Browse Forums Outdoor Living 1 Sep 25, 2012 2:23 pm Hi. I’m planning to build a deck over a concrete slab, the place has a roof over it but still some weather might come in. I was having a look at this site: http://www.thelogfactory.com.au/categories.aspx?catid=5 to see which joist size I’m going to use. There is to many specification and sizes and I don’t exactly know what I need.. Basically the joist will be dynabolted with brackets to the slab. The problem here is that I only have 150mm to the house floor, so taking out the 19mm of the deck I only have 131mm for the joists. Questions: 1) What timber and size should I use for the joists? 2) Should I leave a gap between the slab and the joist? How much? 3) Depending on the joist size I’m going to use, I might have to raise the joist 30-50mm, how do I do this? Supplementing the joist with joists offcuts and then using a larger bracket? Any suggestions? Thanks guys! Re: Joists timber and size 2Sep 25, 2012 2:47 pm 1. low level decks normally require and smaller joist that is laminated. 2. yes, at least 15mm 3. nylon chocks or similar. I'd suggest you work out the bracket you are going to use then work out your heights and then you can see what size timber you need to laminate to get close to the correct overall height. Re: Joists timber and size 3Sep 25, 2012 4:37 pm The smaller the timber size the more supports will be required. It really comes down to designing the deck to the span you have to the height available. What are the dimensions? Landscape Design & Construction http://cherub.squarespace.com/ Re: Joists timber and size 7Sep 26, 2012 5:22 am Run three battens 70 x 45mm on the flat (so 45mm high) evenly spaced across the 2400mm These can be directly fixed to the concrete with batten screws or similar (say at 500mm centres, pack up 10mm or till level using horse shoe packers) Then fix 70 x 45mm on edge for joists at 400mm centres With deck that will be 145mm Landscape Design & Construction http://cherub.squarespace.com/ Re: Joists timber and size 8Sep 26, 2012 11:37 am Thanks! that was really helpful! About the timber specs, should I use these? 70 x 45mm F7 Treated H3 http://www.thelogfactory.com.au/categories.aspx?catid=7 Re: Joists timber and size 9Sep 26, 2012 4:17 pm That's correct, your welcome Landscape Design & Construction http://cherub.squarespace.com/ Re: Joists timber and size 11Sep 26, 2012 6:50 pm ![]() Another question, can I dynabolt from the top of the bearer through the packer into the concrete? Is that a good idea? It should be cheaper than using L brackets dynabolted to the slab... Yes you can but use concrete screws rather than dynabolts, makes it a lot easier. Re: Joists timber and size 13Oct 01, 2012 6:59 pm the green shed (bunnings) sell metal U clamps, that you can dynabolt to the concrete floor.. 20mm taken by clamp and dynabolt. Use 90 x 45mm x 2 (two pieces per clamp) timber as joists.. using joist hangers (also from bunnings) fit cross members inbetween the joists every 1m or so for extra support. Lay deck. This way, the wood is all off the ground, and your right to go. I did a 70sqm of deck with 150mm clearance (130mm if you include the decking) and this was how we did it. ![]() Re: Joists timber and size 14Oct 02, 2012 8:00 pm Thanks humble, but I'm sticking with cherub's suggestion to use 45x70 bearers as it seems easier. Should I use 8x100mm or 10x100mm concrete screws? The bearer will be 45mm plus 15mm packers. Should I put a screw every 500mm or more? Cheers Re: Joists timber and size 16Oct 04, 2012 11:22 am Yep, Cherub suggested that. Those will be fixed with concrete screws directly to the concrete slab. I'll use 15mm packers to raise them a bit. You say they will bend? every how many mm should I put a packer to prevent bending? Re: Joists timber and size 19Oct 04, 2012 12:53 pm ![]() Humbles way would be far better, space the brackets out 450mm all round, set up some string lines and screw in the joists, easy! You could use 90x90 rather than two 90x45 Good diagram! ![]() I would do it using the above method.. like this.. that way you end up with this.. (rough) To hang the supports inbetween (just for stability more then decking use) use these: http://www.multinail.com.au/deploycontr ... age1_l.jpg You will find the brackets and the hangers in bunnings, brackets are about $3 each, come with 10mm wholes for bolting across your joists.. and into the slab. The hangers are about $1 each. 45mm Bolts are 50 for $50, galvanised steel, the brackets themselves are about 110mm high.. you will have heaps of room and your deck will not move. you do not need to ledger board this to the house. Hi All, about to commence a bathroom renovation and need some advice on subfloor works. Current subfloor is hardwood T&G floorboards on 90x45 joists, but intention is to… 0 5849 Thanks for all replies. I just noticed now the pictures I added to post right on top of page were wrong. I attached pictures showing "current" and my "suggested" floor… 9 14652 |