ᐅ Basement slab poured, now awaiting cold days with frost

Hello everyone,

On Friday afternoon, the concrete slab for the basement was poured. From Friday to Saturday, temperatures were close to freezing. From Saturday to Sunday, it definitely dropped below 0°C (32°F).
We haven't measured temperatures inside the excavation pit, but we are currently unsure if this is okay.
The forecast for the next few days also predicts nighttime temperatures around -2 to -3°C (28 to 27°F).
The slab has been covered with a plastic sheet since Friday.

Is this something to be concerned about? How should we approach the general contractor regarding this?

Thanks and good luck

As far as I know, a concrete slab can be poured at temperatures down to 5°C (41°F), and it must not freeze until the concrete has fully cured. I would recommend that you note your concerns in writing to the general contractor, including the temperatures on the relevant days.

The first few days are critical; after that, it can freeze occasionally. During curing, concrete generates heat, and if it is covered (just plastic sheeting or fleece plus plastic sheeting?), temperatures around minus 2-3 degrees Celsius (27-26°F) are generally not a problem. However, it will take significantly longer for the concrete to fully harden.

I would still recommend politely checking with the general contractor (GC) by email, but if there is an issue, it would already be too late now.

@WilderSueden
Thank you very much! In my opinion, the membrane is without insulation, so just a standard sheet.

The general contractor and shell builder are locally experienced companies. I will proceed as you suggest and ask politely.

If there is damage, can a layperson recognize it? I read online something about lens-shaped formations.

You can save yourself the trouble of asking the general contractor. They will tell you it’s no problem because of reasons XYZ and that it has often been done this way before. If cracks appear, it’s their problem anyway.

No matter what I asked—why the vapor barrier on the slab got blown away by the wind after only 3 hours, whether it’s a good idea to pour an intermediate floor deck in pouring rain, or if it’s wise to apply exterior plaster just before a frost at night—I always got the same kind of answer 😀

What else could the general contractor say? If they assumed it was problematic, they simply wouldn’t take on the work.

It is more about documenting evidence in case of any issues. He can certainly state that everything is fine and standard practice. However, if a dispute arises, there is written proof.