Foundation Underpinning

[jjeng2]

Have used this fix once before in a situation where contractor screwed up and had to come up with something. This time I think it lends itself to the application. Wanted to know if anyone had any opinions on my methodology.

Have an old brownstone that has brick walls in pretty bad shape. They are lowering the existing on grade floor level about 18" to below the bottom of the existing wall/ftg. My only role is to create a detail for the lowering of the foundation. Im trying to avoid the typical fix of shoring the wall and adding a new footing and wall below the existing walls in sections because I want to minimize disturbance to the existing walls, save the contractor the hassle of doing this, and also the walls are shared with the adjacent building. I proposed cutting the soil flush with the face of the wall down to the proper elevation and putting a 12" concrete retaining wall with the footing reversed(on inside of building) to essentially act as permanent sheet piling and confine the soil. The back of the new wall will be in contact with the face of the old wall. I would worry about wall rotation/movement causing a loss of confinement and analyze the whole thing as a retaining wall with a surcharge from the exisitng footing loads but im not overly concerned with a 12" concrete wall only going 18" deep.

 

[jjeng2]

PEInc,
Ive alreaddy scrapped that idea because the wall will also be acting as a retaining wall. Ive spoken with two contractors and nobody wants to touch this one so Im in the process of trying to find the client an engineer who specializes in underpinning and get this off of my hands.

 

[PEinc]

Moretrench didn't want to do the job because it is small and residential. This is a common problem with underpinning projects. The people who know what they are doing don't want to do small, residential jobs. The people who want to do small residential jobs frequently don't know what they are doing. Consequently, very few home owners ever have the needed underpinning performed.

You may want to try:
Latorre Construction Concrete & Mason Contractors
357 Monroe Avenue
Kenilworth, NJ 07033
Ph: 908-497-1400
Mr. Carmelo Latorre

They did a couple of underpinning projects that I designed. Tell them I sent you.

http://home.comcast.net/~peirceengineering/wsb/html/view.cgi-home.html-.html

 

[jjeng2]

PEinc,
Thanks and thanks for all your help. I gave them several solutions that would avoid the need to underpin and im hoping they will choose one of them or im just going to pass them on to someone who can actually figure out how to do this in the field without collapsing the building. Got your contact info and you will be my first choice if I ever need the services you provide. I do a lot of foundation work in NY and NJ including southern Jersey on everything from single family houses to NYC buildings.

http://www.structuralworkshop.com

 

[PEinc]

Design and construction of underpinning requires experienced engineers and contractors. Or, you could have a big problem. Many engineers and contractors think they know how to underpin buildings. Most do not.

See the following link about an apartment building that was being underpinned. The contractor dug along and below the bottom of the wall footing, leaving a sloped excavation along the wall. The intent was to then dig into the slope to install underpinning piers. Although commonly done, this is not the proper way to underpin a building.

http://abclocal.go.com/wpvi/story?section=local&id=3438587

 

[DRC1]

I am joinig late but would like to put my 2 cents in.
1.) Whatever you do since you are working below an existing footing, will require a PE stamped drawing to comply with OSHA. The 4 ft exemption does not apply to this situation.
2.) Masonary walls exert considrable load and do not tolerate movement well. Things you can do with an RC wall should not be attempted on a masonary wall.
3.) Building and curing an RC wall you describe will require the soil to stand for several days.
4.) I you were to do it, odds are frankly it would work. Soil often stands when it should not. The problem is is that some times it won't work and you never know when that will happen.
5.) Finally 18" of underpinning is not a rocket flight to the moon. It should go quickly and easily. There are several contractors in the area that could do that. Moretrench is certianly capable. If I had to do this I think the fastest and most affordable way to do it would be conventional underpinning.