Permadeck®
the permanent roof
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Permadeck with  soft single ply systems

E&OE      The text and graphics of this website are Copyright © 1996-2015 all rights reserved by Seamless Roofing Ltd.  Permadeck, Thermadeck & Flexiroof are registered trade marks.  The contents of this website are subject to review and are a guide only and do not represent a binding offer. The BBA logo is Copyright © British Board of Agrément.  

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Insulation = 220mm (average)

Eg TR26: K = 0.024, R = 0.22/0.024 = 9.2, U-value = 0.10


Rest of roof standard values: Ext.surface = 0.045, Permadeck = 0.06, upper deck = 0.13, thermal break = 0.13, t&g liner = 0.13, int.surface = 0.105. Giving a total of 0.6.  The whole roof resistance is 9.2+0.6 = 9.8, and the U-value = 1/9.8 = 0.10


If this is too good, a U-value of 0.16 can be achieved by 90+(25 to 75 tapered) ie 140 ave.


Example3: Timber deck Eco Roof with Exposed Beams


DryPly™ over parapet

 Permadeck trim on o/s

18mm DryPly™ countersunk fastenings to suit

Tapered insn. eg 50 - 150

Thermal break layer, 18mm sheathing ply

Vapour barrier

T&G liner



If the laminated beams are sloping, the tapered insulation can be a standard flat board instead, giving greater insulation thickness.

300 x 100 exposed laminated beams at 1200 centres

Permadeck 20, BBA 93/2967


Highly Insulated Eco Roofs

The ‘standard’ highly insulated roof with a single ply membrane poorly attached to insulation has proven to have many drawbacks. These soft roof designs are vulnerable to damage, difficult to trace and repair faults and have very limited design flexibility.

Whereas Permadeck, bonded to its DryPly™ deck, can easily withstand impact & abrasion and have anything designed onto it or into it: gulleys, rooflights, vents, micro generation, flues, air con etc.

Permadeck 20 on 12-18mm DryPly™, with countersunk fastenings through 50mm - 150mm insulation on thermal break layer of 12-18mm sheathing ply with Tek fastenings on 50-80mm insulation on vapour barrier on metal deck to falls or tapered insulation.  Total insulation 100-230mm.

































k fastenings on 50mm insulation on vapour barrier on metal deck to falls or tapered insulation.



Example1: Metal deck Eco Roof inc thermal break & Permadeck solid roof

Ideal where a solid roof is required.  Can be walked on, can incorporate gulleys within the top insulation, easy fix for rooflights, water housings, parapet details, micro generation mounts, ventilators, aircon, heat pumps etc.

Example2: Timber deck Eco Roof

18mm ply with countersunk fixings into lower deck.  50mm or greater insulation on vapour barrier on 18mm sheathing ply on firring on joists with ~120mm  insul-ation packed between joists and hard against lower deck. Foil-backed plaster board below.  No cold voids, warm void for sealed LED low temp downlights.

Permadeck on DryPly with trim to o/s face.

Roofs over high high humidity areas such as bathrooms, laundry areas, swimming pools should have an additional vapour barrier below the joists.  Downlights and wiring should not penetrate this layer.

5 or 7w LED

Permadeck20   BBA 93/2967