I need to install a new mailbox. I will use a PT 4x4 sunk about 24" into the ground and the mailbox slips over the post. I am not certain what I want to use to secure the post. I could use a concrete mix or the polyurethane foam stuff. Does anyone have experience with the expanding foam? I am looking at 24" deep and realize the frost depth is over 36".
I would go with the concrete mix. Just do it like a fence post dig the hole dump the bag and pour some water in. I only used spray foam for insulation around windows or to fill a gap. Never tried it to support something.
I've never used it, but I would give it a try. I found several on Amazon, they all say it's as strong or stronger than concrete and definitely easier to use. Here's one
It will be interesting. Here, we have to worry about frost heave which is something one does not consider in California. All I can do is try. If it fails, chip it out and use concrete.
My preferred method is packed 3/4 minus gravel. Put an inch or so in the bottom of the hole Treat the bottom of the post. I use roofing tar Set the post in the hole Pour 3 or 4 inches of gravel in on all sides Pack it down tight with a 2x2 and a heavy hammer. Pack until it's solid Repeat until hole is filled.
We get a lot of rain here. Posts rot easily. I have pulled out posts that I have set this way after 20 years and they look new.
Thanks Steve for your suggestion. It is tough getting old and picking the way.you do things based on the amount of work. What you suggested is the way I would have done it 10 years ago.
I'm reminded of a story about a neighbor farmer in his 90s. Used 2 canes to walk. He was out in the field pulling fence posts.
It's hard to describe but he backed his truck next to the post, wrapped a chain around the base of the post and hooked the other end to the truck. The he wedged a short timber under the chain with the other end in the ground so the timber was was at a shallow angle. Then he pulled the truck forward. The timber would rotate up and lift the post out of the ground.
Each step would take him several minutes but after 20-30 minutes the post would be out. He probably pulled a dozen that day.
I like to get creative. I would make a bulb shape at the bottom and about 3/4 of the way down I would carve some 2" holes into the sides about 4 or 5" deep on all 4 sides to act like arms. Don't think it's necessary. but fun to think it helps.
Figuring out how to do something you have never done is what makes a good challenge.
The foam looks interesting. The first Amazon link that Bentlyj shared has a couple of videos that show how easy it is. I certainly like the idea of not moving 80lb bags of concrete around.
--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.
