The sheets must be laid at the bottom of the surface where the concrete slab is to be placed. Joins in laying must be overlapped by at least 200mm and taped with a 50mm duct tape for the full length of the joint.
Any penetration by pipes or services must be sealed with a 50mm duct tape and a minimum of 200mm overlap. This is in accordance with AS2870 to prevent any leakage through the penetration.
Care should also be exercised to ensure that no stones, roots or other material that could pierce the membrane are protruding above ground level to ensure integrity of the barrier. In rocky areas, it is advisable to place a layer of sand on the prepared pour area before laying down the builder's film.
The film must follow the contours of the slab at thickened beams so that no strain is placed on the film resulting in potential tears, incorrect thicknesses and voids under the slab.