The loads are based on adjusted roof snow loads from the governing building code. But I'm not aware of a prescriptive table that covers the combination of some 2x purlins plus thinner OSB sheathing. Rafter spans are tabulated for the most common roof loads. Spanning between the rafters is a separate check, and the info so far in this thread has been that 2x T&G decking can span 48", or that sufficiently thick plywood or OSB could work. The table states that 2 X 6 rafters spaced 16 inches on center (o.c) can span a maximum distance of 13 feet 5 inches. If the snow load is higher, then you'd need to check something like the WFCM to see if it has an applicable span table, with or with out the load doubling trick. Looking through the center of the table, we can find a couple of options. should span 10' (and be stiffer than typically required, as the deflection limit is L/360, not the L/240 or L/180 of the rafter span tables). So the 2x10 rafters with 10 psf dead, 20 psf live, and 48" o.c. If you halve the loading and double the spacing, the load per member is identical. If the dead load is 10 psf or less, and the snow load is 20 psf or less, then IRC Table R502.3.1(2) tells you than any of the species in #2 or better can span over 10' with 20 psf dead, 40 psf live, 24" o.c. So strong that in a smallish structure it seems like the main concerns for the uprights will be making sure they are properly attached and braced to prevent lateral movement/wiggle, and well protected against decay/damage.Click to expand.On the rafters, what is the dead load and what is the snow load? I'm pretty sure I'm unqualified to interpret these! Buuut I think the main takeaway is, vertical columns/posts of wood are REALLY strong. Is 'Outdoor Structures' Time Life any good or is it only fences, pergolas and deck type things?Īccording to 'The Timber Framing Book', pine on end can support 600lbs per square inch, so a standard 4x4(3.5"x3.5" true dimensions) pine post, on end, can support 7350 pounds.Īnnoyingly, the book does not seem to have a table of vertical strengths of other woods.ġ) A 'capacity of wood column calculator', allowing selection of various parameters including a variety of species: Ģ) A PDF published by the American Wood Council with a LOT of information in it: Can anyone point me in the right direction, please? I am thinking some arrangement of posts and beams, but I can't find any usable info on dimensions thicknesses etc. It seems anything goes on top of what folks in the US call stick framing, but I would rather not have too many uprights to work around and at 7m longest measurement, I am going to need some sort of support in the middle, where I really want open space. MAXIMUM CLEAR SPAN OF FLAT ROOF JOISTS IN METRES FOR SC3 TIMBER Spacing between joists Size of roof joist 400mm 450mm 600mm 47 x 97 1.84 1.81 1. So the actual roof is fairly straight forward, it's just 'how to support it' that's the problem. should refer to TRADA Document span tables for solid timber members in floors, ceilings and roofs (excluding trussed rafter roofs) for dwellings or ask your LBC Surveyor for advice. On the plus side, I can find no end of tables with detailed info on rafter spacing, span, loading etc. ROOF LOADS Rafter spans are tabulated for the most common roof loads. Sadly there is no source of round timber within sensible distance, so it's got to be standard flat roof construction, with rafters and EDPM. Regs also make building above 2.5 m high, prohibitively expensive so a proper timber frame is not really needed. It will only be small by US standards, 30m2 max due to local regs (UK). I am trying to figure out what size timbers I need for it's basic frame. CALIFORNIA CODE OF REGULATIONS, TITLE 24. but I digress, the current decision to be made is about supporting the roof:- First Version: Jul 2019 All Codes » California Legend Information Sections Notes 2019 California Residential Code, Title 24, Part 2.5 COPYRIGHT. I have made a 'freestyle' strawbale shed, and it's ease of construction makes strawbale very tempting, but I would like to make use of passive solar heating and I gather that solid cob is best for that, but then again, not much sun is going to hit the back wall if any. Sadly, at this stage, there isn't anything particularly permaculture about the workshop I am planning, except that I intend it to last a very long time! Once the roof is up, I can choose/experiment with solid cob, wattle and daub and rendered straw bales.
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