![]() ![]() ![]() Thanks for all the advice, sure learning lots. Rafters are just one component in a roof system, along with collar ties, ceiling joists, rafter ties, strong backs, and weight-bearing walls. I wanted a 3 foot knee wall and was planning on a brace from top of each beam to post extending above beam, I could sacrifice and go to a 2 foot knee wall but i know that will reduce my headspace above. Could you place pulins down from the ridge until they would interfer with dormer, then run rafters down from the last purlin but at right angle to ridge to a plate? to frame in dormer opening? I kinda have my heart set on gable dormers and 1/1/ stories. Also it seems as though purlins, running parallel to the ridge would make dormers diffucult to frame since their ridge would run at right angle to the purlins. Learn about residential roof framing basics in part two of our three-part series. With this sort of span would I also need a king post or queenposts support? I plan on 3 bays 12, 8 and 12 again and the interior walls on second floor would be on same demensions so the posts will not be an obstruction as long as the tie that connects rafters and post can be set high enough for a door. So the principal rafter (i think this is the correct term for large 8x8 beams? that go top of each post, meet at ridge) and purlins is what I need. I have done 2 small timber frames and both used this type of roof but it sounds like it will not work for a larger building. If my idea seems structurally sound I would skip a pair which on the 2 foot spacing will leave my 6 foot for the dormer. ![]() Also would like to have 2, 6 foot wide gable dorms in each roof, but am not sure if they would affect what I have planned. I would rather overbuid some then cut it close as I am cutting my own timbers so within reason a little bigger timbers or closer spacing is O.K. The roof will be an 8/12 pitch with the rafters 2 feet on center and will be covered with Foam panels and then metal for a house in Vermont. If I set the ties 3 feet down from peak that still leaves decent head space but I am not sure if that will be a good solid roof. The steps are in accordance with Chapter 8 of IRC 2018 and Clauses 23.4, 28.1.1, 28.2.1.1 and 28.3.1 of IS 875-1987.All relevant formulas used are shown. The rafters would be just a little over 13 feet long from plate to peak. But that starts to reduce my head space below. Ceiling joists in most houses also serve as rafter ties. A lack of rafter ties is a significant structural issue in a conventionally framed roof. My problem is I know the closer to the center (lower down from peak) the ties are the more they help prevent rafter spread. Other facts about rafter ties: Rafter ties are always required unless the roof has a structural (self-supporting) ridge or is made with engineered trusses. I would like to use 4X6 whitepine rafters with an open mortise at the top and the same size collar ties. I am trying to design a frame for a 22X32 foot, 1 1/2 story with a full plate set on top of a 3 foot kneewall, 4 bents total all 8 x8 posts and 8 x8 beams(?). ![]()
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