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Old 09-18-2010, 03:37 PM   #1
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Insulate existing cantilever

I have a 3' cantilever that extends about 20' across one side of my tri-level home (built in 1967). Last Christmas when I was hanging lights in the extreme cold, I noticed that the bottom of the cantilever felt warm to the touch and we have a massive problem with getting the bedroom over the cantilever to heat properly.

Not much of a leap to assume that the cantilever isn't properly insulated.

What is the least invasive way to insulate the cantilever?

I don't know exactly how blown in or spray foam insulation works but wonder if it's possible to drill holes in the outside bottom of the cantilever between each joist and spray insulation, followed by sealing the holes?

Or is it better to open up the ceiling in the room below the cantilevered room and insulate between the joists that way? Not sure if access would be open to the cantilever from underneath.

Thanks in advance for any advice.


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Old 09-18-2010, 08:17 PM   #2
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Here is an article well worth reading.

I found it a few weeks ago when faced with insulating a cantilevered floor on a new porch I'm building.
I used 1" foam on top and warm side (for vapor barrier) and caulked it in place- then filled the remainder of the cavity with Roxul, and finished with 3/8" exterior plywood to seal it up.
Good luck.


Last edited by orange; 09-18-2010 at 08:23 PM.
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Old 09-18-2010, 09:29 PM   #3
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lol: Insulating an Overhang

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