Timber House (670 Union Street)

Two Union Street lots, 668 and 670, were assembled into a single 6,668-square-foot parcel; the small structures on them were demolished under 2018 permits. What replaced them is a six-story, 70-foot building with a glue-laminated timber frame around a reinforced-concrete core, clad in long, thin Danish brick from Petersen Tegl — the same maker whose brick appears on a handful of the more carefully specified small buildings in Brooklyn, and a choice consistent with the level of detail throughout.

Fourteen residences occupy the six floors, distributed two on the first, two on the second, three on the third, two on the fourth, three on the fifth and two on the sixth. Rooms are large by the standards of a building this size — the homes run the depth of the structure and carry ceiling heights near eleven feet, with the glulam beams left exposed and LED tape lighting recessed directly into the wood. The architect designed the hexagonal floor tile specifically for the building; kitchen cabinetry and vanities are from Reform. PLUTO records 22,116 square feet on the tax lot, of which 20,586 is residential; the Department of Buildings filing records a total construction floor area of 30,888 square feet, the difference being cellar and garage area outside the PLUTO measure.

Ten parking spaces are deeded condominium units with their own tax lots — P1 through P10 — rather than licenses, and the developer's record describes electric-vehicle charging at every space. A deeded space is a separately conveyable asset that carries its own common charge and tax line; confirm what conveys with any particular apartment.

This is a self-contained fourteen-unit condominium, not a serviced building, and buyers should size their expectations accordingly. There is no attended lobby. The published amenity set is package storage, a bicycle room, the deeded parking with EV charging, and a landscaped, furnished roof deck with views to the Brooklyn and Manhattan skylines. Management arrangements and the current staffing model should be confirmed with the managing agent; a building of this size in Brooklyn is commonly handled by a small local firm or a part-time superintendent arrangement, and this page will not guess which applies here.

The operating profile is where the design work pays back or does not. An all-electric building with a Passive House–level envelope, heat pumps and rooftop solar should carry a materially lower energy line than a comparable gas-heated building of the same vintage — that is the design intent — but intent and performance are not the same thing, and the four completed years of actual operating history are now on file with the condominium. Ask for the operating budget and the actual utility history rather than the projections in the plan. For a building whose principal selling point is performance, that comparison is the most useful piece of diligence available, and it is the one a seller here should want a buyer to run.

Because the condominium is small and the structure is unusual, the reserve position matters more than it would in a hundred-unit building. Read the current reserve balance, the assessment history since 2022, and any board minutes concerning the envelope, the roof array or the timber structure.

Purchaser review: Condominium mechanics — a board right of first refusal rather than cooperative approval. Closings of 30 to 45 days are typical.

Property taxes: No 421-a and no other exemption on any Department of Finance roll, for the condominium or for any of its 24 unit lots. The building is fully taxable, which means no future step-down and no year in which the carrying cost jumps — but also that today's number is the permanent one. When comparing against abated buildings on Fourth Avenue or in Gowanus, run those comparables to full assessment.

Parking: Ten deeded parking units with EV charging per the developer's record. Confirm whether a space conveys, and what its separate taxes and common charges are.

Pets: Permitted, per the developer's published building record. Confirm any weight, number or breed conditions in the current house rules with the managing agent.

Subletting, pied-à-terre and flip tax: Governed by the offering plan and the current house rules, neither of which is settled in the plan record on file at the time of writing. As a New York condominium, pied-à-terre ownership and leasing are permitted in principle, subject to the Board's right of first refusal and to any minimum-lease-term rule. Confirm each before making an offer that depends on it.

Recent sales

Recent closings at this building, curated by The Roebling Team research desk. Prices are the transfer amounts recorded with the NYC Department of Finance; apartment-level detail is checked against the building’s own file in The Roebling Research Library before publishing.

Market read. Most recent trades (2026) cleared a median $1,852/sf across 2 sales. Median listing discount -1.8% over ask.

Sales sourced from NYC Department of Finance recorded transfers (BBL 3-00955-7507) and verified listing data. Apartment-level facts (line, condition, asking-price context) curated and cross-verified by The Roebling Team research desk. Not all transactions cross-verify with ACRIS records — sponsor and LLC purchases sometimes record at stipulated values rather than market price; square footage from recorded condo declarations and offering plans.

Confirm your lender and your insurer are comfortable with mass timber, in week one. Most are. But the construction type is unusual enough in New York residential lending that it is worth clearing before you are in contract rather than after.

PLUTO has no year built for this property — do not let a data feed date it for you. The primary record is unambiguous: permitted 2020, first temporary certificate of occupancy 17 October 2022, first closings November 2022, final certificate of occupancy 14 February 2023.

Ask for the actual energy history, not the projections. This building's central claim is performance. Four years of operating data now exist. If they support the claim, that is the strongest argument for the price; if they do not, you should know before you bid.

There is no abatement, so today's tax line is permanent. That removes step-down risk entirely, and it means abated comparables nearby must be run to full assessment before they mean anything.

Understand what a fourteen-unit building is. No attended lobby, a small reserve base, and a handful of owners funding any capital event. Read the reserve position and the assessment history since 2022.

Ask about sound between floors. Acoustic performance in a timber structure is a function of the specific floor assembly. Read the specification and ask residents.

Lead with what cannot be replicated. A mass-timber condominium with exposed glulam structure, eleven-foot ceilings, an all-electric plant and rooftop solar is a category of one in this market. That belongs at the top of the marketing, stated plainly and sourced.

Bring the numbers to the design story. Utility history, the solar array's output, and the actual common-charge history convert an architectural argument into an underwriting one. Sellers who present them do measurably better than sellers who describe the wood.

Frame the tax position as certainty. No abatement means no cliff. Buyers arriving from a 421-a building are budgeting for a future step-down; here there isn't one.

Answer the mass-timber questions before they become objections. Fire rating through charring, code-permitted exposure, lender and insurer treatment. Having the answers ready, with the record behind them, keeps a curious buyer from becoming a nervous one.

Your comparables are the design tier and the block, in that order. Anchor to Brooklyn's small architect-led condominiums first, and to Fourth Avenue and Gowanus-edge new development second, adjusted for abatement and service level.

If you're considering Timber House, also evaluate:

• 345 Carroll Street — the closest peer in ambition and scale: a boutique Carroll Gardens–edge condominium with deeded parking and storage
• 205 12th Street — the smallest comparable new-construction condominium in the immediate market; the six-unit alternative
• 243 4th Avenue (Parlour) — a nineteen-unit Fourth Avenue condominium of similar vintage and boutique scale
• 229 9th Street (Luna) — Gowanus-edge new construction with a deeded garage; the mid-size alternative
• 251 7th Street (The Argyle) — Park Slope condominium with a resident manager and full garage; the more serviced comparison
• 445 5th Avenue (The Slope on Fifth) — the newest Fifth Avenue condominium inventory in the neighbourhood
• 575 Fourth Avenue — the larger, amenitised Fourth Avenue product a buyer will cross-shop on price