Asbestos in mortar: render, masonry mortar and grout

Mortar can contain asbestos if it was applied or laid before 1994. Possible places are render, indoor masonry mortar, fire-resistant mortar in fireplaces, and the bedding and grout mortars of tiled surfaces. Hard grey mortar looks the same with or without asbestos, so the only way to be sure is a laboratory analysis. The sample should be taken before the mortar is chiselled, sawn, drilled extensively or repointed.

This article explains how mortar differs from filler and concrete, which mortars may contain asbestos, when mortar is worth testing, and how to take a sample of hard or crumbly mortar.

What is the difference between mortar, filler and concrete?

The three are easily confused because they are all hardened mineral materials. The difference affects where you take the sample and how you label it.

• Mortar is a mix of binder, sand and water. It is used in masonry between bricks and blocks, as render on wall surfaces, and for bedding and grouting tiles. The layer is typically from a few millimetres to a few centimetres thick.
• Filler is a finer material applied in thin coats to finish a surface before painting or wallpapering. Fillers are covered on the page asbestos in filler.
• Concrete also contains coarse aggregate and is used for load-bearing structures, slabs and precast elements. Asbestos in concrete is covered in the article asbestos in concrete.

Which mortars can contain asbestos?

Render

Render is found on interior and exterior walls, plinths, basements and stairwells. Traditional render is applied in several coats, a scratch coat, a floating coat and a finishing coat, and the surface often has paint or later repairs on top. Asbestos was sometimes added on site to the gypsum mortar used for interior plastering, and it could be added to facade render to improve adhesion. Rendered surfaces were also treated with coatings that contained asbestos. Each coat can be a different product from a different period, so a render sample is taken through every coat down to the masonry. Paint on render is covered in the article asbestos in paint.

Masonry mortar

The joints of brick and block walls are filled with masonry mortar. Asbestos was sometimes added on site to the lime or gypsum mortar used for indoor masonry. Fire-resistant mortars often contained asbestos at least in the 1950s, so pay particular attention to the masonry mortar of fireplaces and bread ovens. These are covered in more detail in the article asbestos in fireplaces.

Tile bedding mortar and grout

Under the tiles there is bedding mortar or adhesive, and between them grout. In Finland, asbestos was commonly used in indoor tile bedding mortars and grouts in the 1960s and 1970s. Grout is the only visible mortar layer in a tiled surface, and it always breaks when the joints are redone or the tiles removed. The layer under the tile is covered on the page asbestos in tile adhesive.

Repair and patching mortars

Mortars and compounds used around pipe penetrations, to patch holes and to level floors are often a different product from the rest of the structure. Especially in the 1960s and 1970s, many sealing and patching compounds, such as putties for penetrations and caulking compounds, contained asbestos. They may have been added later, but in an old building a patch can also date from before 1994. Materials in pipe renovations are covered in the article asbestos in pipe renovation.

When should mortar be tested?

Intact mortar in a wall does not release fibres into the air. You need the information before work that breaks the mortar and releases dust:

• chiselling off or removing render during facade and basement renovations,
• demolishing a brick wall, fireplace or chimney,
• repointing masonry, where old mortar is raked or ground out,
• regrouting tiles or removing them,
• extensive drilling and sawing, for example for new penetrations or openings.

Chiselling and sawing hard mortar produce fine dust in any case, so dust control is worth planning even if no asbestos is found.

How many mortar samples are needed?

A good rule of thumb is one sample of each different mortar. The facade render and the interior wall render are separate samples, as are the original masonry and a later repair. If both the grout and the bedding mortar of a tiled surface are to be removed, they can go into the same sample or be labelled as separate samples. How to estimate the number of samples is covered in the article how many asbestos samples are needed.

How to take a sample of mortar

Mortar is hard and can chip or crumble when you take the sample. Use hand tools, not a drill or an angle grinder.

1. Wear disposable gloves, a respirator of at least class FFP3 and safety glasses, because hard mortar throws off chips.
2. Choose a spot you plan to demolish. On render, a crack, an edge or an area that has already come loose is a good place. On a brick wall, take the sample from the joint between two bricks.
3. Lightly mist the sampling spot with a spray bottle.
4. Hold an open zip-lock bag under the spot, or tape it to the wall, so that the crumbs fall straight into it.
5. With a chisel and hammer, remove a piece of about 2–5 centimetres. For render, take every coat from the surface paint down to the masonry. From masonry joints and tile joints you can dig out mortar with a narrow chisel or a jointing tool.
6. If the mortar crumbles, collect the crumbs in the bag until you have roughly as much material as a 2–5 centimetre piece.
7. Seal the bag, put it inside a second bag and mark it with the location and material, for example "facade, north wall, render all coats" or "sauna, brick wall masonry mortar".
8. Cover the spot with tape and wipe the area with a damp cloth. Do not vacuum the crumbs with an ordinary vacuum cleaner.

Protective equipment and cleaning are covered in more detail in the article how to protect yourself when taking an asbestos sample.

What does the result of a mortar sample mean?

Onelab analyses the sample with a JEOL SEM-EDS electron microscope in accordance with ISO 22262-1, and the result is sent by email, typically on the day the sample arrives. The result tells you whether asbestos was detected in the sample you sent.

• No asbestos detected: the result applies to the mortar at the sampling spot and similar material. Render from different periods, repair masonry and patches are tested separately.
• Asbestos detected: the mortar is treated as asbestos-containing, and chiselling, demolition and repointing are planned as asbestos work. If the sample contained several coats of render, the whole render is treated as asbestos-containing. The removal is carried out by a company authorised for asbestos removal work.

If the mortar is part of a larger renovation or demolition that requires an on-site asbestos survey, the survey is carried out on site by a qualified surveyor. Onelab is a laboratory, and on-site surveys are handled by our sister brand AsbestiPro.

How much does the analysis of a mortar sample cost?

The analysis costs €39.90 + VAT per sample, and the price is the same for 1–100 samples. Orders of more than 100 samples can be priced separately. Postage is not included. You can order the analysis online and send the sample to the laboratory by post.