Deck heaved with frost

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Old 02-27-14, 11:36 AM
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Deck heaved with frost

Ok I'm sure this has been asked a lot of times but I'm gunna ask again anyways. I have a new house almost 6 yrs old now and I built almost all of it myself the question is what can I do to prevent my deck from heaving. The deck is over a walk out basement and has an attached roof to the house roof it is post to post pillars with no headers and the sono tubes are four feet in the ground like required for NE Wisconsin where I live. When I put the tubes in a few of the holes had water in them because I am built near a swamp and I insulated with 2 inch foam around each one to help prevent any thing from happening well it happened and my deck is now pushed up about 4 inches on one end. What more can I do?? Any help will be appreciated thank you
 
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Old 02-27-14, 01:09 PM
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In Alaska I've seen smooth plastic used as forms instead of cardboard sonotubes. The plastic tubes were left in place so the ice could not grip the sides of the footing and would just slide instead of gripping and lifting. Another trick was they would let the concrete escape out the bottom of the form tube forming a bulb or upside down mushroom head on the bottom to help key it in place and prevent heaving. Maybe you could excavate and clad your concrete footing columns in plastic? Maybe get the appropriate sized PVC piping and cut vertically down it's length so you can put the two halves over your footers.
 
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Old 02-27-14, 02:59 PM
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I would say that every 20 or 30 yrs we get an abnormally cold winter. Guessing 48" wasn't deep enough this winter. Did the sonotubes have a footing and are they isolated from any surrounding concrete that is not on a footing?
 
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Old 02-27-14, 03:51 PM
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No the sono tubes do not have any footings under them the holes were drilled and the tubes inserted. I have heard about using plastic and surrounding them so the frost cannot grip them and push them up that sounds like it would be the cheapest and easiest fix. It was also suggested to me to make an adjustable post so as the frost pushed I could adjust accordingly but that does not sound to me like a good fix more of a rig job but idk
 
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Old 02-27-14, 04:05 PM
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Also they are isolated from any other concrete they are 8 feet away from the walkout part of the basement which also is sitting on a four foot frost wall beneath it on the side if the deck
 
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Old 02-27-14, 04:24 PM
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In a sense, the posts were pulled up gradually, since the ground freezes from the top down and raises them gradually over time and there is magical depth when they immediately are thrown up. Exposure and soil types are important depending on the amount of water held in the soil since heavy soils expand laterally and can get a good hold on a post to move it up.

Even using sand between the Sonotube could also reduce the "grab" on a post/foundation. Hand digging posts is asking for problems, especially if the deck or roof is attached to a permanent structure. Ledger attached decks can be a problem every year and the main reason for free-standing systems that are cantilevered back a couple of feet to the home, but not attached to it.

If you have a cold weather some areas and soil types will have more problems.

Dick
 
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Old 02-27-14, 04:56 PM
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The soil here is mostly clay and holds it's fare share if moisture. Maybe that wouldn't be a bad idea to dig the tubes up some and put plastic around them and backfill with sand
 
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Old 02-27-14, 09:05 PM
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Since it's just one end of the deck that's heaving excessively, could it be that ground water or roof runoff could be channeled to that end of the deck? You mentioned some of the holes had water in them when the concrete was poured, but didn't say what you thought the source of the water was. I suspect big, soggy gobs of mud, when frozen solid, can easily lift most sonotubes full of concrete. Maybe a plan of action (come warmer weather) would be trying to dry out the ground on that end of the deck, possibly by installing an intercepting drain of some sort. Either that, or even installing some heat tape wrapped around and below the misbehaving sonotube footings--the cost would be minimal, and you'd only have to plug them in when the forecast calls for extended time below zero.

Hearing stories like yours reminds me of why I don't miss Wisconsin weather. I left after graduating from UW in '67, wandered around the West for the next 40 years before settling in central Oregon. I was out in short sleeves today, working on the chicken coop, even though it was a bit chilly at 55 degrees F.
 
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Old 02-28-14, 04:33 AM
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Wow 55 degrees that a temp we won't see until June it's -17 here this morning and windy. I guess it is an unusually cold year that could be contributing to my deck issues but I would like to fix the problem so it don't happen again. Thank you all for the advice
 
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Old 02-28-14, 04:43 AM
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Old 02-28-14, 06:03 AM
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Many people think that just getting the bottom of a post below the frost line is all you have to do. In reality it's a tug of war between the freezing ground on top pushing up and the unfrozen grounds ability to hold the post in place, especially if there is little load on the post to further hold it down. Even if the ground does not freeze to the bottom of the post all it takes is freezing deep enough and up comes the post.

In your situation, now that I think about it more, I would not try to save your current footer for that post. I would install temporary supports on either side. Remove the heaved footer. Install a footer foot like JoeCaption linked and use a section of PVC pipe for the form and leave it in place. Backfill the bottom half of the hole with soil to firmly engage the lower half. Fill the top half of the hole with clean stone or pea gravel to minimize it's ability to grab the footer. Then re-attach your column/post.
 
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