Cement boards

Z

zombie

Private Member
Chaps,

Sure this will have been discussed before.

Do cement boards need pre treating prior to skimming?

Yamos!
 
I done the inside of a garden room the other day rendered came in to do the outside thought he leave them to it three days later lit on the floor had a giggle to myself
 
Depending on which board you've got you will usually find pva ain't good enough.


Get sbr or acrylic or any tile primer, (much more concentrated). You could find it suck too much and shrink and crack.
 
Hi Guys

You have to be careful when applying a gypsum based plaster directly to a cement board that has a high suction..... I have seen lots of projects where a gypsum skim applied to Knauf Aquapanel Interior has shelled..... I believe that the board soaks the moisture from the skim and effects the bond during curing (cannot comment with regards to other cement based boards)

Knauf's Ready Mixed Plasters are marble based and do not have the same issue, they have a lower water content and bond to lots of surfaces without issues or need for primers

Knauf do have a Knauf Aquapanel Board Primer - not sure what its composition is TBH, but doubt it is a common or garden PVA
 
I skimmed over wedi/wadi board before just pva and skim no problems as far as I know, wedi board is like a dark grey used in bathrooms I'm assuming it is a cement based board?
 
Just get blue grit. It's Polymer sealer like tilers sealer with sand in but cheap enough from toolstation I find, unless you get good rates at merchants. Pva wound probably do it but blue grit would be a sure bet
 
Cornelius said:
I skimmed over wedi/wadi board before just pva and skim no problems as far as I know, wedi board is like a dark grey used in bathrooms I'm assuming it is a cement based board?
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Yeah wedi is ok. Pva would do on that fine. Extruded polystyrene core I think.

Cement boards are the heavier aqua panel type or hardi backer. They can be aggro to skim when pva'd.
 
Sorry to hijack the thread. But I put this somewhere and can't remember. If someone find it can u please give it back to me.

Cement boards
 
Cornelius said:
I skimmed over wedi/wadi board before just pva and skim no problems as far as I know, wedi board is like a dark grey used in bathrooms I'm assuming it is a cement based board?
Click to expand...

These are diferent story mate, nothing to do with cement based boards. Suction is unbelievable and can kill any render if not done right . Remember once I had to render 3 columns in very famous shop in Watford and the air conditioners were on max to dry all the paint etc. I asked you f they can turn them off till I finish, answer was no. I said I have to grit them first then and will come tomorrow- no time has to be done today, shop is opening tomorrow. f**k me never experienced anything like this. Watered the board and you can see how the water disappears right in front of you. The render was just crumbling literally and that was wetherby- some serious sticking s**t. Gave up at the end and went home .
@zombie hope is not too late mate:D
 
vfr12 said:
These are diferent story mate, nothing to do with cement based boards. Suction is unbelievable and can kill any render if not done right . Remember once I had to render 3 columns in very famous shop in Watford and the air conditioners were on max to dry all the paint etc. I asked you f they can turn them off till I finish, answer was no. I said I have to grit them first then and will come tomorrow- no time has to be done today, shop is opening tomorrow. f**k me never experienced anything like this. Watered the board and you can see how the water disappears right in front of you. The render was just crumbling literally and that was wetherby- some serious sticking s**t. Gave up at the end and went home .
@zombie hope is not too late mate:D
Click to expand...

Its on the floor!
 
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