ALT-1 vs ALT-2: The Only Guide NYCTownhouse Owners Need (2025 Update)
The definitive permit guide for brownstone renovations — clear, technical, and written for serious buyers and homeowners.
Understanding NYC Department of Buildings permit classifications is essential for any brownstone or townhouse renovation. Yet ALT-1 and ALT-2 remain two of the most misunderstood terms in the entire renovation process — even among many real estate agents and contractors.
Getting this wrong early can:
• Add months to your timeline
• Change whether you can live in the home during construction
• Dramatically alter cost structure
• Determine whether you need a new Certificate of Occupancy
• Trigger unexpected inspections and requirements
This guide breaks down the differences clearly and technically, using Hudson Brownstone’s experience managing full-gut renovations across landmark districts and DOB-heavy buildings.
Why Permits Matter So Much in Townhouse Renovations
Townhouses are not like apartments or new construction buildings. Personal decisions — moving a bathroom, opening a parlor floor, adding a bedroom, or converting a multi-family — all impact:
• Use
• Occupancy
• Egress• Fire safety
• Structural loading
Because brownstones are 100 to 150 years old, the DOB treats them with heightened scrutiny.
Understanding ALT-1 and ALT-2 is non-negotiable.
What an ALT-2 Permit Is (Most Common for Brownstones)
An ALT-2 is used when the scope of work DOES NOT change:
• Use (residential remains residential)
• Egress (stairs remain in same position)
• Occupancy classification (1-family remains 1-family, 3-family remains 3-family)
Most townhouse renovations fall into this category.
ALT-2 Allows:
• Full non-structural renovations
• Kitchen relocations (in many cases)
• Bathroom upgrades
• Mechanical, electrical, and plumbing work
• Layout changes if they do not change legal occupancy
• Interior reframing that does not impact primary structure
ALT-2 is typically:
• Faster to approve
• Less expensive
• Shorter in inspection requirements
• Compatible with homeowners living in the building (case-by-case)
Curbed-style insight:
Most “renovated brownstones” you see on StreetEasy were done under ALT-2 permits — it’s the backbone of NYC townhouse remodeling.
What an ALT-1 Permit Is (The Heavyweight Permit)
ALT-1 is required when the renovation changes something fundamental about the building.
ALT-1 Is Required If You Are Changing:
1. Use
Examples:
• Converting a 3-family to a 1-family
• Converting a 1-family to a 2-family
• Turning a cellar into living space (complex)
2. Egress
Examples:
• Moving the main staircase
• Changing the configuration of exits
• Opening up floor plates in a way that impacts fire egress
3. Occupancy
Anything requiring a new Certificate of Occupancy (C of O) is automatically ALT-1.
4. Major Structural Reconfiguration
Examples:
• Removing bearing walls across multiple floors
• Adding steel beams that alter load paths
• Rebuilding floor systems
ALT-1 requires:
• Longer DOB review
• Multiple inspection stages
• Sign-offs from additional departments
• More involvement from architects and engineers
• Often, temporary relocation of residents
StreetEasy-style insight:
If the scope “changes the building on paper,” it is ALT-1 — guaranteed.
What About ALT-3? (Almost Never Used in Brownstones)
ALT-3 is for tiny, single-item renovations that do not change layout, structure, egress, or MEP systems.
Examples:
• Installing a handrail
• Replacing a non-structural exterior step
• Minor façade repair
Townhouse projects almost never use ALT-3.
| Criteria | ALT-2 | ALT-1 |
|---|---|---|
| Structural Work | Limited | Allowed; major structural changes |
| C of O Required | No | Yes |
| Converting Multi-Family | No | Yes |
| Stair Modification | Rarely allowed | Yes |
| Timeline | Shorter | Longer |
| Inspections | Standard | Extensive |
| Owner Occupancy During Renovation | Often possible | Rare |
How Hudson Brownstone Diagnoses Permit Type
Our permit review process includes:
• Complete building history research
• LPC status verification
• DOB envelope review
• Structural load path evaluation
• Layout coding implications
• Egress evaluation
• Use/occupancy classification analysis
This allows us to tell clients exactly which permit type applies before architecture begins, saving months of wasted design work.
What Curbed, StreetEasy, and Most Architects Don’t Tell You
1. ALT-2 Doesn’t Mean “Small” — It Means “Non-Structural”
Many clients are shocked to learn that even a full gut renovation can be ALT-2 as long as you’re not changing use, egress, or occupancy.
A complete Parlor–Garden duplex with new bathrooms, new kitchens, new HVAC, new
plumbing — all can be ALT-2.
2. ALT-1 Takes Longer Because It’s a Different Universe of Scrutiny
ALT-1 often requires:
• Fire Department review
• Borough Commissioner review
• Egress analysis
• Structural narratives
• Multiple rounds of objections
Timeframes can range from 4 to 12 months, depending on complexity and borough.
3. ALT-1 Often Requires Tenants to Vacate
If you're converting a multi-family or touching egress paths, DOB may require temporary vacate
orders or alternative accommodations.
4. ALT-1 Nearly Always Needs Post-Approval Amendments (PAAs)
Curbed-style honesty:
Designs frequently evolve during construction. PAAs add cost and time.
5. ALT-2 Still Requires Good Architecture
Homeowners underestimate ALT-2.
Even “straightforward” ALT-2 filings can get DOB objections if:
• Plumbing is relocated without proper diagrams
• Mechanical venting conflicts with code
• Structural assumptions are not documented
• Fire separation is unclear
Hudson Brownstone eliminates these delays with complete pre-file reviews
Expected Costs for ALT-1 vs ALT-2 Filings
(Market-based, extremely useful for buyers and renovation planners)
ALT-2 Filing Costs
• Architect: $15K–$40K
• Engineer: $5K–$15K (if needed)
• Expediter: $3K–$7K
• DOB Filing Fees: $2K–$5K
ALT-1 Filing Costs
• Architect: $35K–$150K+
• Engineer: $15K–$50K
• Expediter: $5K–$12K
• DOB Filing Fees: $5K–$20K
• Possible Temporary CO: additional fees
• Fire Department involvement: added time and cost
Top 5 Mistakes NYC Townhouse Owners Make With DOB Permits
Mistake 1 — Assuming the contractor will “figure out the permit”
Townhouse permits must be architect-led and strategy-driven.
Mistake 2 — Designing a 1-family conversion before confirming if ALT-1 is
viable
This mistake adds months and sometimes tens of thousands in redesign fees.
Mistake 3 — Buying a building without checking the existing C of O
StreetEasy listings frequently misrepresent legal configurations.
Mistake 4 — Filing ALT-2 when ALT-1 was required
DOB inevitably issues objections or stop-work orders.
Mistake 5 — Starting demo before filing
Illegal demo causes:
• Immediate stop-work
• Civil penalties
• Future red flags for refinancing
• Delays that can last months
Hudson Brownstone ensures no stage begins without verified compliance.
FAQS
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If your renovation changes use, occupancy, egress, or requires a new C of O, it is automatically an ALT-1.
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Often no. Egress or structural changes typically require temporary relocation.
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Yes. ALT-2 is typically approved within weeks to a few months. ALT-1 can take 4–12 months
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Not always. If it does not alter legal occupancy or egress, kitchen relocation can be filed under ALT-2.
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Yes. Any change in occupancy classification requires ALT-1 and a new Certificate of Occupancy
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DOB will issue objections or stop-work orders, delaying construction significantly
