HELP - cracking paint????

[nelsan]

hi, got a huge problem. i am trying to decorate my bedroom, but when the emultion dries its cracking.
i used pva on the walls. but the same just happens.
i think i know what the problem. before i started to paint i noticed that on the walls there was(is) like a latex i assume sealant?? is that the cause of my problem, if so how do i solve it??? PLEASE HELP

 

[JohnD]

I don't use PVA under paint, so I haven't had this, but I think it might be softening from the moisture of the paint. Then the paint dries first and goes hard, then the understuff dries slower and shrinks causing the cracks.

Is it clean dry plaster underneath, or some other coating (e.g. old wallpaper paste; dusty filler, distemper, whitewash, gloss paint?)? I don't know what this "latex" coating is. might be something to do with old wallpaper.

I assume you don't mean the plaster is cracked and the cracks are showing through?

Try a sample section of wall, clean it off to bare plaster, apply a mist coat of emulsion thinned with water that will soak into the clean plaster and when dry, apply a finish coat of emulsion.

If you are cleaning old deposits off a wall, water and a wide paint scraper will usually take it off, then rub with a damp sponge and keep rinsing it and squeezing it out to avoid re-depositing stuff on the wall.

 

[Third_Eye]

What type of emulsion are you using at present ?

 

[versioncity]

I need help on a similar problem. I live in a flat. Had the living room re-plastered about 1 year ago. Painted it. then about 6 months later paint started coming off the wall. I painted over it but the spliting in the paint came back.
It only occurs on one small strip of the wall about 1.5 ft wide from floor to ceiling inbetween the window and balcony door.

I'm thinking that originally the plaster maybe didn't dry properly as this is a cold outer wall. Basically tha paint doesn't seem to want to stay on. The plaster looks fine.

what should i do to sort it out.?

 

[Third_Eye]

This is a odd one, though i assume it is painted gyproc that has been plastered over. Though you will need to explain first how did you paint over plaster, what type of emulsion u used and is there any water marks surrounding area ?

 

[Zampa]

So many factors..the paint, the painter, the wall surface..outside forces such as damp..

Its very rary down to the paint itself..

Did you do a mist coat first?...thats crutial otherwise the paint, if its too thick the water content will soak into the wall leaving the paint just sitting on the surface.

The plastered section may have been 'polished' up by the plasterer...leaving the surface virtually impervious...so its a bit like painting a sheet of glass or plastic.

In answer to the other post.....was you painting over vinyl silk?...I did that recently, with vinyl matt and it crazed really bad..like a mini crocodile skin...that was caused by the surface of the silk being ultra shiney...bordering on semi gloss.

 

[versioncity]

With mine, the plaster underneath looks fine. I painted it originally with Matte emulsion. I think maybe what i should do is try and remove all the paint in the area affected, leave for a while and try again. there doesn't seem to be any damp and the plastering is good.
The area affected is right infront of a structural girder, maybe this has some effect, maybe this was particularly cold area that had'nt properly dried before painting?

ZAMPA... your suggestion that the plaster has been "polished". What would i do to sort that? Rough it a little? Then try painting with a very thin first coat?

 

[Third_Eye]

Over polishing can cause loss of matt emulsion adhesion, but the new plaster has to be like glass for this to happen. But there again maybe you have condensation between your window and balcony door causing a "trapped" miosture area. If so, then maybe some miosture is penatrating through the breathable matt emulsion ! Once again, if so, then you may need an vinyl soft sheen applied to your walls or a kitchen and bathroom emulsion. Anyhow the best thing to do is if there is no evidence of penatrating or rising damp, is scrape loose emulsion, then rub down area and try to slightly break into plaster by at least 1mm, then apply a PVA mix of PVA 1/5 water (do this twice in terms of applying PVA mix of PVA 1/5 water, but allow 2 hours to dry between coats), then fill over area with filler and try and keep level with trowel or caulker, then rub down (fill again once dried if not happy with bumps caused by rubbing down), then apply a 20% thinned down matt emulsion over filled area (once dried), then apply two coats of vinyl soft sheen on all your walls as vinyl soft sheen is flexible. ALSO IS YOUR MATT EMULSION "RICH MATT EMULSION" OR "ONE COAT EMULSION" BY ANY CHANCE ?

 

[Zampa]

ZAMPA... your suggestion that the plaster has been "polished". What would i do to sort that? Rough it a little? Then try painting with a very thin first coat?

No i'd use a thinned coat of oil based primer sealer..rubbing bare plaster down can do a lot of damage to it.

Thrid eye..sorry, have to disagree slightly here..

If there is moisture behind the plaster or in it somewhere then sealing it over with a vinyl emulsion could be very risky..the whole lot could blow..emulsion isnt really meant as a sealer is it..I hope you havnt got a damp problem..if you have..befroe you do anything..you need to check the source of the damp out and stop it...contract emulsion will let the wall breathe..but the source still has to be sorted first.

ALSO IS YOUR MATT EMULSION "RICH MATT EMULSION" OR "ONE COAT EMULSION" BY ANY CHANCE ?

I wondered that too...are you thinking what im thinking?

 

[Third_Eye]

No dispute please, hehe. However by using an oil based sealer then this is creating a non-breathable area of the prob area. Cos it appears that adhesion is the problem and most adhesion oil based primers are not breathable and if any mioture is trapped (if there is any) by oil based sealer by any water pentration then it would make the scenrio worse (unless he used a breathable oil based damp seal, but then again he states that no damp appears to be prob and also damp seal may not adhere to hard to stick areas) ! Also the reason i advized to use the matt emulsion previously used as a sealer is cause of all the other walls having this used. Cos if not used then u would have flashing caused by different materials used. But i suppose we would need a photo of prob area to make a painters assesment.

 

[Zampa]

No dispute please, hehe. However by using an oil based sealer then this is creating a non-breathable area of the prob area. Cos it appears that adhesion is the problem and most adhesion oil based primers are not breathable and if any mioture is trapped (if there is any) by oil based sealer by any water pentration then it would make the scenrio worse (unless he used a breathable oil based damp seal, but then again he states that no damp appears to be prob and also damp seal may not adhere to hard to stick areas) ! Also the reason i advized to use the matt emulsion previously used as a sealer is cause of all the other walls having this used. Cos if not used then u would have flashing caused by different materials used. But i suppose we would need a photo of prob area to make a painters assesment.

Dispute what dispute..careful you'l have the MODS locking the thread lol lol...

I totally agree about the oil primer..only use that if there is no damp otherwise its no different to sealing it up with vinyl emulsion or kitchen and bathroom paint (god I hate that stuff!!)...its the only cure ive ever known for highly polished walls..had to do it a couple of times in the past..(must have upset the plasterer! )

I was thinking, if the problem was down to the paint being too thick ten the problem would be all over the walls and not one area..so we are back to the surface..or dampness

Nelsan..does the wall feel damp or sweaty?..any mould?..is the plaster a darker shade of pink?
A picture really would help

 

[versioncity]

Thank you so much for thoughts on the matter. i ain't got a digital camera, but will try and sort a pic out. its obviously going to make the discussion easier.

I've pulled off more of the paint today and can't see any mold or damp. the plaster is very smooth, i'd be a bit loathed to start taking the plaster off. Its odd how its just one spot. i used same paint/concentration all the way round the room and the rest of the exterior wall is fine. I can't remember exact Matt paint I used. Think it was possibly B&Q traditional Matt, but not sure on this.

 

[Zampa]

Did you thin the first one?

 

[Growler]

I'm thinking that originally the plaster maybe didn't dry properly as this is a cold outer wall.

Your original thought is probably correct.

 

[versioncity]

yeah the first one was thinned.

Whats the best way of removing paint from plaster? Theres a few patches where the paint is intact, the rest of it I've now taken off.

Do you think I should treat the plaster in some way before i re-paint?