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building foundation walls under existing house non structural


brett14's Avatar
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Join Date: Apr 2015
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NJ

12-10-17, 08:05 PM   #1  
building foundation walls under existing house non structural

the house is supported by cinder block piers. im fine with that
what i want to do is properly make a cinder block skirt basically around the house. non structural...more for a air tight crawlspace to help with heating and cooling.

now my question is. without raising the house how do i put the last block in under the sill plate and have it tight?

my best thought was to have precise measurements and leave an 1-1/2 and add a new sill plate and hammer it in after the block wall has dried...

any suggestions

 
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Pilot Dane's Avatar
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NC

12-11-17, 04:55 AM   #2  
First, it might be easier than you think to jack up part of the house slightly so you can build your wall to the desired height. Then once the mortar has cured let the house back down. A couple hydraulic bottle jacks and scrap blocks of wood are all you'd need.

You can build your walls of CMU blocks or bricks. The thickness of the grout joints can be varied a bit so you can get your last course to end up close to the height needed. Then pack mortar in between the top row of block and the house to seal the gap.

 
marksr's Avatar
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TN

12-11-17, 05:05 AM   #3  
I underpinned my stepson's mobile home with block. What I did to make up the small gap between the block and the MH siding was to add a piece of flashing under the siding to cover the gap.


retired painter/contractor avid DIYer

 
brett14's Avatar
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12-11-17, 09:06 AM   #4  
i would consider lifting but the majority of the section i need to do is tiled and i feel like a lot of tiles will be popping. i may consider doing that in the section where there is wood floor. or would it be safe to lift it maybe a 1/4 inch without tiles popping or grout cracking or sheetrock cracking

 
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12-11-17, 10:43 AM   #5  
You would have to measure very carefully as you pour your footing and lay your initial courses of block so that when you get to the top, you would have about 8 1/4+" left for the top course. You would staple a roll of 1/4" foam gasket to the bottom of a 2x8 sill plate (install it first) Then you will slide the last block into place, (dry fitting it), lift it up as high as possible... insert some plastic shims under the center of the block... use a pry bar to lift it up so you have 3/8 - 1/2" of shim under the block, then tuck point mortar around the side and bottom... doing this inside and out... then strike it off with a concave striker.

 
brett14's Avatar
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12-20-17, 08:24 AM   #6  
That actually makes perfect sense and doesn't seem terrible going to be a big job but with that method it doesn't seem too bad. My next question is since this is non-structural how deep do you think I should go with my putting I live in New Jersey my code footing need to be 36 inches deep. And how thick?

 
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