DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Framing and Foundation > Makingcantilevered floor impenetrable





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Old 04-23-2008, 09:35 PM  
edlank
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Default Making cantilevered floor impenetrable

I bought a 1990 house that has a cantilevered wall. I noticed the basement had a draft from below that wall, so I removed the insulation bats at the sill plate to find fiberglass insulation between the joists beyond the sill plate, but only siding across the bottom of the joists below that beyond the sill plate. In other words, my hand was about 1/8" from sub-zero temperatures, with leaky siding as the barrier. I sealed the joist spaces at the cellar sill plate from sill plate to subflooring and joist to joist with small plywood pieces and caulking. I expected to wait until spring to better seal the cantilevered portion. Spring is here.

What I have is shown on some images I posted at
http://home.comcast.net/~edlank/BayWindow.html

The cantilevered wall is 8' wide by 2' deep. The outside wall extends down almost to the ground. I expected to dig out below it and remove the siding on the bottom across the joists, and the insulation. I was going to seal the joist to end plate joints with caulking, and install foam sheets, with the top one faced, filling the space between joists and building it up in thickness until almost as thick as the joists are high. I expected to cover with outside plywood and recover with siding.

Now I have questions.

1) What do I do to avoid animals from making the space below the floor an attractive home? They may eventually decide they should chew through the siding to enjoy the indoor heat in the winter, like I think mice have already done. The posted images show that animals (squirrels?) already are digging out below it and using it as a secure home.
2) If I pour some concrete to avoid tunneling under the space, what should I do to avoid it filling with organic debris and still becoming a wildlife kingdom?

3) If I do something to fill the space, what do I need to do to avoid enhancing termite tunneling through the space into the house?

I thank you for considering this.



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Old 04-24-2008, 06:19 PM  
Square Eye
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You could.....

Install blocks between the floor joists.

Dig out under it, form up a footer/retaining wall, and pour concrete up to a new treated sill plate. (use metal siding for the inside forms and cover the ground underneath with a sheet of plastic)

OR

Dig out, insulate the floor and attach Hardi-board to the bottom of the floor joists with screws and glue. Would take a LOT of digging though.



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Old 04-25-2008, 04:05 PM  
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Hey, I got the same situation but, the outside joist already have an OSB cover on them and insulation between the joist from the basement. I had a nasty draft in the basement. I caulked around the perimeter of the OSB but, it didn't seem to help as some of the gaps were in excess of 3/4". I'll be interested to see how this turns out.

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Old 06-15-2010, 07:06 PM  
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It is aluminum siding on the bottom...24" pieces, each 12" wide, running perpendicular to the foundation. There are channels holding the siding. How do I remove the aluminum siding on the bottom without destroying it? I expect to have to move the channels down about 3/8" once I get the plywood installed, or cover the plywood with a single sheet of aluminum.

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Old 10-26-2010, 08:04 PM  
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Once I got the aluminum siding pieces out, I noticed there was space for a 1/2" pressure treated plywood above the siding. One 8' by 2' piece with a corner cut off at 45 degrees and a 2' by 2' right triangle covered it, tight up against the end plate. I caulked around the perimeter and between the pieces, and it looked tight. I then noticed that there was space between the furring strip used to hold the retainer channel for the siding and the block wall, so expanding foam filled that space. From the basement, I used expanding foam at the outside ends of the cantilevered joists to help seal it, and replaced the fiberglass faced bats to fill out the space. I put the blocking boards between the joists, and it is very air tight now. The aluminum siding slid back in place with no modification necessary. I had only about 3 bushels of dirt to dig out to give me enough space to work under there.

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Old 11-07-2010, 10:32 PM  
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The holes in the plywood is for air vent s worn wet air can get out your problem is insulation only. Closing it solid will induce rot.

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Old 11-08-2010, 07:12 PM  
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There was no plywood. There were just loosely fitting aluminum siding pieces below the cantilevered joists covering a 10' by 2' area, and then basement. I am sure I was getting tens of cubic feet of air infiltration per minute on a cold windy night, because with wind gusts, we could feel the draft feet away when playing games. With that very loose barrier, the mouse welcome sign must have been seen from the neighboring farm in cold weather.

I could open the joist spaces to the basement, and that would allow moisture equilibration with the basement air. Does that sound better than sealing everywhere?

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Old 11-09-2010, 12:37 AM  
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Vapour poly the basement basement side of the studs right up between the joists sealed to the foor and joists with that black good that never gets hard area under the insulation in cantilever is a cold zone all by it self like your attic. replace alum. with wire mesh. thats the way it is done in canada . air will always get past insulation with out poly. everything behind poly is outside and is subject to moisture and every stud bay nees some air flow from outside. Thats why you see a gap between wall plywood when they frame a house. Air is your friend
Here's the deal
Siding stops the rain
plywood adds stiffness to the house
insulation only holds heat if that is no air flow around.
poly stops the drafts and keeps worm wet air out of the framing
you will get some condensation behind the poly when air oustide the poly warms and this needs to be vented out
I hope this helps
Neal

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Old 11-09-2010, 12:50 AM  
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Ed one more thought lately I have seen this area between the joists insulated with 2' sterrofoam with the edges sealed tight including above the wall at the cantilever



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