DIY Doctor

Decking excavation depth when replacing paved patio

Postby rick1632 » Sun Jun 21, 2020 9:16 am

I want to replace my paved patio (cheap 30mm paving slabs) with decking, but I don't want to raise the level too much for various reasons. Ideally it would be about 3" higher than current.

I had one suggestion to deck on 2x2 supports on top of the slabs, but I'm not convinced this is a great idea.

Alternate is to remove the slabs which are likely laid on sand with a mess underneath - where I have dug out it was hardcore (building rubble) with soil mixed in.

I'm thinking if I remove the slabs (30mm) and dig out 175mm, including the 3"(75mm) rise that would leave me with 280mm to play with - 100mm for the decking supports, 25mm for the deck and 150mm for the 6" joists.

That should leave me with 3 cubic metres of material to dispose of.

I could omit the supports and lay the joists directly onto the hardcore underneath I believe, but I'm guessing they'd rot far quicker that way.

Any alternatives I've missed?
rick1632
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Postby stoneyboy » Sun Jun 21, 2020 9:26 pm

Hi rick1632
Have a look at composite decking joists, they will be more expensive than timber but you could lay them direct on the existing patio saving a lot of digging.
Regards S
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Postby stoneyboy » Sun Jun 21, 2020 9:26 pm

Hi rick1632
Have a look at composite decking joists, they will be more expensive than timber but you could lay them direct on the existing patio saving a lot of digging.
Regards S
stoneyboy
Rank: Project Manager
Posts: 4372
Joined: Wed Dec 10, 2008 6:44 pm



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