the permanent roof
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Info for preparing a deck for a Permadeck balcony
This information sheet should be read along with the general sheet on
joinery works prior to installing Permadeck.
joinery works prior to installing Permadeck.
Whilst Permadeck is the most effective balcony surface, water can still get around the finish if the following guidelines are ignored!
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The deck should have a minimum fall of 1:40 ie 100mm over 4.0m.
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Railings should not be fitted until the Permadeck has been laid.
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Railings should be attached to pre-
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Falls should drain to either an external gutter or hopper head. Pipes through the deck should be avoided.
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If the balcony has a parapet either the Permadeck is used to encapsulate it or a lead cap should be fitted across the cavity and down the inside a minimum of 100mm. Coping stones, pillars etc are then cast or mortared over the lead. Water conduits through parapets are not recommended but if you are stuck with them they must be lined with lead and angled down to the outside a min of 20°.
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Recessed balconies ie where a section has been cut out of a pitched roof can have Permadeck dressed up the cheeks if required. If cladding is specified it should not be fitted until after the deck surface has been laid.
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Patio Doors are a subject in themselves. If in doubt please speak to us as this the most critical area. You must assume that water will penetrate the frame AND cill and run off the ends and the back of the cill ie beyond the Permadeck surface.
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Start by fitting a 100 x 100 threshold beam. (See diagram below).
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Fit a lead apron onto the beam using Polysulphide or waterproof NoNails or SUMOGRIP so that it dresses DOWN 100m on the outside and UP on the inside AND at the ends.
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Fit a door cill using Polysulphide, No Nails or SUMOGRIP to the lead apron. Do not penetrate the cill or lead.
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Fit the door frame using mechanical fixings into the cill but not through it.
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Fit the doors. NB Doors should open OUT so that driving wind and rain pushes the doors onto their seals. Sliding doors should be avoided as their bottom tracks are prone to gathering water and leaking.
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Finally, clad the back of the threshold & cill to hide the upturned lead.
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The commonest mistake arises when the floor joists inside the room are used as the structure for the balcony. A warm deck is then laid onto the joists ie a ply/insulation/ply sandwich thus raising the balcony HIGHER than the internal floor. The threshold described on the Architectural page then becomes a considerable step up and over to get out onto the balcony. If you have to do this at least it will be wind and watertight. Building Control may accept a cold deck if the insulation is held tight below the deck and an undamaged vapour barrier is fitted below.
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Unless we are moulding a tray for the door system, under no circumstances should a patio door be fitted tight or just slightly above the outside deck. This cannot be made watertight and the doors will need to be re-
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Please email or send any sketches to Seamless Roofing for comment before construction.
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Railings fitted with plates and screwed
onto moulded blocks (stanchion pads). Use stainless steel Tek screws that don’t penetrate the membrane below the pad. Bed the plate on mastic. Read more...
onto moulded blocks (stanchion pads). Use stainless steel Tek screws that don’t penetrate the membrane below the pad. Bed the plate on mastic. Read more...
Q. I already have a patio door and it's been fitted incorrectly; it has little or no threshold, no lead apron and fixings screwed through the bottom frame. Can this be made watertight?
A. Probably not! The design you see above works. Other designs that miss out ANY of these details may leak, REGARDLESS OF THE WATERPROOFING SYSTEM. The more details you don't have the more likely it is to leak. Patio doors usually get fitted by window fitters and, not surprisingly, get fitted like windows, which is wrong. A typical window fitter's reaction to getting the above details is usually unprintable. But HE isn't going to live under the patio door! Send us a picture of your door detail, all may not be lost, though you may need to get the door set removed and a new one fitted properly.
If you’re planning to use a tensioned system that will transmit force through the uprights, please contact us to discuss the best way of securing your stanchions. Stanchions that penetrate the roof are unlikely to be made permanently watertight, they may require to be fastened onto the wall(s) below. In the long run, being able to make the roof watertight is far more important than aesthetics.
Patio doors
Patio door frame on cill on lead on threshold (100x100mm).
Lead turns up behind the cill & frame and forms an apron down over the Permadeck.
Also, turn the lead up at the ends. Skirting on the inside and in-
To avoid penetrating fixings along the bottom, the lead should be bonded to the threshold and the cill to the lead with waterproof ‘no nails’ or equivalent building adhesive.