Constructing Roof for Shed

Eugbug · 2016-10-08T13:44:23+00:00

So this is my first ever shed construction, about 20' x 10' by 8' highat the front, built from 4 x 2 s. Slope is about 1 in 9.5 or 6 degrees.I plan to use 4 x 2s on the edge for the roof rafters, and sheet withmetal cladding. At a 2' spacing, and with a 10 foot span, 4 x2s seemstrong enough with not much sagging. I haven't decided yet what to usefor the purloins, maybe 2 x 1 1/2 or 3 x 2 which would give bettersupport for walking on the roof if any maintenance needs to be done,plus less likely to be split by the Tek screws.So some questions:When I rest the upper top plate on the lower one, it doesn't sitproperly because the top plate of the front wall is level (see 4th and5th photos). Should I worry about that or just clamp everything down andnail? I could perhaps mitre the top of the stud at the back wall so thatthe plate seats better.For a 4 x 2 what's the recommended depth of the heel cut of the birdsmouth? I don't want to weaken the overhang of the rafters if I cut intoo much. I've seen figures of 1/3 or 1/4 of the width of the timbermentioned as a rule of thumb. Other suggestions are to make the seat cutthe width of the top plate ( 3 3/4" in my case). I tried this on a testpiece of timber and the heel cut is quite short for the slope of theroof, about 3/4 inch.When attaching the box profile sheets, I'm going to space the purloinsabout 3 feet apart. So do I need a purloin at the front and back of theshed in line with the top plate, or would the sheets bend down to thelevel of noggings which would be just above the top plate? (do I neednoggings here or just rely on a board nailed on to the overhanging endsof the rafters?)+-------------------------------------------------------------------+|Filename: ||Download: ||Filename: ||Download: ||Filename: ||Download: ||Filename: ||Download: ||Filename: ...

Oct 08, 2016 40 Replies

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The sheets would be supported in the middle of the span by the blocking which is spaced at 3 foot intervals. I know the blocking isn't resting on the rafters and the nails which would be taking a shear load, rather than the timber. However if I use 3 nails at the end of each blocking piece, this should take a reasonably large load. Also If I use purlins, all that's holding the roof and purlins onto the rafters and preventing uplift are the nails holding the purlins onto each rafter where they intersect. The only problem is making sure I screw into the right side of the centre line of the blocking because of the staggering effect.

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