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Lean-to roof

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  • 09-10-2020 11:54am
    #1
    Cattleman101
    Registered Users Posts: 25 ✭


    I have a yard 30ft x 16ft that I want to roof. There is an existing stone building beside it and a 6ft wall on the other side. What I am planning to do is put up 3 10ft girders along the wall and put the rafters from them into the building (roughly 15 degree angle). Would 9x3 timbers do for the rafters or is there a need for steel rafters?

    edit: Also wondering if I go for timber rafters, whats the best way to fix them to the girders?


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    #2
    J.O. Farmer
    Registered Users Posts: 2,429 ✭✭✭J.O. Farmer


    Assuming the span is 16ft, will an 18ft timber do it.

    6x3 timbers should be heavy enough, I'd put in maybe 6 of them.

    Weld plates to the side of the girder so you can bolt the timbers on.


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    #3
    Cattleman101
    Registered Users Posts: 25 ✭Cattleman101


    J.O. Farmer wrote: »
    Assuming the span is 16ft, will an 18ft timber do it.

    6x3 timbers should be heavy enough, I'd put in maybe 6 of them.

    Weld plates to the side of the girder so you can bolt the timbers on.

    When you say 6, do you mean to put 1 each side of the girder? I'd like to rest the timber on top of the girder if possible so the weight is down on the top of the girder rather than a plate along the side.


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    #4
    Earnshaw
    Registered Users Posts: 198 ✭✭Earnshaw


    Is the head height going to be 6 foot on one side of the shed?


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    #5
    minerleague
    Registered Users Posts: 1,030 ✭✭✭minerleague


    Cattleman101 wrote: »
    When you say 6, do you mean to put 1 each side of the girder? I'd like to rest the timber on top of the girder if possible so the weight is down on the top of the girder rather than a plate along the side.

    If you cut the top of girder at the angle of the roof and weld on 3x3 angle iron.
    Drill a hole then in the upright part. Instead of 9x3 timbers get 6 9x2 and bolt 2 together to form 3 9x4 ( much stronger with grains in different directions)


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    #6
    Cattleman101
    Registered Users Posts: 25 ✭Cattleman101


    Earnshaw wrote: »
    Is the head height going to be 6 foot on one side of the shed?

    No 10ft on one side and roughly 12ft on other side


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    #7
    Farmer_3650
    Registered Users Posts: 574 ✭✭✭Farmer_3650


    2 brackets 3 inches apart on top of the girder like this with the 9x3 in between them should work. Could put 2 bolts across on it then.

    Apologies for the picture being sideways. The faint blue lines are the rafter and the dark blue are girder. Red then is the brackets.


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    #8
    Cattleman101
    Registered Users Posts: 25 ✭Cattleman101


    minerleague wrote: »
    If you cut the top of girder at the angle of the roof and weld on 3x3 angle iron.
    Drill a hole then in the upright part. Instead of 9x3 timbers get 6 9x2 and bolt 2 together to form 3 9x4 ( much stronger with grains in different directions)

    Angle Iron on the angled side or on the lower side of the girder? The 2 9x2s is a great idea, think I might do that.


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    #9
    Cattleman101
    Registered Users Posts: 25 ✭Cattleman101


    Farmer_3650 wrote: »
    2 brackets 3 inches apart on top of the girder like this with the 9x3 in between them should work. Could put 2 bolts across on it then.

    Apologies for the picture being sideways. The faint blue lines are the rafter and the dark blue are girder. Red then is the brackets.

    Thanks for the drawing, another good idea. I wonder would I be better to put 1 bracket on the lower side though as someoene else suggested and bolt into the end of the timbers rather than the side. Which would be more prone to crack.


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    #10
    J.O. Farmer
    Registered Users Posts: 2,429 ✭✭✭J.O. Farmer


    Cattleman101 wrote: »
    When you say 6, do you mean to put 1 each side of the girder? I'd like to rest the timber on top of the girder if possible so the weight is down on the top of the girder rather than a plate along the side.

    Sorry missed about only 3 girders. That leaves a long span for the cross members. Could you get even a 4th girder in. It'd reduce the span to 10 foot instead of 15.


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    #11
    minerleague
    Registered Users Posts: 1,030 ✭✭✭minerleague


    Cattleman101 wrote: »
    Angle Iron on the angled side or on the lower side of the girder? The 2 9x2s is a great idea, think I might do that.

    angle iron on the cut (top) sloped part of girder. could make the angle iron 2 or 3 feet long to support the timber rafters. you will need to know the slope of the roof to make this work ( put girder in place, propped not set, and pull a string to other side, should be able to mark girder then )


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    #12
    Farmer_3650
    Registered Users Posts: 574 ✭✭✭Farmer_3650


    Cattleman101 wrote: »
    Thanks for the drawing, another good idea. I wonder would I be better to put 1 bracket on the lower side though as someoene else suggested and bolt into the end of the timbers rather than the side. Which would be more prone to crack.

    not sure what way would be more prone to crack, thinking about it the other idea is probably a better option though.


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