01
Rear Extensions
Rear yard additions that extend kitchens and living space into the yard — new foundations, steel, glazing, and roof, tied into the existing structure.
Extensions & Additions
Home extensions and additions in NYC.
AGC NYC is a residential general contractor for rear extensions, vertical additions, dormers, building expansions, and cellar and garden-level conversions across New York City — starting with the zoning, FAR, and structural questions that determine how much space an existing house can gain.
- Homeowners
- Row House Owners
- Townhouse Owners
- Architects
01 — Overview
More square footage, without guessing at what's allowed
Adding space to a New York house is a zoning problem before it is a construction problem. Available floor area (FAR), rear-yard and side-yard requirements, lot coverage, height limits, sky exposure planes, and — in a landmark district — Landmarks review all determine whether an extension should go back, up, or down. We start with a feasibility review so the design is scoped against what the lot and the code allow, not against a drawing that has to be redone after filing.
From there the work is structural: underpinning and foundation work for cellar and garden-level conversions, steel and new bearing lines for rear extensions and bearing-wall removal, and framing and envelope for vertical additions and dormers. Party-wall conditions, adjoining-owner access agreements, and neighbor notifications are part of nearly every row-house addition in the city.
This page covers expanding a building that already exists. If you are building a new house or a new multi-family building on a lot, that work lives on our new home construction page.
02 — Capabilities
Extension and addition work we deliver.
02
Vertical Additions & Dormers
Added floors, rooftop pavilions, and dormers engineered against existing structure, FAR, and height limits.
03
Cellar & Garden-Level Conversions
Underpinning, waterproofing, egress, and ceiling-height gains to make lower levels usable and legal.
04
Building Expansions
Side and side-yard expansions, enclosed porches and extensions of existing floors, and envelope work that ties new square footage into the existing building.
05
Interior Work Inside an Addition
Mechanical, electrical, and plumbing extensions, insulation, drywall, and finishes so the new space is delivered complete rather than as a shell.
06
Structural & Zoning Work
Steel framing, foundation underpinning, and bearing-wall removal, with zoning and FAR analysis carried out before drawings are finalized.
03 — Process
How we build.
01
Feasibility
Zoning review, FAR analysis, and preliminary budgeting before drawings begin.
02
Permitting
DOB filings, neighbor coordination, and ConEd / DEP approvals handled end-to-end.
03
Delivery
Single point of accountability from groundbreaking to certificate of occupancy.
04 — Related Projects
See the work.
05 — Related Services
Often part of the same scope.
New Home Construction
Ground-up single-family and multi-family construction when the project is a new building rather than an addition.
Explore →
Brownstone Restoration
Facade, masonry, and landmark work when the addition sits on a historic row house.
Explore →
Kitchens & Bathrooms
The kitchen and bath scopes that usually sit inside an extension or renovation.
Explore →
06 — Questions
What owners ask us first.
How do I know if I can extend my house?
It comes down to the zoning district, your remaining floor area (FAR), rear-yard and lot-coverage requirements, and whether the building is landmarked. We run that feasibility review first and tell you what the lot supports before design work starts.
Do I need a DOB permit for an extension?
Yes. Any addition that changes the building's footprint, height, or structure requires DOB filings with architect- or engineer-stamped drawings, and Landmarks approval as well if the property is in a historic district.
Can I live in the house during construction?
Often, for a contained rear extension, a dormer, or a single-floor scope where the work can be sealed off from the living areas. Larger additions that open the roof or remove bearing walls usually require the house to be vacant for part of the schedule. We tell you which case applies during scoping.
Do you handle work that affects a neighbor's property?
Yes. Party-wall conditions, license and access agreements with adjoining owners, and required notifications are a normal part of row-house additions and are coordinated as part of the filing process.
Is an extension different from building new?
Yes. An extension adds to a structure that already exists, so the work is governed by remaining floor area, the condition of the existing foundation and framing, and how the new structure ties in. A new building on a lot is a separate scope and a separate filing — see our new home construction page for that work.
What should I have ready for an extension consultation?
Start with the property address, survey if available, any existing drawings, the space you want to add, and your intended timeline. We can then identify whether zoning, structural, or design feasibility should come first.
Considering an extension or addition?
Share your site or address and a principal will respond within two business days.
studio@agcnyc.com