Post vs Pier

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woodydiver

New User
curt
Hello all,
Just though i would ask what experience, concerns or opinions are on treated posts vs. concrete piers.
Wood wrangler and i are looking at building additions to our houses and both rooms will be 16' long by 12' wide. Part of the problem is that the areas we are both building on arent very level and really dont need a full slab.
One option is to dig some holes fill and pack the bottom with crushed stone, use green treated 4x4 with bolts crossed ways at bottom (help secure it in the concrete) and fill around the post with concrete. This is a simple and easy way to support the room. Possible problems would be wood rotting over time, putting more chemicals in the ground, and possible termite problem in future.
Another option is to dig a hole and pour a pad on the bottom, use some type of form or tube to increase height and pour full of concrete, then put metal bracket on top of concrete to fasten to beams. I will probably use some rebar for stength. this method is probably a little more expensive and harder to do but has the advantage of being stronger, last longer and not as likely to be bothered by termites.
Either way i know the frost line is only about 6 inches for nc and sc and would probably sink either around 18" to make sure.
thanks,
curt
 

JimmyC

New User
Jimmy
Curt,

I have a pole barn, so the 6x6's are into the ground, I myself have wondered about them. If you are going to go that way, make sure the posts are for ground contact, not all p.t. wood is. My building is sturdy enough the posts are 8' on center and the building is 32'x40' with an interior height of 12' to the bottom of the roof trusts, it's not going anywhere thats for sure.

I think that the posts in the ground might be sturdier ( if needed), but over time I think that the piers might hold up longer. I think that either one would work, and last your lifetime if done properly. So if I were you I would go with what's more comfortable for you.

Just my opinion, not that it's worth much:lol:

Jimmy:)
 

DaveO

New User
DaveO
I would check to see what code is in your area. I know in Raleigh they require piers/footers for decking, and I would think it would be the same for dwellings.
Dave:)
 

Gotcha6

Dennis
Corporate Member
Having built a few of these myself, I prefer the following for this area:

1. Dig (or drill) hole to minimum 2' deep for short posts >3' out of ground, 3' for taller posts. Hole diameter should be minimum 4x post diameter.
2. Pour 8" concrete in the bottom of the hole & float level.
3. Set posts atop concret when firm & frame building. Tie posts top & bottom to assure alignment.
4. Pour hole to top with concrete.

This method assures the posts are bearing on a wide stance as well as encasing them in concrete to avoid chemicals leaching into the ground or excess moisture going into the wood. In the case of an open shed it also adds ballast to the structure for uplift. Don't forget those truss tiedowns!
 

scsmith42

New User
Scott Smith
For a home addition, there is no question in my mind that concrete pad and piers would be the best way to go. You would not have to worry about rot, bugs, etc

For a shed, barn, deck, etc, posts would be acceptable. Deck and Barn posts are usually fairly accessible in the event that you ever need to replace them.

If you're dead set on posts, use Gotcha's method for installation.

Scott
 

John Reeves

New User
John Reeves
Curt,

the building code in your area will dictate what you should use. If you want to do something different you will probably have to have a PE sign off on it so the building inspector is not liable for an "out of compliance" situation. The building code protects subsequent owners of the property and get sues some times in something is not in compliance.

The footer in the trench is probably what you will end up doing. That can mean a lot of "spade work" or renting a small back hoe.

In reality you should do it right. We have so much differential movement of our foundations because of expansive soils leading to the cracking of brick veneers, interior walls and out of square doors and windows I am a bit cautious with foundations.

Another issue may be that you need to duplicate the existing foundation of your home if that is a reasonable thing. This may reduce differential movement and provide you a better addition.

My two Civil Engineering degrees sometimes get in the way.
 

junquecol

Bruce
User
May not be suitable for your needs, but research "All Weather Wood Foundation." Quickest and simplest form of creating exterior walls. You can add a brick ledge if current foundation is brick. You will have to have a "daylight drain, no pumps.
 

JohnsonMBrandon

New User
Brandon Johnson
I'm pretty sure you will have to dig a footing, and probably bring the area up level with either block or a small concrete wall to the existing structure. I don't believe the NC residential building code will allow you to use pole construction for a inhabited dwelling. I design commercial structures on a daily basis and I don't know all the nitty gritty details of the residential code, but if it were my house I would go with a true continuous footing instead of pole construction. Essentially it would be the same construction as a house with a crawl space.
 

woodydiver

New User
curt
the room the woodwrangler is building is more like a shed, he is going to put his air compressor, dc and other things for storage. i should have gave a better description.
thanks
 

JohnsonMBrandon

New User
Brandon Johnson
Cool deal it kid of sounded like it was an addition to a home. If a shop then you would probably be fine either way. There is some debate over letting the post sit in the ground vs having it sit on a concrete pier. If sitting on a concrete pier just make sure to use a bracket to attach it so that water will not pool under the post and you should be fine.
 

WoodWrangler

Jeremy
Senior User
Today I spoke with the inspector for my area. He told me I'd have to go at least 12" into the ground for the footings and once the hole is dug have him inspect it. He also said they recommend the concrete footing with the wood above ground.

Hopefully I can get this show on the road soon. I've got a guy coming out this weekend with a bobcat to level the area a bit and move some gravel out of the way.
 
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