Frost heave at interior spread footing 2

[ASCII]

I am having an addition built and the spread footing for a 28 foot long central girder has heaved. There are three concrete filled columns approx. 7 feet apart, and all of them have forced the girder to rise, one by about 1.5 inches. What should the builder do to correct the problem, cut the columns down, excavate the footing and pour a new one? The winter has been extremely long and cold, and the exterior wall foundation shows no signs of heaving. The footing depth is about 7' below grade but the interior footings were subject to freezing because the house is not insulated or heated yet. Any thoughts would be appreciated. ASCII

 

[boo1]

Frost heave is very common in cold climates. Moisture in the ground freezes and the concrete pushes upward. It will be better to remove and replace the concrete. There is an apparent, faulty concrete construction.

Recommend you request the contractor hire a structural engineer to evaluate and approve a repair or have the contractor remove and replace the faulty components.

 

[CarlB]

Boo1 is correct that an expert should review and evaluate the specific conditions. That being said, one could argue that the same soil that has recently heaved has done so in past winters and settled back down after thawing. IF it does settle upon thawing, there may not be any loss of bearing capacity. Contractor could tent and heat the footings, start thawing the ground, and if column/footing returns to original location you could decide to leave them as is. If they remain above original elevation, the difference is what you may expect as future settlement.

 

[Rjeffery]

Boo1 is absolutly correct to suggest an evaluation by a licenced structural (or geotechnical) engineer. If it is the contractors fault the contractor should pay for the engineer's services and repairs but YOU should locate and retain the engineer NOT the contractor.

CarlB's suggestion is also one to consider except it has been my experience that once soil has been disurbed it like worms in a can will not fir back into the same volume.

 

[Watermelon]

ASCII:

I'm not sure what you mean by concrete filled columns. If you have concrete posts supporting your floor beam then I'd say it's an unusual structure. I'm guessing what you meant to say was "buried concrete piers, with a post of some kind on top of the pier". And the post supports the floor beam. Yes?

 

[VAD]

ASCII(computer)

If your problem is frost heave then there are 3things which must be present - a frost susceptible soil, water and freezing temperatures. According to the theory, the absence of one of these would prevent frost heaving from occuring. The depth of founding of the footing (2m approx) in some areas is sufficient by rule of thumb. However, this might not be the case in your situation. Presumably you had an investigation done to determine athe subsoil conditions. Too often this is not done and past experience is used.

Patios or walkout extensions to homes that are not to be heated are often founded on piles to go deeper than the depth of frost penetration. In your situation it might not have beeen a problem if the extension was done in the summer and the heat was on for the next winter etc. What happens, however,if your heat is off a winter for some reason after the building is in service. Then the situation you are experiencing is likely to occur. It is good that the situation is caught now than after the extension is completed and in service.

Regarding fixing the problem. There are a few possibilities. However, you may have to await the warm weather when the heaving has subsided. If this is impractical based on work to be done then some heat will have to be used to keep the footing areas warm as Carlb has suggested and allow the heave to subside. Other solutions are the use of insulation over the area encompassing the footings, or screwpiles to retrofit existing foundation. Both of these are best done in the spring/summer after heave has subsided. There are probably some other solutions depending on site conditions.

It would be a good idea to monitor the heave/subsidence. Curious why the exterior footing shows no sign of heaving


Good luck

 

[ASCII]

In response to Watermellon, yes the footing is 2' wide by 10" deep by 17' long and it is covered by a concrete slab. On top of the footing are 3.5" steel columns filled with concrete. The columns are held in place at their bottom by metal plates and the 4" of concrete that is the slab and the tops are held in place by way of metal plates.

ASCII

 

[dik]

I've just prepared a report for an insurance company regarding a frost heave problem... Movement of the SOG, the interior spread footing and the exterior strip footing varied from a few inches to approximately 9" to 10". The contractor had removed 1 and 1/2 courses of masonry pier 12", but at the time of my review, movement was only 10". All the concrete foundation walls had cracked ranging from 0.15mm to 40mm (I've got a graduated pocket 'microscope' that I use for the finer cracks). Excellent source of water, coldest winter in 13 years, with the coldest period of a few days occurring when the foundation was unprotected, and the general soil is clay... this one had a silt seam..., the only one for miles, it would seem...

If a 1/2" bar can be pounded down in the vicinity of the footing without encountering a void (possible to miss it) then it can likely be constructed on the same footprint. Local geotekkies have a bar and heavy pipe with handles and an endcap to drive the rod (seems to work OK in clays). Because of the extreme movement of the foundation that I did the report on, my recommendation was to use a different location (some other place on site that had adequate frost cover) or to found the new footings on soil below the depth of penetration (and hope there wasn't a more pervious seam to keep from pumping the lake)

CarlB:
My earlier querie regarding supercooled water in clays was in reference to this project.

 

[BigH]

One of the first jobs I did was involving frost heave of a building under construction - a computerized rack system for warehousing. Can't have "out of levels". They didn't hoard and heat during the winter season and we found that the slab lifted about 50mm. It thawed, fell down to the same level (about) and it was left like that. Subsequent winters the building was heated. Haven't heard of any problems since and our company did a lot more work over the many years. (Soil was about 10m of glacial clayey silt till over Queenston (red) shale bedrock.)