I was visiting with a client in Portland the other day. He had a carpenter ant problem by his back door. The large ants were appearing regularly inside the house when the sun came out. I was puzzled by their presence in this location. There were none of the usual contributing factors like vegetation, trees touching, or bark dust too high. This was a concrete stoop and sidewalk connecting to the back door. I dropped to my hands and knees and noticed a gap behind the step next to the house. I then realized that this area had a south west exposure. This meant that this area receives a lot of driving rain. Bingo!!
The rain was being slammed up and under the juncture of the siding and the concrete step. And where there is wet wood, there are (or will be) ants. The homeowner tip of the day is to carefully check the caulking around windows and doors especially on the wet ‘south west’ side of the house.
And inspect along the top of any brickwork,