How to paint over damp wall?

[blackcloud]

Hello all

I would be most grateful of some advice.

some strange bubbles have appeared on kitchen wall over a period of 6 months, they appear to have air in and if you press them the paint breaks off it.

Here are some photos of them.

http://s8.postimg.org/qx0vio585/Photo0003.jpg

http://postimg.org/image/pknruix69/

So I removed the paint, it was easy as it just pulled right off, the paint wasnt even stuck to the wall. So here are the results of that.

http://s21.postimg.org/j0pq0hs3r/Photo0008.jpg

http://s21.postimg.org/pfoqx5ytj/Photo0009.jpg

Over the last 6 months I didnt know why this wall would always get water on it while cooking? It turned out the cooker hood fan was not installed properly and was not working, it has now been installed properly and no water appears on the wall anymore.

Now I need to know

How to treat the damp part of the wall, maybe use something like this?

POLYCELL ONE COAT DAMP SEAL

http://www.wickes.co.uk/Polycell-One-Coat-Damp-Seal-500ml/p/227974?CAWELAID=120135120000000389&CAGPSPN=pla&utm_source=google&utm_medium=cpc&utm_term=&utm_campaign=Google Shopping - Building Materials&tmcampid=&tmad=c&tmplaceref=KHIKiwU2&tmcustom=mkwid|sKHIKiwU2_dc|pcrid|43364522812|kword||match||plid|&gclid=CLnQv5OEu8sCFUORGwoduIwL8w

To fix it should I follow this procedure?

a) If its a damp/grease mark (which it looks like it is) clean it first with biological washing powder,

https://www.persil.co.uk/wp-content/uploads/2014/01/Persil-Laundry-Powder-Bio-500x500.jpg

b) followed by sugar soap.

http://www.ebay.co.uk/itm/Everbuild-Sugar-Soap-Liquid-Concentrate-500ml-Cleaner-Grease-Stains-Grime-Cleans-/172125176725?hash=item281375c395:g:FcwAAOSwZ8ZW3T6 U

c) Paint with stain block or use an oil based primer/undercoat, but it's no cheaper, and less effective.

http://www.ebay.co.uk/itm/Stain-Block-Paint-for-Covering-Damp-and-Mould-Patches-on-Walls-and-Celings-250ml-/310795622436?hash=item485cdcd824:g:B1oAAMXQV0BSIKK i

d) Then use ordinary emulsion (wall) paint, and finish with kitchen emulsion paint (or just use the latter). Gloss is for bare wood. Or should I use POLYCELL ONE COAT DAMP SEAL rather than emulsion paint?

z0AAOSw-nZTpCef" target="_blank">http://www.ebay.co.uk/itm/Crown-SILK-Emulsion-7-5-L-Pure-Brilliant-White-Wall-Ceiling-Paint-Wipeable-/161990929494?hash=item25b7696c56:gz0AAOSw-nZTpCef

I have noticed around some of the edges the paint is not sticking to the wall, should I pull those parts off? Most of the edges of the paint are stuck tight to the wall and I really would have to scrape it off, but some edges are loose, should I pull those away until I reach a part where the paint is stuck tight to the wall or should I just leave it?

What would be the best type of paint brush for this? Maybe these?

HsAAOSwpRRWoBS 0" target="_blank">http://www.ebay.co.uk/itm/Harris-T-Class-Delta-Paint-Roller-Kit-Set-6-Sleeve-Trade-Pack-9-/221796552069?hash=item33a41acd85:gHsAAOSwpRRWoBS 0

Out of interest, what type of wall do people think that is? Plastboard or hardboard?

What colour paint does that look like on the wall? Brilliant white maybe?

Does it look like there was an undercoat on the paint I stripped off? How can I tell if there was? I know the paint peeled off very very easy, does that mean it probably did have an undercoat?

 

[misterhelpful]

The first pictures show efflorescence, which was caused by the damp drying out and pushing salts to the surface. This should ideally be sealed with an alkali resistant primer to stop any further salts coming through. However, if you have allowed the surface to dry out thoroughly, and there appears to be no more 'blooming', you may not necessarily need to do, although it would be a wise precaution as salts can still come through many months down the road. If you go with this route, don't use anything to wet the wall before applying the ARP, as it will reactivate the efflorescence, but give any rough high spots a good sand. Make any repairs with filler after the primer has been applied.

Stain blocking, damp seal paints do a good job if the area is now free of damp, so this wouldn't be a bad option if you can guarantee the problem is resolved. Just bear in mind that it will say on the tin that they are not suitable for areas suffering efflorescence.

As for just painting the bare plaster without using ARP, you should use a mist coat of contract matt emulsion mixed with around 25% water to seal the surface - for the paint to peel off so easily back to bare plaster, it suggests this wasn't done correctly in the first place, or done with a vinyl matt. (The vinyl would still have peeled off the top of any contract matt due to damp, but the majority of the mist coat would have remained because contract matt is breathable.) Once totally dry, you can proceed with your finish emulsion - trade acrylic eggshell is the best option for a kitchen, or a specific kitchen paint is the closest retail equivalent. Only go with this method if the area is 100% guaranteed free of salts, otherwise the blistering will re-appear, albeit without the damp all over the wall in the wall.

BTW, gloss isn't for bare wood, but is for suitably primed/undercoated wood.

 

[Chrispy6169]

Has the wall dryed out since the problem was fixed? If it has, i would scrape all the loose paint off to the hard edge then feather it out. You could thin down some oilbased undercoat which would seal any stains but i would try some thinned down emulsion first to see how it looks

 

[blackcloud]

thanks for your replies. I have bought

1) LEYLAND TRADE ALKALI RESISTING PRIMER WHITE
and
2) Johnstone's One Coat Matt Emulsion - Brilliant White
and
3) Thompsons Damp Seal

The wall has now dried out. I think the problem is resolved with the salts/efflorescence but I am not totally sure to be honest.

So which of the products would you recommend I used that I have bought?

 

[Chrispy6169]

If it was me id thin down some of that emulsion 25% and give it a coat and see how it dries back. Those other products are expensive so no point using them unless you have too. From experience, if the salts start to come thru, nothing will hold them back and all you can do is dry remove them until they stop.

 

[amfisted]

Given that the problem hasn't reoccurred since you fixed the cooker hood, I'd be of the opinion that the problem has been caused by condensation.
I would remove all loose paint, rub down all the edges of the bare areas until they are feathered to the level of the surrounding surfaces, apply a coat of PVA then skim with Easy fill, or (if you're not confident in your plastering skills and can afford it after buying all that special paint) get a plasterer in to do a decent skim on the wall. Once the finish is dry and sound, paint it with the anti condensation kitchen/ bathroom paint which is available from many high street retailers. Its slightly more expensive than ordinary paint, but I've found that the Wilkinsons version in particular is very effective.

 

[Chrispy6169]

Given that the problem hasn't reoccurred since you fixed the cooker hood, I'd be of the opinion that the problem has been caused by condensation.
I would remove all loose paint, rub down all the edges of the bare areas until they are feathered to the level of the surrounding surfaces, apply a coat of PVA then skim with Easy fill, or (if you're not confident in your plastering skills and can afford it after buying all that special paint) get a plasterer in to do a decent skim on the wall. Once the finish is dry and sound, paint it with the anti condensation kitchen/ bathroom paint which is available from many high street retailers. Its slightly more expensive than ordinary paint, but I've found that the Wilkinsons version in particular is very effective.

Really?! Id say this is way over the top!! The paint has blown from a damp problem which has been sorted, all your doing now is painting a wall that is bare plaster....don't bother with pva, waste of time! Thinned down emulsion is all you need to deal the wall

 

[blackcloud]

Thanks for the replies, I was worried incase it was efflorescence, so I thought just incase it was what if I use the PVA and then either the emulsion or the damp seal on top?

 

[Chrispy6169]

Like I said, from experience nothing will hold it back! All you can do is keep removing it until it stops. You'll take a chance by just using emulsion but at least if the salts come thru you haven't wasted money on expensive products

 

[Chrispy6169]

If in doubt contact the manufacturers technical advisory team, they can tell you a products limitations

 

[blackcloud]

Can PVS be painted over with emulsion or the damp seal on top?

 

[blackcloud]

What colour paint does that look like on the wall? Brilliant white maybe?

http://s8.postimg.org/qx0vio585/Photo0003.jpg

http://postimg.org/image/pknruix69/

http://s21.postimg.org/j0pq0hs3r/Photo0008.jpg

http://s21.postimg.org/pfoqx5ytj/Photo0009.jpg

 

[misterhelpful]

Do not use PVA with any water based paint. If you check the back of the tins, e.g. Unibond, it will state that it is not suitable for use with water based paints.
There are so many threads about problems on this forum where PVA has been used, I'm beginning to wonder how anybody couldn't know that it's a very bad practice.

 

[amfisted]

I've used PVA in the past before applying water based paint and its never caused any problems, but as an occasional visitor who cannot possibly claim to be privy to all the issues aired on this forum, I bow readily to the contrary word of the numerous experts who have countered my suggestion so enthusiastically.
NB: not a single exclamation mark in my reply. ;0)

Edit:
Just done a quick trawl of good ole Google and there are numerous examples of exchanges on DIY forums where the use of PVA is discussed, and indeed where that discussion has at times become a little bit heated. But the overriding point, as has been said, is that you don't use PVA when preparing a surface for water based paint.
I can understand manufacturers telling you to avoid it and to use their expensive stabilising solutions instead, but theirs are not the only voices speaking up against PVA in such circumstances.
So for me, this is a revelation, and a lesson to be borne in mind.

 

[blackcloud]

So I can not use Johnstone's One Coat Matt Emulsion - Brilliant White or Thompsons Damp Seal ontop of PVA?

Is there anything I can use ontop of PVA or just leave the PVA on by itself? with no undercoat or overcoat?