Hello, I have a garage with a wood floor. There is a full basement in the garage. How can I seal the floor to keep water from getting into the basement? It isn't heated but in the winter the snow & ice from the car melts & leaks through the floor. Is there anything to use or anyway to seal it? Thanks WB

The difficult issue here is that the wood will expand and conract with weather conditions. So even if you were able to poly the floor to prevent moisture from getting through it would start leaking once the weather changed. Also the weight of any car or truck would break the seal between the boards.

The difficult part of this is putting something over the floor that would resist cracking as the wood floor moves under the weight of the car. You could place cement on the top with a plastic placed on the wood. But you would need a fair amount of cement in order to make it strong enough to resist cracking as the wood below would bend.
You could place a fibergass cap like they do on decks but once again the flexing of the wood would end up cracking this as well. Even if you think the wood is not flexing it is. It may only be a little amount but any flexing is to much.
The only way around this issue is to remove the wood floor and place steel sheets down and put down cement with a plastic vapor barrier. The steel will drop the floor so you would not end up being to high once you put down about four inches of cement.
Good luck on this one.

I would look at a high build elastomeric membrane. There are products that are liquid applied and will build to 1/4 inch or better. They will bond to wood and are flexible enough to remain adhered while still bearing the weight. Most of these are urethanes and will stink plenty while being applied, but after curing are pretty much inert. Most will resist chemicals such as oil and automotive fluids. Polycoat is one manufacturer that comes to mind. There are others, but be sure that you use a product that is rated for traffic and not a roof coating material.

I thought about that same type of product but the amount of movement on such a floor may be to much for this type of product to withstand. Which is why I did not suggest this. The weight of the car will flex the floor between the joints of the wood an awful lot. Even though it would not be visual, its enough to cause failuer to the sealant. But its worth a try. AS the option is much more expensive to do.

A high build elastomeric would absorb the amount of flex you'd have in the floor (provided that the floor is in good condition). It would need to be a substantial coating, not just a paint job though. A thin coating would likely tear between the flooring planks. Also a thin membrane will scrub off if you steer the wheels while setting still. What I'd recommend would be at least 1/4" thick. It certainly won't be a cheap affair.