It sounds as though at 1 time the drywall got some moisture in it,leaky roof,or is it really old drywall?Because I know in bathrooms with no air flow years of moisture can build up in the drywall and then you can paint all you want it will keep happening.
Some people scoff at this but I have seen it many times,some of these I won't even paint or I make them sign a waiver so im not liable to redo every time it happens.
Depending on your bathroom set up an easy fix is either take down the drywall or use some kind of barrier for moisture to stop it from runing the tounge and groove then put tounge and groove right over the top.Put a coat of sealer or 2 on it then a top coat on that.
#1 pine tounge and groove is pretty inexpensive and easy to install.

OK - First of all - oil based paint it the worst thing for a mildew problem - alkyd binders are natural materials - THEY ARE FOOD FOR MILDEW!!! Your painter gave you some horrible advice there.

You must clean the mildew off - a 3:1 bleach/water solution - leave it on 20 minutes - then rinse with clear water.

Apply one coat of Glidden Ultra-Hide Gripper (Primer) - it is latex and will stick very well to oil.

Then apply TWO coats of Glidden Ultra-Hide or Ralph Lauren latex semi-gloss paint. Two coats provides more paint - thus more protection.

Finally - use your fan as you have - make sure you leave it on 1/2 hour after a shower. Additionally - once a month or so (or however often you clean the bathroom - wash the ceiling with the 3:1 bleach water solution.

IF you follow these directions - you will never have a mildew problem again.

Mr. Paint

ps - mildewcides are toxic - and leach out ( dissipate completely) in about 2 years - making them an ineffective - and potentially hazardous long term solution.

mp

Thanks for all the help. Is it possible to put on too many layers of paint/primer? We know it's already been primed and painted twice; we don't know how many layers of paint are under that.

And Mr. Paint, did you mean 1 part bleach to 3 parts water? Or 3 parts bleach to one part water?

[This message has been edited by marshall1942 (edited September 14, 2003).]

I hope the forum leader will delete the multiple copies. Thanks.

[This message has been edited by marshall1942 (edited September 14, 2003).]

Yikes, I don't know why this message appears three times.

[This message has been edited by marshall1942 (edited September 14, 2003).]

I disagree with advice not to use a mildewcide as they do work and are safe as they have to be because of all the government regulations the paint companies have to go through. No you don't have to much paint on your walls.

5 - if you check with your tech services - you will find I am correct on the mildewcides - they are toxic - and they don't last forever.

Washing once a month (or so) with bleach/water - 3 bleach/1 water - is the best mildewcide there is!

Mr. Paint

No matter how you look at it you will always have this problem,and have to use a bleech solution quite often and eventually it will spread to a larger area.Thats whay I suggested what I did it will eliminate the problem and most bathrooms are pretty square and any home owner should be able to do this with a skill saw,tape,and a half days labor.