Ant Control in Brooklyn Heights

Why is an ant problem in these houses usually a water problem?

Because the buildings are masonry, the masonry is a hundred and sixty years old, and every one of the failures it develops ends with water held against something that would rather be dry.

The Landmarks Preservation Commission’s rowhouse manual states the general case without hedging: water is the eventual cause of most masonry deterioration. In this neighborhood that general case has a very specific form, because the dominant facing material was brownstone — a reddish-brown Jersey freestone quarried in Passaic County — and brownstone fails in a characteristic way.

Brownstone is sedimentary. Its bedding layers run in a direction called the grain. When it was used as a veneer, it was quicker and simpler to set it with the grain running vertically rather than horizontally. That single labor-saving decision is the reason these fronts fail: water finds its way between the layers, freezes, expands, and forces the stone apart layer by layer. Spalling exposes fresh surface to the next freeze, and it accelerates. A front that has begun to spall no longer sheds water. It holds it.

The horizontal details go next. Sills and the tops of lintels were meant to be slightly pitched so that water runs off rather than collecting on them. A cornice exists specifically to stop rain and melted snow washing down the face of a building. On a house repaired repeatedly over a century and a half, sills get replaced apartment, lintels get parged over, and cornices get patched, boxed in or removed altogether. Each of those changes turns a component that shed water into one that delivers it into the wall.

What that produces behind the facade is a wall cavity with a persistent moisture source and softened timber wherever timber is embedded in or behind the masonry: window framing, blocking and nailers, and the joist ends bearing into the wall. That is the material carpenter ants excavate. They do not create the condition — they report it, and they are frequently the first thing that tells an owner the wall has been wet for years.

So the sentence worth remembering in this neighborhood is that an ant problem on an exterior wall is a roofing and stonework problem wearing a disguise.

Which ants turn up on these houses, and what is each one reporting?

Three, and each points at a different condition and a different budget.

Pavement ants are the most commonly reported. They nest in and under paving — the joints between flags in an areaway, the sand or rubble bed beneath them, cracks in a garden path, and the edge where paving meets a wall. Indoors they appear as a trail along a baseboard or a threshold heading for something sweet or greasy. A pavement ant finding is a paving and drainage finding: somewhere within a short distance there is a damp bed of sand or soil under a hard surface, and the colony is in it.

Odorous house ants are the moisture indicator indoors. They nest in wall voids, beneath insulation, around plumbing and in any sheltered space that holds damp, and they shift between outdoor and indoor sites without difficulty. A persistent trail inside the house with no obvious food target is a strong signal that something is wet inside a wall. They also form multiple sub-colonies with several queens, so a treatment that eliminates one nest and not the others leaves the problem where it was.

Carpenter ants are the structural indicator. They excavate galleries in wood that has already been softened by water, and the galleries are smooth and clean rather than packed with debris. On a masonry rowhouse they are typically behind a front wall, in joist ends bearing into a wet party or exterior wall, in a rear extension where old and new construction meet, or in the timber of a cornice. They are invisible from the street and from the room, and the only external sign is often a small accumulation of coarse excavated material — a mixture of wood shavings and other debris — on a sill or a floor below the gallery. Large dark ants in numbers indoors in spring, particularly at night, are worth taking seriously.

One species to rule out rather than assume. Pharaoh ants are very small and yellowish-brown, nest deep in warm wall voids and around plumbing, forage day and night, and respond to repellent or contact material by budding into multiple satellite colonies. They are more a large-building problem than a rowhouse one, but converted buildings here do produce them, and misidentifying them is the one error that reliably makes an ant problem structurally worse.

Where does the areaway and the yard fit in?

They supply the nest bed for everything that nests outdoors, and both are usually wetter than they were designed to be.

The areaway is the sunken space at the base of a rowhouse, behind and below the stoop line, holding the cellar door, the meters, sometimes a hose bib, and a quantity of leaf litter that nobody has a job title for. It is paved, generally on a sand or rubble bed laid a long time ago, and its drain is very often partially blocked. That combination — warm in summer, protected from disturbance, permanently damp, with paving joints opening over time — is close to ideal pavement ant habitat, and it sits directly against the cellar wall and a few feet from the cellar door.

The rear yard does the same job with more variety. Paths and terraces on sand beds. Planting against the rear wall. Raised beds built up over the years so that soil now sits against timber that was never meant to be in ground contact. A downspout discharging at the base of a wall instead of into the drainage. And, on many of these lots, a yard that has been regraded upward over a century until it falls toward the house rather than away from it.

The block interior matters here in the same way it does for rats, though less dramatically. Thirty gardens backing onto one another form a continuous strip of soil, planting and paving, and colonies move through it without regard to fence lines.

The interventions at this level are cheap and physical. Clear and repair the areaway drain so the bed under the paving can dry. Repoint or repair open paving joints. Set planting and raised beds back from the wall. Take the downspout into the drainage. Correct the grading where a rear yard now falls toward the house. None of that is pest control as most people picture it, and all of it removes the condition rather than the organisms.

There is one further outdoor source worth naming because it is invisible until you look for it: honeydew. Aphids and scale insects on garden plantings, on climbers against a rear wall and on street trees produce a sugar secretion that several ant species farm and defend. A yard with an aphid problem has an ant problem attached to it, and treating the ants while the aphids continue is a recurring expense with no end.

Why does spraying the trail make things worse?

Because the visible ants are the least important part of the colony, and destroying the trail destroys the only map you had.

A foraging trail is a thin slice of a colony out searching for food and water. The queen, the brood and most of the workers are in the nest, somewhere you cannot see. Contact material applied along a trail kills the foragers on it and reaches nothing else. Within days the colony sends more.

Three further effects make it actively counterproductive:

It erases the evidence. A live trail is a line pointing at the nest. Followed patiently — along a baseboard, up a wall, behind a cabinet, into a gap at a pipe, into a crack in plaster — it leads to where the work needs to happen. Wipe it out and the next trail may take a different route.

It causes budding in some species. Pharaoh ants, and odorous house ants to a lesser extent, answer chemical pressure by dividing the colony and moving parts of it elsewhere. One nest becomes several, distributed further through a building — and in an attached house, potentially through a party wall.

It leaves every condition untouched. The blocked areaway drain, the spalled stone, the flat sill, the leak under the sink, the aphids on the climber. None of them is affected by anything applied to a baseboard.

What works instead is slower and duller. Identify the species. Follow the trail to the source. Use material the foragers will carry back to the colony rather than material that kills them where they stand, placed where they are already traveling. Correct the moisture and close the entry. And in a converted or attached building, check whether the same trail exists in the apartments or houses adjoining, because a colony inside a shared wall serves more than one household.

How do you trace a colony behind a masonry front?

By working from the water rather than from the ants, and by using the building’s own history.

Start with what is wet. Ants need water more urgently than food. A trail heading toward a bathroom, a dishwasher, the base of a pipe run or into a wall and not toward any food is a water trail, and the nest will be near the water. That reframes the question from “where are the ants” to “what is wetting this wall”, which has a much shorter list of answers.

Read the facade from the top down. Roof and parapet, then cornice, then the wall above the affected room, then the window head and sill directly above or beside it. Water travels down and sideways inside masonry, so the defect is usually higher than the symptom. A blocked roof drain, an open coping joint, a lifted flashing, a failed cornice return, an open mortar joint or a spalled stone face are the recurring findings.

Look at the rear and the extension junctions. Where a rear extension was built against the original wall — and most of these houses have at least one — the junction between old and new construction is a seam. Different materials, different movement, and a flashing detail somebody made up on the day.

Sound the timber where you can reach it. Tapping along an exposed joist or a window frame gives a hollow response over a gallery. On a cornice or a sill, softness under a probe is more useful than appearance, because a repainted rotten sill looks fine.

Use the history. Recent plumbing work, a roof repair, a leak that was fixed six months ago and left the wall wet, a party wall opened during a neighbor’s renovation, a yard relaid — each is a plausible origin, and the timing usually matches the first sighting more closely than anyone expects.

Check the vertical and lateral neighbors. In a converted house a trail on a kitchen wall is worth checking against the same wall one floor up and one down. In an attached house it is worth asking whether the neighbor has seen anything.

What does the party wall do to an ant problem?

It gives a colony a shared address, which is a smaller problem than it is for mice but not a negligible one.

The joist pockets — the recesses where floor framing of both adjoining buildings bears into the shared masonry — were rarely closed on nineteenth-century construction, and every later penetration through the wall connects them further. For ants that matters in two specific circumstances.

Where the party wall is wet. A leak, a failed flashing at the junction with a neighbor’s extension, or a shared chimney stack with a deteriorated crown can wet the joist ends bearing into the shared wall from both sides. Carpenter ants nesting in that timber are nesting in a structure that belongs to two houses, and treatment on one side addresses half of it.

Where a colony is using the void as a route. A nest in one building foraging into the next through the shared wall produces exactly the pattern people find inexplicable: a trail appearing on an interior party wall with no outdoor route, no food source in the room, and no result from treatment.

The practical response is the same as for every other party-wall problem in this neighborhood. Close what is accessible from your side, during renovation or wherever a ceiling or wall is already open, in material that cannot be worked through. Fix the water on your side and encourage the neighbor to look at theirs. And where the source is genuinely shared — a chimney stack, an extension junction, a valley between two roofs — the repair is a conversation between two owners rather than a job for one. The sealing discipline is set out at structural exclusion in Brooklyn Heights.

What changes when the house holds several households?

The responsibility moves, the routes multiply, and a statutory layer arrives.

A building arranged for occupancy by three or more independent households is generally a multiple dwelling, and roughly 80.4 per cent of the real estate in this neighborhood is classified as apartment buildings — largely because so many of these houses were long ago cut into flats.

Physically, a conversion adds the improvised plumbing chase to everything already described. Kitchens and bathrooms were stacked onto a single new line cut through original framing and masonry, and that line is warm, damp and open into cabinetry and wall voids at every level. Odorous house ants and pharaoh ants both exploit it, and a trail in one apartment is frequently a symptom of a nest serving several.

Legally, the Housing Maintenance Code places the duty to keep the dwelling free from insects and other pests on the owner and requires extermination where infestation is present — see the NYC Housing Maintenance Code and pests. Local Law 55 adds periodic investigation of units and common areas plus remediation by integrated pest management, including eliminating the water sources pests depend on, and states explicitly that pesticide use does not substitute for those physical measures. For ants specifically, the water clause is the operative one, and a building that treats repeatedly around an uncorrected leak is not meeting it in substance. Where material is applied in a multiple dwelling, notification rules apply — Local Law 36 and the New York neighbor notification law — and the applicator side is at New York State pesticide applicator requirements. Owners letting apartments should read landlord and tenant pest responsibilities; board-governed buildings, co-op and condo board obligations.

Businesses along Montague Street, Henry Street and Atlantic Avenue add a further layer: a food premises at ground level supplies a food source that will sustain colonies in the paving and wall voids around it, and the residential floors above share the walls and often the refuse arrangement. That work runs through the commercial program and restaurant pest control.

What does a proportionate scope look like on a house like this?

A short sequence with an end to it, most of which is not chemical at all.

Identify the species from the insects rather than from a description. It takes five minutes and it determines everything downstream — whether the answer is a paving bed, a wall void or a wet joist end, and whether the material used is safe to use at all.

Find the source by following the trail, not by assuming. Where it disappears into the fabric, the next question is what is behind that point and where the void goes.

Find the water, which is the correction that ends the recurrence rather than deferring it. The areaway drain, the roof drain, the coping joint, the cornice, the sill, the spalled stone, the downspout, the yard grading, the leak under the sink. These go to a plumber, a roofer or a mason, and a pest scope on a house like this should say so plainly instead of absorbing them into an indefinite service. Where the front is involved, the repair may need Landmarks review, which is a schedule item to plan around — one more reason to survey in spring rather than in autumn.

Assess the timber where carpenter ants are involved. Wet structural timber is a building issue in its own right, and knowing how far the softening extends is a question for whoever will repair it.

Use material in the smallest quantity that will do the job, placed where the ants already travel and chosen so foragers carry it back to the colony, applied by an appropriately certified applicator.

Close the entries. Threshold and frame junctions, the gap at a pipe penetration, an open mortar joint, a crack in plaster at a party wall. Small, permanent work, and the same discipline as structural exclusion in Brooklyn Heights.

Come back once to confirm the trail has not reappeared on a different route, which for a disturbed colony is a real possibility.

That is a job with a defined finish. A proposal for ants in a rowhouse consisting of recurring visits with no identification, no source finding and no repair attached is describing a subscription — the questions worth asking before comparing it against anything else are at choosing a pest control contractor.

When does this happen, and what should be done in which season?

Spring through early autumn outdoors, year-round indoors — and the difference tells you where the nest is.

Spring is when it starts and it is the most important season on this housing stock for two separate reasons. Colonies become active as the ground and the paving beds warm, so the first pavement ant trails appear at areaway doors and thresholds. And a winter of freeze-thaw cycling has just finished writing its record on the facades: spalled brownstone, open mortar joints, a cornice that has moved, a coping joint that has opened, a sill that has cracked. That damage is visible in April and it is cheaper to correct then than to live with through another winter. Correcting it removes the water that will otherwise drive the summer’s interior activity. Winged carpenter ants emerging indoors in spring are the strongest single signal available that there is a mature colony inside the structure rather than outside it, and that report deserves a survey rather than a spray.

Summer is peak foraging. Heavy rain drives nests to relocate, which is why a settled house can report a sudden trail the day after a storm. It is the practical season for the outdoor work: regrading a rear yard that falls toward the house, clearing and repairing areaway drains, taking a downspout into the drainage, dealing with honeydew-producing insects on the plantings.

Early autumn sees outdoor activity tail off while indoor sightings can rise, as colonies near a heated structure exploit it.

Winter. Outdoor-nesting species are inactive. An active, well-established trail inside a heated house in January therefore means something specific: the nest is inside the building, the building is keeping it warm, and there is very likely a water source in a wall or a chase. That is the report worth taking most seriously and the one most likely to be dismissed as a few stray ants.

For the general method, see ant control. For everything this housing stock generates across the other services, pest control in Brooklyn Heights draws it together, and the New York City hub explains how the city work is arranged. The water that drives this also drives the cornice failures under wildlife management in Brooklyn Heights, and the damp cellar it produces supports cockroach control in Brooklyn Heights. Across the river, ant control on the Upper East Side deals with the same species in terraces and riser chases instead; on Long Island, ant control in Huntington is the frame-house version where sill plates and band joists do what brownstone does here.

If there is a live trail, photograph the ants and leave the trail intact. Tell us where it goes and what has recently been wet.

Related

• Ant Control — 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