If the building has a foundation, spray the skirt where the wood meets the cement with resmethrin or bifenthrin or hornet kiiller (piperonyl butoxide)...they won't cross that line for a long time. Ants must drink, if you salt their water supply...sinks, tubs, they disappear quickly too.

__________________
A third rate theory forbids.
A second rate theory explains after the fact.
A first rate theory predicts.
A. Lomonosov