Silicon K1 on during the day then cold overnight, how long does it need to stay above 5 degrees?

[dougray]

I posted about our job before and it's now underway, meshed HP12 base with k1 on. Hoping for one last bit of advice.
The guys who are doing it got most of the house done by Monday but have one gable and one side of the extension left to do. The weather's been crap and rainy this week so they've not been back on it but they were planning to come back sometime from tomorrow onwards when it's not supposed to be raining. Just noticed the weather forecast says it might go down to 1 degree (give or take) overnight until Thursday but up around 10-12 degrees and a bit sunny during the day. The other panels have all been put on in the afternoon then scratched back the next morning except one which went on first thing and got scratched back from 7pm.
I've seen a variety of opinions on here about what temperature you can get away with and K rends info just says that it should be set enough to avoid frost damage (doesn't say what set enough is though). They'll maybe just decide for themselves to leave it until it's warmer but I've a feeling they've other work to get into and are keen to wind ours up so might try and get away with it if it's borderline.
Should I put my foot down and tell them to leave it until the cold snap passes, or if applied would it have set enough over the course of the day to cope with a cold night?

 

[Jimbob9]

5c and rising if you want to maintain spec. Water starts to crystallise at just below 3c not ideal for a setting cement and apparently easy to spot under a microscope.

The 5c limit is obviously to maintain a bit of margin above where problems start to happen.

 

[dougray]

5c and rising if you want to maintain spec. Water starts to crystallise at just below 3c not ideal for a setting cement and apparently easy to spot under a microscope.

The 5c limit is obviously to maintain a bit of margin above where problems start to happen.

Cheers for the advice. They've come to finish prepping the remaining surfaces today but are happy enough to come back later in the week when it's warmer to get the render on and scratched. To be fair, it's been milder recently and I don't think it occurred to him it was getting that cold overnight at given it's allegedly spring now.

 

[Rigsby]

1c is imo ok. Anything up to -3c is usually a ground frost, hardly ever on a wall.

Cement on setting creates a lot of heat so that helps and if you are still worried leave your heating on. Heat loss will stop so called frost.

Having it left overnight on a warm night is also not good. Last thing you want is it rock hard next morning.

I have never come across failure due to frost but plenty of failures due to rapid drying.

 

[dougray]

1c is imo ok. Anything up to -3c is usually a ground frost, hardly ever on a wall.

Cement on setting creates a lot of heat so that helps and if you are still worried leave your heating on. Heat loss will stop so called frost.

Having it left overnight on a warm night is also not good. Last thing you want is it rock hard next morning.

I have never come across failure due to frost but plenty of failures due to rapid drying.

Thanks Rigsby, that's reassuring. The weather isn't likely to be warm enough to cause a problem when they come back on Tuesday. The forecast says 12deg during the day and 5deg overnight. It also looks reasonably clear and dry so fingers crossed it'll get finished ok.
They have another job to get on with in the meantime anyway so no skin of their nose to put it off a few days.

 

[Rigsby]

Thanks Rigsby, that's reassuring. The weather isn't likely to be warm enough to cause a problem when they come back on Tuesday. The forecast says 12deg during the day and 5deg overnight. It also looks reasonably clear and dry so fingers crossed it'll get finished ok.
They have another job to get on with in the meantime anyway so no skin of their nose to put it off a few days.

I would be putting that on 5pm if the heating is on.

K rend is a slow setter.

 

[dougray]

That sounds about right from the timings they used on the other gable and back elevation. They were on in the afternoon and scratched in the morning. They got the front done in one day, render on first thing then scratched back from 7pm-9pm but that day was sunny and 17deg plus south facing.
Typically for Scottish weather the forecast we looked at during the weekend is out the window. Today was rainy after predictions for sun so it's been put off again for Thursday. Sally I've not much faith it'll stay dry then either. If they put it on in the afternoon and it rains lightly after a few hours of setting will it be a disaster? Just want to keep myself right with whatever they propose.
Thanks again for all the advice.

 

[owls]

It will take a light shower a couple of hours after being scraped. If it rains a few hours after it's been put on the wall once it's skinned over, again it will be fine.

 

[dougray]

Cheers, good to know. Fingers crossed the weather's ok tomorrow and Friday then.