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First time post'er. Looking at installing a timber decking (90x19) on a concrete patio (red dotted line). The Concrete Slab also has ceramic tiles on it that i might need to drill through.
The slab is 75 mm below the house floorboards (door on top left that opens outwards). I would like to have the decking just below the floorboards (if not flushed).
Decking is 4.2m L and 3.0 m W. There are steps going down (bottom left and top right) as shown in drawing that I would like to cover with decking (blue highlighter marks showing direction of laying).
Joists are 70x45, laying them as shown (green highlighter), 70 wide and 45 high. That way, 45 + 19 (decking) gives me about 65cm. I am still unsure if I need to anchor the joists onto the concrete slab (through the ceramic tiles). Need some clarity on this and whats the minimum number i can get away with?
I was also thinking of using those spacers/footing protectors attached under the joists at regular intervals all through so that there is about a 5 mm gap under the joists and it doesnt come in direct contact with the ceramic tiles and has space for any water to run off.
The slab is curved (as shown), but I am making the decking rectangular so it will jut out and plan to support it with 3 posts (90x90). The height of the decking where the posts are going down will be 600 from the ground. So, i plan on taking the posts 450 deep in the ground and the balance 600 above ground.
Plan on using 10G-50mm SS screws (countersunk), Zenith?
Area is exposed and is North facing, exposed to run/no cover.
Stuff i am confused/need clarification on:
Do I need to dyna bolt the joists, if so, whats the least i can get away with? I will be staggering joists supports as shown.
Home floorboards are tassie oak (stained it a bit darker....) so, getting Merbau decking.... would look odd?
I was also going to pre-drill holes using smartbit countersunk and then use the decking screws.
No council permission is required as this is classified as regular maintenance.
Would love for you experts to cast your eyes on this post and the attached drawing and let me know if there are any gotcha's or things i might have missed (or validate some of my thoughts).
Thanks in advance...
19mm decking is adequate and I can't see any significant advantages of stepping up to 22mm.
The larger the gauge of decking screw the more holding force it has. The compromise is that the heads also get larger and more noticeable. 12 gauge stainless steel decking screws would be more than adequate for your deck. 50mm would be fine but if you did decide to use 22mm decking I would suggest 65mm instead.
Since your joists are 90mm wide you'll need to heavily countersink a 65mm screw to get much penetration into the joists/noggins. For joining the frame to the joists I would recommend countersinking Buildex 14-10 x 100mm Climacoat Bugle Head Batten Timber Screws - 25 Pack 50mm into the frame and two screws per join. For joining the noggins to the joists you could use Buildex 14-10 x 75mm Climacoat Bugle Head Batten Timber Screws - 25 Pack countersunk 50mm in the joist and two screws per join.
Mitchell
