Best primer for humid bath.

pezzy669

As usual a weekend bath project turned nightmare in 5 seconds flat.

Upon pulling down wallpaper in the second bath we fell into the living nightmare of black mold. The sheetrock crumbled from around the showerhead and the stench of moldy air came flowing into the bathroom. I was unsuprised as the previous owners seemed to have lacked a brain based on many of the stupid things they did. The shower head they installed took about 2 more turns before it was tight and was missing teflon tape so it has been spraying INSIDE the wall for who knows how long.

Well the problem has been fixed with about 3X2 section of new sheetrock and some bleach. The problem was not as bad as we originally thought (it was a rarely used spare bath with the prior owners and us). After repair I was able to pull down the 2 coats of wallpaper and am now down to bare sheetrock to work with.

Now my question is what is the absolute best primer for a humid bath that will resist mildew and mold the best. Basically since I found I have absolutely brand new sheetrock to work with with zero imperfections we want this to be a showcase bathroom.

Thanks for your help!

J187

Well, it might depend on what paint company you've decided to use. I use Sherwin Williams paints. I recently did my bathroom w/ preprite problock. It resists water and is designed for drywall and curred plaster - I have a little of both. For mildew, they have prewallcovering primer, but I'm not sure how well it works as far as anchoring goes because I haven't used it. The Problock surprised me w/ how well it anchored.

MrNoMaintenance

It’s actually not the primer but the top coat you need to worry about. It’s the outer surface that will come into contact with the moisture the most. The other thing to keep in mind is that the words used are mildew resistant (not mildew proof). To protect your sheetrock the best line of defence will be paint [and caulking where necessary]. I have found that the simplest, easiest and most cost effective way to deter mildew is a good quality --- translation: Quiet --- high CFM (without over killing) exhaust fan. Turn it on while taking a shower and leave it on for 20-30 minutes after. I get no condensation on the walls outside of the shower and it helps dry (less chance for mildew to develop) the shower faster also.

J187

Agreed that the top coat is more important, and great info on the fan. but that's not to say that he or she shouldn't pick out a good primer too. I just want to clearify to the poster, I just don't want the impression to be that it doesn't matter what type of primer they use. It matters even for bonding purposes, whereas some primers don't bite well into curred plaster, etc.

MrNoMaintenance

I absolutely have to agree with you, J187. Without a good quality primer, the top coat will end as a waist of time. The only point I was trying to make (not as well as I originally thought) was that the top coat is the first to make contact with moisture.

slickshift

BIN shellac-based primer
It's a little over-kill if you've fixed the moisture problem, but it is the best m/m resistant primer

handypilot

This being the case, you can buy mildewsides for any oil or latex paints. It comes in little jars or pouches that you mix into your paint. Mold and mildew need three things to grow: moisture, darkness, and a food source. The food source can be virtually anything, such as paint on your walls. Eliminate any of these, and you don't have mold or mildew. Remove moisture with a exhaust fan, remove darkness...well you can't have lights on all the time, remove food source (paint). Well...you need to paint your bathroom, so instead, you can poison the food source! (mildewside)

slickshift

Actually it's moisture, food, and warmth
Although it's true strong UV light, such as the sun, can inhibit growth, send m/m dormant, or in extreme cases kill it (as in a man-made UV mold killing machine), most household light has little effect

handypilot

Tell that to the mold in my frig!

Your right about the UV, spores survive anything but UV. Hence mildew on north-facing or shaded vinyl siding.

J187

True, however I can offer professional knowledge as I have been working with a lab on some mold issues currently. The truth is this

Mold can grow in light, but not all types can.
Mold does not survive UV
ALL mold growth is enormously accelerated by the darkness.
No mold will reach maturity without darkness.

Originally, when the lab gave the test to do, I missed the part about putting the petri dish in a very dark place after I collected the sample. When we realized this, the above info is what I was given by the lab. When I took another sample and put it in the darkness - BOOM. Major mold growth.

slickshift

True...true...
Lol
Technically that's a different type of mold, and warmth is relative, as even that mold won't grow in your freezer
But I wouldn't be surprised if Antarctica had some sort of mold

For bathroom/flood/leak/drywall/rafter mold, the best process is:

Kill...kill...kill...
X-14 or 50/50 bleach/water soak
Allow to sit but not dry (5-10 min.)
Wipe off mold/mildew
Repeat if needed

If there's still a stain left, or if you are worried about re-occurrence, seal it with a shellac-based sealer/primer

The best m/m resistant paint is Zinnser's Perma-White
The only drawback is it can only be tinted light colors and pastels

The next best is Moore's K&B (Ben Moore)
It's not quite as good, and can chip a bit, but I am really picking nits here
I hear from pros Sherwin Williams K&B is just as good

The next best is to make your own, by having the mixer at the paint shop add a shot of m/m resisting additive

All of these are great, but the Z's P-W is tops bar none
With that over BIN you can't have better m/m armor

handypilot

I second Zinsser's Perma-White! I've never had the need for it, but if I did, that's what I would buy. Zinsser makes a superior product, I absolutely love thier Peel-Stop.