Replacing Foundation

[tracyhbg]

I live in a 1-story house built in the 1940's. Previous owner dug out a section of crawlspace on right side of house below original foundation and shored up with wood on one side of house . The section of house that is compromised is the right front and right side. The rest of the house seems supported properly or still has a crawlspace. Also the floor joists are not being supported by the sill but by vertical posts resting on the old foundation.

From what I have learned so far we need to support the existing structure, jack up house, remove old foundation, pour new footer / lay new foundation, replace sills (assuming they are rotted), and do something with the joists so they lay on the sill.

What is the procedure for jacking up the house? What do we do about these joists that are too short?


Thank you for your time,
Tracy

[Fischer]

On any 1 story and most 2 story houses, I have used 2 1/2 or 3 ton hydraulic car jacks with great success. I would suggest that you have a couple of those and maybe a corkscrew house jack at the very least. Once you get the house to level cut a post to that height, jack that section up another 1/4 inch, place the post lower the jack slightly and fix the post. After that go along to the next spot and repeat.

If the floor joists are too short, best bet is to sister in a joist or two along side the ones that are too short. Slide the sistered joists back to the last bearing point and then slide it forward to the new foundation. If you don't have that much maneurvering roo, you can lay the joist flat, slide it in, and then take a 2 lb. sledge and a block and roll it to upright. If you have wires and plumbing, things are going to become more difficult. Let us know

[tracyhbg]

So I jack up the house from below but do I also need to raise the exterior wall at the same time since the joist are not resting on the sill? If this is suggested, what is the procedure? Thanks!

[Fischer]

Are the joists resting on a beam? That's what it looks like in the photo. You will have to raise both if there's no means of connection. You may be able to put a short length of beam (such as 6 x 10 or 4 x 10) that spans the joists (beam) and the rim board at the same time and jack from the center of the short length of beam. You'll have to excavate the exterior wall so that a jack can be placed till you pour the foundation. The area where you jack it up will have to have a pad that will be able to support the jack without sinking it into the dirt.

Also, if the rim board (exterior wall) and the joists are different thicknesses you will have to shim the less thick one before you jack the wall up. The floor and the exterior wall will have to be raised at the same time. You're going to have to have a least 2 pours. 1 to fill everything except where you jack, and 2 to fill in the spots where the jacks where. Concrete with plasticizers will allow a better pour.

[Bob Cougham]

That's a complicated situation you have there. It's tough to tell exactly what's going on. It looks like you have two foundations the lower, earlier one and the expanded later one. How short are the joist of the sill/rim joist and what is supporting the gap?
My wild *** guess is that some hack made a bump out addition and cobbled together everything he hadn't thought of first (which looks like most of the important stuff)

One important note that I think you may already know but it's not clear from your post. Aside from the odd framing, those pictures are a textbook case of an undermined foundation. Anytime you have exposed dirt underneath the footing it will dry out, lose it's cohesion (kinda turn to sand) and fall away, thus lowering the footing above it until it finally gives way. Long story short, when your finished you can't have any vertical dirt.