The ridge-beam approach is simple except for the sizing of the beam, for which the IRC does not provide guidance. In an actual ridge-beam roof-rather than in our imaginary flat surface-the center beam can be raised to any height (see Structural Ridge Beam illustration), creating a vaulted ceiling below without an attic space (although the code does allow for building an attic by adding properly sized ceiling joists). The other ends of the rafters bear on the exterior walls. Again, picture deck joists connected to a beam with hangers. The rafters are then connected to the beam and transmit their full vertical load downward. The ends of the beam must be supported as concentrated loads, generally by posts inside walls or in the middle of a room. The ridge is constructed as a beam that runs from end to end. The rest of the roof framing then follows suit.Ī roof with a ridge beam can be more easily understood if it's imagined to be a flat surface-like a deck in plan view. They're most easily identified by the type of ridge used: either a ridge beam, which is a structural or load-bearing member, or a ridge board, which is a non-structural framing member. But when it's boiled down, there are essentially two standard methods of roof construction, each having some flexibility. Understanding this history provides perspective on why the treatment of roof construction in the IRC and the associated Wood Frame Construction Manual(WFCM) allows for such broad interpretation. Combining these disparate styles and standards into a single code-the International Residential Code (IRC)-was no easy feat, and seemingly fundamental aspects of roof construction are still up for debate. Between the Eastern and Western codes, there were even different names for identical parts. In the past, methods described by the three main building codes (BOCA, UBC, and SBC), though similar, differed based on climatic factors-such as expected wind and snow loads-local habits, and available materials. Long before any building codes were published, conventional roof framing methods developed through practice, resulting in approaches to roof framing that are as varied as the framers themselves. YMMV, there are always exceptions, never say never. The two are similar but a collar tie is IMO aways up higher and helps some with wall spread but mostly with stopping ridge sag. Maybe thats a angle to look into ?īTW collar ties connect to rafters, joist sit on wall plates and /or ledgers. Could be those rafters where code when the place was built. Span charts have been changed over the years as new wood isn't as good. Generally if it's existing and your not doing "to much" ( ya whats to much, ever building dept / inspector will have a different opinion on that) existing slight over spans in older buildings are allowed, not always, but the local inspector going to be the only one who can say, "Ya it's OK." Or his boss the local building offical.įor what it's worth a 1' 6" over span on a other wise well built building as in 16 " OC framing, 1/2" or better sheet good or 3/4 " real boards, etc. involved you need to ask them what they want you to do, or if they being public servants WHO you are in a way paying, think taxes, and they will not help you will have to hire a engineer, or maybe a architect / designer in your area, to design what your looking for / need to do. With all the weird screen names we use it sometimes gets blurry as to who's who and whats what. Rak it is sort of hard to keep every ones "job" sorted out. An inspector probably wouldn't care for it but it ought to be strong enough. That would triangulate the structure very nicely. Top plate to 2/3 of the way up the opposing rafter, joined in the middle. If there is no code and it has held up for some years, but you just want to reinforce it some I'd be inclined to do some kind of scissors rafter ties. If the powers that be want this to meet current code you will need to work with them. Almost certainly would need a structural engineer to sign off on that one. The other would be to use the existing rafter as the top chord of some built in place truss. A doubled 2x8 might satisfy them or a 2x10. One would be to "sister" the existing rafters. If the existing rafters are too small and you need to satisfy an inspector I can only see two solutions. Neither would substantially change the ability of the rafters to bear a 60 psf load. Ceiling joists that attach to the top plates & rafters & span the building do the best job of tying the walls together. Rafter ties, collar ties, whatever stiffen the roof structure a bit and help resist the outward forces that the roof exerts on the walls. ![]() I've never seen a roof spread at the peak except in a total failure, think hurricane or tornado. I hope PEG rides in to the rescue here 'cause I'm confused.
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