Deck Posts Heaving

leakygoose

Okay it's spring and the weird calls are coming in. The latest is a deck that has all the 6x6 posts heaving about 3'' to 4'' out of the ground.

I've never done this sort of repair before so I'm tossing it out there to see what you all think.

Nice homes 3/500 thousand range and looking down the back yards I see almost all the decks have the same heaving problem going on. I'm confident all post holes were inspected 42'' below grade when built.Sub soil has a lot of clay /hence most of the problem but I believe piers and sand back fill would have been a better building technique of course this is hind sight ,HO's are looking to me to fix the fault correctly.
I added pic's Post #17

Feed back is appreciated ,this could land me a lot of work .

I'll post some pic's if I can get this darn camera working.

neolitic

Yes pix.
Maybe concrete flares above
the frost line?

You are in Michigan?

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K2

In my neck of the woods expansive clays would be the problem. The solution would be to drill through the clay or keep the clay dry by drainage and or covering.

Golden Rule

I live in Anchorage. The soil hear varies from sand, to silt, to boulders, to swamp, to clay and so on. The only way I feel comfortable building decks up here (and I have built at least 50 in Anchorage) is to put them on piles. Piles are the bomb proof way to go. I don't know how common they are in the lower 48, but up here we can have 2" piles driven for about $270.00 and 3" for about $355.00. They drive them to a minimum of 10 feet. They get driven until you reach a certain kipcount which can be much much deeper than 10 ft sometimes. Then a saddle is welded on the bottom. If you you don't have room for the pile to be driven directly below the deck, you can do whats called a battered pile, a pile driven at a slight angle so u can avoid the deck above you. This may not work in your case but if it does, I would definitely go with piles. I have done all sorts of sonotubes w/ bigfoots and still had heaving issues. Up here we have to go 60" for our tubes. You would think that would be idiot proof, but nature says otherwise.

B.K

A good drainage bed (Crushed Stone or Sand), with a tapered pier. All dug down to frost depth.

That should work, a tapered pier should if built correctly resist the heaving of the soil, and with a good drainage bed below, it should be able to drain all water.

greg24k

Sounds like soil condition has excessive hydrostatic pressure. I ran in to the same soil conditions in a town near by when I was doing a finished basement with the bathroom. We had to do a concrete pit with rebar for the ejector pump under the slab. They had a few cases where the pit was pushed up by hydrostatic pressure. For a footing you have to do what Golden Rule suggested drive piles to support the girder, but first I would talk to an engineer and get a remedy for a fix instead of wasting time and money.

Good luck

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K2

Sounds like there could be foundation problems in their future too. Around here they have demoed rows of newer hillside homes because of soils and poor engineering.

naptown CR

You did not mention your location but this is a problem around here in some cases. dig a test hole or go to your building department and see if they have any information on soil type. The last time I ran into this was many years ago. County made us ge an engineered footing with gravel and drainage down minimum of 5 feet (Frost line here is 24") and continuous for the length of the deck. This was a royal Pita. I was glad i worked for somene else at the time as they paid dearly as HO would not pay more. I have always had a subsurface exploration/ soils clause in my contracts to cover against this as it happens. Looks like some investigation is in order to truly determine the cause.

neolitic

Maybe Leaky will be back?

I have done well following advice
given long ago, "When you hear
hoof beats, don't start out by
looking for zebras."

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leakygoose

My apologies to all responses for being MIA and thank you for your impute.

Been busy as hell and this computer is a freaking mess[guy coming tomorrow to fix if] I blame it on my teenagers.

Anyways ,I've done a test hole and found clay /sand and mostly water at 12'' down . Yard slopes gently 40' back to marshy area . This is 40 miles west of Detriot .

neolitic

Did you find out how deep
the footings go?
Are they smooth sided?

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leakygoose

From what I can tell [feeling around in the water ]the post holes were dug to 42'' ,some concrete poured in for a flat area and the 6x6 post placed on top and some more concrete around the bottom of the post . I can't tell if just the post is lifting or all the sub concrete .

concretemasonry

Sonotubes (waxed concrete forms) with smooth walls prevent the frost from raising the concrete as the soil freezes downward, but the bottom should be below the frost level. You can even get a flared bottom to give more area if you have bad soil.

Hand dug holes with a rough unformed, dug surface are notorious for heaving even if the bottom is deep enough because the frozen soil can easily raise them.

The posts should be attached to a bracket that embedded in the Concrete (Simpson is one brand). This eliminates wood rot.

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neolitic

Did you put a level on the deck?

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leakygoose

Did I put a level on the deck ,thats goes with out saying ,but yes I did just for a laugh . 78'' level showed 2 1/2 '' . This deck reaches out 16'

neolitic

Just sometimes the most
obvious gets over looked.

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leakygoose

some pic's of the problem;

Attached Thumbnails

     

neolitic

Did the spiral stair heave too?

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leakygoose

Oh ya ,and it's coming down for good , Ho doesn't care for it any more and I pointed out how it's pulling away from the deck[bolts pulling out ] I suggested the old yellow caution tape and the HO said no one would be using it.

Leo G

I suggest you get your level recalibrated. Problem solved.

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