GB2158479A - Adhering mortar or plaster to a wall - Google Patents

Abstract

Mortar retainer 50 comprises a rigid horizontal support 52 providing a shelf for the mortar or plaster above it. The support is anchored to the wall and the mortar or plaster is keyed to the shelf, preferably the mortar retainer 50 is moulded in plastics material, and has a vertical rib or flange 54. In the figures, the end of a cavity wall 10, 14, 12 adjacent to a window frame 16 is shown 18 is an extruded cavity closer, and 30 is a tie. <IMAGE>

Description

SPECIFICATION Improvements in building construction In the construction of buildings, vertical walls are frequently rendered with mortar and/or plaster.

Throughoutthis specification the word "mortar" is used in a broad sense to cover any mortar-like substance, including cement mixtures, mortar and plaster. Where the wall itself is made of bricks or cement bound building blocks, there is generally no difficulty in adhering the mortarto the wall. However, modern building constructions employ features made of metal, timber and plastics, and it is difficult if not impossible to cause mortartoadheretothesurfaces ofthese materials, so that mortar rendering is difficult and in some cases regarded as being impossible.

According to this invention a building construction in which a vertical column of mortar or plaster is applied to a wall, is provided with a mortar retainer comprising a rigid support extending substantially horizontally across the column and providing a shelf forthe mortar or plaster above it, the rigid support being anchored to the wall and having a retaining formation whereby the mortar or plaster is keyed to theshelfJorming part of the support.

Preferably at least one vertical rib orflange is formed on the supportto act as a mortar retainer. In one construction, the support has a horizontal web which providesthe shelf, and a vertical flange which provides a mortar retainer.

According to another preferred feature, one or more holes is or are formed through the part ofthe mortar retainerwhich extends acrossthe column, so that mortarcan flow into the hole(s) to provide a mortar key or keys.

According to another preferred feature ofthe invention,there are interengaging formations on the wall and the mortar retainerfor anchoring the mortar retainertothewall,theformation on the wall extending substantiallythroughoutthe heightofthe wall, whereby a mortar retainer can be located at any height on the wall. Preferablytheformation on the wall comprises an undercut recess, and the formation on the mortar retainer comprises a projection adapted to fit in the recess. In one construction, the recess in the wall is of dovetail-shaped horizontal cross-section and the projection on the mortar retainer is of a corresponding dovetail shape.

ltisfurtherpreferredthatthe mortar retainer has an enlarged head which fits into mortar between two horizontal courses of a wall to tie the retainerto the wall.

The mortar retainer may be moulded in plastics material.

Other preferredfeatures of the invention will become apparentfrom the following description of a part of a building, given by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a horizontal cross-section through the end of a cavity wall adjacentto a window openi ng, showing a stile ofthewindow, and Figure 2 is a view looking in the direction of arrow II in Figure 1, but with a mortar basecoatomittedfor clarity.

In Figure 1,there is illustrated part of a structural assembly, which occurs atthe end of a cavity wall, adjacent to an opening for a window frame. The cavity wall has an outer leaf 10 and an inner leaf 12, with a cavity 14 between them. In this particulars construction, it is assumed that both the outer leaf 10 and the inner leaf 12 are built up from blocks secured together by builders' mortar, and in a typical construction, the outer leaf 10 would be made of breeze blocks. It is to be understood however, that alternative constructions such as are now used in the building of cavity walls could be employed.For instance, the inner leaf could be constructed as a timberframe with plaster covering, although for the purposes ofthis invention, it would be necessaryto provide horizontal courses in thatframe, as will hereinafter appear. In the particular construction which is being described, it is assumed that the cavity between the two leaves is 75 millimetres in width, although the invention can be employed with narrower cavities.

One jamb 16 of a timberwindowframe is illustrated, and it will be noted thatthis is disposed closely adjacent to the end of the outer leaf 10 of the cavity wall. There are alternative positions forthe window frame in relation to the thickness of the cavity wall, but buildersfrequentlyprefertofittheframein the outside leaf of the wall, in the position illustrated in Figure 1. The present invention is intended to locate the window frame in this position.

It will be appreciated that it is always necessary to close the end of the cavity 14 at each opening in the wall for a window o r door frame. Traditionally, this was done by laying three-quarter bricks and quarter bricks acrossthe end ofthe cavity, and using a flat strip of conventional damp-proofcourse material arranged vertically between the outer leaf ofthe wall, and the parts ofthethree-quarter bricks and quarter bricks closing the end of the cavity. This traditional construction is illustrated in Figures 1 and 2 of United Kingdom Patent Specification No: 1 302 694. There are various disadvantages in this traditional construction, not least being that it is time consuming and expensive to roduce.Forthis reason, plastics cavity closers have been devised, as described for example in the specifications of United Kingdom Patents Nos: 1302 694; 1 302695 and 1 302 696. Such a plastics cavity closer can be manufactured economically, by an extrusion process, which means that its cross-section is constantthroughout its length.Providing it is correctly constructed and fitted, a plastics cavity closer can close the end ofthe cavity; provide a damp-proofcourse between the two leaves of the cavity wall (traditionally provided bythe flat strip of damp-proof course material); provide a damp-proof course between the end ofthe cavity wall and the door orwindowframe (not provided by the traditional method) and tie the two leaves of the wall together adjacent to the window or doorframe opening (a The claims were filed later than the filing date within the period prescribed by Rule 25(1) of the Patents Rules 1982.

feature not provided bythetraditional method).

Stringentfire regulations in some countries now require that there shall be a layer of mortar (in the general sense previously mentioned) extending acrossthe end of the cavity. There is no provision for such a layerofmortarwhen using a cavity closer ofthe kindillustratedforexamplein United Kingdom Patent Specification 1302694. The present invention has been made, largely in responsetothe requirementfor the provision of such a fire resistant mortar layer. It must be apparent however, thatthere are problems in attempting to provide such a fire resistant mortar layer, when using a plastics cavity closer, because mortarwill notnormallyadhereto a plastics surface.

In seeking to solve this problem however, the invention has also provided a structural assembly, and a method of providing such an assembly, which is superiorin several respects, to known structural assemblies incorporating plastics cavity closers.

Reverting to Figure 1, an extruded plastics cavity closer 18 is employed. Essentially, this closer comprisyes an outerpart2O,aninnerpart22,andastep24 joining the parts 20 and 22, so that the inner part 22 is offset rearwardlyfrom the outer part 20, by the width of the step 24.As illustrated in Figure 1 the outer part 20 is intended to be sandwiched between the end of the outer leaf 10 of the cavity wall and the jamb 16 of the windowframe, and in use, it abuts againstthe end ofthe outer leaf 1 0.The step 24 abuts againstthe insideface ofthe outer leaf 24, and the corner between the outer part 20 and the step 24 ofthe cavity closer strip 18 provides a location forthe cavity closer 18 on theouterleafofthecavitywall. Furthermore, because oftheoffsetting of the inner part 22 with respectto the outer part 20,when the strip 18 is fitted to the end of a cavitywall,the innerpart22 is set back into the end of the cavity 14, and provides a reveal on the inside ofthe outer leaf 10.

The inner part22 ofthe cavity closer strip 18 is of the same width as the nominal cavitywidth, so thatthe inside leaf 12 ofthe cavitywall can abutagainstthe inner end ofthe inner part 22. However, if closer 18 is to be used with a narrower cavity, then it is only necessaryto cut off part of the inner part 22, to ensure thattheremaining inner part is of the same width as the cavity in which the inner part isto fit Indeed, a line of cut may be pre-marked on the inner part22,fora 50 millimetres wide cavity.

The outer part20 ofthe cavity closer strip is formed with a dovetail-shaped forward protrusion 26, but the thickness ofthe outer part20 is constant, so that a dovetail-shaped recess 28 is provided in the rear face of the outer part 20. This recess is intended to accommodate the root of a plastics wall tie 30, which is of a known kind, developed for use with extruded plastics cavity closers. Briefly, the wall tie 30 is a moulded flat member, having an enlarged head 32 through which there is formed a substantiallytriangular hole 34, and a root portion 36 which is generally dovetail-shaped forfitting into a dovetail-shaped recess such asthatformed at28 in the cavity closer strip 18, butwieh a notch 38 which will alowsome slight deformation of the parts ofthe root on each side of the notch.Such a tie can be fitted into a recess 28, by firstfiltingabouta longitudinal axisofthetie30, until dovetail-shaped root 36 can be pushed through the open narrow rear opening ofthe recess 28, and then turning the tie about its longitudinal axis until its top and bottom faces are in planes at rightangles to the rearfaceofthe outer part20, so thatthe root 36 becomes interengaged with the dovetail-shaped recess 28.In practice, the root36 is made slightly larger than the recess, so thatthere is some slight compression ofthetwo parts of the root towards each other, thereby ensuring that the tie isfirmly anchored in the recess. Itwill be appreciated,thatwhen this tie is fitted between two courses of the outer leaf 10 of the wall, mortar is able to flowthrough the opening 34, and that mortaronthefrontsideoftheenlargedportion 32 togetherwith that extending through the opening 34, keysthetie to the outer leaf, and prevents it being pulled in a longitudinal direction out the end of the leaf.The arrangement of the wall tie 30 and the undercut recess 28 provides a means whereby the outer part 20 of the cavity closer strip 18 can be firmly secured to the outside leaf 10. Furthermore, itwill be appreciated that since the undercut recess 28 extends throughoutthe length ofthe strip 18, it is possible to fit the ties 30 as and where they are required, in orderthat they match up to the mortarbetweenthe courses of bricksforming the outside leaf.Also, mortar is inevitablysqueezed outfrom between the courses as the end bricks are laid, and some ofthiswill engage in the undercut recess 28 between the ties 30, and when this mortar in the recess 28 sets, it forms another key securing the strip 18 to the outer leaf. Indeed, it might be possible to dispense with the wall ties 30, and rely simply on the engagement of the mortar in the recess 28 as a means of securing the outer part 20 of the cavityclosertothe outer leaf 10 of the cavitywall.

Lips 40 and 42 are formed on the longitudinal edges ofthe outer part 20, and in fact the lip 42 forms an extension of the step 24. These lips 40 and 42 project from thefrontface ofthe part 20 bythe same depth as the projection 26. Hence, when the frontface ofthe outerpart20 is butted up againstthe outside face of the jamb 16, contact is established between the jamb 16 and the outer part 20 atthree positions across the width ofthe outer part, namely atthe lip 40, at the projection 26 and at the lip 42.

Another lip 44 projects inwardly of the step 24, and formsashortcontinuation of the outer part 20. The purpose of this lip will appear hereinafter. In addition a dovetail-shaped formation 46 is provided on the inner part 22 of the cavity closer strip 18, this formation 46 being similarto the dovetail formation 26 on the outer part, excepting that it faces in the opposite direction, and provides an undercut recess 48 open on thefront face ofthe inner part 22.

Aspecial innertie or mortar retainer50 is provided, and takestheform of a plastics injection moulding.

The retainer 50 has a flat web portion 52, which takes the form of a straight rectangularstrip, and a flange 54, disposed at rightanglestothe web 52, but extending along a length of the web 52, which is approximately equivalentto the length of the reveal formed between the inside of the step 24, and the outside ofthe inner leaf 12, when the cavity closer strip 18 is fitted in position. As illustrated in Figure 2, the flange 54 extends both above and belowtheweb 52.

A dovetail-shaped "root" 56 is formed on the rear edge of the retainer 50, and this root 56 is similar to the root 36 formed on one ofthe wall ties 30 previously described. Its location on the web 52 is such, that it engages in the dovetail-shaped recess 48 ofthe inner part 22 ofthe cavity closer, when the outer end of the retainer is engaging with the innerface of the step 24.

When in this position, the flange 54 extends across substantially the full width of the cavity 14 (see also Figure 2) but part ofthe retainer 50 extends inwardly ofthe cavity, and has to be fitted between two courses of the inner leaf 12 of the cavity wall. A series of circular holes 58 is formed through the web 52 ofthe retainer 50, and it will be noted that some of these holes 58 are in the part ofthe web which lies across the cavity, and the others are in the part oftheweb which extends into the inner leaf 12.

In ordertofitoneofthe retainers 50 to the cavity closer 18, it is first necessary to tilt the retainer about a transverse axis, until the root 56 can be pushed through the narrow opening of the undercut recess 48, and then the retaineristurned backto a horizontal orientation, in which the root 56 engages tightly in the recess 48, in the same way as described above with relation to the wall tie 30. Since the groove 48 extends throughoutthe length of the cavity closer 18, it will be appreciated that it is possible to fit the special mortar retainers 50 to any desired position along the length of the cavity closer. Referring to Figure 2, an arrange ment is shown, in which the special retainers 50 are fitted at everythird horizontal joint ofthe inner leaf 12.

It will also be appreciated, that mortar in the horizontal joints ofthe inner leaf, flows through the holes 58 which are in the inner leaf, and this provides a very strong means of securing the retainer 50 to the inner leaf 12.

It is now possible to describe the method of constructing the cavity wall adjacent to the window frame opening, and building in the windowframe.

When the wall has reached the level ofthe sill, a section of the extruded cavity closer 18 equal to the depth of the window frame is cut from the supply. (It should be mentioned, that it is possibletosupplythe cavity closer strip in quite long lengths, so that the builder can cut itto required shorter lengths on site.) The outer part 20 of the cut length of cavity closer strip isthen butted against the outerface ofthejamb 16 as illustrated in Figure 1, and the strip is secured to the timberframe 16 by nails or screws.It will be understood of course, that it is possible to drive the nails or screws through the plastics strip, and this provides a quite adequate method offastening the strip to the timberframe. The first course of bricks in the outside leaf 10 is then laid, and the windowframe can then be offered up to the outer leaf of the cavity wall, with the rearface of the outer part 20 abutting the end ofthis first course of the outer leaf in line with the window opening. Also, the step 24 is butted against the innerface of the outer leaf 10, so thatthewindow is properly located relatively to the opening.Itwill of course be understood, that a similar cavity closer strip will be nailed or screwed to the other jamb ofthe window, and will be similarly located relatively to the first course of the outer leaf on that side of the window epeoing Atie 30 is fitted as previously described, and laid on the first course ofthe outer leaf 10, so that it will become embedded in the mortar laid on top ofthat course.It is then possible to start building up the inner leaf 12, with thefirst course abutting the inner end of the inner part 22 of the cavity closer-that part thereby establishing the width of the cavity at the end ofthe wall - and as soon as one course of bricks has been laid in the inner leaf 12, one ofthe special mortar retainers 50 can be fitted as previously described, so that part ofthe retainer is laid on top of the first course ofthe inside leaf. This partwill become embedded in the mortar laid on top of the first course of the inner leaf, in orderto anchorthe retainer Soto the inner leaf.

It is then possible to build up both outer and inner leaves of the wall, but at intervals, ties 30 and retainers 50 will be fitted. When the wall has been built upto the full height ofthe window opening, the end of the cavity at the opening will be bridged by the inner part 22 of the cavity closer. The dovetail-shaped projection 46 on the inner part 22 provides a moisture barrierto prevent water migrating from the inside face of the outer leaf 10,to the inner leaf of the wall. Another advantage of the construction is that the two leaves of the wall are tied togetheratthe end ofthewall, whereas in the traditional method of closing the cavity at this point, it is not possible to tiethetwo leaves together.The outer leaf 10 is tied to the cavity closer by the mortar in the recess 28 and the ties 30, and the inner leaf 12 is tied to the closer bythe mortar passing through the holes 58 in the retainers 50, and the anchoring of those retainers in the recess 48.

When the wall has been built up, a rendered base coat 60 of mortar or rough plaster is applied in the reveal formed bythe step 24 andthe inner part 22 of the closer. This base coat fills the reveal, and the lip 44 provides a trowel line forthe plasterer applying the base coat. A scrim 62 is then applied over the exposed front face ofthe base coat 60 and the front faces of the flanges 54, some of this scrim 62 extending over the end of the inside leaf 1 2 of the wall. Finally, plaster is applied overthescrim 64 in the conventional manner.

If required, a timber quadrant 66 can befitted in the corner between the plaster 64 on the inside of the window opening, andthewindowframe itself.

Apartfrom providing the advantages previously mentioned, the construction also provides a mortar base coat 60, across the end of the cavity 14 of substantial thickness. In a practical instance, the thickness may be 19 millimetres. This in effect provides a barrier against flames entering the cavity at the window opening.

An importantfeatureofthearrangementdescribed above, is the provision for supporting the vertical column of rendered base coat 60. If a plastics cavity closerisfitted across the cavity, it is not possibleto apply a base coat of mortar, plaster or the like to the front face of the cavity bridging part of the closer, because the mortar will not adhere to the plastics surface. However, by providing the undercut recess 48 in the inner part 22 of the cavity closer, and by providing the special mortar retainers 50, it is ensured that the column of mortarwill remain in place.

Obviously, some of this column of mortar becomes keyed into the dovetail-shaped recess 48, but in addition, shelves are provided at each position where there is one of the retainers 50, to support the section ofthevertical column above each shelf, and below the next higher shelf. Furthermore, the flanges 54 on the retainers 50 help to retain the column of mortar in the reveal formed by the innerpart22, and incidentally, the frontfaces oftheseflanges 54 provide a guide for the plasterer applying the base coat. The ties 30 and mortar retainers 50 may be moulded in polyethylene, although they could also be moulded in other plastics materials such as nylon.

Claims (16)

1. A building construction in which a vertical columnofmortarorplasterisappliedtoawall, provided with a mortar retainer comprising a rigid support extending substantially horizontally across the column and providing a shelfforthe mortar or plaster above it, the rigid support being anchored to the wall and having a retaining formation whereby the mortar or plaster is keyed to the shelf-forming part.

2. A building construction as claimed in Claim 1, in which at least one substantially vertical rib orflange is formed on the rigid supportto act as a retaining formation.

3. A building construction as claimed in Claim 1 or Claim 2, in which one or more holes is or are formed through the parts ofthe mortar retainer which extends across the column, so that mortar can flow into the hole(s) to provide a mortar key or keys.

4. A building construction as claimed in any one of Claims 1 to 3, in which there are interengaging formations on the wall and the mortar retainerfor anchoring the mortar retainer to the wall,the formation on the wall extending substantially throughout the height ofthe wall, whereby the mortar retainer can be located atany heighton thewall.

5. A building construction as claimed in Claim 4, in whichtheformation on the wall comprises an undercut recess, and the formation on the mortar retainer comprises a projection adapted to fit in the recess.

6. A building construction as claimed in Claim 5, in which the recess in the wall is of dovetail-shaped horizontal cross-section and the projection on the mortar retainer is of a corresponding dovetail shape.

7. A building construction as claimed in any one of Claims 4 to 6, in which the formation on the wall is formed on an extruded element which is itself anchored to the wall.

8. A building construction as claimed in Claim 7, in which the extruded element is a cavity closerwhich itself has a part extending across a cavity in the wall, the vertical column of mortar covering this part of the closer and itself extending across the width of the cavity.

9. Amortarretainerforsupporting avertical column of mortar or plaster in a building construction, comprising a rigid support on which the column of mortarcanstand,a retainerformationforretaining the column of mortar on the rigid support and means for anchoring the mortar retainerto a wall.

10. A mortar retainer as claimed in Claim 9, in which at least one vertical rib orflange is formed on the rigid supportto provide the retaining formation.

1%. A mortar retainer as claimed Claim lOin which the rigid support comprises a horizontal web which provides a shelf forthe column of mortar.

12. A mortar retainer as claimed in any one of Claims9to 11, in which one or more holes is orare formed through the rigid support, so that mortar can flow into the hole(s) to provide a mortar key or keys.

13. A mortar retainer as claimed in any one of Claims 9 to 12, which is provided with an extension which is adapted to fit into mortar between two horizontal courses of a wall, to tie the retainer to the wall.

14. A mortar retainer as claimed in any one of Claims 9to 13, which is moulded in plastics material.

15. A building construction in which a vertical column of mortar or plaster is applied to a wall, substantially as herein described, with reference to the accompanying drawings.

16. Amortarretainerforsupporting a vertical column of mortar or plaster in a building construction, constructed and arranged substantially as herein described with reference to the accompanying drawings.