Any experience with pier foundations in a freeze thaw climate? My concern would be that even if the pier reaches the required footing depth to be below the frost line, the freeze thaw action on the top of the pier could cause movement. Similar to squeezing a popsicle out of its plastic wrapper...
The goal is cheapest cost while maintaining structural integrity. Pier foundations could significantly lower the cost, but my concern is quality. Eliminating the basement could save money by simply installing frost wall footings. Might be the best compromise.
chigurh
Sep 3, 15 7:04 pm
as long as you are below the frost line...shouldn't matter, make sure that is clearly stated in your soils report...CYA.
geezertect
Sep 3, 15 7:05 pm
If by piers you mean drilled concrete caissons, then I have never heard of problems. The foundation wall acts as a grade beam and spans from pier to pier. The concentrated loads on the piers should overcome any frost heave. Plus, I would assume you are putting continuous void under the walls between piers, so any frost heave would be absorbed by the void. If in doubt, ask your structural engineer.
JeromeS
Sep 3, 15 8:16 pm
I would wait for Balkins dissertation on the subject before I moved any dirt
snooker-doodle-dandy
Sep 3, 15 8:19 pm
If your looking a pier footings you should be well below the frost line as per the state building code if it is a bell pier. Most of the companies like big foot do have recommendations for depth. Not so much about the top wanting to wiggle about but more about the frost adhering to the sides of the pier and lifting it with the frozen adjacent soil. Think about it if frost can make the earth move.... what is it to keep a cylinder of concrete with a 12" dia. from moving. Depth will vary by Region. Listen to what the manufacture of the bell pier footing has to say.
bowling_ball
Sep 3, 15 9:04 pm
What scale of project are we talking? Almost all of my projects require precast concrete piles due to the soil here, where it also gets to -40 with regularity (aka stupidest place to live/build in the world).
Carrera
Sep 3, 15 9:22 pm
Most piers carrying any amount of load would be tied to a bell or footing to spread the load. If a light load like a deck it my fly solo but friction would hold it.
Bench
Sep 3, 15 9:55 pm
Geezer - wouldn't having a foundation wall null the point of doing piles?
I worked in the arctic for a co-op placement, and about 99% of our projects used piles, even our commercial/institutional ones (basements just didnt exist there). However, anything requiring egregious loads, like heavy machinery garages, had a rediculously huge raft slab with massive foundation walls and footings.
bowling_ball
Sep 3, 15 11:08 pm
Bench, that's fairly unique to the arctic/ shield. All sorts of crazy things happening up there, including artificially cooling foundations so they don't melt the permafrost. Cool stuff, pun intended.
A little further south, even (new) homes are on piles up here, below full basements in our clay/silt soil.
the point is, there's more than one way to skin a cat, but you really should talk to a geotech if you're unsure.
Miles Jaffe
Sep 3, 15 11:40 pm
Slab on grade, insulated underneath, with perimeter footing and wall insulated on the inside. Thermally break the slab from the wall and provide integral pad footings in the slab where required for bearing. No exposed insulation or exterior finishing problems, radiant mass for active or passive heating, minimum excavation. Subject to soil conditions, etc.
Basements suck, but a root cellar / storm shelter is pretty cool.
Carrera
Sep 4, 15 12:15 am
FLW wouldn't allow basements or put doors on garages because he said his clients would fill them with junk.... he wasn't wrong on that either.
bowling_ball
Sep 4, 15 1:25 am
Miles, why insulation on the interior? If I have a big thermal mass like a concrete foundation, I want to use that to my advantage. And then aren't you having to add things to the concrete to deal with freeze/thaw/waterproofing?
I only ask because where I practice, we deal with temps from -40 to +100 and exposed concrete gets destroyed rather quickly in those conditions, at least at/below grade....
Miles Jaffe
Sep 4, 15 9:03 am
Thermal mass buried in the ground (wall) with almost no radiant area (basement) is useless. I've found that - in a more temperate climate - exterior insulation is problematic in regard to maintenance and finishing. Or you can skip the wall insulation entirely and focus on isolating the slab. Details, details.
I don't know anything about arctic conditions and wonder how deep your frost is. Here we rarely get below 5-10F and I've never seen more than 24" of frost (which is huge).
Non Sequitur
Sep 4, 15 9:21 am
Frost is 1525mm deep where I practice and continuous exterior insulation is mandatory for new construction.
To the op's question... frost wall footings is often what I do when budget constraints or program requirements cause us to skip on the full basement. You just need to check what size and thickness of horizontal insulation you need to compensate for shallow footings.
Miles Jaffe
Sep 4, 15 12:54 pm
5' of frost!
I'll bet it's muddy in the spring.
Non Sequitur
Sep 4, 15 1:22 pm
^ yes, unless there is a river nearby to flood.
bowling_ball
Sep 4, 15 5:45 pm
Yup, it's 6' here with pockets of 8' in bad winters. Exterior insulation is not required, but you'll have terrible getting to R28+ walls without it. Underside of slabs also have to be insulated, can't do that with batt, at least not that I've ever seen.
Any experience with pier foundations in a freeze thaw climate? My concern would be that even if the pier reaches the required footing depth to be below the frost line, the freeze thaw action on the top of the pier could cause movement. Similar to squeezing a popsicle out of its plastic wrapper... The goal is cheapest cost while maintaining structural integrity. Pier foundations could significantly lower the cost, but my concern is quality. Eliminating the basement could save money by simply installing frost wall footings. Might be the best compromise.
as long as you are below the frost line...shouldn't matter, make sure that is clearly stated in your soils report...CYA.
If by piers you mean drilled concrete caissons, then I have never heard of problems. The foundation wall acts as a grade beam and spans from pier to pier. The concentrated loads on the piers should overcome any frost heave. Plus, I would assume you are putting continuous void under the walls between piers, so any frost heave would be absorbed by the void. If in doubt, ask your structural engineer.
I would wait for Balkins dissertation on the subject before I moved any dirt
If your looking a pier footings you should be well below the frost line as per the state building code if it is a bell pier. Most of the companies like big foot do have recommendations for depth. Not so much about the top wanting to wiggle about but more about the frost adhering to the sides of the pier and lifting it with the frozen adjacent soil. Think about it if frost can make the earth move.... what is it to keep a cylinder of concrete with a 12" dia. from moving. Depth will vary by Region. Listen to what the manufacture of the bell pier footing has to say.
What scale of project are we talking? Almost all of my projects require precast concrete piles due to the soil here, where it also gets to -40 with regularity (aka stupidest place to live/build in the world).
Most piers carrying any amount of load would be tied to a bell or footing to spread the load. If a light load like a deck it my fly solo but friction would hold it.
Geezer - wouldn't having a foundation wall null the point of doing piles?
I worked in the arctic for a co-op placement, and about 99% of our projects used piles, even our commercial/institutional ones (basements just didnt exist there). However, anything requiring egregious loads, like heavy machinery garages, had a rediculously huge raft slab with massive foundation walls and footings.
Bench, that's fairly unique to the arctic/ shield. All sorts of crazy things happening up there, including artificially cooling foundations so they don't melt the permafrost. Cool stuff, pun intended.
A little further south, even (new) homes are on piles up here, below full basements in our clay/silt soil.
the point is, there's more than one way to skin a cat, but you really should talk to a geotech if you're unsure.
Slab on grade, insulated underneath, with perimeter footing and wall insulated on the inside. Thermally break the slab from the wall and provide integral pad footings in the slab where required for bearing. No exposed insulation or exterior finishing problems, radiant mass for active or passive heating, minimum excavation. Subject to soil conditions, etc.
Basements suck, but a root cellar / storm shelter is pretty cool.
FLW wouldn't allow basements or put doors on garages because he said his clients would fill them with junk.... he wasn't wrong on that either.
Miles, why insulation on the interior? If I have a big thermal mass like a concrete foundation, I want to use that to my advantage. And then aren't you having to add things to the concrete to deal with freeze/thaw/waterproofing?
I only ask because where I practice, we deal with temps from -40 to +100 and exposed concrete gets destroyed rather quickly in those conditions, at least at/below grade....
Thermal mass buried in the ground (wall) with almost no radiant area (basement) is useless. I've found that - in a more temperate climate - exterior insulation is problematic in regard to maintenance and finishing. Or you can skip the wall insulation entirely and focus on isolating the slab. Details, details.
I don't know anything about arctic conditions and wonder how deep your frost is. Here we rarely get below 5-10F and I've never seen more than 24" of frost (which is huge).
Frost is 1525mm deep where I practice and continuous exterior insulation is mandatory for new construction.
To the op's question... frost wall footings is often what I do when budget constraints or program requirements cause us to skip on the full basement. You just need to check what size and thickness of horizontal insulation you need to compensate for shallow footings.
5' of frost!
I'll bet it's muddy in the spring.
^ yes, unless there is a river nearby to flood.
Yup, it's 6' here with pockets of 8' in bad winters. Exterior insulation is not required, but you'll have terrible getting to R28+ walls without it. Underside of slabs also have to be insulated, can't do that with batt, at least not that I've ever seen.