Help pls: Plaster cracked off external wall

wimbleQ

Hi

Last summer we rendered a low external brick wall. With the frosts the plaster has begun to crack off - oh joy!

Not sure what we did wrong. We put PVA on the bare brick wall and then used a mix of sand and cement with plasticiser in it. Then when dry painted it with a masonry paint.

Looks like we'll be doing it all over again this summer.... please does anyone know why it has cracked and what we did wrong? Really would like not to have to do it a third time....

Ta muchly!

ormus

what mix did you use and how thick was the render?

keystone

Builders sand or sharp sand? The former won't work and if the latter suspect not enough cement in the mix.

Cheers

wimbleQ

Hello

Thanks for the above replies. I'm embarrassed to say I can't remember what sand we used . I know we were doing some brickwork as well so suspect whatever sand the DIY place said to use for that we used also for the rendering....

It was probably around an inch or so in thickness and I think we did one lot and then built it up the following day - could it have been that the first thickness hadn't dried properly? We haven't had any problems with it until the frost/bad weather.

keystone

wimbleQ wrote: »

Thanks for the above replies. I'm embarrassed to say I can't remember what sand we used . I know we were doing some brickwork as well so suspect whatever sand the DIY place said to use for that we used also for the rendering....

It was building sand then - wrong it should have been sharp sand. How on earth do the sheds get away with employing these people giving such poor advice. :mad:

It was probably around an inch or so in thickness and I think we did one lot and then built it up the following day

How did you prepare the brickwork and did you key between coats? T'was really rather thick though TBH.

could it have been that the first thickness hadn't dried properly? We haven't had any problems with it until the frost/bad weather.

More likely that water has got between it and the brickwork and the problem didn't surface until that water froze recently and popped the whole lot off.

Cheers