Would this be good for pier installation?

[yesyes]

I just came across a video on YouTube where they use expanding foam to install fence posts.

My first thought was whether this would be good for a pier similar to the concrete filled waste pipe?

Or would the missing weight make this not vibration-free enough?

I haven't been able to find a price for it and it doesn't seem to be available in the UK yet.

[Jessun]

I'm not fortunate enough to have a pier, but if I ever get to construct one it will be as heavy as I can possibly make it. I'm not sure I'd even use this foam for a fence post...

[nmoushon]

My guess is that it works fine for a small fence but if you want something very rigid and string it wont last. First thing that comes to mind is the foam-in-a-can stuff you see people using on their cars and around wall mounted A/C units. Works great at first but after a year or two it just decays and starts falling apart. We also don't know how it last over time. How the elements effect it. Especially freeze/thaw cycles, which are the most damaging. Also not sure how pests will like it or not. So basiclly best thing is to wait to see what the real reviews are for customers not from the company reps. But my money is still on concrete.

[Freff]

It's not a system I'd use. After all it is only polyurethane, and no substitute for a 2 tonne plug.

[cantab]

AB foam is pretty dense and sturdy stuff, but the most obvious concern to me is that with a pier, mount, and scope fixed to a blob of it the whole affair would be top-heavy compared to a concrete foundation.

[Steve Ward]

Biggest problem will occur when the ground goes through it's usual wet/dry cycle and shrinks away from post , beit concreted or foamed in place .

Personally i have never concreted gateposts in the ground but prefer to use compactable hardcore and compact properly .

If posts do work a little loose after a few years you just recompact the packing .

When concreted posts work loose you have no way of adjusting.

Piers need a large mass of concrete at their base , ideally 1m cube or 1 ton of concrete , (with a layer of open polystyrene round outside in heavy clay-rich soil to accommodate the heave you get in wet weather)

I would personally use a steel pier bolted to said base.

[yesyes]

Right, so the main problem is the missing weight. Makes sense. Thanks