Calling Royc

[self builder 123]

Hi Roy

Many thanks for you comments on re-harling over previously scratch coated concrete blocks.

I have read right through every page of the Plastering & Rendering section and found a great deal of useful information. There are many great contributions from many people including both yourself and Roughcaster.

As the blocks have now been scratch coated twice and are to be stripped again ( ! ) woudl you recommend coating the blocks with SBR or Exterior PVA before they are scratch coated to be 100% sure that the scratch coat will adhere to the concrete blocks ?

I called the builder who did the roughcasting ( wet harling ) back to see all the cracks and to show him the boss areas on each of the walls.

He agreed that it was boss, but could not explain what had happened ?

He offered to remove the boss areas and then patch over, but he happened to say that when he was actually harling the house that you could never patch wet harl - patches would always be visible.

I learned from this site that the boss area sould be removed to check why it had failed. This area should then be scratch coated. At the same time the rest of the wall should be checked to see if is sound everywhere else. Assuming it is then the whole wall should be re-harled. Is this fair to say ?

Cheers

 

[roy c]

Generally on concrete block all it needs is to damp them down a little before putting the scratch coat on, I have known lads "scut" them first with a mix of pva,cement and sand , but I dont think that is necessary. If the scratch coat is mixed to right proportions and applied evenly I cant see any problem with it taking the next coat..

But you must put your questions to "open forum" and get the opinions of the other lads on here .... Good Luck...

 

[self builder 123]

Cheers - Many Thanks !