![]() One corner has suffered with significant damp issues, which we're working on, but the outcome is rotten joist ends in a corner of the ground floor. We're renovating an 1880 Victorian stone/rubble house. If the original rafter design did not call for the splice, then the structure below was probably not designed to take roof load at that location.Hi folks - would very much welcome some DIY advice. And that is provided that the roof load was designed into whatever supports the load-bearing wall at the lowest level. If there is a load-bearing wall directly beneath the splices, then a row of studs with spacing no greater than the rafter spacing could carry the loads, but then, a double top plate would be normal. That 2x4 on the flat isn’t even close to enough to do so. With the splice in the rafters, a girder is necessary to carry the two end loads of the rafter sections. It would be the rare master carpenter who could calculate the loads on a structure and design beams or girders to support those loads. ![]() Any structural member which spans a distance is a beam. Rafters, joists, and girders are all beams. The definition of girder is a beam which supports several other members. When repetitive primary members such as rafters or trusses need intermediate support, a girder is introduced. Purlins reduce the spans required for decking. So, in that case, secondary framing members are introduced, running perpendicular to the primary members, and these are called purlins. Obviously no decking can span that distance. Sometimes, especially in commercial buildings, they are widely spaced, perhaps in the order of 25 feet in steel structures. They could be rafters, trusses, or any other kind of structure, such as in steel buildings. There are primary framing members in a roof. Odds are good that any competent framing contractor could not only evaluate but correct this little problem for what you’d have your client pay just to have an engineer look at it.Ībsolutely positively wrong. There are also members called girders which are part of a truss roof assembly. Girders are framing members installed under floor framng. I don’t know how you define “secondary member”, but what you’re descibing is known to us master carpenters as a “block”. A truss roof never has a purlin assembly and a purlin assembly is designed to cut rafter spans and brace down to the tops of walls. The roof framing is improper, and requires evaluation by an architect or structural engineer.Ībsolutely wrong. I’d expect to see something like a pretty beefy double LVL where that 2x4 is, but without knowing the exact roof load nor the span of the girder, that’s all that can be said. Since there is a rafter splice, the rafters are structurally compromised, and must be properly supported under the splice by a beam or girder which is designed to carry the loads of the roof to points in the structure below, where such loads have a direct path to the earth. The 2x4 in the picture has a lot of growing to do before it can assume either of those names. Such a support is called a “beam” or a “girder”. A purlin is not a support for trusses or rafters. Therefore, the rafters illustrated in the photos above… violate IRC Code… and remain illegal under any circumstance where the IRC is employed.Ī “purlin” is a secondary member that spans between primary roof framing members such as trusses. Unless each end of the ‘splices’ of rafters are supported at the ‘splices’ (as Richard Hetzel rightly stated a few posts back) by a structural support at least 1 1/2" wide under each end… these ends ‘spliced by plywood’ do not structurally* ‘bear’* on anything…only ’air’…and therefore do not meet code minimums… ![]() ![]() “The ends of each rafter or ceiling joist shall have not less than 1 1/2 inches (38mm) of bearing on wood or metal and not less than 3 inches (76mm) on masonry or concrete.” Try section R802.6 of the 2003 IRC or 2006 IRC: Since Texas uses the International Residential Code in most jurisdications, you can view Chapter 8 of the 2000 through 2006 versions of that Code to help you understand proper rafter construction techniques. Could you tell us about this code that its violating? I would like to know so I can reference it. ![]()
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