Air cavity

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jeremymcl

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Hello
I live in Canada with very hard winters. My house was built in the 60’s. When I bought this house it was a flip. Here’s the problem. The guy took down all interior drywall and added strips on 2x4s to make 6 inch walls. His top plate was brought up to the existing ceiling tile (ceiling that’s stapled to plywood that was used instead of drywall). Some parts of the top plate are not tight against the ceiling. Then he put up a drop ceiling to cover ceiling tiles. Now my problem is that over the years with no air movement above drop ceiling one day I noticed damp ceiling tiles and some staring to get moldy in some spots along outside wall.
I put up ventilation tiles to get air moving which Helped. Now Can I use sprayfoam to fill in the cavity’s? Will the foam hold moisture and condense on wall and ceiling?
i was thinking trimming of excess foam and tucking taping over it. I was also gonna take doing drop ceiling strap roof with 2X3s then add drywall to cover old ceiling tile. Will the air cavity between new ceiling drywall and old tile condense?
Really need some help

Thank you
Jer

Edit
 
I had a similar situation in our living room when we remodeled. Changed to a vaulted ceiling. I sprayed foam in any little wall to ceiling cracks that even hinted they may leak attic air into the living space, 20 years later we have no issues. If I'm reading your post right, it looks like a similar situation. Your possible leak would be between the living space and attic air? (can you post photos) I think if you can stop the air movement with the foam, your chance of moisture forming is pretty low. It's when cold air leaks into the warm living space, that you get condensation. Or a temperature change on 2 sides of a material that has little or no r-value. Like cold water in a glass, the glass sweats because it has no r-value. Put that same cold water in a thermos and it doesn't sweat. Same principle applies. Stop the cold temperature from contacting the warm temperature, no condensation. Maybe someone will be along to explain it a little better than I did.
 
Last edited:
Thank you for responding
jeremymcl said:
Hello
I live in Canada with very hard winters. My house was built in the 60’s. When I bought this house it was a flip. Here’s the problem. The guy took down all interior drywall and added strips on 2x4s to make 6 inch walls. His top plate was brought up to the existing ceiling tile (ceiling that’s stapled to plywood that was used instead of drywall). Some parts of the top plate are not tight against the ceiling. Then he put up a drop ceiling to cover ceiling tiles. Now my problem is that over the years with no air movement above drop ceiling one day I noticed damp ceiling tiles and some staring to get moldy in some spots along outside wall.
I put up ventilation tiles to get air moving which Helped. Now Can I use sprayfoam to fill in the cavity’s? Will the foam hold moisture and condense on wall and ceiling?
i was thinking trimming of excess foam and tucking taping over it. I was also gonna take doing drop ceiling strap roof with 2X3s then add drywall to cover old ceiling tile. Will the air cavity between new ceiling drywall and old tile condense?
Really need some help

Thank you
Jer

Edit
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Eliminate the double layer ceiling.
Take off the drop ceiling and remove stapled tiles.

Increase insulation and ventilation in the attic above the ceiling.
Seal all the cracks and gaps in the plywood ceiling with spray foam and shave it flat.

Paint the plywood with mold killing primer or Concrobium, and apply second coat of interior paint with extra heavy dose of
mildewcide.

Put up a new drywall ceiling screwed to the plywood.
Use mold-resistant drywall without paper outer layer.
Before installing, paint the upper surface with mold killing primer.
 
Jeff Handy said:
Eliminate the double layer ceiling.
Take off the drop ceiling and remove stapled tiles.

Increase insulation and ventilation in the attic above the ceiling.
Seal all the cracks and gaps in the plywood ceiling with spray foam and shave it flat.

Paint the plywood with mold killing primer or Concrobium, and apply second coat of interior paint with extra heavy dose of
mildewcide.

Put up a new drywall ceiling screwed to the plywood.
Use mold-resistant drywall without paper outer layer.
Before installing, paint the upper surface with mold killing primer.
Click to expand...
Thanks Jeff

what would happen if I left up the layer of ceiling tile? Moisture between drywall and old tile?

thanks again

Jeremy
 
The old ceiling tile is already growing mold, it has to go.
Full of spores.
It is too porous to try to sterilize it, and is full of air gaps anyway, they will create pockets of condensation.

And being trapped between any kind of new ceiling layer below it, it will just keep growing and spreading more mold.
 
OOOh. That's more gap than I was visualizing. I was thinking a small gap like 1/4" or less leaking in outside air. I'd say Jeff has the right idea.
 
Jeff Handy said:
The old ceiling tile is already growing mold, it has to go.
Full of spores.
It is too porous to try to sterilize it, and is full of air gaps anyway, they will create pockets of condensation.

And being trapped between any kind of new ceiling layer below it, it will just keep growing and spreading more mold.
Click to expand...

If I was to leave drop ceiling up and remove damp tiles would I have to fill gap? Or should I leave gap so plywood could breath. I foamed one corner and plywood still condensed where sprayfoam was. Not as bad as when tiles where there.

thanks
Jer
 
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