The purpose of a Black Sheathing Felt or Glass Fibre Tissue separating membrane is to isolate the mastic asphalt from the base to allow for any relative movement between them. It also helps to prevent the formation of blisters and ‘blowing’ of asphalt.
The separating membrane is laid loose with 50mm laps
The application of flooring asphalt should be in accordance with BS 8204: Part 5.
If the asphalt is delivered in blocks and melted down on site any additional coarse aggregate is incorporated at this stage. Alternatively the asphalt can be delivered molten in a hot charge transporter in which case any coarse aggregate is incorporated during manufacture.
The area to be covered is divided into bays of convenient size. The molten asphalt is then spread by means of a wooden float. Timber or metal gauges are used to obtain the required thickness.
Asphalt flooring is normally laid in one coat and special care is taken in effecting junctions between bays to provide a smooth and even surface. For suspended floors where wet processes will occur two coats are normally necessary, the first coat being an underlay of roofing or tanking asphalt.
Falls to Clear Water
Where wet processes or regular cleaning of the floor is a user requirement it is essential that careful consideration be given to the provision of adequate falls to channels and gullies to prevent ponding.
Falls are essential where acid and chemical resistant mastic asphalt is laid, in order to facilitate washing down. In shower rooms similar provisions are required.
Protection of Surface
The floor should not be subjected to traffic until the mastic asphalt has cooled to ambient temperature. The finished asphalt surface should be protected against damage from following trades and special care should be taken to avoid spillage of solvents, diesel fuel or paints.
Concrete, mortar, cement grout or plaster should not be mixed directly on the flooring.
To help ensure accurate tendering the following information should be provided by the specifier: