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As the build gets closer (the 24" topper is suppose to be installed this week), I have a few maybe picky questions.  I plan on building the van to travel from the humid south, to the deserts, and hopefully Canada and Alaska.

1...I noticed on the youtube van builds most people run the floor all the way to the metal van wall.  This means that there is insulation under and over the plywood floor, but the wood is touching the outside metal.  It seems like this would be a condensation point.  I'm thinking about stopping the wood before it reaches the wall and having polyiso there.  I will be gluing the floor to floor "joists", with polyiso in between the joists, the joist will be glued to the metal van floor...which, of course, will be touching the metal floor.

2...Also on youtube, I have notice most van builders don't paint the wood framework supports or the inside and underside of plywood or luann.  I'm thinking that using a strong anti-mold paint on every UNSEEN surface of the wood including the floor joists, and then paint or stain and seal the visual surfaces for my preferred colors.   
Thanks, Virgil
You will be creating an above average conversion if you follow your gut.

Moisture, condensation, insulation, humidity and actual water leaks are all very real concerns that few builders recognize and even fewer take steps to remediate and prevent.

Dave
Thus why I put polyurethane on both sides of myour plywood floor. I will say though that condensation is less likely at floor level vs ceiling. Also there is a product at Home Depot called Blind Stop which is compressed vinyl. It can be used instead of wood and will not mold or rot.
VJ, In my still-learning position, I see no reason NOT to paint the wood touching the floor. It seems to me to be less likely to absorb moisture -- isn't that why clapboard houses were always painted?

And if you feel better about leaving a bit of a gap at the walls, why fill it with anything? If it does act as sort of a gutter, just let it dry out. If there is a moisture problem where floor meets wall/skin, why fill it with another material that prevents evaporation?

It just seems to me that if metal sweats when temps go up and down, why NOT leave some gaps for moisture to vent? If you left a quarter-inch gap (for instance) at each edge of your polyiso (or other rigid material), would it help or hinder moisture from sweating? And... would it really decrease the insulation value enough to worry about it?
(11-13-2016, 04:34 AM)Virgil Jones Wrote: [ -> ]As the build gets closer (the 24" topper is suppose to be installed this week), I have a few maybe picky questions.  I plan on building the van to travel from the humid south, to the deserts, and hopefully Canada and Alaska.

1...I noticed on the youtube van builds most people run the floor all the way to the metal van wall.  This means that there is insulation under and over the plywood floor, but the wood is touching the outside metal.  It seems like this would be a condensation point.  I'm thinking about stopping the wood before it reaches the wall and having polyiso there.  I will be gluing the floor to floor "joists", with polyiso in between the joists, the joist will be glued to the metal van floor...which, of course, will be touching the metal floor.

2...Also on youtube, I have notice most van builders don't paint the wood framework supports or the inside and underside of plywood or luann.  I'm thinking that using a strong anti-mold paint on every UNSEEN surface of the wood including the floor joists, and then paint or stain and seal the visual surfaces for my preferred colors.   
Thanks, Virgil

You may want to read the MSDS's on anti-mold paints before using them.   Using a lot of strong anti-mold agents in a small enclosed space is too scary for my taste.  From what I understand, doing so significantly raises the probability of getting one of several cancers.