Plaster bead

Abstract

 A plaster bead for an expansion joint between two adjacent areas of rendering (10) on a substrate (3). The bead is fixed to the substrate (3) and comprises a flexible U-section (6) the free ends of the arms of which are connected to rigid flanges (5). In use, the flanges (5) are substantially flush with the rendering (10). The flanges are connected to respective wings (8) of perforate material which are arranged to be embedded in, and keyed to, the rendering (10). A removable strip (11) is provided in the free ends of the arms of the U-section (6), and connected to the arms (11) by lines of weakness (12) along the edges of the strip (11). This strip (11) positively retains the free ends of the arms of the U-section (6) at the correct distance apart during fixing of the bead to the substrate. The strip (11) can be removed when the rendering (10) is dry leaving the arms of the U (6) correctly spaced apart.

Description

[0001] The invention relates to a plaster bead for an expansion joint between two adjacent areas of rendering on a substrate, the bead being arranged to be fixed to the substrate and comprising a flexible U-section the free ends of the arms of which U are connected to substantially rigid flanges, which, in use, are substantially flush with the respective faces of the areas of rendering, the flanges being connected to respective wings of expanded or other perforate material which are arranged to be embedded in, and keyed to, the rendering. Such a bead is hereinafter referred to as of the kind described.

[0002] With such a bead, the areas of rendering are able to move slightly relatively to one another, carrying the wings and flanges with them, the movement being accommodated by flexure of the U-section. However, there is sometimes a problem in that, when the bead is initially fixed, e.g. by stapling or nailing, to the substrate, the U-section is stressed and distorted with the arms of the U-section displaced towards or away from one another. The prestressing of the U-section can affect the movement which can be accommodated at the expansion joint.

[0003] In accordance with the present invention, a plaster bead of the kind described is provided with a removable strip extending between the free ends of the arms of the U-section, and connected to the arms by lines of weakness along the edges of the strip. With this arrangement, the strip acts as a strut which positively retains the free ends of the arms of the U-section at the correct distance apart during fixing of the bead to the substrate and subsequent rendering. When the rendering is dry, the strip can be torn or knocked out, leaving the arms of the U correctly spaced apart.

[0004] The strip also has the advantage of avoiding the ingress of rendering into the U-section between its arms, without the need for the provision and subsequent removal of the protective tape which is conventionally applied to the flanges across the U-section.

[0005] The whole bead may be made as an integral extrusion of plastics material, the wings being perforated after the extrusion step. Advantageously, however, the wings are made of metal, such as expanded metal, and may be embedded in the flanges, which, together with U-section and removable strip are formed as an integral plastics moulding.

[0006] Conventional plaster beads of the kind described have only been used with coplanar areas of rendering. It is now appreciated that a bead in accordance with the present invention may be used at a concave corner between areas of rendering meeting at substantially 90°. In this case, one of the flanges may be substantially a continuation of one of the arms of the U-section.

[0007] Two beads constructed in accordance with the present invention and their use are illustrated in the accompanying drawings, in which:

Fig. 1 is a section of rendered wall using a first example of a bead in accordance with the invention;

Fig. 2 is a section of rendered wall using a second example of a bead, in accordance with the invention; and

Fig. 3 is a perspective view of the second example of the bead.

[0008] The bead shown in Figure 1 is fixed to a brick or block wall 3, forming a substrate. The bead has a plastics moulding 4 consisting of flanges 5 interconnected by a flexible U-section portion 6. The rear parts of the flanges 5 receive formed ends 7 of metal wings 8, the outer parts 9 of which are cut and stretched to form expanded metal.

[0009] The closed end of the U-section is made of soft flexible PVC and provides the flexibility for the bead. The rest of the moulding 4 is made of rigid PVC.

[0010] Figures 2 and 3 show part of a similar bead for use at an internal corner and parts corresponding to those in Figure 1 are given the same reference numerals.

[0011] One consequential difference is that the flanges 5 of the plastics moulding 4 are at right angles to one another and one of the flanges forms a continuation of an arm of the U-section 6.

[0012] In use, the bead is fixed to the substrate by nails or plaster dabs passing through holes in the inner portions of the wings 8 and two areas of plaster or mortar rendering 10 are applied to the substrate 3, encapsulating and being keyed to the expanded portions 9 of the wings 8. The front faces of the flanges 5 are then substantially flush with the front surface of the rendering.

[0013] In accordance with the invention, the free ends of the arms of the U-section 6 are interconnected by an integral strip 11, which is thinned to form lines of weakness 12 at each edge where it is connected to the arms of the U-section.

[0014] The purpose of the strip 11 is to maintain a required distance between the free ends of the arms of the U-section 6 during fixing of the bead to the substrate and rendering, whereafter the strip is torn out, as shown in Figure 3, to the leave the arms of the U-section free to move towards and away from one another and provide the desired movement at the joint.

Claims

1. A plaster bead for an expansion joint between two adjacent areas of rendering (10) on a substrate (3), the bead being arranged to be fixed to the substrate (3) and comprising a flexible U-section (6) the free ends of the arms of which U are connected to substantially rigid flanges (5), which, in use, are substantially flush with the respective faces of the areas of rendering (10), the flanges (5) being connected to respective wings (8) of perforate material which are arranged to be embedded in, and keyed to, the rendering (10); characterised by a removable strip (11) extending between the free ends of the arms of the U-section (6), and connected to the arms by lines of weakness (12) along the edges of strip (11).

2. A plaster bead according to claim 1, wherein the wings (8) are metal.

3. A plaster bead according to claim 2, wherein the wings (8) are expanded metal.

4. A plaster bead according to claim 2 or claim 3, wherein the U-section (6), flanges (5) and removable strip (11) are an integral plastics moulding and the wings (8) have folded ends which are embedded in the flanges.

5. A plaster bead according to any one of the preceding claims for use at a concave corner, wherein one of the flanges (5) is substantially a continuation of one of the arms of the U-section (6).

Drawing