Joist thickness for a deck

**tryer** · 8th March 2010, 01:54 PM

Hi,
I recently contacted my local mill about purchasing some 190 x 38 hardwood for a post and rail driveway entrance and they will sell me a pack of random lengths for about $1 per metre (I have to buy 270 metres) so that's what I'm going to do.
I'll have a fair bit over and it was suggested to me that as we have to rebuild a deck on the side of our house that this timber could be used for decking.
The issue is that it's a bit thicker than treated pine and won't fit under windows and doors so I was thinking that when I replace the bearers and joists I could use 100 x 75's for the bearers and the same timber for the joists but lay them on the side so that they are only 75 vertically.
I know that the strength in the joists comes from being used with the longer edge vertical but these will be thicker and the decking will certainly be stronger than pine.
Will this idea be successful?
I know the proposed "decking" isn't grooved on the lower edge so I propose to seal the joists.
The joists are at about 550 centres, could I omit every 2nd one and make centres about 110.

Thanks
Tryer

**Rhys Cooper** · 8th March 2010, 02:33 PM

I dont know much at all about decking...but how much thicker are these pieces then the original pieces in place?

If its only a couple of mm couldnt you just plane the end so it fits under the windows/doors?
Or maybe get a timber yard, or someone with a thicknesser, to mill it to the appropriate size?

**tryer** · 8th March 2010, 03:24 PM

Thanks Rhys,
Your suggestion seems to be a really simple answer and after looking at the deck I reckon it'll work.
I could use 100 x 75's with the 100 edge vertically for both bearers and joists and as you simply suggest make the ends fit (guess I'd use a router) under the aluminium window frames.
Now I need to be sure that the 190 x 38's won't rot if they are in direct contact (they don't have grooves) with the joists. The current decking (treated pine) was installed upside down with the airing grooves uppermost and both the pine and hardwood joists have rotted.

Thanks

Tryer

**chowcini** · 8th March 2010, 07:44 PM

1. Joist size depends on span and spacing normally is 450 ctrs ,but these are normally on a bearer.
2. Why cant you check out the difference of height in the joist to fit under windows and dorss etc if not fix them on a pole plate ??
regards Chowcini

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