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Decking over a patio.

Postby nl » Fri Nov 02, 2007 3:09 pm


I'm going to be decking over my existing patio. I'm planning to sink posts either side of the patio in the garden and then span the support beams accross from post to post. However it is quite a long span (approx 5m)so i also need to support the beams at a couple of points on the patio itself. The problem is that i seem to keep finding conflicting opinions of what is the best way to do this.
Some web sites say that the beams can be supported on additional paving slabs. Surley this would cause water to gather at these points? Other sites recomend supporting the timber with angled brackets which i feel would be best as there would be nowhere for the water to gather. I also had the idea to maybe just pack it out with concrete, i could then slope the edges to let the water run off.
Any opinions on the best plan of attack would be much appreciated.

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Simply Build It

Postby MickD » Thu May 29, 2008 4:03 pm

Hello Neil,
I expect you have already done your decking but anyway!
I have done quite large deckings on my last 3 houses with great results and all on excisting patios.
I generally start with the outside frame, remember at ANY given span for the entire build you must have post supports at least every 1800mm but if your decking is large you will need to be inside this say 1500mm this is because if your decking is large you may have 30 people on it at any time, which is fine - if they are all spaced out across the decking! But if a lot of people bunch together, thats when you need the extra strength from the extra posts. Most D.I.Y. superstores now give out free booklet on the size of posts, joists, decking boards etc. When I do the frame I make sure that it level all the way across the two end sides with a Deleted level or lazor with the other ends 1 inch below the other and in the same direction as the groves in the decking boards. This is to allow water to run off in which ever direction you want. The joists that will run from frame to frame (and is what the final decking rests on) need to be no more than 400mm wide. Any more than this and you will get "springy" boards and it will in time "bow" down and effect the water flow and will generally look rubbish!. Always counter sink the decking screws, because the beauty of decking is that kids love to play on it so you don't want raised screw heads. As for the posts on top of the patio, I used excisting flag stones raised a little to allow water to run away and not collect at the post, sure the post bottoms will get wet, but if you use 4in by 4 in posts it will take many, many years for the posts to be comprimised through rotting. Also remember that all the timber you use will be treated. My advise is to buy your timber in one go at a major timber suppliers like Alsford etc. they are a lot cheaper than the D.I.Y. superstores.
Hope this has helped you and anyone else.
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