Plaster additive?

[Privatepyle11]

Hi I have a wall that I want to scim but the wall in question is prone to a little damp in the winter. I think I heard somewhere that you can add an additive to the plaster mix before scimming that will prevent the damp coming through to the surface so the finish will stay fine.

Is this correct and if so what is the additive called and where can I buy it and also what content do I add to the mix.

I am a total amatuar at scimming/plastering I have only scimmed 1 wall so far in my career

However the result wasnt that bad - far better than the wall was before scimming so I am having another attemp on this new wall that is prone to damp

Any help much appreciated

 

[jbonding]

what is causing the damp?

 

[roughcaster]

I reckon you might be thinking of a cement scratch coat with a waterproofer additive, that can be applied to a brick wall etc, to stop efflorescence and salts etc coming through before the wall is plastered. I don't think you can get an additive to put in gypsum plasters themselves to stop damp coming through. They are the world's worst for drawing through damp anyway......The source of any damp must be eliminated, the internal side of the wall should be at least scratch coated with waterproofer added to the mix, and then you could think about the wall finish.

Roughcaster.

 

[Privatepyle11]

Thanks for both the replies above, it seems as though the additive must be added before the final coat so I will get a pro plasterer in for that wall and I will do the easier ones! The reason it gets damp is its just a old house 1800's and the its solid brick so all the external walls are a bit prone to damp .

I am going to try to help prevent this by giving the exterior walls a couple of coats of weatherproof paint over the coming months so that it will hopefully help for next winter.

 

[gregers]

it sounds like you need to install a chemical dpc to the wall in question,check the wall with a damp meter,iirc you can hire a dpc pump from a hire shop who will probably have the chemical as well,then do the replastering,
if you dont get high readings with the damp meter you might be able to spray the outside wall with a spirit based dpc fluid(like grangers)to stop penetrating damp,but before you do check your pointing to the bricks,re point if needed then spray it.

 

[Privatepyle11]

it sounds like you need to install a chemical dpc to the wall in question,check the wall with a damp meter,iirc you can hire a dpc pump from a hire shop who will probably have the chemical as well,then do the replastering,
if you dont get high readings with the damp meter you might be able to spray the outside wall with a spirit based dpc fluid(like grangers)to stop penetrating damp,but before you do check your pointing to the bricks,re point if needed then spray it.

many thanks for the advice, taken on board

 

[roy c]

Any damp above 1200mm will be penertrating damp.So check for leaking down-pipes ,gutters and cracks outside. If you put a chemical dpc in you will have to knock the plaster off inside up to about a metre and scratch coat and top coat and skim and expect "salts to still come thru for a while as the wall dries out. Just brush them off till they dont' come thru then decorate....

 

[diyisfree]

J bonding your back

What have you done with legs? I bet you have plastered him behind a wall somewhere to shut him up

Where've you been hiding me old mucker ?

 

[jbonding]

split up with the missus she got the computer i got the binbags

 

[diyisfree]

Sorry to hear that

 

[jbonding]

worked out sound really, got my self a younger and prettier one now
and i dont mean computer or binbags