What is Fence Post Foam?

What is Fence Post Foam?Post foams, such as Postsaver Pro-Set Rigid Post Fixing Foam are a relatively new product that can be used as an alternative to Post Mix Concrete to set fence posts. When the two chemicals in the bag are mixed they produce a rapidly expanding foam which is fast setting, giving the same lateral strength as Post Mix Concrete. With one bag of fence post foam equivalent to two bags of Post Mix Concrete, could this become the new way to fix fence posts?

What is Foam Post Filler?

Does fence post foam work?

Whenever a new fencing method or product is introduced to the market, especially one which claims to match or even better the use of concrete to set fence posts, it will inevitably cause a level of consternation within the industry. Concrete has been in use since Roman times, so how could anything be better? Well, the Romans didn't have access to many of today's commonly used building products, and they certainly didn't have polyurethane foam.

It's easy to dismiss post foam as a product aimed at the DIY market that a purist would never touch, but in the US fence post foam has been in use for years to secure utility poles such as telegraph poles and power lines. As such, post foam has proved itself as a genuine alternative to concrete.

Is fence post foam environmentally friendly?

At first glance post foam doesn't appear to be very environmentally friendly - how could fixing a fence post with what is essentially a lump of plastic be good for the environment, when compared to concrete? However that comparison assumes that concrete is a natural substance which it definitely is not.

The CO2 produced in the manufacture of a bag of Pro-Set Foam is 3kg, compared to the 8kg produced in the production of two bags of Post Mix Concrete. If you then factor in the additional CO2 generated by transport and distribution (Pro-Set is 3% the weight of two bags of Post Mix) then Pro-Set Foam clearly has less impact on the environment than concrete.

How do I use post foam?

Using post fixing foam is very simple, however the foam reacts very quickly after mixing so make sure that everything else is prepared in advance. In addition, wear protective gloves and ensure that there are no pets or small children around.

What is Foam Post Filler?

One bag of Pro-Set will fill either one fence post hole dug with a spade, or two holes dug with a hole borer, so if you are planning on installing two posts then both holes and posts will need to be prepared in advance.

Dig your hole as usual and position your fence post - having someone else to support the post in position is ideal, or use temporary support joists instead. Simply remove the central safety strip, then agitate the bag to thoroughly mix the two chemicals. Do this for no more than 60 seconds as the foam will begin to expand quickly.

Snip a corner off the bag and pour the liquid into the hole. After only a few seconds you will see the foam begin to expand, eventually filling the hole and even rising above it. Don't worry about excess foam above ground level, this can easily be trimmed back to the bottom of the post with a hacksaw once it has hardened.

While the foam is expanding you can still adjust the levels of the post, and after about 5-10 minutes the foam will have hardened enough to support the post in position.

Leave the foam to fully harden for around 90 minutes, by which time the post will be fully secured in place.

What are the benefits of fence post foam?

One dramatic benefit of Pro-Set over concrete is its speed of use. From application to fully set and load bearing can take as little as 90 minutes, compared to up to 24 hours for fully hardened Post Mix Concrete. 

The other major benefit of Pro-Set over Post Mix Concrete is ease of storage and transport. Because a bag of Pro-Set weighs just over a kilo, compared to the equivalent 40kg of Post Mix Concrete, the benefits are immediately obvious. The small size and weight of the bags also makes them ideal to have on-hand for unexpected jobs.

As as an example, we compared how many bays of fencing materials could fit onto a standard flatbed, first with concrete posts, gravel boards, fence panels and bags of Post Mix; then using DuraPost posts, gravel boards and Pro-Set Post Fixing Foam. The equivalent 1200kg loads are shown below.

Ask the experts

For further advice about your fencing project don’t hesitate to speak to our friendly and knowledgeable experts at your local AVS Fencing & Landscaping Supplies branch. Postsaver Pro-Set Rigid Post Fixing Foam is available from stock subject to availability, click and collect from your local AVS Branch or delivery within our AVS Branch delivery area.

5th Jul 2021 AVS Fencing & Landscaping Supplies