Slab pour in cold weather with night freeze.

[joea99]

I'm putting a 12x16 addition on the south side of house. Foundation is poured, 2" EPS insulation, 6 MIL poly, mesh and PEX (for radiant heat) is in place.

However, the weather has turned here in NY with forecast for daytime temps in the mid/upper 30's and lows (nights) in the mid 20's.

Contractor, said to do a lot of commercial as well, says the slab pour will be fine, as he has insulated blankets that can stay in place for a few weeks and the concrete will generate enough internal heat from the curing reaction to prevent any freeze damage. Forecast for a week after the pour, if it happens, includes a couple of rainy/snowy days. Which may very well freeze those blankets in place.

Feeling a bit uneasy about this. While I do fully trust the concrete guy, my natural inclination is to wait for a break in the weather, just to be safe. I understand he is motivated to get this done now (for final payment, if nothing else), so feel it may be unfair to press him to delay this until, well Spring, the way the forecasts look.

Any experience with such things?

 

[KWentling]

Poured my 40x60 building slab with similar conditions. Covered it with the blankets and it turned out fine. Keeping the blankets in place with our Wyoming wind was a bit of a challenge. I'd follow the advice of your contractor.

 

[joea99]

Poured my 40x60 building slab with similar conditions. Covered it with the blankets and it turned out fine. Keeping the blankets in place with our Wyoming wind was a bit of a challenge. I'd follow the advice of your contractor.

That's a LOT of blankets!

Thanks for the reply.

 

[KWentling]

I think there were 14 of them.

 

[Renze]

Any experience with such things?

We pour or lay bricks in mild freezing temperatures. My mate in Finland pours to minus 10 when the concrete is made with hot water and preservatives added to increase heat production.

When it freezes during the day, i would wait. When its only some night frost i wouldnt worry, the concrete is a huge mass that needs to cool down before it actually freezes.

 

[dstig1]

When it is early in the season like this and it is just turning cold, you can get away with it more reasonably. Once the ground is fully frozen, then no. Right now the ground should not be frozen, especially since you said you have foam down. A little non-chloride accelerant would be a decent idea to give you even more confidence, along with the blankets. If the blankets have to remain frozen in place, so be it. Not like he will need them much as it will get too cold for any work that isn't inside. Once you have it enclosed and get some heat in there, then they will thaw out. And framing + sheathing something that small shouldn't take very long.

I poured my basement slab in similar conditions 11 years ago. It was mostly enclosed (windows and doors not in) by that time, so it was not heated. It turned cold early but the ground was not yet frozen beyond the surface, and I had foam and tubing in place also. Worked just fine and didn't use any accelerant either. That ended up being a brutal winter. Perfect time to build a house!

 

[joea99]

Thanks for all the confidence builders.

I had hoped to get this at least framed and sheathed by now, but, a lot of the materials, windows and doors, were delayed by a month or so, due to disruptions by the hurricane.

Too late to start that now. I went for an "engineered kit" for this addition (4 season sun room) and hope to delay final shipment until spring. The supplier and I both agree that my on site storage, simply "under cover" is not wise, so we have to work something else out.

 

[Racer4]

The blankets help. I’d put a few inches of straw on top of the blankets too.

 

[rangerfredbob]

I did the slab for my shop when it was cold like that, I was worried but it turned out just fine...

 

[BlueKnife]

While I do fully trust the concrete guy, my natural inclination is to wait for a break in the weather, just to be safe. I understand he is motivated to get this done now (for final payment, if nothing else), so feel it may be unfair to press him to delay this until, well Spring, the way the forecasts look.

Any experience with such things?

The conditions you describe aren't an issue, especially with blankets. You should trust your concrete guy.