Drilled piers and frost depth
Drilled piers and frost depth
(OP)
If I have a grade beam on drilled piers (residential with fairly tall crawlspace), Do I need to burry bottom of wall to frost depth? The main level of the house is a little high.





RE: Drilled piers and frost depth
RE: Drilled piers and frost depth
PS: I don’t have a full understanding of your situation.
good lock.
RE: Drilled piers and frost depth
RE: Drilled piers and frost depth
Where I practice the maximum frost depth is 10 feet. Strip footings and perimeter grade beams for HEATED BUILDINGS are required to extend at least 42" below outside finish grade, AND have 2" subgrade insulation against the wall to direct heat below footings to keep frost from penetrating below footing/wall.
Alternate insulation schemes are possible to reduce the 42" cover requiremment but to not less than 2 feet.
RE: Drilled piers and frost depth
RE: Drilled piers and frost depth
Also, the frost is usually occurring in fine sands and silty soils. So if applicable use a free drainage material similar to ¾ inch clean crushed stone.
I hope some one could confirm this.
Good Luck
RE: Drilled piers and frost depth
RE: Drilled piers and frost depth
RE: Drilled piers and frost depth
I recommend the bottom of the grade beam be at or below the frost depth.
RE: Drilled piers and frost depth
Just playing devils advocate, but what if the void gets filled up with water and then freezes?
RE: Drilled piers and frost depth
See threads discussing alternate depths of footings in deep frost locales using granular subbase and insulation.
My opinion: ice has 10% gain in volume over water and if the building requires drilled piers for support then the soil has a potential to deform from the increase in volume when water turns to ice. If the soil deforms, then no damage or detremental effects from frost below grade beams.
RE: Drilled piers and frost depth
I agree that void form (preferably polystyrene) should be placed beneath the piles. 4" is typical for residential applications, 6" for commercial. As a rule of thumb, we generally place the pile to a minimum depth of 15ft (or twice the length of the frost line).
Hope that helps.