Recently I had a contractor ask if I could waterproof the bottom of the t kick..
Before install. He said that he had this request from a customer who did not want to have water absorbed into the exposed MDF or raw wood that touches the floor. This would then cause the paint to eventually blister and flake off.
Does anyone ever waterproof the bottom of the toe kick for this reason?
Also, the bottom of the side panels reach the floor level.

you are not going to waterproof mdf easily , you are better off using plywood or even better solid

I always seal the bottom of cabinets installed in garages using TB-3 or RedGard

A set of Titus or Hafele plastic leveling legs saves you from all these headaches.
No need waterproofing,no need silly shimming and many more.
just update and change your carcass design.
if you want answer to your question just use fiberglass resin and spread to the exposed area.
Good Luck!

Plastic legs with snap on kicks.

Spreading on resin I guess would do the trick, a bit messy and time consuming. Or using the TB-3 or Red Guard makes sense though. Just didn't know how many have had such a request and if even it is something that is remotely going to be more important in the future. Thanks for your comments and tips, everyone.

When kicks are scribed tight as they always should be.. water can be a problem, with any wood,MDF or partical, we scribe the kick ( or dont..) then melt parafin wax with a heat gun soaking the exposed edges. This is the best thing I have come up with, the wax sets fast is transparent and doesnt effect the finish on the other side, this is also done with units that sit on stone tops. Time consuming a little, but so is making all the kicks again.

I've used endgrain sealer (brush able wax ) , wood glue, spray can lacquer, etc.

But as the others have said, with all the end panels, fridge panels and others touching the floor the toe kicks are only part of the problem. We do use 1/4 medex mdf for everything, not sure how much it actually helps in the long run

Maybe use Extria ?? or whatever the exterior grade mdf is

I see there are number of you who actually do take time to protect these areas.
I hardly ever see this done.

Easiest thing to do is to edgeband with bottoms with PVC.

If you ever get in a situation where you need "waterproof" kicks that'll be the least of your worries. LOL

BTW if you try to "waterproof" them which you can't you're setting yourself up being held responsible for damages.

I never tell the client we are doing it, it's just for my peace of mind.

Why not use water resistant mdf like Extira?