I have a neighbor who is going to put a new roof on an extension. A cold storage that will become a warm storage. He is going to replace the existing (snow-cracked) roof joists, which are simple 2x5", with half rafters to also be able to install an insulated ceiling. The width of the extension is about 3.5 m, so it's not a huge project in any way.
What dimension should they be built in? How should the struts be placed between the upper and lower beam, what angle should they be in relation to the beams? How many?
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