Should I seal my house foundation?

(Putting it here because I think it’s more of an opinion than a factual question. If I’m wrong, I’m ok with it being moved.)
I live in the metro-Phoenix area. In my instance it means that my house is of frame construction built on a concrete slab. No basement. The walls have all been stuccoed. To further elucidate: They came out and poured a concrete slab. Then they bolted the frame of the walls (2x4 construction) to this slab. Then the put drywall on the inside, siding on the outside.

Recently I had some work done and the worker–not a foundation specialist I hurry to add–suggested taking caulk and going along the bottoms of the walls–where the “siding” meets the concrete–to seal them.

He claims that this will help keep pests* out of the house and might keep the foundation from cracking because somehow it will help prevent moisture from acting on the joint between the wall and the concrete foundation.
I am skeptical. If this was such a great idea, it seems it would be part of the building process. Also, I don’t know, but maybe there needs to be an air infiltration at that point because of some arcane reason.

I welcome the thoughts of my fellow Dopers. As a matter of fact, I eagerly invite them.

*= He said “pests.” I assume he means small insects and not politicians, bill collectors and the like.

I think the better sealed that bottom edge is, the fewer ants and roaches you will get. Nothing will keep them out 100%, but it will help.
I’ve never used a pest service, and I have only occasional bugs in the house, but I did have some very determined carpenter ants awhile back. Sealing all the gaps helped.

And is that how you’d do it? Caulk all the way around where the siding meets the foundation?
And what kind of caulk woild be good for something like this?

I haven’t used an exterminator since we moved in and I do periodic treatments myself with (knock stucco) few incursions.

I’d use the cheap tubes of Ace-brand siliconized Latex. If the are any big gaps use expanding foam, then cover with caulk, or put in a foam filler strip. You should be able to do the whole perimeter with 2-3 tubes.

I have no experience with stucco walls, but in standard wooden construction you seal the bottom plate, not the siding, to the concrete. There would normally be a thin sealing strip between the concrete and the horizontal 2x4.


But if you do that, there’s still a gap (possibly) between the siding and, well, the interior. Frankly, I was wondering if there was any reason (air flow?) that it needed to NOT be sealed.

I’ve been contemplating getting my stacked stone crawl space sealed with spray foam. I can’t find any information on if this would be a bad idea. Does anyone have any input on that?

Some types of siding will suffer from inadequate ventilation behind them. I believe shingles and shakes are particularly prone to trouble. Cite: going on four decades of watching This Old House.

I’ve just got plain, old, whatever-the-builder-did stuff so I expect that ventilation isn’t an issue for me but would hate to miss an opportunity to overthink it.

There is no gap. The plywood or OSB sheathing is nailed solidly to the studs and bottom plate. There may be a gap between the siding and sheathing but nothing gets inside. I caulked the sheathing to the studs when I built my house and know others who did also. But never tried to seal the siding to the slab.