![]() Particularly as you've had to go through planning I'm assuming you will need to involve Building Control? If that's the case then you will need to get a 'proper' set of design calcs from a qualified structural engineer to satisfy the B.C. Glad to hear that you're had the relevant permissions etc. I am wondering if you think I'll get away with 125mm X 50mm douglas fir if I do that? I was wondering though, if I braced the longer rafters against the supporting wall. ![]() ![]() The longest rafter is 3 metres the shortest about 2.4 metres. The whole roof will be pitched at 30 degrees. Not as heavy as larch.Ī final bit of help with the calcs would really be appreciated. I am thinking of going for Douglas Fir for the rafters rather than cedar (they won't be showing on the outside and will be stained anyway). Your earlier advice / calcs really appreciated.Īnyway, I now have permission so am getting organised again and I'd really appreciate a bit of advice. I really should have done as it is such a great resource. I didn't check back in the forum after I looked at the original replies. The project went on hold as I had to get planning permission. I feel really guilty about not getting back to you, really sorry. Condensation will be the only cause of rotting assuming the roof does not keak, so you wont need extremely durable timber. If the glass rests on rafter gasket they should be quite well protected from condensation internally. Maybe consider doug fir, siberian larch or iroko for the rafters? But thats for C24, iIm not sure WRC would be ok, its a pretty soft timber, often pretty wet. If the 1st rafter is about 3.2m long then maybe 6 x 2 would be fine, maybe down to 4 x 2 at other end. Id be tempted to get a length of softwood joist 5 x 2 and 6 x 2 and see what deflection you get when you stand on the middle of it. If your span is plan view then the longest rafter will be about 3.8m long, and you would need a bigger joist. I realise the calcs dont apply for a pitched roof, but are still relavent If rafter length then as a guide on a flat roof a 6 x 2, C24 will have a span max of 3.1m at 400centres and load of 0.25Kn. Use our calculator above to determine the proper joist span for your deck based on the type of wood or materials used, joist size, and spacing.Im not sure if the span measurement, is the greenhouse depth on plan or the actual rafter length. With this in mind, the joist span can range between 6 ft, 10 inches, to 18 ft. Depending on the size of the deck itself, whether your joists are spaced either 12 inches or 16 inches from the center, and the framing materials and size of deck boards used, deck joist spans may vary. The standard deck joist span can vary due to the size of your deck and the type of material used to construct it. It’s the strength and span that counts! What is the Standard Deck Joist Span? ![]() You can always stain a particular type of wood to match your aesthetic. Treated Hemlock or Pine may be a better solution. Check your local building codes for find out which species of wood are available in your market and - most importantly - check into the strength and spanning capabilities of a species.Įven if you like the look of Redwood, it may not be the strongest material available to you. There are also strength differences between Redwood, Fir, Pine, and other types of wood. Similarly, Southern Yellow Pine is less common on the West coast. For instance, California Redwood, Hemlock, or Douglas Fir are less common in the Southeast. Not every species of wood is widely available in every region. The location where you live plays an important role in choosing wood for your joists. To learn more about deck joist sizing, spacing, and allowable span, reference this chart. For example, joists spaced 16 inches from the center of the joist next to it can span 1.5 times in feet the depth of their inches. As a rule, the larger the deck, the larger the joists. If you just asked yourself “ do I need a permit to build a deck?” remember that the answer is almost always yes. As a critical part to a deck that will last you for years to come, it’s important to find out just how many joists you’ll need to safely support your decking - and that depends on the size of your deck and approved building permit plans
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