Earthen floor over concrete in basement - concerned about occasional moisture

My basement floor is rough concrete. I’m considering applying an oiled earthen floor topcoat to smooth it. Part of the floor gets moist when it rains heavily. Enough to visually darken the concrete and so it feels very cool, but not quite wet, to the touch. Would this amount of moisture be a problem for the earthen floor? If I use a natural fiber to prevent cracking, could it mold from occasional moisture?

I’d like to keep the earthen layer to one inch since the basement ceiling is already low.

Basement is 20’x16’, approx. Damp portion is about 7’x6’. The basement houses a gas furnace and gas water heater. I use two dehumidifiers to keep the humidity at 40%. The house was built in 1912 with a field stone foundation. The field stones have been coated with rough concrete.

Hi William, and welcome. This is an interesting proposition and one I hadn't really considered before. My understanding of earthen floors is that they can help moderate humidity extremes in the space where they are installed, but that you really don't want liquids sitting on them. Your case is sort of in the middle...you have a substrate that gets overly damp and would then wick into the floor above.

I think this would cause problems. One would be expansion of the material when it's wet, especially if there is a lot of clay in the mix. This might lead to bubbling and then cracking as it dries out again. If there's organic matter present, it will decompose. The presence of a semipermeable layer atop the concrete may slow down its ability to dry out after wet periods.

This might be a place where a membrane would be appropriate. A sheet of polyethylene would keep the water out of the earthen floor, but you would need to monitor its presence and might have to add a way to help it leave the basement if it can no longer evaporate by wicking through the concrete. That part sort of eludes me...maybe a dry well with a sump pump?

Hi Phil,

Thank you! And thank you for your response.

When I bought this house the basement was bone dry during a very wet fall. Over the years I inadvertently compromised the drainage around the house until inches of water would flood the basement (this caused a not-insignificant mold problem). I've been learning more and reversing the issues. Most recently, I unclogged a Y-junction in a downspout and the wet invading the basement corner went from puddles to the dampness I described.  I think I will continue to investigate and see if tweaking the downspout/grading/etc. can prevent the dampness altogether. I have a sump pump in a 3ft dry well (though in the northwest corner, not the northeast, which is getting damp) and it almost never kicks on.

Your description of the potential issues caused in an earthen floor by dampness is helpful - I'm trying to learn what the considerations are for this kind of material. I'd like the fiber in the earthen floor to be unnoticeable. I've seen toilet paper used to reinforce clay walls. Do you have any idea of that'd be suitable? Lastly, I'm considering walling off a portion of the northeast corner to make a produce cold-storage room. I'd keep it around 40 degrees Fahrenheit and 80% humidity. Could it cause any issues in the earthen floor for one corner if it to be at a different temperature and humidity than the rest?

can you dig the floor deeper?
After yje drainage issues have been dealt with.

In short, I'm sure I could with enough work, but if I have to tackle that I won't do the project. I don't know if the concrete is an any way structural, supporting the base of the foundation. I'd have to alter the supports or piping for the furnace, water heater, and wood posts. Not to mention breaking up the concrete.

What advantages do you see from digging the floor deeper?