GB2168774A

GB2168774A - A masking plate for pipes

Info

Publication number: GB2168774A
Application number: GB08432007A
Authority: GB
Inventors: George Molyneux
Original assignee: G Molyneux
Current assignee: G Molyneux
Priority date: 1984-12-19
Filing date: 1984-12-19
Publication date: 1986-06-25
Also published as: GB8432007D0; GB2168774B

Abstract

The invention provides a building construction in which there is a pipe passing through a wall with a clearance all round the pipe, to allow for differential settlement of the pipework and the wall, and a masking plate surrounding the pipe and preventing rodents passing through the space between the wall and the pipe. The masking plate comprises at least two sections each of which subtends only part of the perimeter of the pipe, the masking plate fitting in engagement with or closely adjacent to one face of the wall and substantially closing one side of the clearance left between the opening in the wall and the perimeter of the pipe. Because the masking plate is constructed in two sections, it is possible to fit it around the pipe after the pipework is finished. The plate sections may be held together by wire wrapped around lugs 52,54 or by inter-engaging saw-tooth configurations (Figs 6,7 not shown). <IMAGE>

Description

SPECIFICATION Improvements in or relating to pipework for building construction and a masking plate for use therein.

In building construction there is a problem wherever a pipe passes through a wall below ground level, caused by differential settlement of the pipework in the ground and the wall itself. If the pipe section which passes through the wall is cemented into the wall, then that section has to move with the wall, and settlement of the wall can in some cases cause fracture of the pipework.

One method of dealing with this problem is to leave a pipe opening in the wall - sometimes protected by a lintel - through which the pipe passes, the dimensions of the opening being such that there is a substantial clearance all round the pipe section which actually passes through the wall.

Settlement of the wall does not then apply any stress on the pipework. However, regulations require any such opening to be closed, particularly to prevent rodents entering the building (or the cavity if the wall is a cavity wall).

It is the object of the invention to provide a pipework unit, a structural assembly and a masking plate which enable the problem of differential settlement to be overcome relatively cheaply and without the use of skilled labour.

Another object of the invention is to provide a masking plate for use in a structural assembly for closing an opening in a wall around a pipe length, and which can be fitted on to the pipe length after the pipework has been installed.

According to one aspect of the invention a pipework unit for use in building construction comprises a pipe length to which there is attached a masking plate which completely surrounds and fits around the pipe length, and projects outwardly from the pipe length in all radial directions, the masking plate comprising at least two sections each of which subtends only part of the perimeter of the pipe length, so that the masking plate can be assembled on the pipe length without threading the plate over one end of the pipe length.

Preferably each masking plate section is formed with a cut-away wherein the pipe section is received, and the masking plate sections have interengaging means whereby they are securely attached to each other in the assembled condition.

It is further preferred that the masking plate sections are identical with each other and in the preferred construction each masking plate section is made of material which is water -resistant. A suitable material is polyvinylchloride of the grade used for instance in the manufacture of gutterings and fallpipes for buildings.

It is further preferred that the masking plate sections are such that they can be adjusted with respect to each other, whilst maintaining their interengagement, to vary the shape and/or size of the hole formed between them for the accommodation of the pipe section. The masking plate used in this aspect of the invention may have any of the feature of the masking plate described as the second aspect of the invention.

The invention permits the use of an opening in a wall large enough to leave an appreciable clearance all round the pipe section which actually passes through the wall, so that no stresses are applied to the pipework from the wall due to differential settlement between the pipework and the wall. Further, the clearance between the wall and the pipe section is completely closed by the masking plate to prevent rodents passing into or through the wall. Because the masking plate is fitted on to the pipe section radially rather than by threading it over one end, the hole in the masking plate can be a close fit around the pipe section (which is essential to prevent small rodents entering between the plate and the pipe) even though the pipe section has enlarged ends - sockets - as it almost certainly will have.Another advantage of the assembly is that the masking plate can be fitted on to the pipe section after the pipework has been completed and just before filling the excavation in the vicnity of the opening through which the pipe passes.

Moreover, as will become clear hereinafter, the shape of the hole in the masking plate can be varied to fit closely around the pipe section at the position where that section emerges from the wall, since a planar section through the pipe at that position and parallel with the face of the wall is not always circular.

According to a preferred feature of this aspect of the invention the masking plate comprises two sections each of which has a cut-away opening into one edge, so that it has two legs bifurcated by the cut-away, and the legs of the two plate sections are interengaged by engaging one leg of each section with a first face of the other section and the other leg with the opposite face of the other section.

According to a second aspect of the invention a masking plate section for use in masking an opening around a pipe length passing through a wall, comprises a plate having a cut-away opening on one edge of the plate, to receive part of the pipe section by fitting radially on to the pipe section and means on the plate section for interengagement with a similar plate section when the latter has been engaged on the pipe section, so that two or more plate sections when assembled on the pipe section and interengaged with each other, form a mask projecting in all radial directions from the pipe section.

Preferably the cut-away has a substantially semi -circular inner end but extends outwardly from the diameter of the semi-circular portion, so that there are two legs one on each side of the cut-away. In the preferred construction the length of these legs outwardly of the diameter of the semi-circular portion of the cut-away is greater than the length of the said diameter. Thus, when two such plate sections are placed face-to-face with their legs overlapping an effective hole (closed all round its periphery) is formed through the two plates. In the fully contracted relationship of the two plate sec tions (i.e. maximum overlap) the effective hole is circular. In practice the fully contracted relationship is that when the masking plate is fitted on to a part of the pipe section which is circular in the planar cross-section at the location of masking plate.For a Partially extended relationship of the two plate sections (i.e. any partial overlap) the effective hole is nearly eliptical, up to the stage where the extension is so great that the effective hole is palpably a hole with semi -circular ends and straight parallel sides.

In practice, the overlap is achieved by engaging one leg of one plate section with one face of a leg of the other plate section and engaging the other leg of the one plate section with the opposite face of the other plate section. A further preferred feature of this aspect of the invention is the provision of retaining means along or adjacent to one outer edge of each plate section, each retaining means being adapted to hold the edge of the other section which is not provided with retaining means, flat against the face of the plate section in the region of the retaining means. If such retaining means are provided on both the plate sections, then in the assembled condition, the two legs of a plate section lie respectively flat against opposite faces of the other plate section.This is achieved by slight bending of each plate section so that in lateral cross-section, it is a very shallow S-shape.

This method of assembling the two sections of the masking plate provides a simple and effective plate-like structure whioh is relatively stable because of the considerable friction between the interengaged parts of the two sections.

In the preferred construction the retaining means comprises a channel formation, one flange of which is formed by the main planar portion of the plate section, open on the inside (i.e. facing towards the opposite edge of the section) to receive the edge of the mating masking plate section.

It is also preferred to provide releaseable means for securing the two plate sections together in the assembled condition. Such means may comprise simple arrangements such as lugs on both sections disposed so that in the assembled condition it is possible to wrap a wire around one lug on each of the two sections, or holes in both sections which can be aligned to permit a securing pin to be passed through both sections. However, the preferred construction comprises a series of indentations in one face of each plate section and a projection on the mating face of the other plate section so that the projection will engage in one of the series of indentations in the assembled condition of the plate sections. Preferably the projection is in the form of a tooth adjacent to the extremity of one of the legs.It is further preferred that the indentations are of saw-tooth form so that they permit easy sliding of the projection over the indentations in the contracting (i.e. assembly) direction, but offer appreciable resistance to movement between the two sections in the opposite direction.

According to a third aspect of the invention a structural assembly comprises a wall; a pipe length passing through the wall, there being an opening in the wall through which the pipe length passes with a substantial clearance between the outside of the pipe length and the edges of the opening, and a masking plate comprising at least two sections each of which subtends only part of the perimeter of the pipe length, the masking plate fitting in engagement with or closely adjacent to one face of the wall and substantially closing one side of the clearance left between the opening in the wall and the perimeter of the pipe.

Preferably the arrangement of the masking plate is such that the closure of the clearance effected by the masking plate will prevent rodents entering the clearance.

It will be appreciated that a pipework unit in accordance with the first aspect of the invention can be used in the structural assembly of the third aspect of the invention. It will further be appreciated that a masking plate in accordance with the second of the invention can also be used in the third aspect of the invention.

A structural assembly involving a drain pipe passing through the wall of a building and exemplifying all three aspects of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a vertical section through part of a wall showing a drain pipe passing through the wall, Figure 2 is a plan view of a masking plate section, Figure 3 is an end view of the masking plate section looking in the direction of arrow III in Figure 2, Figure 4 is a plan view of an assembled masking plate comprising two plate sections as shown in Figures 2 and 3, Figure 5 is a horizontal section through a wall illustrating a drain pipe passing through the wall at an acute angle, Figure 5A is a detail view of a masking plate as used on the inside of the wall illustrated in Figure 5, Figure 5B is a plan view of a masking plate as used on the outside of the wall illustrated in Figure 5, Figure 6 is a plan view of a masking plate section showing an alternative construction for securing two such sections together, and Figure 7 is a detail exploded view partly in section, showing co-operating parts of two masking plates in accordance with Figure 6.

Referring to Figure 1, there is illustrated part of a cavity wall 10 of a building, the wall being supported on footings 12 in the conventional manner.

The footings and the lower portion of the cavity wall 10 are embedded in the ground, and a drain pipe 14 is shown which leads from the outlet of a water closet (not shown) inside the building to a sewer (not shown) outside the building. Hence, part of the pipe has to pass through the cavity wall 10, and in the arrangement illustrated in Figure 1, there is an elbow pipe section 16 connected to a vertical portion of the pipework inside the building, and to a straight and slightly downwardly inclined portion 18 on the outside of the building. An open ing 20 is formed in the building of the cavity wall 10 to allow for the passage of the drain pipe through the wall, and it will be noted that the opening 20 is of such dimensions, that it leaves a substantial clearance all round the part of the pipework which passes through the wall.In fact, this clearance is preferably a minimum of 50 millimetres. The topside of the opening 20 may be protected by a lintel, although it is sufficient to construct a flat arch from brickwork over the top of the opening 20.

Since the vertical part of the pipework inside the building is usually fitted quite close to the wall itself, a major part of the elbow section 16 is in fact located within the opening 20. As a result, a planar section through the elbow at the position corresponding to the internal face of the cavity wall 10, will be eliptical rather than circular, with the major diameter of the elipse in a vertical orientation. In contrast to this, where the pipe section 18 emerges from the cavity wall, a planar cross-section through that pipe section in the plane of the outer face of the wall 10 will be very nearly a truly circular.

As illustrated in Figure 1, the ground inside the cavity wall 10 is covered by a cement and aggregate floor 22, so that a part of the vertical section of the pipework 14 on the inside of the building is embedded within the flooring 22. That part of the elbow section 16 which is on the inside of the building is embedded within the earthwork of the building foundations.

It will be appreciated that there may well be differential settlement between the cavity wall 10 and its footing 12, on the one hand, and the pipework 14, 16 and 18 on the other hand. However, in the construction illustrated in Figure 1, this will not cause any stress to be applied to the pipework from the wall, because of the substantial clearance between the edges of the opening 20 and the outside of the pipework where the pipework passes through the opening 20. However, it is a requirement that where such a clearance is formed during the building construction, precautions shall be taken to ensure that rodents cannot enter the opening 20, in order to prevent rodents getting into the cavity of the wall itself.For this purpose, the present invention utilises masking plates 24 and 26, which are fitted around the pipework where the latter passes through the cavity wall, each masking plate engaging with a respective inner or outer face of the wall, and completely blanking off the respective end of the opening 20 on the inside or outside of the wall. Whilst the detailed construction of the blanking plates 24 and 26 forms a significant feature of this invention and will be hereinafter described, it should be noted at this juncture, that the two masking plates are attached to the pipework, but are not fixed to the cavity wall itself. Hence, it is possible for the wall to move due to settlement for example, relatively to the masking plates, and again therefore, the presence of the masking plates will not transmit stress from the wall to the pipework.

There are of course certain problems associated with the fitting of masking plates such as those illustrated at 24 and 26 in Figure 1. To begin with, the masking plates themselves must be resistant to moisture and weak acids which could well be present in the earth and/or foundations adjacent to the wall 10. Almost the only satisfactory metal which could be employed is copper, and this is very expensive. Another problem arises out of the necessity to thread the masking plates over the ends of the pipework sections. In the first place, this means that the masking plates must be fitted before the pipework is completed, and if the pipework is connected up before the masking plates are fitted, then there is a likelihood that they will be omitted altogether, because the alternative would involve dismantling the pipework which has been assembled.Moreover, it will be appreciated that it is difficult if not impossible to fit the masking plates closely around the pipes. For instance, in the case of the masking plate 24, in the construction illustrated in Figure 1, the hole through the masking plate would have to be cut to an eliptical shape.

Moreover the hole would have to be large enough for the masking plate to be threaded over one end of the elbow 16. The inside end of the elbow has a socket and therefore the hole in the plate 24 has to be large enough to allow the plate to be threaded over the socket. With such a large hole the masking plate cannot be a close fit around the pipe at the correct location in engagement with the internal face of the wall. The likelihood is therefore, that if masking plates are employed, the holes formed in them for the accommodation of the pipework will have to be considerably larger than the pipework itself, and hence small rodents will be able to find a passage between the masking plate and the outside of the pipe.

Turning now to Figures 2, 3 and 4, there is illustrated a masking plate in accordance with the second aspect of the present invention, which can be used to solve the problems outlined above. This masking plate is made of two identical plate sections 30 and 32 each of which is made as a moulding in polyvinylchloride of a grade similar to that used for gutters and fallpipes. Moreover, as is apparent from Figure 3, each plate section 30 or 32 is generally in the form of a thin plate of substantially square shape, although it will be observed that the corner 34 is somewhat chamfered and curved for a purpose which will appear. Centrally, the plate section 30 is formed with a large cut-away 36 which at the inner end has a semi-circular portion 38 and straight sided portions 40 and 42 extending from the semi-circular portion, so that the cut-away 36 is open at one end of the plate 30. Since the length of the straight-sided portions 40 and 42 is greater than the diameter of the semi-circular portion 38, there are formed two legs 44 and 46 of substantially equal width, one on each side of the cutaway 36 and a circular "hole" formed by the semicircular portion 38 and by an imaginary semi-circular continuation of that portion would occupy a space substantially in the centre of the square plate.

Along the edge 48 of the plate, that is the edge parallel to the straight sides 40 and 42 of the cut away 36, but opposite to the edge which has the chamfer 34, there is a longitudinally extending channel 50 (see Figure 3) the internal depth of which is approximately the same as the thickness of the plate 30. Finally, the plate section 30 is formed with two upstanding L-shaped lugs 52 and 54, the first of these being located near to the edge of the plate opposite to that into which the cutaway opens, and the second being provided near to the edge into which the cut-away opens. Both of the lugs 52 and 54 point outwardly, that is to say they are open on the side which faces outwardly from the plate.

The manner in which two plate sections 30 and 32 are assembled will now be described with reference to Figure 4, although in practice, the, plate sections will not be assembled until the pipework through the cavity wall has been completed.

Supposing that the plate section 30 is held stationary, then the leg 44 of the plate section 32 is engaged with the top surface of the plate section 30, and the leg 46 of the plate section 32 is engaged under the plate section 30. Initially, this is achieved by tilting the plate section 30, so that the distal end of the leg 44 just engages over the top of the distal end of the leg 46 on the plate section 30 and the chamfered corner 34 of the leg 44 on the plate section 32 is engaged in the end of the channel 50 on the plate section 32. It will be appreciated that the chamfer 34 assists in engaging the edge of the leg 44 of the section 32 in the channel 50 of the section 30.At the same time, by tilting the plate section 32, the distal end of the leg 46 can be engaged under the leg 44 of the plate section 30, and the channel 50 on the plate section 32 can be engaged with the chamfered end 34 of the leg 44 on the plate section 30. Thereafter, the plate section 32 can be slid upwardly as seen in Figure 4, relatively to the plate section 30, progressively engaging each of the legs 44 in the respective channel 50. As a result, the two plates are held close to each other, and in fact in the region of each channel 50, the leg which is threaded into that channel will be held flat against the leg which carries the channel. Hence, the overall thickness of the assembled plate is only slightly greater than double the thickness of the individual plate sections.

If the two plate sections are pushed together as far as possible, then the position shown in Figure 4 is arrived at, wherein the effective hole 52 formed through the assembled plate is circular, and this hole is constituted by two semi-circular portions 38 of the two plate sections and is of approximately the same diameter as the outside diameter of the drainpipe 18. It will be appreciated, that if the two plate sections are not pushed into the fully contracted position, or are expanded from the fully contracted position, then the effective hole 52 will be either eliptical, or a hole with straight sides, formed by the straight sides 40 and 42 on the plate sections, and semi-circular ends formed by the semi -circular portions 38 on the individual plate sections.

In order to fit the plate 26, the two plate sections are brought together around the pipe 18 after the latter has been fitted, in other words, the two plate sections are moved together radially with respect to the pipe over which they engage, rather than being threaded over the end of that pipe. Hence, the construction of the masking plate 26 from two plate sections 30 and 32 can be achieved after the pipework has been completed, and indeed can be done as a last step before infilling the excavation adjacent to the opening 20 in the wall. The two plate sections are pressed together until they engage on the outside of the pipe 18.Since at the position where the masking plate is fitted, in engagement with the outer face of the cavity wall 10, the planar cross-section through the pipe 18 parallel with the face of the cavity wall is substantially circular, the two plate sections will in fact be moved into their fully contracted condition illustrated in Figure 4. In that condition, they fit very closely around the pipe 18, and the entire masking plate 26 is large enough to close the outer end of the opening 20 as required in order to prevent the entry of rodents.

The frictional engagement of the two plate sections with each other as a result of the slight twisting in order to engage them in their respective channels, may be entirely sufficient to ensure that the plate 26 remains intact, even though there may be differential settlement between the wall 10 and the pipework. However, as a precaution, it is preferred to wrap a a wire around the two pairs of lugs 52 and 54, which it will be noted from Figure 4 are brought into proximity as a result of fitting the two plate sections together.

It will be appreciated of course, that the distance between each pair of lugs 52 and 54 will vary according to the degree of contraction of the two plate sections on to each other.

Turning now to the masking plate 24 shown in Figure 1, it will be appreciated that the effective hole which has to be formed through the masking plate in order to accommodate the elbow 16 has to be eliptical, but this is quite easily achieved, by simply engaging the plate sections with each other, one from the bottom side and the other from the top side of the elbow 16. When the plate sections engage on the elbow, there will be virtually no clearance between the effective hole formed through the assembled plate and the elbow, and the assembled plate will be large enough to close the inner end of the opening 20.

Turning now to Figure 5, there is illustrated a cavity wall 60 through which a straight drainpipe 62 is fitted at an acute angle. This is not desirable, but is sometimes unavoidable in building construction. It is necessary to cut the end blocks of the wall 60, to form an inclined opening 64, giving the required clearance all round the pipe 62 where the latter passes through the wall. In such a construction, a planar cross-section through the pipe parallel with the face of the wall 60, will be eliptical, with the major axis of the elipse disposed horizontally.Masking plates 66 and 68 constructed as previously described are employed on the inside and outside of the wall 60, but in this case, the sections 30 and 32 are brought together by a horizontal movement from each side of the pipe 62, so that the eliptical or flat-sided effective hole 70 (see Figure 5A) formed in the masking plate 66 has its major axis disposed horizontally. In this way, it is possible to fit the masking plate 66 very closely to the external shape of the drainpipe 62 at the position where the pipe emerges from the wall 60.

Similarly, the masking plate 68 is constructed by bringing together two plate sections 30 and 32 with a horizontal motion to form an effective hole 72 as illustrated in Figure 5B.

Figures 6 and 7 illustrate a more refined construction of the plate sections 30 and 32, which provides for automatic locking of the two plate sections together in the assembled condition. Each plate section has a rectangular formation 80 adjacent to the inner end of the cut-away 36 and as illustrated in Figure 7, this formation 80 provides a series of saw-tooth cross-section indentations 82 in the surface of the plate section 30 on which the channel 50 appears. A single tooth 84 of complimentary shape to one of the saw tooth indentations 82, is formed on the opposite face of the plate section 30, adjacent to the distal end of the leg which does not have the formation 80.

Consequently, when the two plate sections 30 and 32 are being assembled, initially, when the tooth 84 is sliding over a plain surface of the leg 46, it will distort its own leg 44 away from the leg 46 in the region of the tooth. When the contraction of the two plate sections is such as to bring the tooth 84 into register with the formation 80, the tooth will drop into one of the indentations 82 under the resilient action of the leg 44 on which it is mounted. Continued contraction of the masking plate will cause the tooth 84 to ride upwardly out of one of the indentations 82, and then drop into the next indentation. When the assembled condition is arrived at, where the ends 38 of the cutaway are in engagement with the outside of the pipe on which the masking plate is assembled, the tooth 84 will be in engagement with one of the indentations 82. It will then be almost impossible to disengage the two plate sections from each other by a force applied in the opposite direction to that required for assembly. This is because the vertical rear face of the tooth 84 will be in engagement with a vertical face of one of the indentations 82. It will be appreciated that there are of course two teeth 84, one on each of the plate sections engaging with indentations on the other plate sections, so that the securing of the two plate sections together is very firm.

Claims

1. A pipework unit for use in building construction comprising a pipe length to which there is attached a masking plate which completely surrounds and fits around the pipe length, and projects outwardly from the pipe length in all radial directions, the masking plate comprising at least two sections each of which subtends only part of the perimeter of the pipe length, so that the masking plate can be assembled on the pipe length without threading the plate over one end of the pipe length.

2. A pipework unit as claimed in claim 1, in which each masking plate section is formed with a cut-away wherein the pipe section is received and the masking plate sections have interengaging means whereby they are securely attached to each other in the assembled condition.

3. A pipework unit as claimed in claim 1 or claim 2, in which the masking plate sections are identical with each other.

4. A pipework unit as claimed in any one of claims 1 to 3, in which each masking plate section is made of a material which is water-resistant.

5. A pipework unit as claimed in claim 4, in which each masking plate is made of polyvinylch bride.

6. A pipework unit as claimed in any one of claims 1 to 5, in which the masking plate sections are such that they can be adjusted with respect to each other, whilst maintaining their interengagement, to vary the shape and/or size of the hole formed between them for the accommodation of the pipe section.

7. A pipework unit as claimed in any one of claims 1 to 6, in which the masking plate comprises two sections each of which has a cut-away opening in one edge, so that it has two legs bifurcated by the cut-away, and the legs of the two plate sections are interengaged by engaging one leg of each section with a first face of the other section and the other leg with the opposite face of the other section.

8. A masking plate section for use in masking an opening around a pipe length passing through a wall comprising a plate having a cut-away opening on one edge of the plate, to receive part of the pipe section by fitting radially on to the pipe section and means on the plate section for interengagement with a similar plate section when the latter has been engaged on the pipe section, so that two or more plate sections when assembled on the pipe section and interengaged with each other, form a mask projecting in all radial directions from the pipe section.

9. A masking plate section as claimed in claim 8, in which the cut-away has a substantially semicircular inner end but extends outwardly from the diameter of the semi-circular portion, so that there are two legs one on each side of the cut-away.

10. A masking plate section as claimed in claim 9, in which the length of the legs outwardly of the diameter of the semi-circular portion of the cutaway is greater than the length of the said diameter.

11. A masking plate section as claimed in any one of claims 8 to 10, in which there is provided retaining means along or adjacent to one outer edge of each plate section, each retaining means being adapted to hold the edge of the other section which is not provided with retaining means, flat against the face of the plate section in the region of the retaining means.

12. A masking plate section as claimed in claim 11, in which the retaining means comprises a channel formation, one flange of which is formed by the main planar portion of the plate section, open on the inside (i.e. facing towards the opposite edge of the section) to receive the edge of the mating masking plate section.

13. A pair of masking plates each in accordance with any one of claims 8 to 12, provided with releasable means for securing the two plate sections together in the assembled condition.

14. A pair of masking plates as claimed in claim 13, wherein the releasable securing means comprises lugs on both sections disposed so that in the assembled condition it is possible to wrap a wire around one lug on each of the two sections.

15. A pair of masking plates as claimed in claim 13, wherein the releasable securing means comprises holes in both sections which can be aligned to permit a securing pin to be passed through both sections.

16. A pair of masking plates as claimed in claim 13, wherein the releasable securing means comprises a series of indentations in one face of each plate section and a projection on the mating face of the other plate section so that the projection will engage in one of the series of indentations in the assembled condition of the plate sections.

17. A pair of masking plates as claimed in claim 16, in which the projection is in the form of a tooth adjacent to the extremity of one of the legs.

18. A pair of masking plates as claimed in claim 16 or claim 17, in which the indentations are of saw-tooth form so that they permit easy sliding of the projection over the indentations in the contracting (i.e. assembly) direction, but offer appreciable resistance to movement between the two sections in the opposite direction.

19. A structural assembly comprising a wall; a pipe length passing through the wall, there being an opening in the wall through which the pipe length passes with a substantial clearance between the outside of the pipe length and the edges of the opening, and a masking plate comprising at least two sections each of which subtends only part of the perimeter of the pipe length, the masking plate fitting in engagement with or closely adjacent to one face of the wall and substantially closing one side of the clearance left between the opening in the wall and the perimeter of the pipe.

20. A structural assembly as claimed in claim 19, in which the arrangement of the masking plate is such that the closure of the clearance effected by the masking plate will prevent rodents entering the clearance.

21. A structural assembly as claimed in either of claims 19 and 20, in which the masking plate is in accordance with any one of claims 8 to 12.

22. A structural assembly as claimed in either of claims 19 and 20, in which the masking plate comprises a pair of masking plate sections in accordance with any one of claims 13 to 18.

23. A structural assembly constructed and arranged substantially as herein described with reference to Figures 1 to 5 or Figures 1 to 5 as modified by Figure 6 of the accompanying drawings.

24. A pipework unit for use in building construction constructed and arranged substantially as herein described with reference to Figures 1 to 5 or Figures 1 to 5 as modified by Figure 6 of the accompanying drawings.

25. A masking plate section for use in masking an opening around a pipe length passing through a wall constructed and arranged substantially as herein described with reference to Figures 2 to 5 or Figures 2 to 5 as modified by Figure 6 of the accompanying drawings.