building a large pitch roof.

23 May 2011
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United Kingdom
Hello All, This is my first posting. I am building a large outbuilding. (playroom, gym, storage). Size 8.84 by 5.3 meters. Single skin 140mm dense concrete blocks (done) with insulated stud wall (to do). Height 2.4meter with 1.6meter high roof (Total heighe 4meters.) Questions
What size joist, perlin and rafters do I need?
Approx. number of roof tiles Redland roof tile 49 size 382x226mm?

Thank you, Thank you, Thank you.
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just finished having a garage built not far off the size you quoted. Building regs is a must or you can gaurantee someone will complain, only cost £160 ish pending on your council of course.

The wall your building will require lots of pillars to help support the single block construction, 1.5m apart normally.

Council wanted 8x4 RSJ installed front and back of my garage with 2x 9x3 timbers supporting the middle part of the rafters.

Council inspector was very helpful and providing you do as they say they are very helpful and obviously knowlegable

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Hi All, Thanks for your helphul advise. I will contact council about building regs. (I was trying to follow all the regs by researching)

Theoldun, the wall plate is the 8840 side and 8.84m x 5.3m is the overall measurements.

Hope to hear from you soon.
Have a good day all
If you want to go down the cut route, will deal with that first.
30 degree pitch
Ridge allow 3/3600 of 38x200.
Rafters. Half span at 30 degree pitch gives rise of 1530 = hypotenuse of 3060 plus say 400 overhang gives length of timber required for rafters as 3600.
3060 run of rafter will require 47x125 C16 at 400 centres without a purlin. Number required 46. If you want gable ladders you want 50 number.
Ceiling joists. With no spline wall you will need 75x225 C16 ceiling joists at 400 centres. Length 5700. You will have problems in finding this length, but they are about, and you will have to order them in. Number required 23. You could also use either Eco style joists, I joists or glulam beams
Binders. Now you are in queer street as you have no partitions to sit binders on. Answer. Stick 3 rows of herring bone strutting or solid strutting in and tell BC that ceiling joists are designed as floor joist. 63x225 will just about comply as floor joists over that span.
If he will not accept, then you either throw two steels across width of building or make up 2 king post trusses or TDA trusses. And rest binders on them.

Now that you know all that, forget every word we
have said and write to
Donaldson Timber Engineering, Airfield Industrial Estate, Enstone,
Chipping Norton, Oxon, OX7 4NP
For the attention Ian Mathews, Senior Design Technician
Enclosing a small sketch plan showing external measurements and width of walls and ask for a quotation to supply trusses and gable ladders as required with a 450 overhang, 600 centres and would suggest 35 degree pitch.
Bear in mind, if storey height is 2400, a 35 degree pitch will give you a total height at ridge, including tile, batten and ridge tile of 4056.

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