Problems with Paint peeling above shower

[whufc]

the on the ceiling above the shower has jsutstarted peeling, the house is only 18months old,, what should I do before painting it again?

 

[Zampa]

Sounds like you have a steam problem there...do you have an extractor fan in the bathroom?...if not first thing to do is make sure you keep a window open when your using the shower.

The emulsion on the ceiling is probably contract emulsion...give it a good scraping back and then wash it over with warmish water...this should help 'feather' the edges off..then seal the area with some thinned out oil based undercoat, then paint the whole ceiling with acrylic eggshell..couple of coats should do it.

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[confidentincompetent]

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[Nestor_Kelebay]

Whufc:

1. Here is what I believe you need to do to solve the problem:

I agree 100% with Zampa that the problem is that the paint you probably have on your bathroom ceiling is "contract emulsion", which I'm assuming to mean "a typically lesser quality paint marketed to contractors wanting to maximize their profit by purchasing less expensive materials".

I believe that this is entirely what the problem is, and all you need to do is scrape off that paint (as Zampa says) and repaint with a paint specifically made for high humidity like Zinsser's PermaWhite Bathroom Paint (or whatever equivalent is available in your area). Here's a picture of what a can of PermaWhite looks like:

http://www.cornerhardware.com/index.php?main_page=product_info&products_id=16391

2. Here is what I believe caused the problem in the first place:

In North America, most latex paints use one of three different kinds of latex binders:
a) polyvinyl acetate (or "PVA") based binders
(polyvinyl acetate is what you know as "white wood glue")
b) binders made from acrylic or methacrylic acid (100% Acrylic)
(the most common kind of plastic used to make better quality latex paints is actually the same thing you call "Perspex" in England, or "Plexiglass" or "Lucite" over here in North America.
c) styrenated acrylic binders

In general, inexpensive interior latex paints and general purpose latex primers will use polyvinyl acetate (or "PVA") binders because they're about half the cost of "100% Acrylic" binders. The "contract emulsion" paints that I think Zampa is referring to will be of this type.

One of the problems inherant in all PVA binders is that they have poor moisture resistance. Even if they're fully dry, if they get wet and stay wet for a while, they become soft and loose their adhesion to whatever they're sticking to. I THINK THIS IS WHAT"S CAUSING YOUR PAINT TO PEEL.

Better quality interior and exterior latex paints, latex bathroom paints and all new concrete primers will use "100% Acrylic" binders, which not only adhere better to moist surface, but also don't loose their adhesion nor their hardness if they get wet after they've dried. So, me thinks it's really just a matter of replacing that "contractor emulsion" that you have on your ceiling now with a "100% Acrylic" product meant for high humidity, which ANY paint meant specifically for bathrooms will be.

And, just to prove I'm not making all this up, go to:

http://www.paintquality.com and click on the red "For the Seller & Specifier" link

Then, on the list of links on the left, click on the "PQI architect modules" link

Then download the PDF file entitled "The Ingredients of Paint and Their Impact on Paint Properties"

In that PDF file, look at the purple chart at the bottom of Page 4 which states that one of the benefits of using a "100% Acrylic" (pronounced "Plexiglass") binder in a paint is that it has greater resistance to cracking and peeling under wet conditions.

3. a PS

PS: Not all "100% Acrylic" binders are the same. Rohm & Haas makes over 30 different kinds of 100% Acrylic resins for latex paints, concrete primers, water based "varnishes", and other applications, and each one will have different characteristics. To ensure the paint you buy has excellent resistance to peeling under wet conditions, buy a paint specifically made for bathrooms. Anyone making such a paint would have been sure to use a 100% Acrylic resin that has excellent moisture resistance.

 

[Nestor_Kelebay]

Another PS:

Another advantage in using a paint specifically meant for bathrooms is that it will have mildewcides added to it. That is, there will be a mildewcide inside the paint film that is drawn to the surface of the paint film under humid conditions because of it's solubility in water. That mildewcide will kill any mildew spores that land on the paint before they grow, thereby keeping your bathrom free of mildew.

You can buy mildewcide in packets that can be added to any paint, but I would never recommend anyone do that. That's because the rate at which the mildewcide leaches out of a latex paint is highly dependant on the kind of mildewcide and the gloss level of the paint. Anyone making a bathroom paint will have already done the tweaking to ensure the mildewcide comes out at the slowest rate to be 100% effective at killing mildew. That means the paint will remain mildew free for the longest possible time. But, if you just toss a packet of mildewcide in a can of paint before shaking it, you're just taking a stab in the dark. You could have that mildewcide come out of the paint so fast that it's all leached out in one year, and then the paint has no more resistance to mildew.

Post again if you want me to post a good link to read on mildewcide leaching.

 

[Zampa]

Nester..interesting answer there..your half right about contractors using lesser quality paints for economy reasons the other reason is, as whufc (that stands for West Ham Untied Football club by the way) stated, was the building is only 18 months old and its normally specified to use 'contract' emulsion on new work because it allows new sustrates to breath and thus allow any trapped moisture to escape.

You may want to think about swapping the word 'latex' for 'emulsion' when answering posts...us decorators know what you mean but the average DIY'er wont have a clue and if they go in a paint store here the (poorly trained) staff will be totally bewilldered.

Zinser is available over here now but mostly in the trade utlats and not retail...expensive stuff here...about £24 canadian dollers for a quart size tin.

Good stuff though

 

[Nestor_Kelebay]

Zampa:

"You may want to think about swapping the word 'latex' for 'emulsion' when answering posts..."

- agreed. When in Rome, do as the Romans do. I'll try to use the word "emulsion" instead of "latex", but calling it "latex" is second nature to me, so if I slip up, then read the word "latex" as "emulsion".

Do you call it an "emulsion primer" as well to differentiate it from an "oil based primer"?

(Truth is, that neither word accurately describes "emulsion" paints. Technically, an emulsion is one liquid suspended as droplets in another. That's how the very first "emulsion" paints were made; by putting oil based paints into water and shaking the can to emulsify the paint. Those early attempts weren't very successful, but the name "emulsion" stuck, and became synonymous with "water based paint". Nowadays, emulsion paints (and "latex" paints in North America) consist of SOLID plastic particles and colored pigments suspended in a solution of water and a water soluble solvent, so, it would be much more correct to call them "slurry" paints, because what you buy in the paint store is actually a slurry rather than an emulsion. Similarily, when we buy "latex" paints here in North America, there is no rubber tree sap in the can at all.)


"the other reason is, as whufc stated, was the building is only 18 months old and its normally specified to use 'contract' emulsion on new work because it allows new sustrates to breath and thus allow any trapped moisture to escape."

Definitely agree with you that wood in new construction will release a lot of water as it dries, but... wondering if you're suggesting that a "contract emulsion" would breathe any better than a top quality paint of the same gloss level. I'f so, I'd have to give that some thought, but my first reaction would be to disagree. Definitely agree that the flatter a primer or emulsion paint is, the better it's gonna breathe.

 

[Zampa]

Ah nooooooooo...what I meant was contract emulsion as opposed to vinyl matt emulsion, they are our most common emulsions over here, the vinyls can trap moisture in the wall and that can lead to blistering...so its normally recommended here to use non vinyl (contract) emulsion....and as he refered to it as a ceiling it would have been either a plasterboard..or plasterboard with a plaster skim finish not wood,...although the latter of the two should be dry in a couple of days..they are not always given that long to dry and some painters due to time/price limitations will paint them slightly damp.

Saying that ICI Dulux have now made an emulsion paint that you can paint on damp plaster...cant say i fancy risking that myself.

Emulsion/oilbased primers:- No we call it 'acrylic primer' (often shortened to just ('acrylic') normally...or sometimes 'waterbased primer undercoat'

The water based revolution hasnt really taken off here yet...most painters still prefer the traditional oil based systems.

So many words lost in translation eh!

Out of intrerest..how much is a quart of zinseer 123 or bullseye over there?

 

[Nestor_Kelebay]

Zampa:

I will have to get used to the terminology differences. Good thing I don't have to get used to driving on the other side or the road, too.

I think the last time I bought any Bullseye 123, I think it cost me about $32 $Cdn. I like it cuz it sticks well to just about anything, but what I don't like about it is that it has poor hide. Or, at least the stuff I buy here has poor hide.

 

[whufc]

Thanks guys for your advice, Thank you Zampa for the web link, so who are Millwall FC?

 

[confidentincompetent]

Thanks guys for your advice, Thank you Zampa for the web link, so who are Millwall FC?

over to u zampa