New Construction Specification
Copy this detail for a ‘warm roof’ design and its description onto your drawings for Building Control. Note that ‘cold decks’ are still allowed if you can design a continuous vent across the top of the insulation. A picture of this is shown on the Thermal page. We have also seen many situations where height has been a problem and the joist void has been completely filled with insulation or insulation is held tight below the decking ie there is no cold void to ventilate. In this case extra vapour barrier protection should be included.
Roof Waterproofing: Permadeck®20 polyester resin system, Agrément Certificated 93/2967. Fire rated Ext FAA, deck fixings to be adequate for exposure, falls 1:80 - 1:60, min 75mm tissue-faced solid foam insulation on heavy duty vapour barrier on lower deck. Thermal calculation available.
Note on building a balcony as part of a new building:
The secret is to work DOWN from the final surface level when figuring out heights for the structural work. The Permadeck on its plywood deck is about 21mm thick, the insulation and vapour barrier will be ~80mm, the lower deck will be, ideally, 18mm and the firring (tapered pieces) will be ~50mm at the high end. That is a total of 169mm!! and that's BEFORE the threshold (step) is formed. The threshold should be a minimum of 75mm to the underside of the cill, which should have a lead apron below it as shown on the Balcony Prep page.
If the balcony is being cut into a pitched roof the lower edge of the balcony can be formed as a 'mansard', ie the upper deck should be projected over the tiles or slates below the balcony. Mansards
Permadeck is an excellent product for solving the problems of balconies but please talk to us before you build it! The commonest problem is thinking you can just project the floor joists out at the same level forgetting that a slope must be formed with a ply/insulation/ply sandwich on top and then there's the threshold and then the cill and then the door frame. By the time you've finish you'll need a ladder to get out!! But done correctly a Permadeck balcony looks and works great.
Modern 'Mansard' - a flat roof on top of a slated or tiled pitch
Permadeck solves problems AND creates opportunities:
This rear extension is a conventional roof on one side and a mansard on the other.
- Balconies
- Sunken Mansards
- Recessed Balconies
- Barrel Roofs
- Roof Gardens
- Water features
- Carports
- Insulated roofs on conservatories
Your designs can use the potential of Permadeck to the full: roofs can be ANY shape,
ANY colour, low or high traffic, cold or warm decks, roof gardens, lightweight roofs,
balconies, turrets, parapets, wet rooms etc.
If you are designing or building a new roof this is the gateway page to lots of technical
information. If you want to REFURBISH an existing roof CLICK HERE. Note that the
design suggestions here MUST be checked and confirmed by a competent person.
The navigation bar on the left shows all of the technical areas covered.
Permadeck’s BBA certification is for a waterproofing system. The certification does
NOT cover the roof design, which should be designed & approved by a competent person
prior to construction.
Don’t get lost! These are tech pages only, go to HOME for main page list
Lots of ideas for modern extensions and dormers!
E&OE The text and graphics of this website are Copyright © 1996-2010 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.
The Seamless Roofing system and products are now available as a national franchise.
For further info click the franchise button above.
