Block foundation repair

[redtag2010]

I recently bought a house with a block wall foundation. The problem I have is that 3 of the 4 walls are bowing in about 3 inches. There is also a horizontal crack on these walls about mid height 1/4 to 1/2 inch wide. The walls are 7 ft in height from concrete floor to floor joists. I'm looking into cutting out the concrete floor on the interior, placing rebar every foot vertical and horizontal to create kind of like a grid. Attach a new sill plate to bottom of floor joists with holes drilled every foot for the vertical rebar to be slid up into and the horizontal rebar tide to the verticals. Then we would shoot 8 inches of shotcrete against the existing block so the rebar is in the center of the shotcrete. Shotcrete from floor to ceiling. I was wondering if anyone has done something like this and what there results were or if this seemed like the best way besides taking the walls down and rebuilding them? I'm not apposed to rebuilding the walls but think this way might be better and easier because you don't have to shore the house or move any earth. And I agree with other posts that putting beams in or using kevlar straps seems like a bandaid. Just looking for any input on this or if rebuiding the walls would be best option.

 

[ishvaaag]

It seems a worrying condition since the bulge and horizontal crack both are neat indications of compressive (of course, eccentricity makes act of presence) ruin.

Starting from this premise the first thing is to keep people outside the building and influence area and then stabilize the building. Distroying as you pretend initially the inner floor may create a dangerous situation for those there working since any diaphragm action present will disappear, and the buckling height for the walls will increase maybe towards actual ruin itself.

In sort, you are to direct your most inmediate efforts to relieve the walls from load whilst bracing them against further progress of the bulge. Once you have the bulge contained if the standing foundation is reasonable enough you may make metallic adjustable inserts to sustain the perimeter of the house; depending on how they could even be definitive supports.

Since in my view you seem maybe a bit optimistic about the works I recommend you to engage the professional services of some structural engineer to guide you to the more sound, effective, and less costly reparations.

Good luck in all this.

 

[MiketheEngineer]

You (your walls) are most likely suffering from either hydrostatic pressure or the expansion of plastic clay soils.

Check with a couple of local basement waterproofers. Some are very good and can tell you exactly what is going on.

Either way -

You need to excavate down the outside of the wall - install drain tiles and back fill with coarse rock. Also install deadmen outsie the wall and use tie rods through the wall to pull thewm back in line. Many companies make or use them.

This is a ntushell solutions. Obviously there are a lot of details to work out.

Just shot creteing a reinforced wall over the existing will look nice for a few years - but it too will probably suffer the same in a few years.

Good luck

 

[beton1]

Try thread 256-90263. It may have also been discussed somewhere in structural other topics. Try search.

 

[hokie66]

redtag,
Your proposed solution will work, properly designed and constructed. The existing wall had inadequate strength, so it failed in bending. A wall that is strong enough will not fail. I would locate the bars close to the inside face rather than in the center.

 

[JAE]

If you cut the basement floor out - you will create an unstable condition as the bottom of the walls will no longer have anything stabilizing them laterally at their base.

Hire a competent structural engineer.

 

[bridgebuster]

A lot of good advice. Did you have an engineer inspect the house prior to the purchase? If so, the report could give some insight as to the cause.

My preference would be to excavate and backfill with a granular material or stone - 3/4 max. Excavation and backfill are cheap. I would also shore the joists before digging. Depending on how badly the wall is deflected you might be able to push it back into place or if it's localized areas you could remove the blocks and rebuild the wall. If you go the excavation route "CALL BEFORE YOU DIG"! A backhoe can expose the foundation quickly but you don't want to take out your utilities in the process.

Whatever you do - consult an engineer.

 

[oldestguy]

Those walls like this that I have seen were pushed in by frost action, not hydrostatic conditions. Assuming it is frost, with what you are proposing, you have no guarantee that more frost pushing won't move your repaired wall farther in.

If you are in northern country, I'd vote for removing outside soil and shove the walls back vertical, followed by granular fill, not susceptible to frost heaving.

 

[Qshake]

I agree with those in favor of replacing the wall and placing a engineered fill against the wall.

With the shotcrete you've no real way to ensure the house will transfer load to the new portion of wall and even it did it's not likely the shotcrete is going to be uniform and so you'll wind up with more load on certain parts of the new wall.

Anything that has a 1/4 to 1/2" crack needs to be removed so as not to remain a constant PIA.

Good luck.

Regards,
Qshake

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