mcerd1
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| posted on 14/1/11 at 12:54 AM |
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OT - New garage roof design ?
14" of snow on the roof was too much for my old garage (pic)....
so now I need a new roof
its a span 4.5m @ ~11 deg (so nearly 4.6m long rafters) with about 2.5m between the rafters
I'm not going to re-roof the whole thing (35m  ) just 10 to 15m of it depending on how much i can afford
at the low end I recon I'll need to put in some small columns as I don't trust that wall to hold and decent roof (steel or concrete
blocks)
its going to be sheeted in steel, posibly with layer of ply under it (old roof is asbestos cement on to tongue and groove boards) unless there is a
cheap source of those kingspan type insulated sheets
other than that I'm thinking steel rafters (smallish UB's ?) with timber purlins
anyone know any good websites / design guides ?
(any other thoughts or suggestions are welcome too)
I actually do structural steelwork design for a living, but somehow I've never done a roof before - I suppose I'll nead to learn quickly
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alistairolsen
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| posted on 14/1/11 at 07:47 AM |
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Hi
What you really need is 45 x 195 rafters at 600 mm centers, sarking with felt on top, 10 mm counterbattens on top of rafters and 25 x 50 rafters at
max 1000 mmm centers to fasten the steel sheets to.
Sarking and felt will stop any condensation from te bottom of the sheets, battens give the extra airgap reqd.
Above proven to work with two feet of snow in middle of december
Cheers
My Build Thread
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loggyboy
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| posted on 14/1/11 at 10:22 AM |
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Try these, all thought this Part A 1992 has been superseded by 2004 verison, (which doesnt include all the info) these are the best place to get
guidance on sizing of roof timbers. (pages 44 onwards). If you were to use sizes within this document, a building inspector is unlikely to argue, so
should keep you (and the things in the garage) content too.
http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_A_1992.pdf
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caber
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| posted on 14/1/11 at 01:52 PM |
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While your at it why not design yourself a steel structure to support a small electric winch like those sold at Aldi and Lidl for about 5o quid. An
RSJ down the middle would allow you to put it on a rolling carrier. also how about raising the roof and getting hold of a second hand ramp? I would be
for both those improvements. If you put a serious pitch on the roof it will prevent further snow damage and this is a good excuse to raidse the roof
when you have to talk to planning or the neighbours about it!
Caber
PS glad the car wasn't in there when it came down!
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mcerd1
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| posted on 14/1/11 at 02:09 PM |
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any ideas on costs for doing the rafters in wood ?
I'm leaning towards steel because thats what I know, but I might change my mind if timber is half the price...
raising the roof had crossed my mind, not sure I could get away with much if any (trying to avoid dealling with planning)
its not that I'd have any issues with planning (could knock the whole thing down and build twice the size if I wanted) its just that its extra
hassle, time and money when all I really need is a watertight space big enough for 2 - 3 cars and some storage / benches (i.e. just enough that
I'm not in my dads sheds all the time)
besides its my dads shed not mine, so at the end of the day I don't even own it
if it comes to lifting stuff I've got a couple of engine cranes that'll fit in the shed or I can wheel it out the door and use this again
as for a ramp it would be nice to have my own, but why spend more money when I can just use my dad's one thats 200 yards away
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