Hi everyone.

I'm doing work on my house foundation and can't help notice there are some small holes inside the perimeter, holes for ants to get in and out of the ground.

Now, since i plan on having an earthen floor of sorts, this leaves me a little worried.

The plan is to have a layer about 15-20cm (6-8") of tamped crushed stone followed by some form of insulation and the earthen floor.

While the tamped crushed stone will protect from rodent ingress, it will do little against the ants.

A plastic sheet will get punctured during installation so not very helpful.
A layer of clay won't stop the ants.

Maybe if i stabilize the base soil with some lime it will help.

People around here just pour a concrete slab and be done. I resent this for many reasons.

Ideas, experiences, anything ?

Interesting question! I also live in ant country so this seems like a concern worth consideration.

It would seem to me that if there's nothing to eat down there and limited points of entry, the ants may not bother.

I wonder how an application of borax and/or DE would fare, if pored between the rocks?

As long as the top layer is sealed completely, would you be disturbed by them? Be it Tadelakt or even just a beeswax/linseed oil finish that should effectively seal out ants or other critters. Your floor would have to be ant proof to be water proof, I would think.

These probably aren't the best solutions... Maybe we'll get lucky and Jay C. Whitecloud or some of the other wise and generous natural building experts hereabouts will stop in to offer what's worked for them, and what traditionally limits that kind of problem.

We ran into a similar situation when building our house.  There was a large fire ant hill in the middle of the house location.  I dug in a 4 pound box of borax into the ant hill its self with a backhoe (the colony went about 5 feet deep). Then before placing the gravel for the floor base, I dusted the ground with another two boxes of borax (over about 700 square feet). So far there haven't been any intruders through the floor.  I don't think the two boxes dusted over the floor area was excessive.  The ant hill area was well dusted but most of the rest of the floor barely had any.  If I had to do it over again, I would use another box or two. That said - there haven't been any issues.

Do you have a reason to think they will be a problem?  Do you have fire ants or unusually many ants in your area? I've lived in a house with earthen floors for some 20 years, and though I certainly see an ant in the kitchen once in a while, I don't see them very often. There is occasionally an ant's nest in the garden right outside my kitchen door, and the first time I saw it I was alarmed and smoked it with incense, but then the next year I decided to wait and see. They never actually became a problem, so now I let them be. I've never had the mouth of an ants' nest appear inside the house, and if I did, I guess I'd try the incense-down-the-hole trick again, or sprinkle boric acid powder around it. I don't worry about it.