Best practices

[AldenStan]

I'm demolishing an existing, derelict 3-story brownstone in a residential/industrial area of Brooklyn and building a five-story residential building in its place. The building shares a party wall on one side with a building of similar size. The other side is directly adjacent to a 60' four-story building. The lot is 20' wide.

A contractor has suggested that, rather than demolishing/underpinning/foundation/steel as a 4-step process by separate trades that we leave up the existing structure and do these tasks under and around the existing structure saving the demo for later. He suggests this so that the water and power remain, the need for scaffolding is reduced and the effect on the neighbors is masked and kept to a minimum.

Since my experience is limited to wood-frame single family construction, I'm wondering how sound this plan is.

Coincidentally, I could also use some recommendations on expereience trades in the area since all my connections are several counties north and trades won't travel.

TIA

 

[bridgebuster]

You won't have any trouble find any needed trade. Keep in mind the unions are still very strong. A lot of demo work is done non-union. Sometimes they're harassed.

One word of caution about working in the city - if you don't know how "things" work you might be asking for trouble.

 

[csd72]

This sounds very similar to a project I did.

The critical issue is that at each and every stage the building is stable. This can be best achieved by getting the stabilising members (such as shear walls e.t.c.) up as soon as possible and then demolishing the existing structure around it.

Economy can often be best achieved by using your temporary bracing as part of the permanent structure. This requires agreat deal of coordination and lateral thinking, but it can really be worth it.

Keep in mind that the floor membranes in this type of building are crucial to the stability, and removing any part of them can cause stability issues that need to be addressed.

For our design, we actually provided a demolition drawing giving the stages of construction and location of temporary/permanent props. You need to at least do this for yourself to make sure it works as you plan it.

To what extent are you underpinning the existing walls?
What type of construction are you proposing?