Installing door in existing foundation wall....what to do about frost 2

[Jmeng1026]

A client would like to remove a 6' wide portion of his existing 8" concrete foundation and install a doorway and make it walkout. The problem would be he would be removing 4' of existing grade in that area and my area requires the footing to be 4' below grade. Any suggestions on how to provide frost protection under the foundation wall where the existing grade will be removed? His footing would be right at grade level once he removes the material.

 

[dik]

Rigid Insulation?


Dik

 

[JAE]

Per dik's suggestion - see attached:

 

[PEinc]

Underpin the wall footing under the new doorway.

http://www.PeirceEngineering.com

 

[r13]

Sounds like the owner wants to install a door and make a stairway from the basement to the grade, correct? A sketch with some detail may help.

 

[oldestguy]

I did this in Wisconsin. However outside the wall area where this door was to go I excavated and built an entry stairway. The exterior surfces of this stairway, except for the folding door above (a Bilco door)had a rigid insulation placed. It was 1" thick outside the walls and 4" under the slab. Has been in use now for 10 years and no problems.

Edit. If I was to not have a stair, I'd extend the excavation out to daylight and do this insulation out as far as sat least 4 feet. In my case with the stair, I think the stairway is about 8 feet out from the house and that was also the extent of insulation.

 

[r13]

It could be a half basement as dimension suggests.

 

[dik]

Maybe either side?

Dik

 

[Dvdt18]

We typically require it up the existing foundation walls on the exterior, extending around the existing footing to the subgrade, and installed below the proposed footings and foundation wall encasing the stairwell and extending out beyond the proposed footings in each direction as required for frost depths as JAE provided above.

Some in-situ subgrade conditions may alter the rigid insulation detail as the subgrade materiel can be evaluated to determine the frost susceptibility of the subgrade material.