Cob Advice!

Hey all! My partner and I are planning on building a cob house next year around 400sq ft. We are wanting to do something similar to the Smiley at the Cob Cottage if anyone is familiar (small living space kitchen and bathroom with a small loft for sleeping and a desk) We live in Upstate South Carolina. It’s pretty humid and rainy here but also hot as get out. We live in predominant red clay area and the sun seems to bake the heck out of it on a clear day. But we are wondering about drying time for the cob. Does anyone have experience building cob in a similar climate or know of any other cob builders in this area? We also wanted to know if anyone has any tips for preventing mold in the building. We are planning on a French drain with a concrete bond beam and stone foundation over that. I’m hoping that will be okay, but I’ve read some mold horror stories and I know how easy it is to grow mold in our humidity. Any advice or tips about those topics or really anything for a first time cob builder would be greatly appreciated!

I thought I replied to this earlier?

You replied to my round pole question! this is similar but more looking for advice about the cob itself in our wet climate.

Air flow often beats mould growth.
What have you heard?
This video may help.

The clay content of cob inhibits much of the fungal and bacterial activity. Once it's dry and protected from the elements with good breathability, the moisture levels won't be high enough to support growth. Some folks add borax to the mix as an inhibitor during the drying process.

We did not have trouble with it cobbing in Southwestern Virginia. I have had trouble with molding plasters in enclosed rooms (on lath, not over a dry cob wall), even with borax, but the problem was short-lived; when the plaster finished drying out, the mold died.

Thanks for the responses y’all. In general I haven’t heard about many mold issues, except one or two experiences that have me scared. One thread on here titled “Mold in Cob” that mentions a magazine article where a man was having trouble with mold on the bottom 15% of his walls where condensation would collect up from his cold foundation. Luckily we have much more mild winters than his location, but we do have some stretches below freezing in the winter and I worry about a cold stone foundation. I suppose most of my fear comes from the lack of information or examples of cob building in my area and the insistence of folks (that aren’t natural builders) that it’s just not suitable here. Every structure I’ve been in here without a powerful climate control system has been very susceptible to mold and I’m nervous that the cob will be able to handle all of the moisture here.

It’s great to hear that you didn’t have trouble cobbing in VA! Every time I hear of someone in the SE building cob I feel a little more at ease

I always ask naysayers where their information comes from.
They all mumble about things and sometimes admit 'they heard....'
Never take to heart what they say!!!

I built a cob house in humid NW Arkansas, and the only mold issue I've had is a slight spotting of the pale clay paint that I put over my earthen plaster each summer. (Then I would paint fresh in Fall).  Interestingly enough, the unplastered, unpainted walls of my cob greenhouse deal with even more humidity, and do not have any spotting that I can see. I put a bit of lime slip in my last batch of pale paint, upped the borax, and did not have any spotting last year.
The other humidity issue which I've written about in other threads, is the floor getting soft enough to dent in the heat if summer. Heavy maintenance oiling and a few throw rugs is the answer, I believe.

I've built in a super humid area. Super rainy. Had some mold growing on the wall. You can use lyme plaster, it's what i used, very durable plaster and no mold at all. After the cob dries you won't have many issues. Build a roof on top of construction to allow drying without having to cover the walls when it rains. Main issue is straw going bad. I actually had plants growing out of my wall during the wet winter season here from straw sprouting. Keep the air moving. You'll do great. Cob is very permissive.

Here in central Ga. I built a small cob cottage. I'd say it took most of a year for it to completely dry out. After a year I started building a rocket mass heater. During construction a small patch of mold developed on the wall near the floor. Cutting a hole in the wall for the heater I'm sure was the culprit. Took care of the mold repair and finished the rocket heater. It's now been over 2 years. And no sign of mold. After a heavy rain I would run a fan for a few days. But now that everything is dry, no need for a fan. And no sign of mold.