Renewing a Flat Roof
If the roof is covered in felt this is normally stripped back to the decking. If the decking is timber, this may have been affected by water ingress and may require partial or complete replacement.
Existing or new decking is then cleaned and prepared for a new felt covering. Any abutment walls will be chased out approximately 25mm x 25mm.
A standard three layer specification consists of three separate layers of felt which are laid accordingly:
On a timber deck the first layer is 36kg 3B glass fibre based roofing felt which is mechanically fixed, i.e tacked to the deck.
The second layer is a 2mm lcopal polyester based underlay roofing felt fully bonded to the first layer (vapour barrier) by torch application.
Finally the cap sheet (third layer) is laid which is an Icopal High Performance polyester based Tecnatorch 2000 green mineral elastomeric cap sheet.
Again, this is fully bonded by torch application to the base layer. All upstands, edgings and flashings are laid using the same Icopal green mineral felt.
Finally, upon completion any flashings which have been bonded and tucked into an abutment wall are into position using 3-1 sand and cement mortar.
This specification is generally termed a “cold roof”. A “warm roof” is the same specification but with the addition of a Kingspan TR21 High performance rigid urethane insulation board – thermal conductivity 0.025-0.027 W/mK.
These are available in various sizes; specifications are available upon request.
There are alternative specifications to the above, notably if the existing roof is finished in asphalt there are options to clean, prepare, prime and lay felt over the existing roof.
Also there are separate specifications for a concrete or metal deck which differ slightly from the above.
Please contact firstname.lastname@example.org for more details or call us on 020 8868 3554 or 020 8429 1445.