Render cracks

[atomant48]

any plasterers or render experts on the forum? Having the final bit of our extension done - render to the block walls and gable ends. Should I be worried about cracks in the render top coat or is this relatively normal ?

 

[Al Strachan]

when you tap it, does it sound hollow?

 

[atomant48]

No sounds and feels solid.

 

[gaz1]

they should be no cracks in any of the top layer otherwise water can get behind it

that and freezing weather can bring it back off again

 

[angellonewolf]

cracking in new render generaly means dryed to fast and shrunk

 

[Olderisbetter]

The stuff i did on the small wall next door has cracked even though it is a modern render, I think the brand was eco rend, it looked fine the day i did it but 24 hours later a few small cracks appeared, It was hot the day i did it and the wall was in direct sunlight, i have since painted it to match the old wall so i painted the cracks to stop water getting in.

 

[Turbo]

Can be caused by drying too quick or using too much mortar plasticiser in the mix. Either way it will let water through & paint won't be much help as it is usually porous!

 

[slim_boy_fat]

Cracks don't self-heal, they have a nasty habit of migrating instead.

 

[colaboy]

You have to be really careful with that. If it lets water in behind it and then freezes, it can blow off large patches.

Ideally you need to dry it and then seal the cracks.

It doesn’t have to be anything fancy or technical, an external masonry filler will sort it.

Something like this:
https://www.screwfix.com/p/toupret-...VTbXtCh1_XggrEAQYAyABEgJ-PPD_BwE&gclsrc=aw.ds

It’s something you would want to do before winter sets in ideally.

Paul

 

[atomant48]

Thanks for the replies. The builder is coming to look at it this week. There’s another coloured top layer of render to go on apparently - I am guessing the discussion will be whether that mid coat in the photos is solid enough.

 

[angellonewolf]

That's ok but you still don't want cracks there v out fill dry and then another coat

Gaps behind will even if don't get water in there will have damp moisture from the air condensation as well all if that can freeze Nd crack blow the render