garage roof help

15 Sep 2011
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United Kingdom
I plan on replacing a garage roof and need some advice.
the garage runs along the gable wall of the house (8mtrs)
It's a duo-pitched roof joined to a porch roof at the front with ridge tiles.
The porch rafters will also have to be replaced.
Imagine looking at it side-on as two right angled triangles sharing an upright.
the small triangle (porch) is 650mm high with 1400mm span.
so pitch is about 25deg which I want to keep as it forms part of a porch roof across front of the house with concrete tiles.
The large triangle (garage) is 650mm high and 7000mm span
so pitch is just over 5 deg.
I plan on covering this with tile effect eves-to-ridge metal roofing ( min pitch 5degs and load 10 kg sqm).
There is a steel girder support about 1/2 way along the 7mtr span.

I plan on doing the thing myself and would like advice on timber sizes
and truss make-up if poss .
The garage is 2.5 mtrs wide and the 650mm height is max I can go.
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If it were me, I'd be measuring what size timber is already in there and using that size and design as a minimum.

If you currently have tiles on there, then it should be ample strong with just sheet steel roofing.

We are using that tile effect steel on our new house, but were advised not to go to less than 30 degrees. We do have somewhat heavier rain than in the UK though.
Thanks Morris,
at the moment it's 4x2s every 500mm across the width .
as I need to raise the roof about 750mm I won't have a wall
to fix to (party wall with neighbours roof over it will be too low)
I'll need the rafters on the long span and it would be a bit
over-engineered .
I dont want to build my own wall as garage already tight.
can't get neighbour to compromise either even when I offered to
do the work to re-roof his garage.
Thanks again.
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When I built my workshop below I was not sure whether to use 2 x 4 or 2 x 6 timber, to take the weight of a tiled roof, so I sent the details off to a truss manufacturer and asked for a quote. They sent me an accurate drawing and a price back. :D

I thought it was a bit expensive, so decided to make them myself, to their design. ;)

Looking back, I'd have been far better off just paying the money and using their trusses, as when I calculated the cost of the timber, materials, and the sheer work cutting and building every truss in place by myself, I saved nothing. You might do as well to do an accurate drawing and get the trusses made for you.

It was a very interesting experience doing it myself though, and very satisfying.

I think these are called open trusses, or something like that, because I specified I wanted a usable loft space.




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