Low pitch roof - UK specific quiz? Having built the walls of our extension we are at the...
Having built the walls of our extension we are at the stage of putting the roof on.
Trouble is when I calculated the pitch I forgot that the depth of the joist and thickness of the wall plate would hold an effect on the roof pitch. We have 1.1m rise contained by 5m giving a 10.4' pitch ( I was aiming for 12.5 point but .) I cannot change the pitch by lowering the front wall (would look really bizarre on the house with skylight door and floor heights) The rear wall is constrained by window so no adjustment there.
I am face with using a particularly low pitch tile OR using a board, felt and tile finish.
Two question
1) what would the group choose , with reason if poss
2) If its option 2 ( board and tiles) what exactly is the variety up of this : what thickness board, batten, counter battens ? what feel or membrane is used and how is it fixed.
In short could somebody walk me through the layer of a board , felt and tile finish roof . please
any give support to as ever...
M
forget the adjectives option ..you wont attain any tile to go that low ...you might gain an interlocking slate but they are very dear .no its 18mm ply and torch on feel with celotex within between rafters
travel to the builders merchants and get some info and/or speak to your architect, you didnt use one did you
you inevitability to speak to planning and building regs as permission have been given on the appearance specified and structure/energy consumption. amend in roof have need of to be agreed with them previously doing the work. info first lets you put alternatives to them
Answers: The way I see it you enjoy two options.
1. Consider and treat your 10.4 scope pitched roof as a flat roof, e.g. 18mm boarding with three level of 'torch on' built up felt. I would seize a professional flat roofer in for this,as it is skilled and chancy work.Then put the tiles/slates you were going to put on, on 25 x 50 batten, on 25 x 50 counter battens directly resting on the felt. (the final lode does not have to be mineral finish,making that module of it slightly cheaper...and you don't have to dress the edges any. You have the piece of mind that it won't percolate and you can still have the finished look you require, and it will finishing a lot longer than a majority flat roof as it will be protected from the elements. (your fascias/ barge boards will have to be around 70mm deeper than they would have be.
2.Start by building the roof as high as you can, eg10.4 degree, then screw and paste firring pieces built up directly onto your rafters, 2x2 to 0 or 3x2 to 0 (depending on which is best for your span) until you accomplish the magic 12.5 degree the building regs require. Around the bottom of the window/s form 'wells' by removing the firrings to suit, and put noggings in between the rafter to create a flat roofed area near the required fall, and cover beside code five lead dressed up below the sides of the tiles and dressed over (at least six inches) onto the pitched roof. (get hold of a copy of the 'Cookson well-mannered lead guide' for handy tips and diagrams from your local Jewsons/builders merchants)
Edit:
Having read what I've written and surrounded by veiw of what other have said I feel the need to give more.
Regarding my option one, I ought to clarify that your roof would still be pitched -as dignified as you can- with a tile finish,(as per your building regs approval or planning permission) but beside three layers of built up feel underneath. this would need vent in the tradition attitude with soffit or beneath barge board vents, as any flat roof would. Drape the front frame of the felf into the gutter as usual and fill the frontage of the gap on the front cause by the counter batten and battens near strips of black plastic 'over fascia' vents, these allow any hose to run through. You do not need any underslaters feel or 'Tyvek' as this area -above the flat roof- does not involve venting, just around the rafters.
The function the manufacturers of the tiles put a minimum pitch on their products is because of the effects of capilary behaviour of water, travelling pay for under the headlap.You WILL want counter battens to consent to any water run down the torch on feel.
Batten sizes are usually 19 x 38 or 25 x 50, never 38 x 50
Wind driven rain' would not get into the roof any more than any other pitched roof.
This soultion be first made aware to me by my local building inspector, as so was approved.