Polythene And Polyethylene Sheet
Polythene or polyethylene sheet is often used as a damp-proof membrane with oversite concrete for all however severe circumstances of dampness. It's endorsed that the sheet must be at least 0.25 mm thick (1200 gauge). The sheet is equipped in rolls 4 m huge by 25 m long. When used below concrete oversite the sheet must be laid on a blinding layer of sand or compacted fuel ash spread over the hardcore.
The sheets are spread over the blinding and lapped one hundred fifty mm at joints and continued across surrounding walls, under the dpc for the thickness of the wall.
Where site conditions are reasonably dry and clear, the overlap joints between the sheets are sealed with mastic or mastic tape between the overlapping sheets and the joint completed with a
polythene jointing tape as illustrated in Fig. 29.
For this lapped joint to be successful the sheets should be dry and clean else the jointing tape won't adright here to the surface of the sheets and the joint will rely upon the weight of the concrete or screed urgent the joint sufficiently closely to make a watertight joint. As clean and dry situations on a building site are rare, this type of joint ought to be only used the place there is unlikely to be heavy absorption of ground moisture.
Where site circumstances are too wet to make use of mastic and tape, the joint is made by welting the overlapping sheets with a double welted fold as illustrated in Fig. 30, and this fold is saved in place by weighing it down with bricks or visqueen dpm securing it with tape till the screed or concrete has been placed. The double welt is fashioned by folding the perimeters of sheets together and then making a welt which is flattened.
The plastic sheet is successfully inconceivable to fold and so stiff and elastic that it'll all the time are likely to unfold so that it requires a deal of persistence to fold, hold in place after which contrive to fold along the joint. Through the use of the utmost dimension of sheet available it is attainable to minimise the number of joints.
The sheet ought to be used in order that there are only joints one way as it's impractical to type a welt at junctions of joints.
The place the extent of the damp-proof membrane is below that of the dpc in walls it's mandatory to show it up in opposition to walls in order that it could actually overlap the dpc or be. turned over as dpc as illustrated in Fig. 31. To maintain the sheet in place as an upstand to walls it's necessary to maintain it in place with bricks or blocks laid on the sheet in opposition to partitions until the concrete has been positioned and the bricks or blocks removed because the concrete is run up the wall.
On the internal angle of walls a reduce is made within the upstand sheet to facilitate making an overlap of sheet at corners. These sheets which are commonly used as a damp-proof membrane will serve as an efficient barrier to rising damp, providing they are not punctured or displaced during subsequent building operations.
The sheets are spread over the blinding and lapped one hundred fifty mm at joints and continued across surrounding walls, under the dpc for the thickness of the wall.
Where site conditions are reasonably dry and clear, the overlap joints between the sheets are sealed with mastic or mastic tape between the overlapping sheets and the joint completed with a
polythene jointing tape as illustrated in Fig. 29.
For this lapped joint to be successful the sheets should be dry and clean else the jointing tape won't adright here to the surface of the sheets and the joint will rely upon the weight of the concrete or screed urgent the joint sufficiently closely to make a watertight joint. As clean and dry situations on a building site are rare, this type of joint ought to be only used the place there is unlikely to be heavy absorption of ground moisture.
Where site circumstances are too wet to make use of mastic and tape, the joint is made by welting the overlapping sheets with a double welted fold as illustrated in Fig. 30, and this fold is saved in place by weighing it down with bricks or visqueen dpm securing it with tape till the screed or concrete has been placed. The double welt is fashioned by folding the perimeters of sheets together and then making a welt which is flattened.
The plastic sheet is successfully inconceivable to fold and so stiff and elastic that it'll all the time are likely to unfold so that it requires a deal of persistence to fold, hold in place after which contrive to fold along the joint. Through the use of the utmost dimension of sheet available it is attainable to minimise the number of joints.
The sheet ought to be used in order that there are only joints one way as it's impractical to type a welt at junctions of joints.
The place the extent of the damp-proof membrane is below that of the dpc in walls it's mandatory to show it up in opposition to walls in order that it could actually overlap the dpc or be. turned over as dpc as illustrated in Fig. 31. To maintain the sheet in place as an upstand to walls it's necessary to maintain it in place with bricks or blocks laid on the sheet in opposition to partitions until the concrete has been positioned and the bricks or blocks removed because the concrete is run up the wall.
On the internal angle of walls a reduce is made within the upstand sheet to facilitate making an overlap of sheet at corners. These sheets which are commonly used as a damp-proof membrane will serve as an efficient barrier to rising damp, providing they are not punctured or displaced during subsequent building operations.