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Removed old plaster, do I need primer before new plaster?

Postby HankNova » Fri Feb 19, 2021 2:30 pm

We bought a brick house in Belgium built in 1970. The old plaster had quite some water damage and was falling off in a lot of areas, so we decided to completely strip it off and replace it.

We have hired a plastering company to put the new plaster on the walls, they already plastered the technical room so that the plumber and electrician can mount everything on a finished wall. However, they did not seem to use any primer on the wall before putting on the plaster. The company says it isn't necessary, but I don't know enough about this. I have heard from other people that they have used some kind of priming product (from picture it seemed to be some kind of reddish product you paint on).

The product they are using is a sinlge-layer plaster: Knauff Goldband. According to the Knauff datasheet, they recommend a pretreatment with Aufbrennsperre suction block to stop the masonry from absorbing the moisture too quickly. I don't know if this is really necessary or only recommended?

Is this primer necessary and something I should ask the plaster company to use (or put it on ourselves if they don't want to).

A second question: We are also wondering how to properly clean the brick before plaster, as I can't seem to find this information.

For the technical room that they already did, I simply brushed the walls with a stiff broom. I am not sure if this is sufficient and want to make sure we do the rest of the house correctly.

Is it really necessary to get it completely dust free? This is tough because the old plaster is super dusty. I am not sure what it's made of, but it has horse-hair in it.

Any guidance would be really appreciated!!!
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Postby stoneyboy » Sat Feb 20, 2021 9:54 pm

Hi hanknova
It’s down to your plastering company to decide whether a sealing primer is needed. You’ll soon know if they’ve made the wrong choice because the new plaster will craze. The brush down should be adequate for adhesion.
Regards S
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