May 13, 20242 yr I am planning an outhouse/gardenroom/shed. It will be a basic rectangle 6.5m wide by 4m deep. e.g front and back 6.5m and the sides 4m. I want to use corrugated cladding (aesthetic reasons) on the walls and roof so I have decided to build a pitched roof and not the flat rubber one I thought I was going to build. I have cut birdsmouths before and understand the rafter calculations to get all my cuts right but I cannot find any infomation on how to tie the front and back wall together. I know my roof will be relatively lightweight but I can't help thinking that it will push the front and back walls out if they are not braced together. I want to insulate between the rafetres so that when you walk into the room and look up you see the full height, like a vaulted ceiling. I cannpt find any info on how to construct that. Am I being super dense? The stud walls will be made from 6x2 and I am hoping 6x2 will also be good for the rafters. DO I need cross members> If so where can I find details on construction options? Many thanks
May 13, 20242 yr You cannot built a vaulted roof in the same way as a traditional or truss roof. You should talk to a structural engineer about what you want to do. Essentially you need a ridge beam (not a ridge board) to carry the rafters to prevent lateral thrust on the walls / reduce it to a manageable level.
May 13, 20242 yr Author 28 minutes ago, George said: You cannot built a vaulted roof in the same way as a traditional or truss roof. You should talk to a structural engineer about what you want to do. Essentially you need a ridge beam (not a ridge board) to carry the rafters to prevent lateral thrust on the walls / reduce it to a manageable level. thanks George. I don't want to talk to a SE about a small timber building with a lightweight roof. As I understand it you only need a ridge BEAM if your roof is 14 degrees or less. Mine is 22.5 degrees. I read that here https://todayshomeowner.com/roofing/guides/ridge-board-vs-ridge-beam/#:~:text=The ridge beam transfers the,%2F12 and 12%2F12. Edited May 13, 20242 yr by Kombi Camper
May 13, 20242 yr That is talking about shallow pitched roofs. The other reason for a ridge beam is if you have a vaulted roof. In which case the roof pitch is irrelevant (unless it's flat!). Edited May 13, 20242 yr by George
May 13, 20242 yr 1 hour ago, Kombi Camper said: As I understand it you only need a ridge BEAM if your roof is 14 degrees or less. Mine is 22.5 degrees. That is not true, you need either ceiling joists or a ridge beam to stop wall spread. Edited May 13, 20242 yr by joe90
May 13, 20242 yr Contact your local truss manufacturer about scissors trusses. They'll look vaulted from inside and their magic engineering software will do all the hard calcs for you.
May 16, 20242 yr On 13/05/2024 at 15:19, Kombi Camper said: thanks George. I don't want to talk to a SE about a small timber building with a lightweight roof. As I understand it you only need a ridge BEAM if your roof is 14 degrees or less. Mine is 22.5 degrees. I read that here https://todayshomeowner.com/roofing/guides/ridge-board-vs-ridge-beam/#:~:text=The ridge beam transfers the,%2F12 and 12%2F12. You could potentially use a few collar ties in the upper third of the rafters rather than full trusses or rafter ties and still insulate between the rafters and get a vaulted look. That article you quote does clearly show that a tie is required though if using a ridge board:
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