More Q&A Spotlight
Ideally, home building is a year-round job, but in many places, winter can throw a wrench into the works. In this Q&A post, “Emel” is worried about his upcoming foundation pour. He’s in central Wisconsin (Climate Zone 6), and the pour is scheduled for mid-December, when the daytime temperatures in his area average a high of 27°F.
He writes that the 5-ft. stem walls and footings may be exposed to freezing temperatures for a period of time until the forms are stripped, exterior insulation is installed, and the soil is backfilled. Although the contractor plans to use additives that can allow the concrete to cure in colder weather, Emel is concerned that freezing temperatures may cause frost-heave and affect the stability of the foundation. (For a Canadian take on cold-weather concrete, read this). Emel is also concerned that the cold may affect adhesives, tapes, and caulk in the later build stages.
Fresh concrete needs a little heat
Reader Bill Wichers suggests protecting the concrete with polyiso foam. “The concrete and the natural heat from the ground, plus the heat from the curing concrete will be enough to keep things safe,” he says.
“Weather conditions play a big part in this,” Bill adds. “If 27°F is your daily high, it’s probably safe to assume the daily low is a fair bit below that, so you’re probably in the ‘too cold’ [to pour] territory unless you add a heater ($$). In my area, we tent when it will get down to freezing or a little below, maybe down to 25°F or so as the daily low, if that. It’s similar to the difference between a frost, where tenting your garden can save the plants, and a hard freeze, where the plants are going to die regardless of what you do…
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2 Comments
How fitting article here in Ontario, Canada. Thank you for that!
I dare you to find me one residential contractor that first knows any of this information and second, employs any of these recommendations. I've built full (footings to the roof) ICF home and refused to do a pour in freezing weather. Yes it took us 1 year to complete all pours but it was done right, and that’s with ICF. Everyone looked at me like I'm some crazy OCD guy. I ignore it and smile. It’s my home. One of my friend’s contractor, that was building in different city, called me “condo builder” when I started advising him about what he should do in his house and he was building on a swamp in Colingwood area.
During one winter, it was mid to late January, a contractor placed forms on pretty much frozen duggout for a basement, poured footings and baseemnt walls in -25deg C, very next day took the forms off and backfilled it 2 days later. That concrete doesn’t have even 5% of its bearing capacity.
Nobody puts any rebar in the foundation walls, they tell me they compensate with thicker walls.. Like that is doing anything for soil movement etc.
I think that right now your are an odd builder if you don’t have a crack in the basement. I can’t even describe how I feel about entire construction industry. From concret work all the way to HVAC etc. It’s just disgusting,
Until someone starts enforcing these rules and best practices we will just keep looking at garbage being built all around us. Also, average customer should start to get educated on a very basic level what makes one house better than the other. I realized that this sounds more like a rant then a constructive comment to this article. My apologies..
Fortunately, like most building science issues, full failure seems relatively rare. Though one structural engineer I work with has a booming side business doing expert witness work and his foundation details are a bit extreme as a result.
I have only had one frost-heave failure on my projects, as far as I know; I had designed it but did not oversee construction or get too involved in the construction details. It was a pretty similar situation to the one described here, but on rocky, sloped soil so they didn't think they needed to take precautions. The corner of the foundation lifted but 2-3" and they asked me for advice. All I could say was to talk to an engineer.
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