Crazed plaster

[jstrong]

Afternoon all

I've just plastered a bricked up doorway and the whole lot crazed within 1/2 hr!

The opening was bricked up using Celcon blocks and 1/2 hour before I plastered I brushed a coat of diluted pva over the area but the blocks still sucked all the moisure out of the plaster!!

Any ideas on the best way of going about it?

P.S. I've removed the crazed plaster.

 

[huddsspread]

What did you plaster it with?

 

[jstrong]

Multi finish

 

[huddsspread]

There is your problem. Multi finish is a finish, you need to use backing plaster on the blocks, and leave it a few mill below the top, then skim with multi finish. Or use sand and cement. The blocks have sucked everything out of the plaster.

If you have any sand and cement left over, float the wall with it, and as i said leave it a few mill down. Then skim it the next day.

If not go and buy a bag of bonding, and a bag of multi. Bond it out, then use the multi the next day.

Dont worry, its a learning curve...i know someone who knocked up a bucket of bonding with dirty water...he washed his mixer, drunk his drink, turned round and it had gone off solid in the bucket....

 

[jstrong]

I've got a bag of wickes one coat kicking around, coulI use that as the bonding coat then perhaps pva that the next day then finish with multi finish?

 

[Micilin]

I wouldn't use PVA on those bloks and to seal up the blocks you would be better using Bondit, WBA or SBR but leaving it for a day.

Also if you put PVA or SBR on a high suction wall, and go over it the same day you are effectively just damping the wall rather than sealing it up. And high suction blocks need more than just a damping down with a brush to stop sucking the goodness out of your plaster, as huddspread said.

If you were to wet down rather than seal, I would soak them the night before and then test next day to see how much they needed a drink before you went at it.

Also as mentioned you need a basecoat . The 'one coat' will do if that's what you have, but you need to deal with the suction

 

[peaps]

As micilin says, if you are going to wet the blocks give them a good soak night before and for good measure again before you start.

I only sue bonding agents when nothing else will work but that's me, I prefer not to seal walls to control suction but it's not always the solution.

 

[jstrong]

Many thanks all, i've used my 'one coat' and all is well so far!!