I’m considering building and installing a Little Free Library. In researching installing the 4x4 support post, several places online suggest digging the hole, pouring the concrete mix in dry then adding water. Example:
I can see the appeal of this - no messy mixing - but will all of the mix get saturated?
I just never heard of this method.
I used to think the same thing, it works great for small projects like your library. I removed a post that I did it with about 10 years prior and it was a solid chunk of concrete.
I’ve set posts this way before, and it works just fine. It’s important to make sure that the post stays plumb while the concrete sets.
You can also use a product like this expanding foam backfill. I haven’t used this before but it looks a lot faster.
If your soil is reasonably dense, you can also just use gravel. It’s easier than concrete and MUCH easier to deal with if you ever want to remove the post. I set a mailbox post in gravel about 10 years ago and it’s still rock solid. Just make sure you dig the hole deep enough and tamp the gravel well as you’re setting it.
We had a cedar fence installed that way. I was dubious at first, but they guaranteed it, and the fenceposts were rock solid for 20 yrs.
Can’t speak to the gravel method, but I can attest to the Quikrete. I have done several over the years using this. Works well.
I’ve actually heard that gravel can be better than concrete is some situations, because gravel ensures that water drains away from the post, while depending on the soil and geometry, concrete can cause water to pool up around the post and accelerate deterioration of the wood.
Gravel or concrete. Nail a couple of cross pieces to the post at right angles and just rocks and dirt will do fine also.
You don’t even need to add water to the concrete if you can keep the post in position long enough. It will absorb water and turn into a rock over time.
My sister lives on a lake. At one spot she wanted a couple of steps at the waterline. She simply stacked bags of sakrete in the formation the wanted. The contents hardened and the bags wore away.
This. Someday your wood post WILL rot or break, and you’ll want to replace it. If you’ve used concrete to secure it, the job will be much, much harder.
Gravel in bottom of hole, post bedded on the gravel, then put in the concrete mix.
Reason: So post does not rot down at the concrete.
Post, being wood will take in water over time, and the water will go down.
Post needs to be able to drain or it becomes waterlogged and rots at the bottom, and gravel makes a good stable drain bed.
Thanks for the suggestions everyone. I’ll consider the gravel idea.
Had a friend who used it. He tells a hilarious story which boils down to, “best used by professionals or someone who knows what they’re doing.”
The purpose of concrete for a post is as a counter weight that encourages the post to stay plumb. It is not a ‘glue’ that fixes the post in the ground. From the perspective of architecture earth is fluid that moves with moisture and temperatures changes. In places with freeze thaw cycles it can move quite a bit. Think of the post like a bouy in water.
The concrete should only be in the bottom half of the hole. The post should be put in the hole first, preferably pounded a little to compress any loose material so it does not sink later; this also minimizes waterlogging issues as mentioned by Weisshund. I have seen many rotted posts due to over zealous use of concrete
The main advantage of concrete as opposed to an earth or gravel packed post is basically labour. Setting posts with concrete is much faster, packing requires a lot of effort with a steel bar and quite a bit more time. The advantage of packing is much less risk of rotting, easier removal and the ability to straighten a leaning post at a later time by more packing. It is much harder to near impossible to plumb a leaning concreted post, especially if the concrete is to high.
The foam stuff is expensive gimmicky crap as far as I am concerned.
For a single post like the OP asked about, I don’t think the labor is a major concern. When I set my mailbox post, the packing took maybe 10 minutes. I’d be much more concerned about the long term issues like rotting and removal.
Try to get SB2
It’s a special gravel mix that hardens. I’ve used it in several landscaping projects.
Gravel comes in several sizes of crushed rock.
I also prefer the gravel and pre-mixed concrete method. I installed my 4X4 treated posts this way and 37 years later, they’re rock solid.