More Thoughts on High Density Polyurethane Foam for Column Backfill
Reader STEPHEN contributes a question regarding high density polyurethane foam for column backfill:
“Hello, I have this question I would like to pass along to the “pole barn Guru” to be answered, I doubt I will get the answer I need in the time frame, but I think its going to come up more often, so I am guessing now is a good time to ask.
With the idea of burying a 6x6x14 into concrete, the risk of Rot is very high. At a cost of about 50$ per post, you want to protect your investment, so many people are using a 6x6x10 and using the Study-wall brackets, but that drives up the cost to about 80$
So my question is, has anyone looked into using the new polyurethane instead of concrete?
Hopefully this response will prove to be timely in regards to your project.
Mike the Pole Barn Guru responds:
Let us begin with a discussing to overcome a fear of a “risk of rot is very high”. Actual field studies have proven an ability of properly pressure treated lumber to withstand decaying forces for greater than human lifespans: https://www.hansenpolebuildings.com/2017/12/will-poles-rot-off/. Trick, of course, is finding properly pressure preservative treated timbers. Five years ago I penned this article for a post frame industry magazine: https://www.hansenpolebuildings.com/2014/05/building-code-3/. Little has changed since then – lumber dealers and big box stores continue to sell pressure treated timbers without advising consumers as to what those timbers can actually be used for.
Now let’s discuss using high density polyurethane foam for setting columns, rather than concrete. At this year’s National Frame Building Association Expo there were several vendors promoting using their high density foam for setting posts – all of them having experience only from setting of utility poles. Utility poles carry a minimal downward load, so their holes are barely larger than column diameters, making calling for a pre-mix concrete truck impractical. Lateral loads on utility poles are also minimal as compared to columns in a post frame building, so a little high density foam easily provides a solution (and sets up quickly – allowing crews to move expediently from pole to pole).
Here is some more reading on this subject: https://www.hansenpolebuildings.com/2014/02/high-density-foam/.
Besides not being Code conforming, there is an issue of cost. Your suggested product provided at The Home Depot will provide a volume equal to five 80 pound bags of concrete (or 1/10th of a yard) for $37.63 or $376.30 per yard. With pre-mix concrete prices being roughly $100 a yard, concrete being Code conforming and not contributing to decay any more than would high density foam, it seems to me to be a no brainer.