Mastic Asphalt Warm Roof on Metal Decks

On Cork, Mineral Wood, Cellular Glass, Perlite, Rigid Urethane (PIR), Phenolic or Composite Insulations

Two coats of mastic asphalt R988 T25 to a total thickness of 20mm laid on to sheathing felt. The surface is to be painted with solar reflective paint or stone chippings are to be embedded in bitumen based adhesive.

Or:

Two coats of 20mm polymer modified asphalt laid on sheathing felt. The surface is to be painted with solar reflective paint or stone chippings are to be embedded in bitumen based adhesive.

Deck

A metal deck is normally fixed by a specialist contractor as part of a single responsibility roofing operation comprising deck, thermal insulation and waterproofing. The load bearing performance of steel decks should be calculated in accordance with BS 5959:Part 6: 1995.

For high humidity applications, aluminium decks are normally recommended. If steel decks are used under these conditions, a protective coating to both sides of the deck should be specified.

Vapur Control Layer

The requiremnt for a vapour control layer should be assessed in accordance with BS 6229:1982.

Vapour Barrier

First Layer: Type 5U or polyester 180 bonded to deck flats.

Second Layer: Type 3B Fully Bonded.

Or:

One layer metal lined polyester bitumen roofing. Side and end laps fully sealed. All laps supported on the flats of deck or additional sheet metal strips.

Vapour Check

One layer type 5U or polyester 180 bonded to deck flats.

U- Values

The tables below show the thickness of insulation required to achieve specified U-values for the total roof construction.

Metal Decks

Please click the following link for more information: Asphalt Roofing