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Frost-protected shallow foundation near sloping landscape

i am building a house with a frost-protected shallow foundation (see attached) in brandon manitoba canada (49.8485° n, 99.9501° w) and the particular area has a very high water table. because of this, the engineer included the following note: “design assumes ground water level is consistently no less than 3’ below bottom of footings”.

so, just to be on the safe side, i am building up the area for the house approximately 3’. my plan was to have a 4:1 slope from the house to the surrounding landscape (see attached). however, i was starting to wonder how that might affect the ground temperature underneath the slab.

would the frost line push further under the slab due to the lack of soil depth near the edge of the horizontal insulation? if so, is there information available to determine the horizontal insulation required to compensate for that effect?

any information greatly appreciated. thanks!

: )

Foundation.pdf1.38 MB
4:1 Slope.pdf26.47 KB
Asked by Loretta Gurr
Posted Apr 28, 2018 7:03 PM ET
Edited Apr 29, 2018 5:38 AM ET


3 Answers

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My guess is that, assuming you proceed as shown in your drawings, everything will be OK. But I'm not an engineer.

Fortunately, you have hired an engineer to help your with your project. So ask your engineer.

Answered by Martin Holladay
Posted Apr 29, 2018 5:42 AM ET


Yes, the frost line will push in farther if there is a slope. It may or may not be enough to matter. In case your engineer is not up to speed on frost protected shallow foundations--many are not--show them this guide (pages 9-11 in particular) and tell them to read the ASCE 32-01 design guide.

Foam size over water lines and other useful data for foam below grade.pdf 1.23 MB
Answered by Michael Maines
Posted Apr 29, 2018 10:08 AM ET


thanks very much! i will harass the engineer about it although prior questions have gone unanswered. i guess i hired an engineer that thinks all i paid for was the stamp. or maybe that IS all i paid for!!

: )

Answered by Loretta Gurr
Posted Apr 29, 2018 12:03 PM ET

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