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Diy Metal Cladded Roof - Need Help!

  • 15-07-2011 7:57pm
    #1
    rustynutz
    Registered Users, Registered Users 2 Posts: 797 ✭✭✭


    Hi, I'm building a garage at the moment and may need some help with the roof construction. I intend on using box profile roof cladding, On 3x2 battons fixed to 6x2 rafters. The garage is 22 foot wide with a 40 degree pitch, I also intend on using the attic space for storage so need to keep as much space as possible. I have a couple of things I'm unsure of:
    1. What distance between the rafters? (I was thinking 800mm would be enough)
    2. What distance between the battons? Would 1200mm be too far apart?
    3. Would a purlin be required (like in a dormer house) under the rafter bearing in mind the rafter would be 16 foot long and I am using the attic for storage?

    Any comments appreciated from anyone in the know


Comments

  • #2
    1chippy
    Closed Accounts Posts: 1,716 ✭✭✭1chippy


    you havent given the lenght but if at all possible metal purlins from gable to gable would probably be your best option. if you using the attic and going with 800 centres you will have to put in extra joisting so it can carry any weight (usually at 400 centre).


  • #3
    rustynutz
    Registered Users, Registered Users 2 Posts: 797 ✭✭✭rustynutz


    1chippy wrote: »
    you havent given the lenght but if at all possible metal purlins from gable to gable would probably be your best option. if you using the attic and going with 800 centres you will have to put in extra joisting so it can carry any weight (usually at 400 centre).

    Thanks, the garage is 48 foot long so I'd say metal purlins would be expensive, would a 9x3 be good enough propped off the joisting like in my house?


  • #4
    1chippy
    Closed Accounts Posts: 1,716 ✭✭✭1chippy


    @48 you would have to put in a metal substructure to take purlins. could get costly but then again so will the timber. you shouldnt need a purli n 800 should be ok and then jo.ists at 400 with plenty of bridging so you can store stuff on it. not sure im allowed to give info on structural items but mods; delete if not appropriate. 20 ft is a wide span for joisting that has to be loaded so you will need heavy joists i know for a domestic house i believe 16ft is about as far as you can go with a 9 x2


  • #5
    rustynutz
    Registered Users, Registered Users 2 Posts: 797 ✭✭✭rustynutz


    1chippy wrote: »
    @48 you would have to put in a metal substructure to take purlins. could get costly but then again so will the timber. you shouldnt need a purli n 800 should be ok and then jo.ists at 400 with plenty of bridging so you can store stuff on it. not sure im allowed to give info on structural items but mods; delete if not appropriate. 20 ft is a wide span for joisting that has to be loaded so you will need heavy joists i know for a domestic house i believe 16ft is about as far as you can go with a 9 x2


    I know of a shed of the same width with a lower pitch roof that is built without a purlin under the rafters, just a collar tie(I think it's called?) about a third of the way down the rafter from the top and that's still standing after 8 years. I suppose the corrugated sheeting would have some strength along it's length unlike a slate or tiled roof. I hear what you are saying about the span for 9x2 joisting, might look into either 9x3's or maybe run I beam from wall to wall every 16 foot to carry the 9x2 in the opposite direction, whichever works out cheaper. Thanks for the advice so far 1chippy, any more advice would be welcome!


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