Wildlife Management in Brooklyn Heights

What actually gets into a Brooklyn Heights house, and where?

Three animals, and each of them has a favorite detail on this particular kind of building.

Eastern gray squirrels account for most of it. They are diurnal, they gnaw persistently, and they enlarge an existing weak point rather than searching for a bigger one. On a rowhouse their entries are at the cornice, at an uncapped or poorly capped chimney flue, at the junction where a rear extension roof dies into the main wall, under a parapet coping where the mortar has failed, at a roof drain or scupper, and at a gable or bulkhead louvre whose mesh has corroded away.

Raccoons are less frequent and much more consequential when they occur. They use chimneys as den sites — a flue is a vertical shaft with a ledge at the bottom, which is precisely what a raccoon looks for — and they will open a poorly secured roof hatch or bulkhead door. A raccoon in a chimney or a roof void of a four-story house is one ceiling away from a bedroom, and the mess and the damage are proportionate to the animal.

Big brown bats roost in very small high-level gaps: behind cornice fascia, in parapet cavities, under coping, at expansion joints and behind loose flashing. They need almost no room. They are also protected wildlife in New York State, they roost communally, and any exclusion is constrained by law and by the maternity period. With bats the first action is to stop and establish what the law currently permits, not to close the gap.

Occasionally other things appear — birds nesting in vents and behind signage, and animals moving through the block interior at ground level. But the pattern on this housing stock is consistent, and it points at two elements above all others: the cornice and the chimney.

Why is the cornice the defining weakness of these houses?

Because it was designed to hold water at height, on a timber substrate, and it has been doing that job for a hundred and forty years.

The cornice on one of these houses is timber, or pressed metal wrapped over timber framing, carried out from the top of the wall on brackets. Its purpose is explicit in the preservation literature: a cornice exists to prevent rain and melted snow washing down the face of a building. To do that it has to project, which means it has horizontal surfaces by design, it is exposed on every side, and it is the single hardest element on the building to maintain because reaching it requires access equipment.

Over a century and a half it gets repainted, patched, partially replaced, boxed in and occasionally removed and replaced with something simpler. Each of those interventions leaves a joint. Water gets into the joints. The timber behind the metal goes soft in places along its length. And a soft cornice on a building that nobody looks at from above is an opening waiting for an animal to find it.

The same logic runs down the facade. Sills and the tops of lintels were meant to be slightly pitched so water runs off rather than collecting. On a house repaired repeatedly over a century, sills get replaced apartment and lintels get parged, and each of those changes converts a component that shed water into one that holds it. Brownstone compounds it: because veneer was commonly set with the stone’s grain running vertically rather than horizontally, water entering between the bedding layers freezes and forces the stone apart layer by layer, and a spalled front stops shedding water and starts holding it against whatever is behind.

The practical consequence is that wildlife entries on these houses are almost never random. They are at the places water has already been working on, which means the wildlife survey and the masonry and roofing survey are looking at the same list of defects from two directions. Anyone who repairs the hole and leaves the water will be back within a few seasons.

What does the shared roofline do?

It turns one house’s problem into a pathway above six.

A row of attached houses shares a parapet line, and in many cases an abutting or continuous cornice running the length of the block. There are no gaps to cross. An animal that gains the roofline at one address is at roof level above every house in the row, testing each of them in turn at whatever pace suits it.

Three consequences follow, and the first is the one owners find hardest.

Your repair holds and the pressure does not go away. Closing your own cornice, chimney and parapet is entirely worthwhile and it is what keeps animals out of your house. It does not reduce the number of animals on the row.

A neighbor’s unrepaired cornice is a resident population next to your roof. Once a squirrel is inside a cornice two doors along, it is sheltered, dry and thirty feet up, and it is working along the row in its own time.

Coordination outperforms individual effort, exactly as it does with the rear yards at ground level. Where several houses on a row have their cornices and parapets repaired in the same season, the difference is noticeable. Where one does it alone, the house is protected and the row is not.

The approach routes are worth naming because they are cheap to address. Mature street trees on these blocks put limbs within jumping distance of a thirty- or forty-foot roofline; any limb bearing on or overhanging a roof is a bridge, and cutting it back is usually the least expensive single intervention available on the property. The block interior of rear yards is a continuous corridor of mature planting, trellis, sheds and fencing that carries animals the length of a block at low level and up the rear elevations. Scaffolding and sidewalk sheds during facade work are temporary and extremely effective ladders — a house under scaffold is a house with a new route to its roof for the duration.

What is different about a chimney on this stock?

It is a vertical shaft from the roof into the house, and on these houses there are usually several of them.

A rowhouse built in the 1840s or 1850s was heated by fireplaces, which means multiple flues rising through the building in a stack at the party wall, terminating in a chimney above the roofline. Most of those fireplaces have been out of use for generations. The flues are still there.

Four findings recur:

No cap, or a failed cap. An open flue is a shaft with a ledge at the bottom. Squirrels fall in and cannot climb out of a smooth clay liner. Raccoons enter deliberately and use the smoke shelf as a den.

Redundant thimbles. The round openings where a stove or furnace flue once entered a chimney. Where a system was removed, the thimble was commonly stopped with a piece of tin, a sheet of board, or nothing. A thimble opens into the flue, and the flue is open at the roof.

Ash pits and clean-outs at the base of the stack — a small cast-iron door, frequently rusted, sprung or standing open, opening into a chamber connected to the flues above.

Deteriorated masonry at the crown. Freeze-thaw on an unmaintained chimney crown opens joints between the flue liners and the surrounding brickwork, which produces gaps into the chimney’s interior voids rather than into the flue itself.

Capping a flue is straightforward, and it is one of the few genuinely cheap and permanent wildlife measures on this housing stock. Two cautions apply. A flue still serving an appliance must be capped in a way that maintains its function — this is a chimney specialist’s job, not a mesh-and-wire improvisation. And a flue must never be capped while an animal is inside it, which brings us to the sequence.

Who does which half of a rowhouse wildlife job?

Two firms, and on this housing stock the division is obvious the moment you look at what each half actually requires.

Getting a raccoon out of a flue on Willow Street is animal work. It needs the state license described in the questions above, and it needs someone who does that specific thing constantly enough to read an animal correctly. Graduate coordinates that visit with licensed nuisance wildlife partner firms and schedules the job around it. The state adds further permitting on top of the base license — endangered and threatened species need a separate license, migratory birds need a federal permit, and a list of protected mammals and native reptiles needs a DEC depredation permit — which is a second reason the removal belongs with a firm whose whole practice is that paperwork.

Closing the building afterwards is a different trade entirely, and on a Brooklyn Heights rowhouse it is closer to restoration carpentry than to pest control. The opening is usually in a pressed-metal-over-timber cornice at forty feet, or in a parapet coping joint, or in a chimney crown whose liner has parted from the surrounding brick. Closing it means fabricated sheet metal shaped to a molded profile, mortar matched to soft nineteenth-century masonry rather than a hard modern mix, mesh set back inside an opening so it is invisible from Hicks Street, and mechanical fasteners into something sound. That is a specification, not a patch, and it is the half of the job Graduate does.

The reason it matters here more than almost anywhere is the shared roofline. On an attached row, the pressure never stops. Your neighbors’ cornices stay soft, the street trees keep delivering squirrels to the parapet, and the block interior keeps moving animals along the rear elevations. A house that has been cleared but not properly closed is simply the next available cavity on a row that has plenty of candidates. The removal buys a few quiet weeks. The sheet metal and mortar are what change the outcome.

Which is where most of this market stops. The common shape of a wildlife job on a Brooklyn rowhouse is a one-way door, an invoice, and a hole either left open or filled with expanding foam — which a squirrel removes in minutes, and which then reads as finished work on a photograph nobody revisits. Foam has no place in this specification in any role, and neither does silicone doing a barrier’s job. What goes on a landmarked cornice is 26-gauge galvanised sheet metal, cement and mortar, copper or stainless mesh, and Xcluder fill fabric where an opening has to stay serviceable.

Why is the season a constraint rather than a preference?

Because sealing an occupied entry at the wrong time of year traps dependent young inside a masonry structure, and in these houses that void is behind somebody’s plaster.

The plain version: if an adult is using an opening as a den and there are young inside who cannot yet leave, closing that opening kills them. In a frame house that produces an odor problem in a wall and an unpleasant excavation. In a nineteenth-century rowhouse the void may be behind a cornice, inside a parapet cavity, inside a chimney, or above a plaster-on-lath ceiling in an occupied top-floor room — and reaching it means opening building fabric in a historic district, potentially at height, potentially on a visible exterior element.

Gray squirrels here have two litters a year, roughly in late winter and again towards the end of summer, so there are two stretches of the calendar in which an occupied entry cannot simply be shut. Raccoons den in spring. Bats hold a maternity period when the young are present and cannot yet fly, and in this state that window is a legal restriction rather than a matter of good practice.

The sequence is therefore always the same:

Establish what is using the opening — by observation, by evidence at the entry, by the sound pattern and its timing, and where necessary by a camera left facing the entry for a few days. Assumption at this point is exactly what produces the outcome described above.

Establish whether young are present, which is a question about the season and about behavior at the entry, such as repeated returns at intervals through the day.

Get the animals out before closing. This is the licensed half of the job, and it is handled by a nuisance wildlife partner firm rather than by us, against the DEC credential described below. One-way exclusion devices allow an animal to leave and not return, which is the correct mechanism for bats and usually the right one for squirrels. Where young are present and immobile, the options are to wait until they are mobile or to take the family out together, and which applies depends on species, season and access.

Then close, and close to the right standard — one that resists a determined animal rather than a small one. This is Graduate’s part of the work, and it is the part that decides whether the house is finished with the problem. What a mouse would slip past, a squirrel will simply chew away.

Where bats are involved, establish the current restricted window and requirements with NYSDEC before a program is drawn up at all. That is not a formality on this species.

How is an entry found on a rowhouse roofline?

By reading the roof and the cornice as surfaces that record traffic, and by taking the residents’ description of the sound seriously.

Staining and wear. An entry in regular use develops a smooth, discoloured margin from fur oils and repeated contact. On painted timber or pressed metal this is obvious once you know to look. On brownstone or brick it shows as a darker, polished band at the lower edge of the opening.

Fresh gnawing. Because squirrels widen what they find instead of hunting for a bigger hole, a live entry generally carries recent work around its margin. New gnawing on old timber is pale against the weathered surface around it and darkens over weeks, which dates the activity within a reasonable range.

Droppings and debris below. Material accumulates on a parapet ledge, in a gutter, on a rear extension roof or in the areaway beneath a working entry. Nesting material — shredded insulation, leaves, plastic — turns up in the same places.

Sound, timing and weight. This is the most useful input and it comes from residents rather than from the survey. Light, fast, intermittent, after dark, inside a wall: mice, which is a different job entirely and belongs under rodent control in Brooklyn Heights. Heavy, deliberate, in daylight, concentrated shortly after first light and again in the late afternoon, above a top-floor ceiling, sometimes with something rolled or dragged: a gray squirrel. Slow scrabbling and vocalisation after dark in a large void: something heavier again. Rapid rustling or chittering at dusk near a cornice, repeated at dawn: a possible bat roost, and the point at which the work stops and the rules get checked.

A borescope through a small hole in a soffit, a boxed cornice or a top-floor ceiling answers the “what is in there” question without opening the assembly, which in a landmarked house is a considerable advantage.

None of it licenses the shortcut of shutting every candidate opening and seeing what follows. On a house with occupied rooms directly beneath the roof void, that is how a wildlife job becomes an odor problem inside somebody’s ceiling.

What happens at ground level and in the rear yards?

A different set of animals and a different set of decisions, because the block interior is a shared habitat that nobody owns.

Most of this page is about height, because that is where the entries are. The yard line still produces work, and it produces the questions owners find hardest to answer.

The block interior is a ring of rear yards backing onto one another behind attached houses, with mature planting, sheds, decking, raised beds and fencing. To anything that moves at ground level it is one continuous corridor with cover the whole way, and fences that mean nothing. Animals using it are not resident in any one garden; they are resident in the block.

What turns up there is a mixture. Squirrels use it as an approach to rear elevations and extension roofs. Raccoons move through it and will investigate anything that supplies food — waste containers without close-fitting lids, compost, and food left for other animals. Opossums pass through, and generally do no harm to a building. What all of them share is that they are following food and cover rather than trying to get into anything.

The recurring findings are structural rather than exotic. A shed or a deck with an open void beneath it. A raised bed against a rear wall. A compost arrangement with no lid. Waste containers with lids that do not close. A rear extension with a flat roof reachable from a fence line. A yard regraded upward over the decades so that soil now sits against timber that was never meant to be in ground contact.

What actually helps is unglamorous and mostly collective. Close the void under a shed or a deck with a barrier taken below grade. Set planting and raised beds off the wall. Put lids on containers. And accept that a yard dealt with in isolation, on a block where the other twenty-nine are unchanged, produces a limited result — the same arithmetic that governs rats in the block interior, which is set out under rodent control in Brooklyn Heights.

The one thing not to do at ground level is trap and relocate on your own initiative. Wildlife handling in New York is regulated, several of these species have specific protections and seasonal restrictions, and relocation is frequently both unlawful and lethal to the animal. Where an animal at ground level genuinely needs to be dealt with rather than excluded, that is a question of what the current state requirements permit, and the answer comes from NYSDEC.

What does the historic district mean for the repair?

That the concealed work proceeds normally and the visible work needs planning time.

The cornice is a visible exterior element, and Brooklyn Heights is the city’s first historic district, designated in November 1965, made a National Historic Landmark District in January 1965 and added to the National Register in October 1966, running from Atlantic Avenue to Fulton Street and from the East River to Court Street. Work altering the appearance of a building’s exterior can require review.

In practice that produces three working rules.

Like-for-like repair is a different proposition from alteration. Repairing a cornice to match what is there, repointing a parapet, replacing failed flashing and rebuilding a chimney crown are maintenance of existing fabric. Adding something visible and new is not. Where the distinction matters for your specific scope, that is a question for the Commission rather than for a contractor.

Concealed and roof-side work generally proceeds. Sealing the chimney at the flue, closing a thimble, screening a rear-elevation vent, closing an ash-pit door, working behind a parapet — none of that is the streetscape.

Review is a schedule item. If the scope touches the visible exterior, the review period becomes part of the program. A repair that could have been done in October gets done in March, which is after the winter it was meant to prevent and inside a squirrel breeding window. The response is to survey the roofline early, on a cycle, rather than waiting for the sound above the ceiling.

Materials still have to satisfy both requirements. Mesh set back and concealed within an opening rather than applied across it. Copper or stainless rather than anything that will rust and stain down a stone face. Mortar appropriate to soft nineteenth-century masonry rather than a hard modern mix that will damage the brick. And screening rather than sealing wherever an opening serves drainage or ventilation, because a house sealed by someone who does not distinguish between an opening and a defect trades one problem for another. The sealing discipline behind all of it is at structural exclusion in Brooklyn Heights.

What happens after the animal is out, and who has to authorise it?

Three pieces of work, and in a converted house a decision about who is instructing them.

Closure to the right standard. The opening is closed in materials a determined animal cannot work through — sheet metal, heavy-gauge mesh, hardware cloth, mortar — fastened rather than fitted. Cured foam and sealant are not barriers at this scale or any other.

Clearing what was left behind. Nest material, contaminated insulation and accumulated debris are removed. Where a roof void sits directly above an occupied room or beside mechanical equipment, this is not optional tidiness.

Correcting the water. The omitted step, and the reason some houses do this twice. The entry existed because the timber behind it was soft, and the timber was soft because water was collecting — a failed cornice joint, an apartment or reversed sill, a blocked roof drain, an open parapet coping joint, lifted flashing, a spalled brownstone face. Close the hole, leave the water, and the repair rots from behind.

Authorisation. In a single-family house the owner decides. In a converted building the position depends on the documents: roofs, parapets, cornices and chimneys are usually common elements, which means the corporation or the owner rather than the occupant of the top-floor apartment who can hear the animal. A tenant hearing movement overhead can commission nothing that will end it, and the delay between reporting and acting is where these problems grow. The division is set out at landlord and tenant pest responsibilities and, for board-governed buildings, co-op and condo board obligations.

Spring is the useful season for all of this. A winter of freeze-thaw leaves its record on cornices, parapets, copings, sills and brownstone fronts, and the damage is legible in April. Correcting it then removes the condition before the late-summer squirrel window arrives, and it puts any Landmarks review in the part of the year when there is time for it.

For the discipline in general, see wildlife management. For the rest of what these houses produce, see pest control in Brooklyn Heights; the New York City hub sets out how city work is arranged. The animals that follow a roofline breach downward are covered at rodent control in Brooklyn Heights, and the water that opens these details in the first place drives ant control in Brooklyn Heights. Across the river, wildlife management on the Upper East Side is the same work two hundred feet up on apartment houses.

If something is moving above a top-floor ceiling, what helps most is the hour it happens and how heavy it sounds. Tell us that before naming the animal.

Related

• Wildlife Management — how we approach it
• All pest control in Brooklyn Heights
• Rodent Control in Brooklyn Heights
• Cockroach Control in Brooklyn Heights
• Bed Bug Treatment in Brooklyn Heights