Applying plaster over highly porous render

[meanwhileinhell]

Hi all,

So I am needing to replaster the interior of my porch after removing the lining paper that was up. The bottom half of the wall looks to have been recently plastered but the top was left for whatever reason. There was a very shiny looking finish on the top half and some of the plaster was already coming off the render underneath so I decided to remove it leaving only the render, which I assume to be sand and cement.

I applied a coat of plaster to the render last night and instantly heard a suction sound as the render started sucking all the water from the plaster. The plaster dried very quick and wasn't spreadable for more than a few seconds. Not long after, the plaster started to crack and upon pushing one of the cracks you could see that the plaster hadn't stuck to the render. How can I treat the render.to stop this happening? I have heard that applying water to the render just before plastering can help but this doesn't seem like a real workable solution to me.

Thanks in advance.

 

[dougalhouse]

Apply 2 coats of PVA first following instructions on container.

 

[meanwhileinhell]

Thanks for the reply. Is this the type of product to use:

http://www.diy.com/diy/jsp/bq/nav.j...s/specificationsSpecificProductType=adhesives

Or can you suggest a specific product?

Many thanks.

 

[cotswoldbuilders]

Coat of pva day before, then another coat prior to plastering, wait till it goes tacky before skimming.
An alternatives, WBA or Blue Grit.

 

[meanwhileinhell]

WBA, is that Water Based Acrylic? I like the sound of this and the Blue Grit, if I'm right, they have silicon (or something) in them which gives a good mechanical key?

Where can I get either of these?

 

[cotswoldbuilders]

Wickes do the WBA, for Blue Grit and other bonding agents all the builders merchants will stock them.

 

[peaps]

Just use water. Do a wet test by splashing water onto the render, if it sucks in then wet the wall until it runs down the render. Suction has now stopped and the plaster finish will adhere to the wall as it was designed to do. Keep away from PVA.

 

[meanwhileinhell]

Is this the WBA:

http://www.wickes.co.uk/invt/221807

Thanks.