A basement interior French drain will reduce the water pressure against your walls.

Do you have water pressure (hydrostatic) against your walls.

Did you receive a written estimate?

Have you vetted your prospective contractors?

Thank you, Jim - yes, the funny thing is, there already is a French drain there and I’ve never seen even a drop of moisture in it. The moisture seems to stay above it in the cinderblocks and doesn’t seem to make its way down to the bottom cinderblock in any obvious way. I know the laws of gravity and hydrostatic pressure probably say otherwise, but I was trying to understand how a French drain helps when there doesn’t seem to ever be enough to actually “drain” away. ‍ Yes, I received estimates from well known companies for rather elaborate systems that would run along the entire basement out to my back yard - just wondering what would actually “run” out there? Water vapor?

There are measuring devices, that measure pressure.

Re vetting, has the French drain contractors supplied a previous customer list. Always, the previous customer is a satisfied customer, but do the math, I.e., 3 satisfied customers in 10 years.

Your neighbor may have taken the bandaid/denial approach.

There are many magazine ads for solving issues such as yours. But, not every wet basement is caused/solved with the marketed remedy.

Maybe running a fan will work.

Others may have different experiences, but I haven't had great results from internal drains, and I wouldn't try to use them for a finished cellar.

Often all it takes to reduce or eliminate cellar dampness is making sure that your gutters and downspouts are clear, and that they discharge well away from the foundation. Sloping the ground away from the foundation is also important.

Beyond that, the only sure way to waterproof a cellar is to dig around it externally, apply sealer and a waterproof membrane, and add or repair footer drains that drain into a sump. It will be expensive.

Several years ago I had a similar dilemma. I wound up digging out around my foundation, sealing it and putting in better drainage on the outside. It was expensive but I think worth it in the end. The water is contained on the outside of the house instead of dealing with it once it’s inside the house. I’ve had a nice dry basement ever since.