I have installed and finished several wood floors, but I am planning to refinish a 100 year old floor in the hallway of the building I live in and have a few questions.

First off, the wood floor is currently a subfloor. It is a sturdy floor, but it has some gaps that need to be filled. Has anyone filled gaps with concrete before? A few areas of the floor are concrete instead of wood. I think filling in the gaps with concrete may help bring the look together. If any, what kind of concrete would work best?

I am planning to use an acid based finish (I've used before). Any suggestions I should keep in mind for an old floor?

Thank you for your help.

Chase

The patching material that you should consider would be a latex fortified cement. You can use this type of leveling material after priming the floor with a special primer so it adheres well. The cure time is fast so you will be able to work on the floor sooner than just plain cement. You will be able to sand the patch with coarse paper when it hardens a little to get it smooth. It will be a dark color. The material is somewhat runny if mixed thin, so you will need to keep it from leaking out the hole when you apply it.

You can use latex fortified cement filling in the gaps