Waterproofing is not a value-adding improvement in the way a kitchen is. It is a defect remedy, and defect remedies work by removing a deduction.
How buyers price water
A visibly wet basement produces one of three responses: a walk-away, a demand for the repair before closing, or a price reduction sized by the buyer's imagination rather than by a quote.
That last one is the expensive case. Buyers discount unknown risks far more heavily than known costs, because the unknown might be structural, might be recurring, and might be a great deal more than the actual figure.
What the paperwork does
A documented repair converts an unknown into a known.
The diagnosis, showing what the source was. The scope, showing what was done. Photographs during installation. The warranty, with the transfer confirmed in writing. A record of the system working through subsequent wet seasons.
With that folder, the conversation is short. Without it, "the basement was waterproofed at some point" reads to an inspector as a reason to look harder.
Where finishing the basement comes in
Finished basement square footage adds value where it is permitted, dry and properly built. That is three conditions and all three matter.
Unpermitted finished space frequently does not count as living area at all in a valuation, which removes most of the financial argument.
Space finished over an unresolved moisture problem is worse than unfinished space, because a buyer's inspector who finds moisture behind new framing assumes concealment.
The order that produces value
Fix the water. Document it. Run it through a wet season and record that it held. Then finish, with permits, using an assembly appropriate for below-grade walls.
Doing it in that order is the difference between adding usable square footage and adding a liability.
Disclosure
Known water intrusion and known repairs are material facts in most jurisdictions and have to be disclosed.
Disclosing with complete documentation is a strong position. Disclosing without it invites the buyer to assume the worst. Not disclosing is a legal exposure and, practically, unlikely to succeed — an interior system leaves a visible concrete patch around the entire perimeter.
Repair before listing, or price it in
Repair and document where the work is straightforward, the documentation will be good, and there is time for a season to demonstrate it.
Disclose and price it where the work is large or the timing does not allow it — providing the diagnosis and two contractor quotes so the buyer is negotiating against a number rather than a fear.
The strategy that loses money is repairing without documenting: the cost is incurred and the uncertainty remains.
What actually reassures an inspector
A sump with a working backup, a discharge that runs well clear of the house, gutters and grading that are obviously correct, and a folder.
None of those is expensive. Together they describe a house where the water was taken seriously, which is a different impression from one where a system was installed and forgotten.
Comparing it to other spending
Against a kitchen or a bathroom, waterproofing returns poorly on a dollar-for-dollar basis, because it does not add anything a buyer can see.
Against the alternative of doing nothing, it returns very well, because the deduction for a wet basement is unbounded while the cost of the repair is not.
That is the honest frame: it is not an improvement competing with other improvements. It is the removal of a problem that would otherwise set the price.
Timing before a sale
Doing the work several months before listing lets the trench line settle, the planting recover, and the system demonstrate itself through at least one wet period.
Work completed the week before photographs looks like work completed the week before photographs, and buyers read that as a problem being covered rather than solved.