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Small Cabin Forum / Cabin Construction / How to prevent concrete around posts from cracking?
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Strut
# Posted: 24 Jun 2012 03:11am
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Good Evening. I am planning to build my shack on pressure-treated posts placed in the ground with concrete I will mix myself. In the past I have found that the concrete I put around fence-posts and clothes-line posts often cracks and I don't want my cabin to "lean." Did I not use the right ratio of water to concrete mix or is cracking more-or -less inevitable? If the concrete cracks, will it have a huge impact on the stability of my cabin (20x16) or will the impact be negligible? Thanks for any replies!

johng
Member
# Posted: 24 Jun 2012 08:28am
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concrete shouldn't crack.
My guess is that it wasn't mixed completely leaving dry pockets or not enough room between post and hole. Some people try to save concrete by putting a 4" square post into a 4.25" diameter hole.

VTweekender
Member
# Posted: 24 Jun 2012 08:43am
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Personally, I don't like pouring concrete around a wood post, it significantly increases decay time of the post as concrete holds moisture. That being said, I think cracking would be negligible, with the pressure of the soil around the concrete those things aren't going to move side to side without extreme force.

I like the post protectors they have out now, just pour a footer for the posts with a bolt for the post for upward protection, fill around them with gravel for drainage....I think if you want those 6x6 to last for years then this is a great option, see them here if you haven't seen them before http://www.michianabuildingsupplies.com/post_protector/

Martian
Member
# Posted: 24 Jun 2012 10:38am
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To prevent your concrete cracking:

1) Wet the hole before pouring in your concrete mixture.

2) Run deck screws into the post leaving at least an inch showing. Put three runs of screws on each side spaced evenly from top to bottom.

3) Forget the concrete and just tamp the soil back in. You will know if you have tamped it sufficiently if there is no dirt left over.

Do not put the bottom of the pier into wet concrete; it will hold water, the water will freeze, and the concrete will crack. Instead, put in the pier, position it in the hole, add a couple of inches of dirt, pack it tight, wet the hole, add the concrete.

Tom

neb
Member
# Posted: 24 Jun 2012 11:07am - Edited by: neb
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X2 on the posts above. I agree on tamping in good. The bottom is and the bottem foot is the very most imprtant part of tamping. It needs to be tamped the best. If you ever did any fencing in the ranching world you would no why!!! If the bottom and at least the foot isn't tamped well the post will move side ways. That will cause a lot of problems. The other thing is to bank dirt up 8 to 10 inches around the post when you are done tamping that post in. This is for run off of water and keeps that dug hole from getting to much water around it. Tamp well and bottom half the most important and bank up dirt around the post!!!!!!!!!!!!!!!!! NO need for concrete around the sides or at ground level!!!!!!

rayyy
Member
# Posted: 24 Jun 2012 04:09pm
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Up here in the north east we have to go atleast 42 inches down below the ground level.18 inches wide or bigger at the bottom of the hole,pouring an 80 pound bag of mixed concrette into the hole tamping it out with a garden hoe till it's nice and level.The treated timber pole sit's down on that,after it set's .The dirt that you use to back fill the hole is tamped in place as you back fill the hole,keeping
the pole supported.No need to pour concrete around the poles.Once your building is built,that help's keep everything square and level.

MtnDon
Member
# Posted: 24 Jun 2012 06:49pm
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Quoting: Martian
3) Forget the concrete and just tamp the soil back in. You will know if you have tamped it sufficiently if there is no dirt left over.



Right on , Martian. The best and cheapest method when installing piers/posts is to pack the dirt back in the hole. A digging bar with a round mushroom head is ideal for the task.

DO use a good sized concrete footer though with the bottom of that at or below frost level. 16x16x8" is what I consider a good sized footer... with rebar in the middle, X or # shape (# is best)

If frost depth is shallow I would still recommend that 48" of the pier be below grade and as little as possible above grade.

link to a digging bar

Strut
# Posted: 26 Jun 2012 11:54pm
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Thanks........alot of very helpful replies. I am breaking ground on my 16x20 cabin TOMORROW MORNING!! I am so blessed.......there are no zoning regulations here and no building permits required. County authorities told me to do whatever I want! So I am going to. Thanks again.

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