I haven't checked actual strength of what you proposed, just quoting the bible.ĭouble up studs, at least, under the rafters. This is a heavy roof, so the 1200 mm column on the right side of the table is excluded it only applies to light roofs. The sheathing is too light by code FWIW, they call for 1-1/2" thick but at 4' span it only needs to be Fb 400 psi, thats #3 grade. Choose rafter spacing from Table 10.1 the options are 480, 600 or 900 mm. So what you need to do first is to get the pitch using the following formula: rise run × pitch. The one difference is that we need to calculate the roof rise using the pitch first. Assuming no storage on the joist a 2x8 in y-p would make the span in one piece. The formula used to calculate rafter length from roof pitch is, in fact, the same as the one above. A ceiling joist is one way of restraining this, the calc is telling how many nails it would take to resist that force at the connection to the rafter and in the splice if there is one. 3.2 Typical Assemblies With Trimming Brackets 24 3.3 Roofing & Walling Assemblies 25 3.4 Bridging Assemblies 26 3.5 Bridging Installation 27 SECTION 4 4.0 Purlin & Girt Limit State Capacity Tables 4.1 Design Notes To Limit State Capacity Tables 30 4.2 Index To Limit State Capacity Tables 31 4. ![]() You didn't mention a ceiling joist, notice the outward thrust on the wall under full design load is about 800 lbs pushing out on the walls per rafter pair. Nail load on 16d cc sinkers (hand drive 16's) 102 lbs/nail in poplar The roof you describe would fall under the typical 10 psf dead load assumption. For residential roofing, the minimum requirement for roof sheathing is thick. ![]() Ohio is mostly 20 psf snow I believe, your local building inspectors will know for sure.
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