ᐅ Foundation/Base for WPC Decking

Created on: 8 Apr 2016 11:30
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baudu
Hello dear forum members,

The boss asked me to build a WPC deck. Currently, there is still grass growing there. The area measures 4 x 5 m (13 x 16 ft) and starts from the patio door. I am only concerned with the foundation.

This is what I have planned:
1. Dig to a depth of about 30 cm (12 inches).
2. Lay a geotextile membrane.
3. Spread a 20 cm (8 inch) layer of crushed stone, compacted with a plate compactor, with a 4% slope.
4. Add a 10 cm (4 inch) bedding layer of fine crushed stone, compacted again, with a 2% slope.

On this, I want to place individual rows of concrete edging stones, on which I can install the substructure.
I also plan to edge the whole area to prevent lateral slipping.

So far, so good. This also complies with the manufacturer’s specifications. Then a representative from a landscaping company came to make me an offer and said that he would never do it without concrete and reinforcing mesh and that he could not guarantee the work if done the way I am planning.

As I said, I wanted to do it myself anyway, but now I am a bit unsure.

Please share your opinions and knowledge on this subject.

Thank you in advance and have a nice weekend!
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nordanney
9 Apr 2016 17:06
jfkgerd schrieb:
I was thinking about buying these height-adjustable deck supports

You must have money!
jfkgerd schrieb:
Is that really unnecessary, or how do you make sure there is still a reasonably level surface when compacting??

I don’t care at all whether the compacted surface is level or not (you can see it in my photo). Because I use concrete bags, I always get a perfect base.
jfkgerd schrieb:
Because in terms of price, a solution with concrete slabs is obviously much cheaper.

But the subsoil for the concrete slabs must be suitable. Or you place them on concrete bags as a base and can level them accordingly.
My base for the 75sqm (807 sqft) area didn’t cost even $100. Why is it still so expensive? I bought screed concrete in bags instead of mixing it myself. The stones were leftovers, partly borrowed from neighbors. Otherwise, they would have ended up in construction waste.
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Sebastian79
10 Apr 2016 17:29
And the freeze bags were filled with fresh screed concrete? No space left for the supporting beams? Very nice idea and thanks for the photo.
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nordanney
10 Apr 2016 22:01
Exactly, just mix it lean and apply it. It won’t crack because, first, a substructure isn’t that heavy, and second, the bags are very durable.
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baudu
11 Apr 2016 12:45
And do you create the necessary slope by adjusting the length of the PVC sewer pipes, or do you simply jiggle the freezer bags a bit until it fits?
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nordanney
11 Apr 2016 13:03
baudu schrieb:
And do you create the necessary slope with the length of the PVC pipes, or do you just adjust the freezer bags a bit until it fits?

What slope? I always install the patio without any slope, as the rainwater drains through the joints – in that case, slope is only important for the subbase to allow proper drainage.
A wooden deck has the advantage of being able to be perfectly level.

P.S. You can shape the little bags like modeling clay, as needed.
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baudu
11 Apr 2016 13:39
And once the bag has cured, will you still drill into the structural beam?