plastering question

Status
Not open for further replies.
J

Jimjams

New Member
hi there,
i've been plastering for a while now but want to seek a second opinion on new plaster cracking, yes, that old chestnut. Seems difficult to get a clear cut answer as to why fresh /recent plaster cracks and yes, I'm aware of all the variables involved too.
I recently plastered a victorian house with a long landing, stairs and hallway. The original wall had been papered and the customer had stripped the wall some 12 months earlier. The remaining wall was heavily sand based. I pva'd it 3 times after water spraying the wall so that the 2 plastered coats wouldn't go off too quickly, minimal amounts of water were used at trowelling stage. After a month it's crazy paved (hairline cracks all over kinda 8 inch squared throughout that wall). All other walls i've plastered in that house are fine.
Could it be the old backing coat? Knackered due to age and should have been replaced? or is it a case I over trowelled??
Reason for asking is that I've gone to a similar aged property in that area today and I've been asked to replaster 2 bedrooms that are displaying exactly the same problems, which were plastered in the summer 2010. This customer has fallen out with his plasterer and wants me to replaster, but i'm doubting my sanity now!
sorry for the long question. would be good to get some suggestions from seasoned plasterers. what's going wrong? (plaster was bought same day and had 3 months shelf life)
 
It happens mate.Sometimes when everything is right.But.. certain facters increase the chances
In my opinon it more likely to happen for 1 of 4 reasons,ill list them in order most likely to cause it.

1.Not putting skim coat on thick enough. Its a reskim and not plaster boards !!!
2.Insufficient suction control.
3.Rapid drying out of plaster i.e direct heat (unlikely)
4.seroius structural underlining problem (unlikely)

Id go with first 2 pal.
 
thanks for your quick reply.
I usually skim about 3/4mm (multi finish) on both coats so final overall skim coat is 6/8mm. Should this be thicker?
Suction control? I'm not understanding what you mean on that one. (pva?)
i don't being honest with you consider myself to be a full time plasterer, I only plaster when asked to do it. I'm not worthy! ha!
 
This reminds of a stairwell I did last year fooking walls was bone dry and i mean bone dry you could have giving them 100 coats of pva and it would have still been the same. I think the house was a giant storage heater for the sunshine of the day some how or it had nuclear reactor under the floor. But what I will
say is, the walls was painted in a lime wash or something and this was drawing the moisture out of the plaster. If I had to do it again I would give it 2 coats of plas prime before skimming and my arms would be like the sails of a windmill in a gail of wind.
 
thanks guys (probably the original lime backing coat, which was what my thoughts were anyway) the thickness is something i shall check (as it isn't 8mm, probably more like 6mm to be honest) still, you've given me some food for thought which is what i was looking for. thanx!
 
Another issue could be if it was painted too soon,as moisture would be drawn into the lime then not being able to escape through the paint.
 
first skim coat 2mm, flatten off, second skim coat 1mm... i was told you shouldnt go thicker than 2 x 2mm skim coats as it will crack and/or fall off.
 
Status
Not open for further replies.

Share this page

Back
Top