Jacking up the house 8

[WARose]

I’ve been asked to give input to a friend on their home which is settling. They got an estimate from Ram Jack which is sort of like Micro Piles for houses. Does anyone have any experience with this sort of system?

I’ve looked the brochure over and have a few issues based on what I am seeing:

1. The support will be off center of the wall footing.

2. Assuming the wall footing is unreinforced, (and that it will [upon work completion] be supported only at the pile support points) I get that it does not have the flexural capacity to span between these points.

3. Overall, it doesn’t appear to be engineered (in any way shape or form; from the standpoint of what it will do to the home).

The thing about it is: the home owners seem to have the mindset that something has to be done…..and I agree (it is settling)......but I don’t think much of this solution (without modification to the wall footing).

I do mostly heavy industrial design so I’m hoping someone here has done more residential.

 

[msquared48]

First, before anyything, have the client hire a Geotech to find out WHY the foundation is settling and recommend a solution.

Next, do your homework and run the loads toi the foundation and based on the Geotech's recommendation, engineer a fix baased on those loads.

Underpinning with Micropiles is common 3 to 4" diameter and driven to refusal with jackhammers), but the system should be engineered based on the results of a geotechnical report. Just putting in the system blind is not the way to do it, regardless of any "experience" claimed by a salesman getting a cut of the profits...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[WARose]

Thanks 48. I thought about recommending the getotech myself but since they are guaranteeing the capacity of the pile (about the only thing they are guaranteeing in the warranty)…….I thought I’d omit it. (Chances are, they’d just say something we already know [i.e. part of house near hill edge, existing soil was not compacted prior to foundation placement, etc.].)

Will pass along your suggestion.

 

[PEinc]

Helical piles, such as Ram Jack, are often used for this type of problem. Settlement can be stopped and, other times, buildings can be releveled by jacking the foundation off the helical piles. The piles are usually attached to the foundation very close to the wall (the edge of the footing is notched at the pile locations) so that the edge of the foundation is not being bent. The helical piles are installed close enough together that the bending in the wall footing is minor and neglegible. Also, the foundation wall is usually strong enough to bridge between helical piles. As msquared48 said, an engineering report (borings, analysis, recommendations, etc.) is important. For instance, if there is high bedrock or other obstructions close below the wall footing, helical piles may not be a proper solution. You also need to consider if only the foundations need to be supported or if the slabs-on-grade also need to be supported. I recommend having a geotech engineer look at the problem before you start fixing.

http://www.PeirceEngineering.com

 

[BS2]

Also, depending on the soils, area of the country, and location of nearby trees, watering around the foundation my provide a solution. We see this in our area (Midwest) all the time. We have expansive clay soils and large trees and when we are under a severe prolonged drought, foundations will settle. Watering (A LOT) will often bring the foundations back to their original locations.

 

[TXStructural]

RamJack is relatively reputable, and they use both smooth steel piles driven to refusal and helical piles, depending on the soil and circumstance.
That said, I do not like refusal piles which use the house as the reaction when jacking. Obviously, when jacked sufficiently, the house will go up, but I can certainly see how that may drift over time. I do not have any information on long term performance, but they did level part of my mom's house which sits in very deep, expansive clay soils. So far, so good.

At the other end of the spectrum, I have seen very poor performance with shallow refusal piles (basically, a series of concrete cylinders are feed down a shallow hole and jacked to refusal.) Usually, the problem is that the hole is too shallow to start and there is still seasonal moisture variation below that depth. Refusal takes very little movement since the weight of the house is providing the reaction against a slowly-driven, 6" diameter "pile".

 

[msquared48]

Just a side comment..

Realtors jack up houses a lot too.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JAE]

I thought they jacked up buyers and sellers?

 

[msquared48]

JAE:

You know, I think we are both living in the past, All the jacking stopped four years ago. Now we are dealing with depressed foundations.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JAE]

Well, perhaps we could help the depression by adding a loft....Zoloft.

 

[msquared48]

It is true that engineers have lofty ideas.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[FixedEarth]

I can understand a homeowner starting out with a contractor. However, your failure is soils related, so why not bring in a soils specialist to tell you why it failed? Then hire a structural engineer to prepare the underpinning and finally bring in the contractor to bid? Many homes have been underpinned, just to hear several years later that the embedment depth was not sufficient or differential settlement was not addressed, etc.

 

[PEinc]

In my experience, very few geotech or structural engineers know enough about underpinning methods or design. Most refer this type of work to specialty contractors. Others do a design and then have it changed by the eventually chosen contractor. Starting with one or more experienced specialty contractors is not a bad idea. If a specialty contractor is qualified, he will be able to get the soils information he needs and get the proper design prepared.

http://www.PeirceEngineering.com

 

[WARose]

FixedEarth & PEinc……good posts: I’m trying to talk these folks into doing just what you suggest.