Notches are not to exceed 0.125 of the depth of the joist and are to be located between 0.07 and 0.25 of the span from the support. Timber to be covered, these span tables do not apply to timber which is fully exposed to the elements. These span tables apply only to flat roof and roof with a slope of up to 10 degrees. If insulation is placed on top of the flat roof joists and as such the joists are not fastened to the boarding above, the depth to breadth ratio of the joists should not exceed a ratio of 4 to 1. The dead loads shown at the top of span table above do not include the self weight of the joists, however, the joist self weights are included (in addition to the dead loads) in the calculations used to determine permissble clear spans. The allowable clear spans have been calculated in accordance with BS 5268-2:2002 Structural use of timber - Part 2: Code of practice for permissible stress design, materials and workmanship and BS 5268-7.2:1989 Structural use of timber - Section 7.2 Joists for flat roofs. * Boarding to be fastened on top of flat roof joists with a depth to width ratio greater than 4 First world problems.Dead load per square metre (in kN/m²) supported by joistsĬentre-to-centre spacing of joists (in mm) There's a 6 foot easement on that side to the fence, so the building wall will be reasonably close to the fence. OTOH, the north side where it will actually go did have the advantage that it could be closer to the "effective" line because the actual property line is about 7 feet into the neighboring property because of what had to be done when subdividing it years ago. It would be "logistically" and visually a lot better if it was on the south side rather than the north side but because of the required 15' side setback, a very large and mature willow tree would have to be destroyed. SWMBO is to not have the structure require removing any live trees. Positioning my own building has been an exercise because a "prime directive" for both myself and Professor Dr. Every property has its upsides and downsides. I'm sure that what you put up will meet the immediate need and you've mentioned that you do have a plan to move on in a few years to larger quarters. No way that would pass code now, but it's been there for 100 years and is still pretty straight. The funny thing i that the house is also 16 feet wide and has rough cut 2x4 rafters on 16" centers and a 12/12 pitch. If anyone knows of a rafter span table that goes up as high as 90# I would be very grateful to hear of it. It seems to me on a back of the envelope basis that full size 2x10 should be about right, but I am not an engineer. I think there is some extra strength in the full size rafters, too. It looks on the 70# chart like that would be okay, but I would need to go bigger for 90# presumably. ![]() They will be at 6/12 pitch, 24" centers and the span will be 8'9". ![]() I had specified full size rough cut 2x8 rafters on 24" centers. I would be happy to use whatever size rafters she told me to, but since neither of us knows what is sufficient I seem to be stuck unless I hire a structural engineer, which I would rather avoid if possible. The inspector also doesn't seem to know what size rafters are wanted. I can find rafter span charts for up to 70 psf, but nothing higher. ![]() ![]() The building inspector says that the roof must be designed for a 90 pound snow load. I have run into an obstacle in getting my workshop design approved.
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