New Wet Harl Gone Boss ( Roughcaster )

[self builder 123]

Hi

We recently had our new timber framed house wet harled.

Prior to it being harled the original scratch coat ( cement and sand ) was removed as the builder said that it was soft ?

The scratch coat was chipped off back to the bare concrete block.

The concrete blocks were pressure washed to clean away any dust and also to wet the walls in readiness to accept the new scratch coat. I believe that the scratch coat was formed from Rugby cement, sand and Freeflo additive.

The wet harling was formed from Rugby white cement, sand and more Freeflo additive.

After less than 6 months large cracks appeared. When the cracks were tapped there is a hollow sound which I understand means that the wet harl has come away from the concrete walls.

This has happened all over the house on all the walls to some degree.

Could anyone give an opinion on what could have happened ?

We are going to have the house stripped back to the concrete blocks and then re-harled.

Could anyone give advice on what could be done to ensure that this does not happen again ?

Cheers

 

[Shytalkz]

Basically, the scratch and/or base coats dried out too quickly and was probably too hard a mix for the backing. Can be complicated further if the subsequent coat/s are either thicker or stronger than the one beneath. Although the wall may well have been damped down prior to rendering, it is also important to keep it damp as it cures.

Bad workmanship, in two words.

If you're doing it onto blockwork, it would be better being rendered onto expamet as a min 2 coat render.

 

[self builder 123]

Thanks Shytalkz

When you say Expamet is that the galvanised mesh that is fixed to the bare concrete blocks ?

 

[vancleef]

If Roughcaster can't help you out the guy's i work alongside specialise in wet harling and would be willing to pass on your details and could advise you on different options.They seem to swear by Chaps cement which comes pre coloured to what your specifications.

We are based out in Insch.

 

[Shytalkz]

When you say Expamet is that the galvanised mesh that is fixed to the bare concrete blocks ?

Yep, that's the stuff. Stainless version would be better. Details here