Pouring concrete in cold weather, and more…
The pouring of our foundation walls has been delayed by 3 weeks, and frosty weather has arrived. Daytime highs below 50 F, with lows around freezing. Expecting some lows in the 20’s over the next 4 weeks (climate zone 4).
My contractor is insisting that we don’t need to do anything differently for our pour because the temps won’t stay cold enough long enough to freeze the concrete. What I’ve read online indicates that special procedures need to be done when the temps start dropping below 40 F. Our footings are already cured, but the walls will be 3 feet high and fully exposed to the cold.
Any suggestions on what should be done in this situation?
In addition, the upper row of flat snap ties holding the forms will be above ground level, and the contractor currently plans to leave them unsealed and exposed. Is that normal or allowed? We are using dimple membrane below ground for our damp proofing, in addition to gravel backfill and a foundation drain next to the footer.
Also, I know that concrete work is not super accurate. But is it normal to have the “straight” walls vary as much as 5/8″ within 10-15 feet? Thanks.
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Replies
Debra,
Mixing concrete is an exothermic reaction. When water is mixed with cement, the chemical reaction produces heat. That's why recently placed concrete is warm to the touch, even in cold weather.
I don't have enough experience to know how cold the weather needs to be before recently placed concrete is in danger of freezing, but your contractor's judgment may be correct. Throwing a tarp on top of your recently poured walls is certainly cheap insurance.
Concerning snap tie holes: There is no technical reason to finish them. What to do with snap tie holes is a design and aesthetic decision, not a structural matter.