Perma Jack System

[mehr27]

I am investigating a house in Central Texas built in 1959 with a slab on expansive clays. Over time the house settled down towards one corner as much as 7 inches. The owner installed hydraulically driven steel piers (Perma Jack system) around the perimeter to stabilize the foundation roughly twenty years ago and did not raise the slab at all (most likely did not want to do the interior piers). Recent investigation has shown no further movement. The new owner is interested in raising the slab to make the house level and this will mean interior piers.

Does anyone have experience with the Perma Jack system or driven steel piers? I'm curious if the existing 20-year-old system can still be utilized to raise the slab and if a differential of 7 inches from one corner to the other is a concern, even with installing interior piers at 7 to 8 foot spacing. Or should they scrap the existing system and go with an entirely new plan?

Thanks for your time.

 

[MiketheEngineer]

Many of those systems work about the same. Drive pile to resistance - hook to footing and push back in place.

What scares me is the 7'' difference. Your walls must be way out whack and may have been patched. Pushing this back in place is going to cause a WHOLE new set of problems and repairs.

Good Luck.

 

[TexasGeotech]

How deep (massive) is the expansive clay at this site? How deep did the steel pipe piles get pushed (hydraulic)? Or where they actually driven (percussion)? This type of system is only designed to resist future settlement (from clay shrinkage or compression) and not heave. Subsequent heave can still occur and if the house was not re-leveled, which would create some minor void near perimeter to permit possible accommodation of some clay heave, then subsequent clay swelling would easily lift the house. Heaving could occur in the central area as well where no re-leveling was performed. Was the 7 inches measured before the steel pipe piles were installed? If yes then i assume the perma jack contractor performed some re-leveling. Perform a slab survey now to measure current elevations. Mike is correct, you cannot re-level 7 inches, you will surely cause damage. I practice in Central Texas and can tell you the only foundation repair system i endorse is drilled piers. They can be installed with portable equipment for confined areas typical of urban homes. The steel pipe piles can only work if properly engineered and installed.

Nick

 

[boo1]

Question:
How is under slab plumbing effected or stabilized, when you move a mono slab this much?