While performing home inspections I have run across several houses that have bee hives in the exterior walls. Honeybee swarms can enter walls through small cracks or holes that lead to a cavity, like the exterior house wall. An opening around a light, hose faucet, electrical outlet or a gap between the siding and the house foundation makes an excellent entrance site for bees looking for a new home. Once inside the wall, the bees quickly build honey combs. In just a few days, the comb can be several inches long and the width of the studs. If the colony goes unnoticed, the swarm can grow to around 10,000 bees.
One of the houses I inspected was treated for the bee infiltration, but they did not remove the honey combs and new bees returned a couple of days later. The smell of honey and wax left behind by a colony is also appealing to new swarms. If you don’t clean up the wax and honey you can quickly have another colony take up residence in the same place. After the bees are removed the honey can rapidly decompose and cause moisture damage within the wall. With temperatures in the Gilbert and Phoenix area reaching over 100 degrees, I have seen the stored honey in the wax cells melt and honey run out the bottom of the walls.
Any time bees are found within a wall cavity during one of my home inspections, I recommend the wall be opened up and all damage and/or debris from the bee hive removed. This can typically be done from the inside by removing the drywall (of course, after the bees have been exterminated). It’s cheaper to replace the drywall from the inside of the house than it is to replace the outside of the wall, especially if the exterior siding is stucco or a stone veneer. And don’t forget to caulk or seal the opening in the wall that let the bees enter the wall in the first place.