Hygroscopic salts?

[philipb82]

Hello

I posted the following message in the decorating and painting section and was advised to post it here aswell.

****original message****
Hello

I painted my house a couple of years ago using Dulux Matt White paint. Over the past few months I have noticed in three areas the paint has loosened and come away from the wall so I can just peel it off. Two of the affected areas are very small but one is fairly large. Its also left what I can only describe as a white residue/powdery substance on the floor. Anyway after searching on google I know that I have to scrape the paint away and sand. Would it be best to prime the bare plaster before applying the top coat? Also what could be causing it? The walls in question are interior, the plaster behind looks alright.

I hope someone can help. Its not a big problem but I would like to know what could be causing it and wil priming it solve it.

The problem is at the bottom of the walls just above the skirting board in all cases, if that helps!

Thanks

Phil

I suspect my problem to be hygroscopic salts. One of the replies I had suggested it could be because I didn't thin down the first coat of paint. However most of the affected areas are where I painted over old paint. I can add to the original that a couple more areas have become affected and I have scraped all the paint away. The plaster behind seems to be affected but only in a couple of the cases.

I hope someone can advice me on what to do.

Thanks

Phil

 

[dazdel]

Hi Phil,
If the skim coat is not damaged, just wipe the salts of with vinegar,
and let dry, then paint. The salts have probably come from the few odd
bricks, tend to come through in certain weather conditions.

 

[Richard C]

How old is your property? Does it have cavity or solid brick walls? Assuming we’re talking about the ground floor, what type of floor do you have? Was any building or other remedial works done before you decorated last time? Has any other work been done since & before the problem started to appear?

 

[philipb82]

How old is your property? Does it have cavity or solid brick walls? Assuming we’re talking about the ground floor, what type of floor do you have? Was any building or other remedial works done before you decorated last time? Has any other work been done since & before the problem started to appear?

The house was built in the 1950's.

It has cavity walls which have been filled with that stuff to keep the house warmer!

Ground floor (concrete) just above the skirting boards.

We had a condenser boiler fitted about a month ago but the problem started before this as far as I can remember. Although I have noticed another area today but never checked before so I can't say whether thats before or after.

Phil

 

[dave1953]

Hi Phil, Sounds very much like a wall floor /junction problem.The internal and exterior internal wall skins are probably built off the slab and Dpc's and Dpm's can be somewhat lacking to say the least. Hygroscopic salts are formed from rising ground water[ not neccesarily rising damp in it's worst form as if your walls in question have a Dpc it will have prevented any further contamination]. The salts will absorb any moisture content in your property and will always spoil decoration after a period.I would remove the skirtings. hack off the plaster back to substrate to above Dpc height by 150mm. Apply waterproof cement slurry such as Vandex x 2 coats 100mm onto floor slab and up to plaster removal line, give 2 coats sand /cement render[ first coat waterproofed] at 4to1 ratio then skim finish. If you don't want a visible scar with the new plaster then render to same thickness as existing plaster and skim the whole wall Pva ing old plaster prior to new skim. Materials needed can be found on www.safeguardeurope.com, not cheap but extremely effective and they deliver. Hope this helps

 

[Richard C]

The house was built in the 1950's. It has cavity walls which have been filled with that stuff to keep the house warmer!

When was the cavity insulation done relative to your current problem? Aftermarket insulation is now being offered wholesale as a result of government grants by contractors & energy companies at very low prices but it can lead to problems if not done correctly.

Ground floor (concrete) just above the skirting boards.

OK.

We had a condenser boiler fitted about a month ago but the problem started before this as far as I can remember. Although I have noticed another area today but never checked before so I can't say whether thats before or after.

I don’t think your new boiler is causing the problem but did you have central heating before that? Sorry to keep batting back questions but am trying to establish what’s gone on.

 

[philipb82]

Thanks for your replies

When was the cavity insulation done relative to your current problem? Aftermarket insulation is now being offered wholesale as a result of government grants by contractors & energy companies at very low prices but it can lead to problems if not done correctly.

I don’t think your new boiler is causing the problem but did you have central heating before that? Sorry to keep batting back questions but am trying to establish what’s gone on.

The cavity wall insulation was done just over a year ago now which was through a grant. I've noticed the problem since but again, not sure if its always been there - sorry I can't be more specific.

We've had central heating in the house since we moved in 5 years ago but it was a back boiler.

Phil

 

[dazdel]

Any chance of some pictures phil ?

 

[philipb82]

This is the worst area

[/img]

Not all the bumps in this pic are the problem, some are just wall imperfections. Although the affected paint just looked cracked and if rubbed brought off a white residue. Imagine rubbing your finger just above the skirting board in that pic, white residue/powder will be present.

Hope these pics help.

Phil

 

[Richard C]

Great pics, they make a whole load of difference.
Firstly, your problem nothing to do with new plaster or any lack of preparation before painting. dave1953’s post is exactly at the mark but I would hold off from there as it should not be your problem .

You’ve thrown a small fly in the ointment by saying your not sure if the problem was before or after which is exactly why I was asking those questions Cavity insulation is being pushed wholesale by the government & energy companies to save the planet but it can create damp problems for unsuspecting folks & is this the main reason I’ve decided to leave the cavities of my 60’s property as they were, full of fresh air!

Maybe a bold statement but, from your pics, I would say that the injected cavity insulation has breached the cavity below the DPC & pulling moisture through & is why your now getting damp problems appearing above the skirting; it’s obviously far worse below but you won’t see it unless you pull the skirting off the wall.

I think it’s time invoke your warranty & call back whoever did the work but before you do that, please do some serious homework on what can go wrong with after market CI so you can talk with confidence & be prepared to be very stroppy. They will try to palm you off with a load of old bull ****e carp to dismiss your complaint as, if I’m correct, the solution could be expensive.

Sorry to be a bit dismal but I’m working on “no sight”, limited info here & I may be wrong but, mmmm!!, I'd give you good odds. Come back if you need further advice or info

 

[philipb82]

Even though the problem is interior walls, it could still be due to the cavity insulation? Sorry if I didn't point out its interior!

Thanks for your help.

Phil

 

[Richard C]

Sorry if I didn't point out its interior!

Ohh FFS ; please forgive me being blunt but that really is very important & the basis of my earlier questions. Maybe my fault for not asking the right or even too many questions but your answers led me to believe you were talking external wall here. Just forget everything I said & I’m beginning to think this is some sort of wind up .

I’ve just finished watching the classic Elvis concert in Hawaii which has mellowed me somewhat but I think I’ll go away now, have another double brandy & stick some pins in my eyes; over to the rest of you guys.

 

[roughcaster]

Hello

I posted the following message in the decorating and painting section and was advised to post it here aswell.

****original message****
Hello

I painted my house a couple of years ago using Dulux Matt White paint. Over the past few months I have noticed in three areas the paint has loosened and come away from the wall so I can just peel it off. Two of the affected areas are very small but one is fairly large. Its also left what I can only describe as a white residue/powdery substance on the floor. Anyway after searching on google I know that I have to scrape the paint away and sand. Would it be best to prime the bare plaster before applying the top coat? Also what could be causing it?

The walls in question are interior.

I hope someone can help. Its not a big problem but I would like to know what could be causing it and wil priming it solve it.

The problem is at the bottom of the walls just above the skirting board in all cases, if that helps!

Thanks

Phil

I suspect my problem to be hygroscopic salts. One of the replies I had suggested it could be because I didn't thin down the first coat of paint. However most of the affected areas are where I painted over old paint. I can add to the original that a couple more areas have become affected and I have scraped all the paint away. The plaster behind seems to be affected but only in a couple of the cases.

I hope someone can advice me on what to do.

Thanks

Phil

I'd go along with Dave1953, in saying that the damp/moisture coming up through the solid floor, at the wall/floor junction, is causing the efflorescence on the wall/s, even though it's an internal wall. Treating it the way he suggests, will remedy it.

Roughcaster.

 

[philipb82]

Hello
The walls in question are interior, the plaster behind looks alright.

I did actually mention it was interior walls in my question and I promise you I'm not winding anyone up.

Phil

 

[Richard C]

Hello
The walls in question are interior, the plaster behind looks alright.

I did actually mention it was interior walls in my question and I promise you I'm not winding anyone up.

Phil

My fault then, the cavity insulation bit was a distracting red herring I wasn't entirely on the wrong track though, just the cause; I agree with the others.