Asbestos in joint sealant and window putty

Joint sealants and putties can contain asbestos if they were applied before asbestos was banned (2005 at the latest across the EU, and earlier in many countries). Typical places are the joints between precast concrete panels, the joints between window or door frames and the wall, the putty around window panes, and old joints at penetrations and in wet rooms. The sealant may be soft and elastic or hardened and brittle, and neither tells you anything about asbestos. Only a laboratory analysis gives you certainty, and a sample is worthwhile before you renovate windows, replace windows or renew joints.

In this article we go through which joint sealants and putties are found in older buildings, which steps of a window renovation damage them, how to take a sample of elastic sealant and brittle putty, and what the result means.

Which joint sealants are found in older buildings?

Panel joints

In buildings made of precast concrete panels, the joints between the panels are filled with elastic sealant. Older panel joints used, among other things, polysulphide sealants, which can contain asbestos and PCBs. During facade renovations the joints were renewed, so the same building may have sealants of different ages, and remnants of the old sealant may lie under a new one.

Joints around windows and doors

The gap between the frame and the wall is sealed with sealant on the inside and outside, and there is often more sealant at the junctions of window sills and trims. These joints are always destroyed when a window or door is replaced.

Window putty

In old wooden windows, the glass is fixed in the sash with putty. Over the years the putty hardens, cracks and comes away in pieces. Traditional linseed oil putty was made from chalk and linseed oil, but many putties and sealants, especially in the 1960s and 1970s, contained asbestos, so old putty cannot be classed as asbestos-free based on its appearance. Because windows were renovated and re-puttied at different times, the windows in the same building may have different putty. The putty in outer and inner sashes may also be different products.

Joints at penetrations and in wet rooms

Sealing compounds at pipe penetrations, fire stopping and old corner and connection joints in wet rooms are also joint sealants. Fire stopping is described in the article Asbestos in fire protection, and bathroom materials in the article Asbestos in the bathroom.

Asbestos and other hazardous substances in old joints

In addition to asbestos, old panel and window joints may contain other hazardous substances such as PCBs and lead. An asbestos analysis only detects asbestos; if the joints are to be removed on a larger scale, the other substances must be tested separately.

Window renovation: which steps damage putty and joints?

Intact putty or an intact joint does not release fibres into the air. In a window renovation, however, they are almost always damaged, and different steps affect different materials.

• Removing old putty. The putty is scraped off or first softened with a heat gun or an infrared device. The heat makes it easier to remove, but the loosened putty is still the same material, so it is tested before the work.
• Sanding sashes and frames. Repainting also involves sanding off old paint, and what that contains is a separate question.
• Window replacement. When the frame is removed, the joint between frame and wall is destroyed, often along with the plaster or mortar around the frame.
• Replacing window sills and trims. The sealant underneath and at the junctions comes off with them.

In a window renovation it is therefore worth taking separate samples of the putty, the frame joint and, if needed, the paint. Then you know which step must be carried out as asbestos work and which need not.

How to take a sample of joint sealant or putty

Take a sample of every sealant that differs from the others: for example one of the putty, one of the outer frame joint and one of a panel joint. If the windows were renovated at different times or different facades have different sealants, take separate samples of these.

1. Wear disposable gloves and a respirator of at least class FFP3.
2. Choose a spot you can reach safely, for example the corner of a ground-floor window or a panel joint at ground level. Do not climb a ladder just for the sample.
3. Do not heat the sealant before taking the sample. Lightly moisten the sampling spot with a spray bottle, especially if the putty is dry and crumbly.
4. Use a sharp knife to cut a piece of about 2–5 centimetres from the elastic sealant, through the full depth of the joint. If you see older sealant under the new one, include that as well.
5. Use a putty knife or narrow chisel to prise out a piece of the hard putty, holding an open resealable plastic bag underneath so that the crumbs fall straight into the bag. Take only a small piece so that the glass stays firmly in place.
6. Seal the bag, place it in a second bag and write the location and material on it, for example "Living room window, outer sash, glazing putty" or "South facade, panel joint".
7. Cover the sampling spot with tape and wipe the surface with a damp cloth.

Protective equipment is described in more detail in the article How to protect yourself when taking an asbestos sample, and sending the sample in the article Sending an asbestos sample by post.

What does the result mean for the joint sealant?

Semlab analyses the sample with a JEOL SEM-EDS electron microscope in accordance with ISO 22262-1, and you receive the result by email, usually on the same day the sample arrives at the laboratory. The result shows whether asbestos was detected in the sample you sent.

• No asbestos detected: the result applies to the sealant the sample came from and to identical material. Windows that were puttied at other times and renewed joints are tested separately.
• Asbestos detected: the sealant is treated as containing asbestos. Removing putty, renewing joints and replacing windows are planned as asbestos work insofar as they damage that particular sealant, and the demolition is carried out by a specialist asbestos removal contractor.

If the joints or windows are part of a larger facade or window renovation that requires an on-site asbestos survey, that is done by a surveyor. Semlab is a laboratory and does not carry out on-site surveys.

How much does analysing joint sealant cost?

The analysis costs €49.99 incl. VAT per sample. The price is the same for 1–100 samples. Postage is not included. You can order the analysis online, pay by card and send the sample as a letter or small parcel with your national postal service to the laboratory in Finland.