Strip footing is too shallow..how to deal with frost heave?

[GalileoG]

We have recently designed a low-rise building with perimeter strip footings. These strip footings were placed at 1.5 meters (5') below the top of slab, as recommended by the geotechnical report to prevent frost heaving. There is an issue where on one side of the building, the top of grade is actually 600mm (2') lower than the remaining sides, leaving the foundation wall exposed on that side only. This is an oversight from the design stage. Loosing the 600mm (2') soil cover means that I do not meet that 1.5 meter requirement specified by the geotechnical engineer for frost protection. It is a rather small masonry building (30' x 60'), but the exposed foundation is on the longer, load bearing side. To complicate matters, the property line is only 3' from the exposed foundation.

Any ideas folks as to how I can remedy this situation? Thank you so much in advance!

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[Ron]

Chemical grout injection to displace and react any water adjacent to and below the foundation that could freeze.

 

[JStephen]

Can you put buried insulation along or on top of the footing on that side?

 

[JAE]

Try these links/threads:

thread507-278313

thread256-273

thread592-169967

thread507-197635


See "Design Guide For Frost-Protected Shallow Foundations" (free .pdf download) at this link

http://www.huduser.org/publications/destech/desguide.html

ASCE publishes "Design and Construction of Frost-Protected Shallow Foundations" (SEI/ASCE 32-01)

 

[SteelPE]

AS JAE has pointed out, I have seen smaller canopies utilize insulation to avoid going down below frost depth with the footings. In the US this is allowed by the building code. I believe there is an actual design guide that needs to be followed (ASCE 32????). Check to see if your jurisdiction has a similar allowance.

 

[GalileoG]

Thank you all for the responses. Much appreciated.

This is a footing that is already poured, the structure is constructed. It is very difficult to have the contractor excavate down to the footing and place the insulation, especially given the space constraint. Although this may be my only option.

I am curious as to how chemical grout injection works. I wasn't able to find any material on this subject online.

The soil around and beneath the footing is silty clay and highly plastic. Sounds like very frost susceptible soils to me.

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[msquared48]

Can you put in a small rockery in the exposed area with earth fill behind it?

Mike McCann
MMC Engineering

 

[GalileoG]

Hello Mike,

Yes I can, but this would only add soil cover less than 1 meter away from the face of the foundation wall (the property fence is 1 meter away), would this be enough? I would think you would need at least 2 meters laterally soil cover.

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[msquared48]

I see your point, but what would be the distance from the exposed base of the rockery to the outboard base of the strip footing - could you gain an extra foot or so on the diagonal?

Mike McCann
MMC Engineering

 

[GalileoG]

Hi Mike, I am not sure what you mean by the exposed face, but the edge of the rockery would be slightly less than 3' from the edge of the footing itself.

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[msquared48]

OK.

Next option - could you get an easement to extend the rockery beyond the property line by two feet or so?

Mike McCann
MMC Engineering