Masonry bees in your walls: what they are and how to protect brickwork

In spring, a sunny wall can suddenly look busy, with small bees going in and out of holes in the brickwork or mortar. These are usually masonry bees. They look like a swarm, but each bee is working alone, and the answer is rarely a treatment.

01How to recognise them

Masonry bees are smaller than honeybees, hairy, and often ginger or reddish-brown. They are active from early spring into early summer, and you see them on sunny, south or west facing walls. Many may nest in the same stretch of wall, so it can look like a colony, but there is no queen, no hive and nothing to defend. Each female builds her own nest of a few cells, lays an egg in each with a store of pollen, and seals it, often with a plug of mud.

The young develop inside the wall over the summer and winter, and emerge as adults the following spring. That is why the same wall tends to be busy year after year.

If you are not sure what you are looking at, our bee identification guide will help you tell masonry bees from honeybees and wasps.

02Do they damage walls?

Much less than people fear. Most masonry bees use holes that are already there: gaps in old mortar, weep holes, nail holes and cracks. Some species can dig into mortar that is already soft and crumbling, and over many seasons a heavily used patch can become more pitted. In sound brickwork with good mortar, they do very little.

So if bees are getting into a wall, the wall usually needed attention anyway. The bees are a sign of soft mortar rather than the cause of it.

03Are they worth keeping?

Yes, where you can. Solitary bees are useful pollinators, especially of fruit trees and early spring flowers, and the red mason bee is often encouraged by gardeners and fruit growers for that reason. If they are nesting in a garden wall, an outbuilding or somewhere nobody minds, leaving them is the simplest choice.

04How to protect your brickwork

• Repoint soft mortar. This is the lasting fix. On older buildings, use a mortar that suits the brick or stone, often a lime mortar, rather than hard cement, which can damage soft bricks.
• Fill obvious holes and cracks in walls, render and window surrounds.
• Cover the worst area with fine mesh during the spring flight season if you need to stop new nesting before repairs are done.
• Offer them somewhere else. A bee hotel or a block of untreated wood with drilled holes, placed in a sunny spot nearby, gives the bees an alternative.
• Check regularly. A quick look at exposed walls each spring catches new activity early.

05What about treatment?

Treating masonry bees is rarely needed and rarely lasts, because new bees arrive in the same soft mortar the following spring. We treat bees only as a last resort. For masonry bees, the useful work is identifying them, advising on proofing and repair, and leaving them alone where they can stay.