in accordance with the invention can be adapted for attachment to either of these types of joist, or indeed any other type of joist.
In one embodiment the width enlargement means comprises triangular cross section fillets, which are adapted to be fitted to the opposite faces of the end of a conventional rectangular cross section joist so as to fill the space between each face of the joist and the side cheeks of the hanger.
The fillets may for example be of wood or metal or rubber or plastics material and they may be nailed, screwed or stuck to the joist faces. The joist preferably, but not necessarily, comprises or consists of timber or wooden material.
In another embodiment the two fillets are replaced by a single wedge shaped member having a central slot into which the end of a joist can be fitted. Again such a member may be secured to the joist a by nailing or screwing or by an adhesive or by virtue of interference fit between the sides of the slot and the joist.
In the case of a conventional timber I-beam cross-section joist, the two fillets may be secured for example to opposite faces of the central web of the I-beam.
Alternatively a slotted wedge may be provided wherein the slot is adapted to receive, and be secured to, the end of the central web of an I-beam joist.
Alternatively a metal structure may be provided which is adapted to be fitted to one end of a conventional I-beam section joist, such that when fitted thereto the outer faces of the metal structure are spaced by a greater distance in the region of the upper rail than they are in the region of the lower rail, so as to form the trapezoidal shape.
The metal structure may be constructed from a single part or from two or more parts.
Typically the or each part comprises a sheet metal pressing or casting.
In the case of an I-beam cross section joist the metal structure may be adapted to be secured to the central web alone, or to the upper or lower rails of the I-beam section, or to the web and one of the rails, or to the upper and lower rails only, or to both rails and the web.
However formed, the included angle between the inclined faces of the fillets, or external faces of the metal structure, is substantially the same as, but not greater than, that between the diverging cheeks of the joist hanger of the type described in which the joist is received in use.
The invention is of particular benefit when constructing intermediate floors and ceilings of buildings, in which the area of each floor is such as to require it to be made of two (or more normally a large number of) different panels, and intermediate beams extend across the building to act as supports for the adjacent ends of pairs of such panels, with joist hangers of then type described attached to opposite faces of each intermediate beam, so as to receive and support the ends of the joists of the panel on either side thereof.
Such beams may be the sole support for a panel, but where walls are available to support one or more edges of a panel, one or both of the outermost joists may for example rest on the top of a wall and/or a traversely extending timber closure may be secured to the ends of the joists at one end of the panel to enclose that end and in that event it is the closure which will rest on the top of a wall. In such an arrangement the beam carrying the joist hangers will itself rest on walls at each end and its depth will be selected so that the bridge sections of the joist hangers are located at the correct height to support the undersides of the joists and the upper edge of the beam will be below the underside of the decking sheet secured to the upper faces of the joists.
The invention also provides a joist in combination with width enlargement means as defined above.
The invention also lies in a pre-fabricated floor panel comprising a decking sheet supported by and secured to an array of parallel spaced apart joists in which width enlargement means according to the first aspect of the invention are fitted to at least one end of each joist to assist in guiding these joist ends into corresponding trapezoidal shaped joist hangers. The decking sheet may be made of timber or other wooden material, such as chipboard, fibreboard, plywood or the like. Conveniently the joists will be predominantly formed of timber.
The invention also lies in a method of locating a pre-fabricated floor panel comprising a decking sheet supported by and secured to an array of parallel spaced apart joist, into a building during construction, comprising the steps of:-

a) securing to a wall or beam joist hangers of the type described each having diverging side cheeks defining an upwardly open trapezoidal joist receiving socket,
b) fitting to each joist end which is to be received in, a socket of one of those hangers, a width enlarging means provided by the invention so as to form a complementary trapezoidal profile the included angle of which is substantially the same as, but not greater than, the included angle between the diverging side cheeks of the hanger socket,
c) lifting the panel above the walls of the building and lowering it so that the narrower ends of the enlarged joist ends register with the wider open ends of the joist receiving sockets formed by the diverging side cheeks of the hangers, and
d) lowering the panel so that the joist ends enter the upper wider ends of the sockets and are guided by the converging walls thereof into a final aligned position with the underside of each joist end resting on the bridging section of the socket into which it has been guided.

For the avoidance of doubt it is hereby expressly stated that, unless the context dictates otherwise, the invention may comprise any optional feature described herein in isolation or in combination with any one or more other optional features described herein.
The invention will now be described by way of example with reference to the accompanying drawings in which: -

Fig. 1 illustrates how a pre-fabricated floor panel is lowered by a crane so that the ends of the joists on its underside can be received in pre-fitted joist hanger sockets;
Fig. 2 illustrates a similar floor panel and set of pre-fitted modified joist hanger sockets which present trapezoidally shaped sockets for receiving the joist ends, which joist ends have width enlargement means, so that the joist ends are similarly shaped in accordance with the present invention, and adapted to be received in the hanger sockets;
Figs. 3 and 3A show triangular cross section fillets fitted at the end of a conventional rectilinear cross-section joist in accordance with one embodiment of the invention;
Figs. 4 and 4A show how fillets can be fitted at the end of an I-beam section joist in accordance with another embodiment of the invention;
Figs. 5 and 5A show another way in which the cross section shape of the end of an I-beam section joist can be modified in accordance with another embodiment of the invention; and
Fig. 6 is a perspective view to an enlarged scale of the pre-fabricated floor panel and cooperating joist hangers shown in Fig. 2.

In the drawings Fig. 1 shows how conventional joists such as 10 and conventional joist hangers such as 12 need to be precisely aligned before a floor panel such as 14 can be lowered into position, so that the ends of the joists will slide down between the parallel side cheeks 16, 18 of the conventional joist hangers. Any misalignment will prevent the placement of the floor panel, and can damage the side-cheeks of the hangers.
By providing modified joist hangers such as 20 as shown in Fig.2, having diverging side-cheeks such as 22, 24, there is less need for precise alignment between the joist ends and the hanger sockets.
Modified hangers such as shown in Fig. 2 can be used with conventional rectilinear cross-section joists such as shown at 10 in Fig. 1. However there is no lateral support for the upper region of the end of each joist 10A and therefore as proposed by the present invention, the cross section of at least the end of each joist 10A is modified by width enlargement means (11, 13) so as to correspond more precisely to the shape of each joist hanger socket.
The joists 10A shown in Fig. 2 are of I-beam cross-section and the width enlarging means for such joists are described in more detail with reference to Figs. 4 and 5.
However in the simplest case of a conventional rectilinear cross-section joist 10 (such as shown in Fig. 1) the end width enlargement can be as shown in Fig. 3. This is achieved by securing two wedge-shaped width enlarging members 26, 28 on opposite faces of the joist so as to form a trapezoidal cross-section when viewed end-on. The increased width at the widened top of the joist cross-section is made commensurate with the spacing between the upper ends of the side cheeks 22, 24 of the modified hangers 20 shown in Fig. 2. By using wedges which taper to a V-shape, the lower end of the end cross-section will be substantially the same as the thickness of the joist 10, which corresponds to the spacing between the parallel socket cheeks 16, 18 of joist hangers 12 of Fig. 1
The wedges 26, 28 may be blocks of wood, metal or plastics or rubber or composites thereof and may be solid or hollow. They may be formed in any convenient manner e.g. by cutting, moulding, casting, pressing etc.
Where the joist has an I-beam cross-section as shown in Fig. 2 again two generally wedge-shaped width enlarging members 30, 32 may be fitted, this time to opposite faces of the web 34 of the I-beam cross-section, as shown in Fig. 4. As illustrated the two members 30, 32 are cut-away at their upper ends so as to accommodate the upper rail 36 of the I-beam. The lower ends of the enlarging members 30, 32 rest on the lower I-beam rail 38 of the joist.
As with Fig. 3 the wedge shaped width enlargement members 30, 32 may be of wood or metal or plastics or rubber or composites thereof and may be solid or hollow.
In the case of the embodiments illustrated in either Fig. 3 or Fig. 4 the width enlarging wedges 26, 28 or 30, 32 may be secured in place for example by an adhesive or by staples, nails, screws or pins, or any other convenient fixative.
Although not shown, the wedges 26, 28 or 30, 32 may extend over more of, or even all of the length of a joist, although it is generally preferred to limit the extent of the wedges substantially to the end regions of the joists, which end regions are to be received in the trapezoidal joist receiving sockets of the hanger.
Figs. 5 and 5A show how metal brackets 40, 42 can form width enlargement means. Here upper (37, 39) and lower (41, 43) flanges of metal brackets 40, 42, can be fixed as by staples, nails or screws such as 44 to the upper and lower faces of a joist, so as to produce in the end region of the joist a hollow trapezoidal shape which corresponds to that of the diverging side- cheeks 22, 24 of the modified hangers.
Figs. 2 and 6 also show how the floor panel can be modified so as to resist bending as can occur when being lifted and lowered by a crane as indicated in Fig. 2. Referring to Fig. 6 which is to a larger scale than Fig. 2 a tie rod 45 extends across the width of the panel, the rod is threaded at both ends and is secured in place by nuts and washers at each end, such as 46, 48. Between each pair of joists are noggins of wood, plastics or metal 50, 52 and 54, which may be glued or otherwise secured at their ends to the joists, but are put in compression as the tie rod 45 is tensioned by tightening nuts 46, so as to rigidly space apart the joists.

Claims

Width enlargement means adapted to be attached to a joist end to adapt the latter for use with a joist hanger having diverging side cheeks in a joist receiving socket therein, whereby the width enlargement means causes at least part of the cross section of the end of the joist to become trapezoidal so as to form a wedge, the inclined faces of which in use engage the diverging side cheeks of the socket thereby to provide lateral support for the joist end when fitted in the joist receiving socket of the hanger.
Width enlargement means as claimed in claim 1 comprising triangular cross section fillets, which are adapted to be fitted to opposite faces of the end of a rectangular cross section joist so as to fill the space between each face of the joist and the side cheeks of the hanger.
Width enlargement means as claimed in claim 2 wherein the fillets are of wood or metal or rubber or plastics material.
Width enlargement means as claimed in claim 3 wherein the fillets are nailed, screwed or stuck to the joist faces.
Width enlargement means as claimed in claim 1 comprising a wedge shaped member having a central slot into which the end of the joist is fitted.
Width enlargement means as claimed in claim 5 wherein the wedge shaped member is secured to the joist a by nailing or screwing or by an adhesive or by virtue of an interference fit between the slot and the joist.
Width enlargement means as claimed in claim 1 for use with a joist having an I-beam cross section comprising two fillets adapted to be secured to opposite faces of the central web of the I-beam.
Width enlargement means as claimed in claim 1 for use with a joist having an I-beam cross section comprising a slotted wedge wherein the slot is adapted to receive, and be secured to, an end of the central web of the I-beam joist.
Width enlargement means as claimed in claim 1 comprising a metal structure which is adapted to be fitted to one end of an I-beam cross section joist, such that when fitted thereto, outer faces of the metal structure are spaced by a greater distance in the region of the upper rail of the I-beam section when in use than they are in the region of the lower rail of the I-beam section, so as to form a trapezoidal shape.
Width enlargement means as claimed in claim 9 wherein the metal structure is constructed from a single part.
Width enlargement means as claimed in claim 9 wherein the metal structure is formed from one or more parts, each of which comprises a sheet metal pressing or casting.
Width enlargement means as claimed in any of claims 9 to 11 wherein the metal structure is adapted to be secured to the central web alone, or to the upper or lower rails of the I-beam section when in use, or to the web and one of the rails, or to the upper and lower rails only, or to both rails and the web.
Width enlargement means as claimed in any of claims 2 to 12 wherein the included angle between the inclined faces of the fillets or the wedge shaped member, or the outer faces of the metal structure, is substantially the same as, but not greater than, that between the diverging cheeks of the joist hanger socket in which the joist is to be received in use.
Width enlargement means according to any one of the preceding claims, in combination with a joist.
A method of locating a pre-fabricated floor panel comprising a decking sheet supported by and secured to an array of parallel spaced apart joists, into a building during construction, comprising the steps of:-
a) securing to a wall or beam in the building joist hangers each having diverging side cheeks defining an upwardly open joist end receiving socket,

b) fitting to each joist end which is to be received in a socket of one of those hangers, a width enlarging means as claimed in any of claims 1 to 13 so as to form a trapezoidal profile complementary to the socket profile, the included angle of which is substantially the same as, but not greater than, the included angle between the diverging side cheeks of the hanger socket,

c) lifting the panel above the wall or beam and lowering it so that the narrower ends of the enlarged joist ends register with the wider open ends of the joist receiving sockets formed by the diverging side cheeks of the hangers, and

d) lowering the panel so that the joist ends enter the upper wider ends of the sockets and are guided by the converging walls thereof into a final aligned position with the underside of each joist end resting on the bridging section of the socket into which it has been guided.
A floor panel comprising a decking sheet supported by and secured to an array of parellel spaced-apart joists, one or more of said joists comprising a width enlargement means according to any one of claims 1-13.