Polythene And Polyethylene Sheet
Polythene or polyethylene sheet is commonly used as a damp-proof membrane with oversite concrete for all however extreme situations of dampness. It is suggested that the sheet needs to be at the least 0.25 mm thick (1200 gauge). The sheet is supplied in rolls 4 m large by 25 m long. When used beneath 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 150 mm at joints and continued throughout surrounding walls, visqueen sheeting under the dpc for the thickness of the wall.
The place 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 accomplished with a
polythene jointing tape as illustrated in Fig. 29.
For this lapped joint to achieve success the sheets should be dry and clear else the jointing tape will not adhere to the surface of the sheets and the joint will rely upon the weight of the concrete or screed pressing the joint sufficiently heavily to make a watertight joint. As clean and dry situations on a building site are rare, this type of joint needs to be only used where there is unlikely to be heavy absorption of ground moisture.
Where site conditions are too wet to use 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 kept in place by weighing it down with bricks or securing it with tape until the screed or concrete has been placed. The double welt is formed by folding the perimeters of sheets together and then making a welt which is flattened.
The plastic sheet is effectively impossible to fold and so stiff and elastic that it'll at all times tend to unfold in order that it requires a deal of persistence to fold, hold in place after which contrive to fold alongside the joint. By utilizing the utmost dimension of sheet available it's doable to minimise the number of joints.
The sheet needs to be used in order that there are only joints one way as it is impractical to type a welt at junctions of joints.
Where the level of the damp-proof membrane is beneath that of the dpc in partitions it's necessary to show it up in opposition to walls in order that it can overlap the dpc or be. turned over as dpc as illustrated in Fig. 31. To keep the sheet in place as an upstand to walls it is necessary to hold it in place with bricks or blocks laid on the sheet against partitions until the concrete has been placed and the bricks or blocks removed as the concrete is run up the wall.
At the internal angle of partitions a reduce is made in the upstand sheet to facilitate making an overlap of sheet at corners. These sheets which are generally used as a damp-proof membrane will function an efficient barrier to rising damp, offering they don't seem to be punctured or displaced throughout subsequent building operations.
The sheets are spread over the blinding and lapped 150 mm at joints and continued throughout surrounding walls, visqueen sheeting under the dpc for the thickness of the wall.
The place 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 accomplished with a
polythene jointing tape as illustrated in Fig. 29.
For this lapped joint to achieve success the sheets should be dry and clear else the jointing tape will not adhere to the surface of the sheets and the joint will rely upon the weight of the concrete or screed pressing the joint sufficiently heavily to make a watertight joint. As clean and dry situations on a building site are rare, this type of joint needs to be only used where there is unlikely to be heavy absorption of ground moisture.
Where site conditions are too wet to use 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 kept in place by weighing it down with bricks or securing it with tape until the screed or concrete has been placed. The double welt is formed by folding the perimeters of sheets together and then making a welt which is flattened.
The plastic sheet is effectively impossible to fold and so stiff and elastic that it'll at all times tend to unfold in order that it requires a deal of persistence to fold, hold in place after which contrive to fold alongside the joint. By utilizing the utmost dimension of sheet available it's doable to minimise the number of joints.
The sheet needs to be used in order that there are only joints one way as it is impractical to type a welt at junctions of joints.
Where the level of the damp-proof membrane is beneath that of the dpc in partitions it's necessary to show it up in opposition to walls in order that it can overlap the dpc or be. turned over as dpc as illustrated in Fig. 31. To keep the sheet in place as an upstand to walls it is necessary to hold it in place with bricks or blocks laid on the sheet against partitions until the concrete has been placed and the bricks or blocks removed as the concrete is run up the wall.
At the internal angle of partitions a reduce is made in the upstand sheet to facilitate making an overlap of sheet at corners. These sheets which are generally used as a damp-proof membrane will function an efficient barrier to rising damp, offering they don't seem to be punctured or displaced throughout subsequent building operations.