Seamless Roofing Ltd
the permanent roof
0845 479 5352
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If you’re building a warm roof, the above applies plus:
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If fixing through insulation, Screwfix can supply fixings long enough to screw through the upper ply down through the insulation and into the lower ply. The lower deck should be 18mm so that the fixings don’t protrude, eg 18+90+18 = 126 ie 120mm fixing countersunk and drawn down. It is sometimes better to get the fixings first and then vary the insulation to match. Alternatively longer fixings can be used so long as they penetrate the firring/joists below. Remember to fit your fascias and gutters because the Permadeck trims fix over them tightly. This is a guide only, the joiner is responsible for correct and secure construction. Do NOT use foil-
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If you’re fitting fascias and gutters:
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Fascias should be held 2-
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Tilting fillets, drip (doubling) rails and wall plates are not required.
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Gutters should have their top edge running from 50mm to 75mm below the final deck surface. This gives a 25 mm run over the whole length. Extremely long gutters should have extra outlets. A horizontal gutter should be fitted 65mm below the final surface (use deep-
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If you’re building a balcony:
Read through the Architectural and BalconyPrep pages BEFORE you build ANYTHING or you may have problems with inside/outside heights, patio doors, ponding, abutment details, stanchion fixings etc.
Note: a) Do not use chipboard (V3), OSB or Marine (FE) plywood for the final surface since these materials cannot absorb sufficient resin. Permadeck pre-skinned plywood makes life easy but please lay with resin side UP.
b) Ask for u-values and insulation thicknesses to be specified by a qualified person. The Part L regulations are rarely understood.
This is representational of a cold deck, the firring will in practice run towards the gutter.
This is representational of a warm deck, the firring will run towards the gutter.
Note on ‘falls’ (slope):
From an appearance point of view a good slope is better than none or ponding. For balconies we recommend a slightly GREATER fall than for just a flat roof.. However, nothing disastrous will happen if you have some ponding and at no time has Permadeck exhibited any adverse reaction to standing water. This is in direct contrast to many well known liquid applied systems, but then that’s why fibreglass can be used for tanks, ponds, boat hulls etc. And why Permadeck is great for roof gardens and wet rooms.
E&OE The text and graphics of this website are Copyright © 1996-
Seamless Roofing can supply pre-skinned 18mm ext wbp plywood. This saves time and money trying to keep the timber dry. We also offer a quick tape-up service to joint the pre-skinned boards giving an effective seal INSTANTLY (central Scotland only). Or the site joiner can butt joint the boards with a bead of frame sealant, though NOT silicone. Or use narrow duct tape over the joints.
If you’re building a cold deck, like a garage roof:
Boards should be securely and evenly laid and be staggered in at least one direction on roofs over 50m2. Falls should be between 1:80 and 1:40, ie a 4m run should use 50mm to 100mm firring sloping to 0mm.
Expansion gaps of 10 - 20mm should be left at wall abutments so if the boards swell they don’t buckle up.
Boards should be butt jointed.
Each 8 x 4 sheet should be secured by a minimum of 4 rows of 5 fixings.
Info for joiners preparing decks for Permadeck
On completion of the following details, the plywood must be kept dry to ensure a 100% bond.
The Seamless Roofing system and products are now available as a national franchise. For further info click the franchise button above.