If you’ve noticed small, honeybee-like insects disappearing into tiny holes in your brickwork on a sunny spring day, you’re very likely looking at mortar bees, also known as masonry bees — and in most cases, there’s genuinely nothing to worry about.
What mortar bees actually are
There are nearly 20 species of masonry bee in Britain, the most common being the red mason bee (Osmia bicornis). Unlike honeybees or wasps, they’re solitary — there’s no colony, no hive, and no nest to defend, which also means they’re very unlikely to sting. Each female works alone, provisioning a handful of cells with pollen for her young inside individual holes, usually in soft mortar joints, though sometimes in soft bricks, stone, or existing gaps around windows, doors, or roof tiles. They particularly favour sunny, south-facing walls, since warmth helps their eggs develop.
Do they actually damage buildings?
Generally, no — not significantly. Mortar bees are opportunists: they typically use holes and crevices that already exist (often where mortar has already started to soften or fail) rather than boring through sound brickwork from scratch. A handful of bees using a few holes causes negligible damage.
Where it can become a genuine issue is with larger, recurring populations. Because females are attracted to sites where other females are already nesting, a wall can build up a substantial number of holes over successive years — some properties have reported 70 to 80 holes appearing on a single elevation. At that scale, the holes themselves can fill with water, which then expands when it freezes and accelerates masonry deterioration, and birds occasionally peck at walls trying to reach the bee larvae inside, causing further damage.
What to do about it
For a small number of bees, the honest answer is: nothing. It’s a sign the mortar is a little soft in places, worth noting for general maintenance, but not an emergency. Where an aggregation is genuinely large and recurring, the usual remedy is to rake out the affected mortar joints to a reasonable depth and repoint them — ideally in late summer or autumn, after the bees’ breeding season has finished, since females often return to their natal nesting site the following year, and repointing at the right time helps break that cycle. The replacement mortar should be firm enough to discourage new nesting but not so hard that it damages the surrounding brick or stone. Chemical treatments alone tend not to solve the problem long-term and can stain masonry, so repointing is generally the more effective and durable fix.
