Old Glazing Putty, Caulk and Sealants

Why this matters

Glazing putty and old caulk are the materials nobody thinks of as materials. They are a thin bead, they look like hardened clay or rubber, and the obvious way to get them out is to scrape them, cut them or soften them with heat. Some older putties and caulks contain asbestos, and caulk in some mid-century commercial and public buildings has been found to contain PCBs (polychlorinated biphenyls). Scraping and heat are exactly the two acts that release either one. A window tech, a painter or a handyman who reglazes a sash or recaulks an old joint has disturbed a suspect material without ever deciding to.

This card is built around one gate: what era and what kind of building the sealant came from. Run that gate first and it tells you which hazard you are presuming, which test settles it, and who you call.

What you are looking at

• Glazing putty (glazing compound) is the bead that holds a pane of glass into a wood or steel sash, on the outside face. Traditional putty was linseed oil and chalk; through much of the twentieth century some compounds had asbestos fiber added as a filler and binder. It is usually painted over, so it carries the sash's paint as well. Old putty cracks, shrinks back from the glass and falls out in hard chunks.
• Caulk is the flexible bead at a joint between two materials: window or door frame to masonry or siding, around expansion joints, at curtain-wall panels. Older caulks were oil-based or, from roughly the 1950s on, polysulfide rubber. Some contained asbestos; some polysulfide caulks in that era had PCBs added as plasticizers.
• Other sealants in the same family: window and door frame bedding compounds, roofing mastics and cements, duct sealants, the tar-like seal around old skylight curbs. The suspect logic is the same; this card's examples stick to glazing and caulk.

None of these can be identified by eye. "Appears to be original glazing compound" is a sound record; "asbestos putty" is a diagnosis nobody on site can make.

The gate: era and building type

Asbestos is a broad presumption. EPA and OSHA both list glazing compounds, caulks and putties among materials that may contain asbestos, and the use ran through roughly the 1980s. In a house or building of that age with original windows, presume the putty and caulk are suspect until a lab says otherwise. Asbestos content in these products is usually low, and they are typically nonfriable while intact, which is why they look harmless. They stop being harmless when they are ground, sanded, cut with a power tool or crumbled after decades of weathering.

PCBs are a narrow presumption, and the narrowness matters. EPA's guidance on PCBs in building materials describes PCB-containing caulk in buildings constructed or renovated between about 1950 and 1979, and the buildings it has focused on are schools and other public and commercial buildings, often masonry, where polysulfide caulk was used at window frames and expansion joints. That is where the evidence is. A single-family house of that era is not the population the testing found, so do not tell a homeowner their 1962 window caulk has PCBs; do treat caulk on a 1950-1979 school, office, apartment block or public building as a PCB suspect until tested, and say so to the building owner.

Under federal law (TSCA, 40 CFR Part 761), PCBs at 50 parts per million or more in caulk are not an authorized use, and removed caulk at that level is regulated waste with its own disposal path. That is the building owner's obligation to manage, usually with an environmental consultant, and it reaches you because you cannot dispose of that debris in a dumpster.

Why scraping and heat are the hazards

Intact putty in a sash releases nothing. The release comes from what the job does to it:

• Scraping and chiseling dry putty breaks it into chips and dust at face height, outside, often in wind. Asbestos fiber becomes airborne, and if the sash is pre-1978 the paint layer goes with it as lead dust. See related: Lead Paint - Where It Hides in an Older House.
• Power tools (an oscillating multi-tool, a grinder, a router to clear a rabbet) make it far worse: fine, breathable dust in volume.
• Heat from a heat gun or an infrared softener is the common reglazing method because it lifts putty cleanly. Heat on putty under lead paint fumes the lead, and heat on PCB-containing caulk can volatilize PCBs. A heat gun at 1100 F or higher is a prohibited practice under EPA's RRP rule (40 CFR Part 745, Subpart E) on pre-1978 painted surfaces in any case.
• Weathered crumble. Putty that has already disintegrated in the sash rabbet is the friable state. Brushing it out is a disturbance.

For your employees, disturbing suspect caulk or putty during construction work falls under OSHA's asbestos construction standard, 29 CFR 1926.1101, whatever the quantity. Removing a small amount of nonfriable material during repair is generally Class III or Class II work there, with wet methods, no dry sweeping, and a respirator under a written 29 CFR 1910.134 program where the exposure assessment requires one. A crew without that training and program does not remove suspect material; it stops and routes. Federal NESHAP asbestos rules (40 CFR Part 61, Subpart M) apply to renovation of facilities, and residential buildings of four or fewer units are generally outside them, but many states and localities regulate asbestos work in houses too. Read your state's.

Presume, then test, before you disturb

The default for any trade that meets old putty or caulk on a job: if the work requires removing or cutting it and nobody has a lab result, the material is presumed to contain what the gate above says, and the removal waits for either a result or a crew trained to handle it as presumed. Work that does not disturb it goes ahead. Painting over intact putty, cleaning glass, replacing a sash cord through the pocket without touching the glazing: none of those break the bead.

Sampling belongs to someone trained to do it, and in several states a licensed inspector is required to take an asbestos sample in a building being renovated. See related: How to Get a Suspect Material Tested Without Becoming the Sampler.

Worked example: one gate, two outcomes

Case A. A cracked pane in a 1931 house. A window tech is booked to replace one cracked lower-sash pane, 24 by 28 inches, in an original wood double-hung. The putty is gray, hard, cracked and painted.

The gate: house, original 1931 sash. Presume asbestos in the putty and lead in the paint over it. PCBs are not the presumption here; a 1931 house is outside both the era and the building type EPA found them in.

The disturbance: replacing a pane means removing every inch of putty around it. The perimeter is 2 times 24 plus 2 times 28, which is 104 inches, a little under 9 feet of bead. That is a small quantity, and it is still a removal.

The calls: there is no lab result, and the customer wants it done this week. The tech has three honest choices. Board or tape the crack and leave the glazing intact until a sample comes back (a bulk PLM result commonly comes back within a few business days, faster on rush). Hand the job to a crew trained and equipped to remove presumed asbestos putty under 1926.1101 with wet methods and lead-safe practice. Or, if the shop is set up for it, do that work itself as presumed material. What he does not do is soften it with a heat gun and scrape it into the flowerbed. The sash paint makes this RRP work too if more than 20 square feet of exterior painted surface is disturbed; at 9 feet of an inch-wide bead it is far below that, but the prohibited practices, including the high-temperature heat gun, apply at any size.

Case B. Recaulking windows on a 1968 office building. The same shop is asked to cut out and replace the perimeter caulk on 40 aluminum windows in a two-story masonry office built in 1968. Each window is 4 by 5 feet.

The gate: commercial masonry building, built inside 1950 to 1979, original caulk at window frames. Presume asbestos and PCBs. This is precisely the building EPA's guidance describes.

The quantity: each window's perimeter is 2 times 4 plus 2 times 5, which is 18 feet, so 40 windows is 720 feet of caulk. Cutting 720 feet of PCB-suspect caulk would produce regulated debris in volume and contaminate the masonry it touches, which EPA's guidance notes can absorb PCBs from the caulk.

The call: this is not a quote the shop can price yet. The building owner needs to have the caulk sampled for both asbestos and PCBs by an environmental consultant before any removal, and if PCBs are at or above 50 ppm, removal and disposal run under the owner's TSCA plan, usually by a specialty contractor. The shop's quote waits on the results, and its letter to the owner says why.

Same gate, opposite answers. Both jobs were "replace old window sealant." Era and building type sent one to a short asbestos-and-lead hold and the other to a full environmental assessment before anyone could price it. A shop that ran Case B the way it runs Case A would have spread PCB debris across a parking lot; one that ran Case A like Case B would have told a homeowner to hire an environmental consultant for one pane.

What changes the answer

• A lab result. "None detected" for asbestos and below the regulatory level for PCBs makes the material ordinary debris for those two hazards. The lead paint on the sash is a separate question with its own test.
• Evidence the sealant is not original. A building reglazed or recaulked after the mid-1980s with modern sealant moves out of the presumption, but "it looks newish" is not evidence. A dated work order, a product you can identify as silicone or a known renovation year is.
• The state. Some states require asbestos surveys before renovation of houses as well as larger buildings, or license anyone who removes any amount. That can turn Case A's "do it ourselves as presumed" into a licensed-contractor job. This card is not legal advice; your state asbestos program and your own attorney answer that question.

References

• See related: Recognize, Record, Route - the Rule for Legacy Materials; Asbestos + Lead Paint Safety Reference; Job Site Asbestos Discovery Stop Work Protocol; PCB Capacitors and Ballasts in Older Equipment
• OSHA, Asbestos in Construction, 29 CFR 1926.1101; Respiratory Protection, 29 CFR 1910.134
• EPA, guidance on PCBs in building materials and caulk; TSCA PCB regulations, 40 CFR Part 761
• EPA, Asbestos NESHAP, 40 CFR Part 61, Subpart M; Lead RRP Program, 40 CFR Part 745, Subpart E