Did some searching but didnt find anything in particular to controlling "frost heave" other than the usual foam/frost depth discussions.
Wanted to get some alternative views on setting simple French Drains around the perimeter of a post-pier foundation in cold climates to prevent the "bathtub" effect.
I am planning on a 12x16 structure on eight 10" sonotubes with "Bigfoot" bases. With a "frost depth" of 24", I am interested in keeping the foundation dry (I already have a good grade for runoff).
If you plant those Bigfoot footers at 30 - 36" and use sonotubes for concrete piers that's really about all you need.
Quote from: DirtyLittleSecret on March 03, 2009, 02:00:30 PM
Did some searching but didnt find anything in particular to controlling "frost heave" other than the usual foam/frost depth discussions.
Wanted to get some alternative views on setting simple French Drains around the perimeter of a post-pier foundation in cold climates to prevent the "bathtub" effect.
I am planning on a 12x16 structure on eight 10" sonotubes with "Bigfoot" bases. With a "frost depth" of 24", I am interested in keeping the foundation dry (I already have a good grade for runoff).
It is important to have the slope away from the house even if you need to regrade and ditch as necessary - required by code also, to keep water from running into the pier hole area. That alone will do a lot toward eliminating the bathtub effect. The water will get into the gravel and turn the clay to mush if drainage away from and outside the house is not provided.
I would use the French drains if water was flowing under the ground and then through the footing area. If it is not then good grading and drainage away from the house should do the trick.
You cannot prevent frost heave in exposed soil. If any moisture gets to soil near the piers it will freeze and expand.
As Don suggested, a deep enough Bigfoot system should prevent uplift. You can wrap the concrete pier with something (I forget the specific material recommendation) down to the frost line that will allow the soil to heave while sliding past the concrete.