MCI 8 ceiling

[2starbyrds]

We ripped out the old metal ceiling and replaced with new insulation and ply wood. We came home from 2 week trip to Calif in March to find 2'' mold growing on the ceiling of our bus. We have ripped it all out and found no leaks or wet insulation. We are not about to install another ceiling until we find an answer to this problem. We have talked to a few people and they said it was condensation. My question was why then did it not start to mold till March, we live in NW Washington were we all know it never stops raining! Then the suggestion was it sat in the snow for about a week the 1st of March. And the vents are not meant to sit in snow but only to drain while the bus is moving down the road. So I looked again for vents there are no stinting vents up there, just the escape hatch. This bus came from NY and I know it snows there! Any suggestions on this nightmare.

[niles500]

You need to install a vapor barrier - HTH

[ChuckMC8]

As far as I know, the only reason for condensation would be (for example) you had an unvented gas heater inside the bus.
If you have mold inside, you have a source of water. Look for the source.
Did you remove the factory fiberglass insulation when you had the ceiling out? What kind of insulation is in the ceiling now?
   Finding a leak in a bus roof can be a pain. I hope this helps-Chuck also with MC8

[pvcces]

For a given set of other conditions, mold grows much faster when it is warm. Food, moisture and warmth are ideal for growing it.

Use a humidity gauge if you don't think it is too wet inside the coach. They are inexpensive and fairly accurate!

Tom Caffrey

[Dallas]

Since you live in Washington, I wonder if the plywood was dry when you installed it?
I don't mean soaking wet, but more like moisture from sitting at an open lumber yard. Even if covered, plywood will draw a lot of moisture from it's surroundings.
My thoughts on replacement would be to let the plywood aclimatize inside the bus for a week or so and then paint it with an antibacterial, such as a light bleach solution let that dry and then coat the plywood on all sides and edges with something like  Thompsons Water Seal to keep it from absorbing any more moisture.

Good Luck!

Dallas

[Dreamscape]

Dry it out from the inside before doing anything. I agree with Dallas on bleach and sealing it. Before I installed the insulation and plywood on our Eagle I coated the underside of the ceiling with undercoating. Leave a window or vent cracked so moisture does not have a chance to be trapped. Wood is like a sponge, it will absorb moisture quickly.

Hope you are able to fix your problem, mold is ugly and stinks.

Happy Trails,

Paul

Dreamscape

[Tony LEE]

How was the mould distributed -- evenly over the whole ceiling, along ribs, just one area, patchy, just on one or two sheets.  That would give you a clue as to the cause. Generally water vapour condenses on the underside of the metal roof and soaks into insulation and then wets plywood from the top side.  What type of insulation was installed? Was it wet when you removed it? Was the plywood unpainted?

Heaters were mentioned -- did you use a catalytic heater inside in the few days before closing it up and going on vacation.

[Hartley]

You said Plywood... But Question?

Was it a finish grade plywood like oak or birch?

If so It all has to be fully sealed before installation, Mold grows faster in that stuff than any other plywood.
The only solve is to seal it with polyuerthane.

Next is to help avoid the problem, You should have Mold control bags inside you coach at all times, Especially
when it's closed up. I use StarBrite Mold control bags and have not had any problems since. 4 Bags per coach
or more changed every 3 to 6 months.

I had a problem and it got way out of hand way too fast. A single leak and a whole sheet of plywood went moldy within a week.
I used bleach and killed it mostly but the mold control bags eliminated it completely in about a month.

West Marine sells them online in a 2-pack, You need one bag per 10 feet of space. ( 2 Packages recommended )

I sell them too, But only at Bus rallies in person.

Dave....

[2starbyrds]

The installation of the windows and ceiling were done last summer inside a dry shop, we paid to have it done by professionals. The wood that was used was dry and I don't know the content, but it is 1/4" and kind of spongey, waffery, looking stuff with a middle layer that is very thin. This stuff is pretty flexable, and not finish plywood. The mold ran down all the ribs and everywhere there was a screw, so it crisscrossed the whole ceiling. We never put a heater it the bus we have not plumbed it yet so we saw no need. The insulation used was fiberglass just like the origional stuff, but not filthy and black. We are going to use a spray in foam insalation We are hoping this will take care of the condinsation. As far as the leak we can't find it so we will seal everything we can and install a new ceiling. You know we decided to buy a bus because motorhomes always leak!

[DavidInWilmNC]

In addition to, or instead of, the moisture absorption bags, one can add a dehumidifier.  I picked up a year old one from a surplus sale that works great.  It's going in the bus with its drain going down through the interior floor, the bay floor, and to the outside.  My bus stays plugged in all the time, so this should work fine.  If you haven't used on before, they pull tremendous amounts of moisture out of the air.

David

[buswarrior]

Hello.

This may just be plain old condensation and humidity, with some mold spores happening to be in place to take advantage of the conditions.

The humidity inside a coach sitting outside swings wildly up and down. Leave your maintenance manual out on a table open to a page, and leave for a few weeks. The page that is open will get wrinkled from the damp.

Having a method to keep the air circulating in and out in a stored conversion is a rare topic.

happy coaching!
buswarrior

[Tony LEE]

"The mold ran down all the ribs and everywhere there was a screw, so it crisscrossed the whole ceiling."

Then changing the insulation may not be successful since it sounds as if the condensation occurred on the underside of the ply wherever the ply was cold because of conduction through from the cold ribs and screws.

If the new insulation was wet when you pulled it out that would indicate moisture permeating through the ply and condensing on the underside of the roof.

The one constant that comes up when condensation is discussed is the need for some ventilation at all times, but this is usually to allow moisture generated by cooking and breathing to escape. Your bus was empty during the vacation so is a bit strange -- which is why I asked about having used heaters inside the bus, thinking you might have run a catalytic heater in the days before you shut the bus up and that added an excess of vapour into the air to condense later.
-----------------

If you intend adding some roof vents (with some permanent ventilation openings) then now is probably a good time to do it.

[niles500]

As I said before, apply a heavy mil vapor barrier before installing the NEW plywood and dip your screws in black butyl caulk before screwing them in. You are not going to always be able to deal with the presence of moisture and water vapor - you just want to make sure it doesn't migrate into the wall and ceiling cavities where it condenses and provides, along with the cellulose (not only the plywood but all the cellulose based materials in your coach), the means with which to multiply. mold spores are present everywhere but need moisture and a food source to breed. Also all the posts referencing the need for circulation and ventilation are true, unfortunately unless your full timing it is not as easy to keep track of on a daily basis. HTH