Decking support

[Stephen]

Hi I want to put some decking down over a section of lawn. From what I've read, the normal approach is to sink uprights onto a concrete / brick pad and then bolt joist across these to keep them above ground level.

As we want to combine the decking with a pergola, I was hoping to do the following;

Sink several 10' x 4" posts 2' down into postcreted holes.

Then bolt 4"x2" joists to the uprights above ground level (this would make it far easier to make sure the joists are level).

Finish off with decking bearers and decking itself, and add the pergola cross pieces at the top.

This would create a fairly rigid and strong box structure, but mean that the weight of the deck would be supported by the bolts going sideways through the joists into the uprights (I suppose I could cut the joists into the uprights but wondered if this would be necessary).

Has anyone tried this approach - any comment ?

Thanks Stephen

[David Lang]

Hi Stephen

I built an 18' x 6' deck for my sister in law nearly 3 years ago. One long egde and one short edge rest on 6" x 2" timbers fixed to walls. The other two edges are supported by 4" x 4" posts as you describe.

Exactly what we did, posts at 4' intervals, joists held to them by 8 x 100 coach screws, 3 in each.

If you think about it, not only do you have the strength of the bolts (huge), you have the friction between the timber surfaces as well - 4" x 4". The deck we built is immensly strong & rigid and hasn't moved a millimeter in nearly 3 years.

HTH

Dave

[Stephen]

Thanks - That helps a lot. Only thing left of concern is the span - we want to put down an octagonal deck - spacing uprights every 4 or 5 feet at the corners is no problem, but there will be a span of over 10' across the deck. Does this mean I'll have to put a central support in or do you think the joist structure is enough ? Stephen

[David Lang]

Hi

I suppose it depends on the structure. 4 x 2 or 6 x 3?

Floors in houses span much more than 10' without central supports don't they. Personally I'd play it safe for what it would cost in time, effort & money. That way it won't flex.

Dave