Plaster on wood is no good....or is it?

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spark2010

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Just reading the last post about plastering and wood. The last post they were talking about removing the wooden beads and putting on thin coat beads before skimming which is fair enough and I know if you were floating an int/ext block wall above the window you normally have a wooden beam where you would have to EML before floating.

What is the story with laths. Say if you had to repair a hole in the wall say 2 foot square on a lath and plaster wall. I see some people use bonding straight onto the laths and then skim. The way I was shown was chop it all out to a square and put a piece of plasterboard in. So is it ok to put backing plaster onto wooden laths?
 

S a plastering

Private Member
Just reading the last post about plastering and wood. The last post they were talking about removing the wooden beads and putting on thin coat beads before skimming which is fair enough and I know if you were floating an int/ext block wall above the window you normally have a wooden beam where you would have to EML before floating.

What is the story with laths. Say if you had to repair a hole in the wall say 2 foot square on a lath and plaster wall. I see some people use bonding straight onto the laths and then skim. The way I was shown was chop it all out to a square and put a piece of plasterboard in. So is it ok to put backing plaster onto wooden laths?
its different on laths the first coat is a pricking up coat which used to get a grip inbetween the laths then more consecutive coats were applied
 

Chris W

Well-Known Member
or heres a point...
these days we have a more modern material known as plasterboard...
and we use gypsum based plaster, not lime...
just board it..

easy answer to your question is dont skim, bond or render over timber if you can possibly help it...

bit of board over a timber lintel...
nothing stopping you screwing a peice of board to the face of a timber lintel and rendering round it on the masonary...

better than eml, but with eml you have to stick some building paper over the timber first to stop the timber getting hold of the plaster, then the eml holds the plaster...

timber moves due to its water content, temperature, natural drying out process etc...
lime plaster does too...
so does gypsum to a much lesser extent...
so dont use gypsum over something thats gonna move more than the gypsum...
 

S a plastering

Private Member
or heres a point...
these days we have a more modern material known as plasterboard...
and we use gypsum based plaster, not lime...
just board it..

easy answer to your question is dont skim, bond or render over timber if you can possibly help it...

bit of board over a timber lintel...
nothing stopping you screwing a peice of board to the face of a timber lintel and rendering round it on the masonary...

better than eml, but with eml you have to stick some building paper over the timber first to stop the timber getting hold of the plaster, then the eml holds the plaster...

timber moves due to its water content, temperature, natural drying out process etc...
lime plaster does too...
so does gypsum to a much lesser extent...
so dont use gypsum over something thats gonna move more than the gypsum...
exactly right tha plasteryears ago for lath ceilings were lime based and horse hair for strenth
 

spark2010

New Member
or heres a point...
these days we have a more modern material known as plasterboard...
and we use gypsum based plaster, not lime...
just board it..

easy answer to your question is dont skim, bond or render over timber if you can possibly help it...

bit of board over a timber lintel...
nothing stopping you screwing a peice of board to the face of a timber lintel and rendering round it on the masonary...

better than eml, but with eml you have to stick some building paper over the timber first to stop the timber getting hold of the plaster, then the eml holds the plaster...

timber moves due to its water content, temperature, natural drying out process etc...
lime plaster does too...
so does gypsum to a much lesser extent...
so dont use gypsum over something thats gonna move more than the gypsum...

aah, building paper before eml, didnt know that and it actually makes sense...
this is a very detailed and excellent reply
 
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