ᐅ Setting WPC Fence Posts in Concrete

Created on: 26 Jul 2022 21:47
A
AD1988
Hello everyone,

I hope I can get some help from you here.

After living in our new build for 3 years, we finally want to install a privacy fence. We plan to install 1.80m x 1.80m (6 ft x 6 ft) WPC fence panels along a length of 23 meters (75 ft). At the edge of our property, we have set up Bellamur 50 x 25 x 20cm (20 x 10 x 8 inches) masonry blocks. These blocks are stacked in two rows on top of each other, placed on gravel, and filled with concrete. We did this because there is a slight height difference between the street and our property. At the points where the posts will be concreted in, no concrete has been poured yet. At these spots, we can still drill through the masonry blocks into the ground, and I could also drive steel rebar into the soil.

My question is whether this will be sufficient, as the 1.80m (6 ft) fences already have a large surface area and should therefore be stable.

Thanks in advance for your answers.
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cschiko
27 Jul 2022 14:25
I see it similarly! What might work, but isn’t really a proper solution:

1. Dig down at the corresponding spots on the garden side and then "hollow out" under the stones. The problem here will likely be that the gravel keeps shifting.
2. If you manage to do this somewhat neatly, you could pour a small concrete footing using formwork and then install the rebar and posts from above.

However, this is all a makeshift solution, and I suspect that you can’t properly undermine the wall.
Tolentino27 Jul 2022 14:34
I’m not sure what the 25 dimension refers to. But if that’s the width, which is what it looks like to me from the pictures, then the clear width is about 17cm (6.7 inches) minus 8cm (3.1 inches) for the two wall thicknesses. That corresponds to the diameter of a typical earth auger. If he really left a hole like that every 1.8m (6 feet), he can easily pour point foundations 80cm (31.5 inches) deep there. Reinforcement can be added, and the stone courses can also be reinforced horizontally. In my opinion, that should hold, but I’m not a structural engineer.
Tolentino27 Jul 2022 14:46
Oh, a quick addition. I wouldn’t use WPC for the posts, if that was the idea. They should be made of steel, or at least aluminum. If WPC must be used (for aesthetic reasons or so), then don’t embed them in concrete. Instead, use post anchors and fix them onto the blocks.
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AD1988
27 Jul 2022 21:27
Thank you very much for the many ideas and suggestions. This is exactly why I asked here—I don’t want to put together something I’ll regret later.

For the WPC fence, aluminum posts will be used. I can even order them up to 300 cm (10 feet) in length, so there should be enough material for embedding in concrete.
The holes in the masonry have a diameter of about 15.5 cm (6 inches). I was planning to get a 130 mm (5 inch) drill bit and try to drill at least 50-80 cm (20-31 inches) below ground level. This way, up to 1.2 m (4 feet) of the post would be set in concrete. Shouldn’t that actually be sufficient?

We also had the idea to get a WPC fence with 2-5 mm (0.08-0.2 inch) gaps between the individual panels. Would this make any difference regarding wind load, or would it hardly have an effect?
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WilderSueden
27 Jul 2022 22:14
Using a drill is not a bad idea and could work, but 13cm (5 inches) is really a very small diameter and therefore creates only low pressure in the soil.

I’m not sure if such narrow slots will actually provide any meaningful relief. They will probably cause turbulence on the other side, which in turn creates pressure again.