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Plaster vs. Drywall in bathrooms

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Bldbiz

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Discussion starter · #1 ·
What is the consensus on bathroom ceilings where showers are used?

Thin coat plaster seems to promote mildew more than drywall in my experience. The plaster seals everything up tight with it being primed with oil based primer, whereas drywall although primed (water based) and painted from what I'm told will let moisture through it somewhat helping to reduce mildew.

Anyone have any thoughts or experiences?

I have a client who has suffered a stroke and can no longer do the weekly wipe down of the ceilings and walls. I'm proposing removing the thin coat plaster and replacing with moisture resistant drywall with prime and paint.

The exhaust fan has been upsized and is venting properly.

Interested to hear any input.

Thanks.
 
#2 ·
Irrelevant. Properly used, the exhaust fan will remove more humidity from the room than you can permeate through latex paint and drywall in 1,000 years. A couple of coats of latex is close to a vapor barrier. If the house is more than a few years old it will already have a couple of coats of latex.
 
#4 ·
If the paint mildews, it doesn't matter much what's under it.

Old, traditional plaster won't mildew.

If you have a mildew problem, doing a wet wipe down makes it worse, not better.

A mildew resistant bathroom paint cures these problems. I've used Zinnser and Ben Moore bath paints, they both work. Semigloss is the best choice, IMO.
 
Discussion starter · #6 ·
I concur with you all in some regard and the culprit is obviously the moisture, but I don't have this issue with typical drywall, seems to be with the pro block 200 oil based primer and paint combo. At the suggestion of plaster if they leave the plaster unprimed with no paint no problem.

Short of installing a commercial dehumidifier, what exhaust fans would you recommend?

Combination of exhaust fan and fans to dry out bathroom?
 
#7 ·
I can appreciate what you are saying about the mildew with plaster, BUT i don’t think it just because it is plaster, plenty of drywall has mildew issues too.
I would suggest the premium primers and ceilings paints which have mildewcides in them, Promar line is not the best. If i have additional concerns about mildew then i will add mildewcide.
 
Discussion starter · #9 ·
It sounds like my mildew/mold issue is more of a moisture issue at this client's bathroom which I agree with 100% just wondered if anyone doing thin coat plaster was having issues with ceilings above showers this bathroom is maybe 100sf. with a walk-in closet and linen closet directly attached with absolutely no issues at all.
The only other variable was a furnace issue from filters not being changed as required after clients stroke possibly adding more cellular material to contribute to mold growing.

I'm more inclined to tear it out and get a fresh lid with mildewcide protected paint and upgrade vent fan.

Any suggestions on best exhaust fan. Put in a ceiling fan as well.
 
#10 · (Edited)
Until now I never heard of a weekly wipe-down of the bathroom ceiling.

Is there a sufficient air gap under the door, or was it perhaps filled with a threshold?

I would consider a timer switch for the vent fan to run a bit longer, and a primer/sealer and recoat of the ceiling. Replacing the plaster sounds like an "improper" solution.
 
Discussion starter · #11 ·
MarkJames said:
Until now I never heard of a weekly wipe-down of the bathroom ceiling.
Click to expand...
As my original post alluded to it seems to be more of an issue with plaster. I myself have never wipe my drywall ceiling down in 34 yrs.
Wipe downs are pretty common for some from my searches to prohibit this issue from starting.
Plasterer will drywall finish bath ceilings now if painted. Plaster he will tell HO to leave it unprimed and unpainted to avoid this issue as much as possible. Perm ratings on drywall with paint are higher than plaster when primed with oil base and painted. I haven't had this issue with drywall finishes in shower areas.

Obviously there are several important variables that contribute to the issue (duration of showers, fan size and setup, air quality, etc.

For the suggestions of cleaning and repainting vs. replacement I would rather get back to a clean slate and see if upscaling the fan and air movement has any affect on the issue with the same shower usage.
 
#15 ·
G&Co. said:
Unless it's a very large room, an ordinary 90cfm fan is fine. Just make sure to put it on a timer and instruct the client to let it run for 20-30 minutes after he's done showering. More if he takes long hot showers.
Click to expand...
Also make sure there is space under the door for fresh air to get into the room, I usually leave 3/4-1"

I have never seen anyone wipe down a ceiling in a bathroom, in my experience drywall or plaster does not make a difference with mold
 
#16 ·
Lots of plastered houses. Never heard of it causing an issue; in and of itself.

My guess would be he doesn't leave the fan on long enough, as well as tooo small a gap at the door bottom.

No way would I drop the plaster. Huge mess, no reward. If you are insistent, then cover with 1/4 inch drywall, finish and put an extra coat of paint on it.

Then add a timer to the fan.

If that doesn't work, you may have moisture coming in from outside.

Sent from my SM-S918U using Tapatalk
 
#17 ·
I would use Zinnser Mold gaurd .

Wipe the existing ceiling down with bleach or any other mold remedy, and apply the mold gaurd primer, followed by bathroom paint of paint with mildicide in it.

Put a timer on the fan. Check it's venting outside properly and noting the ceiling cavity above.

You can even install a humidity controlled wall switch or get a fan with the switch built in.

Use a piece of tissue paper to check the suction of the fan a few times. See how far away can the fan pull the tissue into the intake. Then check it again with the door closed.

Also I have seen the vent ducts fill with condensate. Because it's vinyl flex half asked installed creating a trap.

Check if the mold is originating from inside the bathroom or the opposite side of the plaster.
 
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