TN 02.23 Tiling to Asphalt Floors

INTRODUCTION
Mastic asphalt is a mixture of partially oxidised bitumen (Hard grade) and aggregate i.e. crushed stone gravel or sand. Commonly, mastic asphalt is used for floor construction, waterproofing flat roofs.
Mastic asphalt bases for flooring of type F1076, should be laid in accordance with the recommendations given in BS 6925: 1988 Specification for mastic asphalt for buildings and civil engineering.
Roofing grade asphalt should be laid in accordance with the recommendations given in BS 8218: 1998 - Code of practice for mastic asphalt roofing. Where trafficking is required, an additional layer of paving grade asphalt is required and applied over the roofing grade.
INTERNAL ASPHALT FLOORS
Flooring grade asphalt should be laid on a rigid concrete or levelling screed background in accordance with BS 8204-5 2004+A1:2011 - Screeds, bases and in situ floorings. Mastic asphalt underlays and wearing surfaces. Code of practice.
There are five grades of flooring grade asphalt identified in BS 8204-5: 2004+A1: 2011. Two of which are generally considered suitable to receive a tiling finish in internal floor areas. These are:
Grade I – Special Hard Flooring. This is used in hospital wards, schools, shop floors, offices and domestic floors and is designed for situations where the ambient temperature is 25°C to 30°C, but should not fall below 10°C.
Grade II – Light Duty Flooring. Grade II is suitable for Internal shop floors, domestic floor which are not subjected to any point loading and for foot traffic in light assembly factory floors.
Both grades are one coat applications and are deigned to be laid at a thickness of 15 to 20 mm.
PREPARATION
Prior to the application of ceramic tiles, a check should be made to ensure the asphalt is in a suitable condition, ready to receive a tiling finish.
The asphalt floor must be clean, dry and free from all barriers to adhesion, such as oils and other components present within the asphalt. Clean the asphalt surface using sugar soap or a solution of washing soda (Soda crystals) e.g. a 10% solution in warm water using a suitable abrasive pad or brush to remove the dirt/oil stains followed by mopping with clean water. Allow to dry.

If the asphalt has a sand rubbed finish, surfaces should be carefully examined to ensure all loose sand or debris is completely removed from the surfaces prior to the commencement of tiling.
CERAMIC TILE ADHESIVES (FLOORING GRADE ASPHALT)
Provided that the Flooring Grade asphalt base is thermally stable and, in a sound, clean and dry condition, tiles may be fixed in a 3-6mm bed of i.e. BAL FLEX ONE or BAL RAPID FLEX ONE.
For large format tiles, use BAL XL FLOOR ONE.
The solid-bed method of fixing must be adopted ensuring as far as possible that no voids are left beneath the tiles.
Note: The asphalt base must be sufficiently true to the specified plane to permit fixing with an adhesive at a bed thickness not exceeding 6mm.
GROUTING
When the adhesive has set and cured, the tile joints may be filled using BAL GROUT FLEX WIDE JOINT or BAL MICROMAX 3 ECO. Where greater flexibility is required incorporate BAL ADMIX GT1 into BAL MICROMAX 3 ECO (diluted 2:1 Water: BAL ADMIX GT1 by volume).
EXTERNAL ASPHALT FLOORS
For external applications, roofing grade asphalt bases are generally used and are designed to remain deformable even at low temperatures so that it does not crack and provides a watertight layer.
External asphalt should be laid to falls of not less than 1:80 (1.25%) and at least 1:60 (1.7%), particularly where rapid or effective drainage is necessary.
Since the surface temperature of the external asphalt can vary from very hot in direct sunlight to very cold on winter nights, there is a risk of the asphalt cracking if the upper surface is restrained in any way. For this reason, bonded screeds are not applied on top of asphalt base or direct fixing of ceramic tiles or natural stone with a tile adhesive.
Ceramic tiles or natural stone should be applied over a mortar laid on top of a separating layer. For this reason, when installing rigid finishes onto balconies, roof or ground floor terraces, consideration should be given to the application of a suitable drainage screed assembly from the BAL GUTJAHR range.

MOVEMENT JOINTS
Movement joints for internal floor tiling should be provided in accordance with BS 5385; Part 3: 2014. Clauses 6.8 and 7.1.6. Perimeter joints may be filled using BAL MICROMAX SEALANT, whereas joints subjected to heavy traffic may be filled using an epoxy polysulphide sealant or suitable pre-formed movement joint strip.
For external floor tiling BS 5385: Part 3:2014 clause 6.8.1.4 Balconies and roof terraces advises that “Intermediate movement joints should be incorporated within the tile assembly at intervals not exceeding 3 m. Distances between joints might have to be reduced further dependent upon the anticipated movement in the background, the size and format of the tile and the width of the tile joints Movement joints should also be incorporated where there are supporting beams and where the tile assembly abuts restraining surfaces i.e. parapet walls. Movement joints should be continuous throughout the entire assembly”.
The advice given in the BAL Technical Notes is based upon the recommendations given in BS 5385: Parts 1-5, the codes of practice for wall and floor tiling.
TECHNICAL ADVISORY SERVICE
For free expert guidance on the use of BAL products, or any aspect of ceramic tiling with BAL products, contact the BAL TECHNICAL ADVISORY SERVICE on 01782 591120.
THE BAL 25 YEAR GUARANTEE
BAL products are supplied with a 25 year product guarantee. For further details and/or copies please contact the Company’s marketing department.
NOTE
The customer must verify the suitability of any information, opinion, recommendation or advice (“information”) provided by the Company for the particular application for which any goods are intended to be used and the Company accepts no liability (whether in contract, tort or otherwise) whatsoever for any loss, damage or expense arising from the misuse of any information it supplies, nor for the use of any information in or for applications which are unsuitable or inappropriate. Building Adhesives Ltd operates a continuous research and development programme and reserves the right to alter or to update information from time to time.

“Note: Any advice, opinion or information is given to assist the use of the Company’s products on the basis that the user will ensure its suitability for the application intended. In particular the Company cannot accept liability for loss or damage which may arise from incorrect use of its products or from poor workmanship. The Company operates a continuous research and development programme and reserves the right to update information without notice.”