Foam for Fence Posts (1 Viewer)

[45Kevin]

My neighbour used this product instead of concrete to set his fence posts several years ago. The 25' long, 6' high fence is still straight and solid.

So I thought I'd try it on a couple of posts that needed replacing in my yard.

The package advertises that one pack can do two 4x4 posts.

In theory.

I mixed the two parts together for the suggested 20 seconds and the bag got hot and swelled up so when I opened the corner it streamed out like a shook up beer. All over the ground and trees and plants. I managed to get enough in post hole only.

I got a second package for the remaining post and it worked out great. I didn't mix it as long and as soon as the pack started getting warm I cut the corner and poured it in to the hole. It was too much and I had to trim the mushroom off so to speak.

Seems like a good substitute to concrete. Same or less price. Lots less work. Sets in a 1/2 hour.

Your posts have to be set exactly as you want them because there is literally only a few seconds before the foam starts to set and adjusting the post becomes impossible without ruining the foam.

 

[PAToyota]

I've seen some demonstrations of foam being used to stabilize soil or fill in sinkholes. Unlike concrete, it doesn't add to the weight (potentially causing more settlement) and can be easily dug through in the future.

 

[45Kevin]

This product specifically mentioned that it should not be used in that manner.

 

[PAToyota]

I was just commenting that foam products are replacing similar cementitious products.

 

[LS1FJ40]

I sell fencing for a living (one of the things in addition to windows, roofs, decks, siding, etc). We tried this stuff for a customer with the agreement that if it doesn’t hold up we will replace it.

It performed exactly as I expected foam to perform. Poorly. A year later we pulled it out and did it the “right” way.

The only saving grace was that it made it super easy to tear out.

Our method:
Drill down 48” (frost line is 42” here)
3” of river rock
Set post
100lbs of fast set Quikrete

 

[PAToyota]

So, what failed? One potential issue I'd see would be UV resistance - many of the foams aren't. I also see in Kevin's photo a crack around the top of the post in the foam that would let water down in - which could deteriorate both the post and the foam. I could see it possibly loosening up over time with that.

 

[LS1FJ40]

The holes “wallowed” out. So the fence got “loose”. You could move the fence an inch in any direction.

 

[4x4veteran]

I have rail road ties for gate posts at the entrance of my driveway.

I dug down two and a half feet and set them in cement that I mixed.

They had set for over 25 years straight and solid until some butt wipe hit one breaking the tie at the base causing it to lean.

The part of the post in the ground was still straight and solid.

After some digging it took a couple of yanks with a cable hooked to the Toy to get it out.

I guess if it had been foam instead of crete the whole post would have fallen over and I could have reused it.

I put in a new post and mixed up some Portland to hold it.

As for the **** that hit the post didn't have the balls to stick around I can only hope it did some serious damage to his vehicle.

 

[45Kevin]

I also see in Kevin's photo a crack around the top of the post in the foam that would let water down in - which could deteriorate both the post and the foam.

I looked at that and considered cutting the "mushroom" down further until I got to a spot where the foam was tight against the post. I don't expect that to be a problem though I will be watching it.

The holes “wallowed” out. So the fence got “loose”. You could move the fence an inch in any direction.

That's funny because my neighbours fence is holding out well after about 5 years.
When you say wallowed out, do you mean the foam started breaking down, or the dirt around the foam started getting loose?

 

[LS1FJ40]

The area between the post and foam. The post rocked back and forth and compressed the foam. Maybe it was too windy in that area? I know we didn’t have any issues with the concrete in the same application.

 

[Proven]

The last time I built a deck, code enforcement told me that I could not use "post in hole" construction. I had to use the round forms with a bracket mounted to the top.

I have seen foam used to install telephone poles after storms tear them down. After they left a mushroom of foam kept oozing out of the hole, but it is still solid to this day.

 

[LS1FJ40]

The last time I built a deck, code enforcement told me that I could not use "post in hole" construction. I had to use the round forms with a bracket mounted to the top.

I have seen foam used to install telephone poles after storms tear them down. After they left a mushroom of foam kept oozing out of the hole, but it is still solid to this day.

Code here doesn’t allow concrete to be poured around the post. Most often we dig 6’ down in order to get past the frost line. Pour concrete to 48”. Then set 6x6 posts on the concrete then fill with dirt. We use ground contact 6x6s. Filling with dirt allows water to wick away from the post.

We used to pour concrete all the way up above the ground and use brackets to attach to the concrete to divorce the two materials and preventing wicking. I don’t personally care for the look of the brackets.

 

[Rugy]

For wood fence post that go into the ground we do the following.
Hole is 3 to 4ft deep. Our frost line depth is 18".
6 in of 3/4 " clear crush.
PT post held up 5-6 from garvel.
Mix concrete in wheel barrow or bucket, fill hole and slope concrete away from the post so no water sits on top.
No call backs in 30 years.

 

[e9999]

Hopefully this is one of those few products that greatly exceed one's expectations...

 

[Rigger]

My method of setting fence posts:

Dig hole with either auger or hand double clamshell doohickey. Make pile of the removed dirt.

To the removed dirt, add half of a bag of dry Sakrete mix. Don’t batch the Sakrete, don’t add water, just dump it in with the dirt. (Buy the cheapest Sakrete or similar product you can find.) Using a hoe or shovel, blend the Sakrete with the soil.

Place preservative-treated post in hole. Add dirt/Sakrete mixture around the post in shallow lifts, and tamp with the end of a shovel as you slowly backfill. Keep checking for plumbness of the post as you go up. Tamp it nice and tight.

The mixture of dirt and Portland cement will hydrate with naturally-occurring ground water and will make a pretty danged strong soil cement. If you have really dry soil, you can add a bit of water as you tamp. Curing takes a few days to stiffen and a few weeks to get really stout.

I’ve done a number of fence posts like this. It works great, and is pretty quick and easy.

 

[thatcabledude]

Proper technique goes a long way.

 

[Marine7]

My method of setting fence posts:

Dig hole with either auger or hand double clamshell doohickey. Make pile of the removed dirt.

To the removed dirt, add half of a bag of dry Sakrete mix. Don’t batch the Sakrete, don’t add water, just dump it in with the dirt. (Buy the cheapest Sakrete or similar product you can find.) Using a hoe or shovel, blend the Sakrete with the soil.

Place preservative-treated post in hole. Add dirt/Sakrete mixture around the post in shallow lifts, and tamp with the end of a shovel as you slowly backfill. Keep checking for plumbness of the post as you go up. Tamp it nice and tight.

The mixture of dirt and Portland cement will hydrate with naturally-occurring ground water and will make a pretty danged strong soil cement. If you have really dry soil, you can add a bit of water as you tamp. Curing takes a few days to stiffen and a few weeks to get really stout.

I’ve done a number of fence posts like this. It works great, and is pretty quick and easy.

Glad to see others use the technique I’ve been using for years! It’s the best way I’ve found.

 

[swelltimes]

My method of setting fence posts:

Dig hole with either auger or hand double clamshell doohickey. Make pile of the removed dirt.

To the removed dirt, add half of a bag of dry Sakrete mix. Don’t batch the Sakrete, don’t add water, just dump it in with the dirt. (Buy the cheapest Sakrete or similar product you can find.) Using a hoe or shovel, blend the Sakrete with the soil.

Place preservative-treated post in hole. Add dirt/Sakrete mixture around the post in shallow lifts, and tamp with the end of a shovel as you slowly backfill. Keep checking for plumbness of the post as you go up. Tamp it nice and tight.

The mixture of dirt and Portland cement will hydrate with naturally-occurring ground water and will make a pretty danged strong soil cement. If you have really dry soil, you can add a bit of water as you tamp. Curing takes a few days to stiffen and a few weeks to get really stout.

I’ve done a number of fence posts like this. It works great, and is pretty quick and easy.

Yep, I've done the same thing with 6 x 6 posts on my property, and they've held up great. Some of the 6x's have gates on them (with our friends kids climbing on them like ladders), and others are anchor points for long runs of horse fencing that I tensioned pretty tightly. I'd be a little nervous about using foam in a situation like that.

Some pics of when I was installing the posts and fencing. Luckily, a buddy with a tractor and auger helped dig the holes out for me, about 3' deep.