Putting a merbau deck on top of concrete

[justin71]

Hi everyone, this forum came up in google when I was searching for decking

We have a little porch at the front of our house with concrete base. Its only a few metres wide by couple metres deep. The wife wants to put a deck down onto of it so it looks nice and enhances the front of the house.

I was just going to use 70x19 merbau as the decking. We only want the deck just above the concrete, just for effect if u like, so what size timber would I use for the bearers? I was just going to dyna bolt the bearers into the concrete going long ways and then have the deck coming out from the house. I suppose I would have to counter sink the dyna bolt holes so the deck is flush with the bearers.
What distance would I put between the bearers, 300mm or is that too close?
I was just going to use those deck nails that have the screw design so they dont come out, but merbau will crack will it? I was reading somewhere about it just before. I dont have a fancy nail gun. So what are the 'by hand' options?
Thanks a lot
regards
Justin

[brynk]

gday

with merbau you can lay battens at 500 centres & this will give you a little spring in the board. if you dont want that then close it up to 400. you could fix battens using the ramset masonry screw-anchor or even just some spaghetti & a timber screw - whatever you choose aim to have 40mm into the concrete, place them 500 apart also.

for a full discussion on screws vs nails & fixing requirements & methods etcetera read this -
https://www.woodworkforums.com/showthread.php?t=47415

if your concrete is recently laid you must let it cure for as long as possible before you put the decking over the top (a minimum of 1 month). you may also wish to lay black plastic over it, before fixing your battens down to it, to act as a moisture barrier - make sure there are no folds & that any overlaps are done such that the water flows over without getting under the plastic or trapped/ponding etc.

on that note same with your battens - be sure to lay them such that water can trickle around them rather than being trapped, or cut a couple of grooves on the face that meets the concrete, to assist with drainage on the rare occasions when it buckets down

hope that helps you out a bit -
r's brynk

[Tubby2]

Gday Justin, I've just done the same thing. I used H3 Treated Pine 75 x 45 battens dyna bolted to the concrete every 600mm. I had then lying flat so there was a 45mm gap between the concrete and the underside of the decking.
I put 90 x 19 Merbau on top and screwed them in with my battery drill. I predrilled the merbau to stop it from splitting but found that my el cheapo battery drill didnt have the grunt to screw in the 10 guage 45mm Type 17 screws so instead of just predrilling the 19mm decking I drilled down about 20-30mm into the batten as well and found that my battery drill coped well enough then.

The deck out the front was my first attempt and I have a bigger out back that I will try next, I ended up buying an Impact Driver from Bunnings for $99, Ozito is the brand and that also made drilling in the crews much easier.

If you wanted the deck a tad lower you could use 75 x 35mm battens.

Hope that helps.