Estimating the complexity of excavation and underpinning job

[ej4321]

I would like to know how to estimate the complexity of the following job.

Current conditions:
Existing 4 story brick row house on a rubble stone foundation. Cellar height about 6 feet. Built mid-19th century. Brick extention, no cellar. House is located between 20 story building and another 4 story structure (party wall)

Needed:
Excavate existing cellar to 9 feet, create the 9 foot high cellar under the extention.

The groud floor will be vacant during the construction, the rest of the house occupied.

 

[PEinc]

You haven't given enough information for anyone to give a good answer. Are you estimating construction cost for budget purposes or for construction? If for construction, who will do the excavation and underpinning? If you are doing the work, it sounds like you are in over your head. Call a specialty underpinning contractor.

 

[ej4321]

Sorry for not being clear enough. I am estimating for budget purposes. The actual work will be done by somebody experienced in this kind of jobs (we don't want a 20 story neighboring building develop cracks, do we?)

I need a very rough estimate of cost and time.

For instance:
$20,000, 2 weeks - perfect, I am looking for engineer to spec out and contractor to do the job

$2 Million, 2 years - forget about it

Please let me know what details will help in getting a very rough estimate

 

[PEinc]

You should talk to an underpinning contractor who is local to the project. Usually the contractor will be glad to give a cost estimate in exchange for some early job information and the opportunity to bid the job when the time comes.

The contractor will need, at least, some soil borings, ground water elevation, some information on the existing buildings, and some information on the proposed foundation.

 

[ej4321]

The project is in New York city, half a block from subway lines, so ground water should not be an issue.

The project is still in a feasability study stage. Not sure how happy the contractors will be to see something that may come their way a year later.

No plans for existing building available (was built way before the plans were filed)

At this point I want a very rough estimate, and the pitfalls we may encounter during the work.

 

[PEinc]

ej4321,
Call Moretrench Geotec at 973-627-2100. Ask for Tom Tuozzolo (who may be out of town today) or Ken Chadwick. Moretrench can do underpinning, tiebacks, and is a major dewatering contractor with offices in North Jersey and Yonkers, NY.