Jacking up a floor

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Old 01-17-15, 07:32 PM
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Jacking up a floor

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My house was added on to at one time and the added foundation has sunk 1.5 inches over 12 feet. I want to lift the joists with a beam and add another plate on the foundation wall to bring it up the 1.5 inches. I can't afford to have someone jack up the entire foundation but I'm wondering if lifting the house off the foundation with a beam and bottle jacks is a bad idea. Fortunately the joists are going in the direction I need them to. The house was built in 1949 and is single-story. 2x8 24 OC with shiplap. Poured concrete foundation. There is a bathroom in the addition with water supply lines in the attic. There is a cast iron stack in the crawlspace also. I will be remodeling this entire area of the house and considered shimming the floor on top of the ship lap but the ceiling would still be sloping. That seems even hokier. I am a carpenter and have some experience jacking up small areas of floors. The addition has foundation wall on all 4 sides. Any advice? Thanks.
 
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Old 01-17-15, 10:06 PM
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If you are serious about this kind of lifting, you should consider renting some serious movers' jacks (they are heavy, screw-types) instead of trying to use bottle jacks. Is it just the exterior wall on the right of the sketch that needs lifting? A few pix of what you're looking at would be helpful, too, if you want additional suggestions (of the exterior, in the crawl, etc.).
 
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Old 01-17-15, 10:30 PM
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Pictures of the top of the wall and joist area would be helpful. http://www.doityourself.com/forum/el...rt-images.html

You're also going to have to custom shim the entire plate to foundation. You are lifting up the right hand side which will leave from 0 to 1-1/2".

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Old 01-18-15, 03:49 AM
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You said "the added foundation has sunk" and " The addition has foundation wall on all 4 sides."
How old is the addition?
I would be concerned as to why the new foundation sunk. With the addition attached to the old house, the side that sunk was not carrying all of the load. Foundations shouldn't move that much.

Is this a one story addition like a single sloping roof to the right or a gable roof on top?

Bud
 
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Old 01-18-15, 06:35 AM
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What size is your bottle jack? You'll find the job easier with two or three of them. You can probably do it with one but you'll have to do a lot of shimming and moving your jack around.
 
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Old 01-18-15, 07:02 AM
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I have 2 20 ton bottle jacks. I'm guessing the addition was done in the 50's or 60's because of the 2x8's on 24's with shiplap. Also because the bathroom in the addition has cast-iron plumbing. The far right side of my drawing is a gable end and the roof has a single ridge that runs the length of the house. I'll take some pictures today. My plan was to put the extra 1.5 inch plate on the far right foundation wall and custom shim the 2 12 foot foundation walls. Bud9051, the foundation seems to be built well with adequate footing but the area on the far right where the wall sank 1.5 inches is kind of a low spot in the yard where water may collect and who knows how deep they dug for the footing. Bridgeman45, I have been wondering about those jacks but haven't looked into them yet. I'll definitely check them out. I just bought the house about a month ago so I still need to do some exploring in the crawlspace. I'll get some pics uploaded today. Thanks everybody!
 
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Old 01-18-15, 07:06 AM
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Last leveling I did just a couple of months ago was lifting one side of a bathroom floor 1/2" and I used a 20 ton bottle jack. Nearly folded a 1/8" steel plate in half. Houses don't like to move. What is under that addition for you to jack against?

If that is a single slope roof attached to the house and the side shown has dropped 1.5" I would expect to see some separation away from the house and issues with doors and windows on the sides.

Bud
 
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Old 01-18-15, 07:48 AM
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There are definitely issues with the doors in that part of the house. I think only one closes well. I'm also not sure what I'm going to place the jacks on. My thought was a beam under the joists and a beam on the ground under the jacks or steel plates about 2x2 feet.
 
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Old 01-18-15, 08:06 AM
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I like the idea of just shimming the floors on top of the shiplap and not messing with jacking the house up, but that is assuming the house will stop sinking. Do foundations typically stop sinking at some point or at least significantly decrease their rate of sinking?
 
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Old 01-18-15, 09:02 AM
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I climbed up on the roof and discovered it slopes in the same direction but only 1/2" over 12'.
 
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Old 01-18-15, 12:17 PM
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It's really hard to tell if the foundation will sink further. You almost have to track it over time to see if there is any movement. It might be possible to dig down and reinforce the footer but you really need to inspect onsite and have some knowledge about the type of soil in that area. As far as jacking, the wider the base is, the less likely the jack is to push it down.

What type of roof does it have? 1/2" over 12' is basically a flat roof, shingles need a minimum of a 3/12 pitch.
 
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Old 01-19-15, 06:09 PM
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It's a 3/12 pitch but the ridge is sloping 1/2" over 12', which should be level. It should be sloping 1.5" over 12' like the foundation under it. I've decided to shim the floor above the shiplap. I've found some places where the floor is level and don't want to jack those areas up too much.
 
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