Mastic Asphalt is a highly super versatile construction material used for a whole range of production projects, both new build and refurbishment projects, where a easy, seamless, long lasting finish is needed. It offers overall waterproofing for roofing and tanking and acts as a hard deck surface in flooring and paving. If nicely designed and laid it have to be capable of lasting 50-60 years. In addition to this, it's also fully recyclable.
Any provision required to govern interstitial condensation in the roof need to be decided as advocated in BS 6229:1982 but with calculation method modified to conform to BS 5250:1989 (1995).
The boards must be bedded in hot bitumen to the vapour control layer with joints close butted and move joints staggered. An fair margin should be provided among insulation slabs and all skirtings and abutments to allow for an infill.
The variety of coats need to be suitable to the waterproofing necessities and traffic situations of the roof. When laid to falls of 1:eighty or extra mastic asphalt roofing is laid in two coats to a thickness of 20mm, all in accordance with BS 8218:1998.
In which falls are less than 1:80 or a ‘buried’ specification is required, 3 layers of mastic asphalt to a total thickness of 30mm ought to be implemented.
On horizontal surfaces as much as and which includes 10˚ pitch the mastic asphalt ought to be laid in two coats to a thickness of 20mm on a setting apart membrane of sheathing felt.
Difficulties can may be noted in laying mastic asphalt at once over insulants to surfaces over five˚ pitch.
On sloping and vertical surfaces over 10˚ pitch the mastic asphalt need to be laid in three coats to a thickness of 20mm with out a isolating membrane. On sloping and vertical surfaces of timber or lightweight concrete the mastic asphalt should be laid in three coats to a thickness of 20mm on expanded metal lathing over a separating membrane of sheathing felt.
Horizontal surfaces when designed as a roof lawn, reservoirs or as a buried waterproofing membrane, the mastic asphalt is laid in three coats to a thickness of 30mm over a setting apart membrane of grp tissue.
A mastic asphalt vapour barrier should be laid in a single coat no less than 10mm thick on a grp tissue.
On skirtings and upstands as much as 300mm high the mastic asphalt ought to be carried out in coats to a thickness of 13mm.
On skirtings and upstands over 300mm high the mastic asphalt should be carried out in 3 coats to a thickness of 20mm.
Note: two coat work may be permissible to vertical upstands in extra of 300mm in areas no longer exposed to the factors including tank rooms, mechanical services regions etc. In which the arrival of the completed paintings is not of paramount significance.
On skirtings and upstands of timber or light-weight concrete the mastic asphalt have to be implemented in 3 coats to a thickness of 20mm, on elevated steel lathing over a isolating membrane of black sheathing felt.
In sure situations it could be vital to comprise extended metallic lathing to concrete, brickwork or blockwork. In those situations the mastic asphalt ought to be carried out in three coats to a thickness of 20mm along with a separating membrane of sheathing felt, where required.
All asphalt roofing, along with upstands, need to be protected towards static factor loading and mechanical harm. On inverted roofs, the ballast and insulation will offer protection to the mastic asphalt. The insulation and ballasting should be set up at once on crowning glory of the laying of the mastic asphalt or as soon as is almost viable. Care ought to be taken to offer adequate safety at upstands.
On horizontal and barely sloping surfaces, without delay after completion of laying and while the mastic asphalt continues to be heat, clean sharp sand must be rubbed frivolously into the surface of the mastic asphalt with a wooden glide