Frost in the mortar?

[cdh]

I'm having an extension built and 4 rows of engineering bricks were laid below dpm on Tuesday. We had a hard frost Tuesday/Wednesday night and don't know whether this has caused any problems with the setting of the mortar. You can scrape the mortar with you finger nail. Should it have set by now or has the frost got to it?

Thanks

 

[tawelfryn]

sounds like it could well be frost damage.
Main contractors usually don't let us lay when its below 2C and if there's a threat of it falling below freezing, after walls have been built, they should be covered with Hessian at least to help stop freezing mortar

 

[mater]

it does take a few days to go off at this time off the year, not much suction on them type of bricks. as long as the work was covered it should be ok

 

[^woody^]

If its still powdery after three days, then it was frozen.

Don't let the builders carry on, and don't let them re-point it up either - it must be taken down and re-built before work proceeds.

In future, work must be protected from frost and not allowed to freeze - ie no work if temperatures are less than 3 degrees C and likely to fall to 0 at night.

Frost proofer additive in the mix, and insulation or other shelter around the new work may help preventing freezing at night