BASES

Most forms of solid construction will provide a suitable base for Permanite flooring asphalts.

CONCRETE

Concrete surfaces, free from cracks or indentation, provide an excellent base for the application of flooring asphalt.  They should be designed and constructed in accordance with the recommendations in BS 8204: Part 1.  In the case of uneven concrete a leveling coat of asphalt or sand cement screed may be necessary.

CONCRETE BEAMS AND HOLLOW TILES

Where the base on which the flooring asphalt is to be laid is of precast concrete beams, hollow beams or hollow tiles, a sand and cement screed designed in accordance with BS 8204: Part 1 may be required.

STONE FLAGS, QUARRY TILES OR BRICK FLOORS

Old floors of these types can form a good base to receive asphalt flooring.  However, it may be necessary to provide a leveling coat of asphalt to take up irregularities in the surface.

TIMBER BOARDING

Asphalt can be laid over timber boarded floors providing the structure is free from deflection.  Minor deflection can be catered for by the inclusion of a 10mm cushion coat of roofing or tanking asphalt.  In all cases a separating membrane of black sheathing felt is required.

METAL FLOORS

A thin coat of bituminous primer must be applied by the asphalter after the surface has been prepared.  The asphalt is laid direct without the use of a separating membrane and to compensate for deflection a 10mm roofing or tanking layer should be specified as a cushion coat.

SEPARATING MEMBRANE

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

TYPES OF MASTIC ASPHALT

Mastic Asphalt for Flooring (limestone aggregate) BS 6925: 1988 Type F 1076 and Type F 1451.

Although Kitemarked and covered by BSI Certification the following grades are manufactured to within much narrower requirement than those set out in the British Standard specification.

GRADES

Special hard grade, light grade, medium grade, heavy grade.
Each grade has its own special quality, selecting the correct grade will involve discussion with the asphalt contractor.

COLOURED ASPHALTS

Where a decorative finish is required, for example in domestic premises, offices, schools and hospitals, flooring asphalts can be supplied in red.

FLOORING FOR UNHEATED BUILDINGS

Many internal floor areas fall outside the categories previously mentioned in that the buildings are unheated or subject to rapid changes in temperature e.g. sports halls and warehouses.

For these applications special flooring/paving grades are available which are less sensitive to temperature variations.

APPLICATION OF ASPHALT

The application of flooring asphalt  should be in accordance with BS 8204: Part 5.

PREPARATION

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.

LAYING

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 THE 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.

DESIGN REQUIREMENTS

To help ensure accurate tendering the following information should be provided by the specifier:

• Use to which the floor will be put and nature of traffic.
• Loaded weight of any trolleys, stating size of wheels and type of tyre.
• Maximum weight of standing loads and area of contact with floor.
• Details of any acids, other chemicals, greases, oils or solutions, including concentration and temperature, which may come into contact with the floor.
• Ambient temperature range within the building. This is particularly relevant on suspended floor applications where the slab may attain a relatively high temperature.  Mastic asphalt is a thermoplastic material.  Its resistance to indentation will be reduced with increase in temperature.  As they are liable to be damaged at very low temperatures, flooring grades should never be laid externally.
• Details of floor finishes e.g. non-slip surface etc.
• Any falls or drainage facilities required
• Details of applied finishes and adhesives
• Details of fixtures and fittings, particularly where these penetrate the asphalt.