Wood – How to properly clean hardwood floors

Yes indeed, prep is required and very important. First step is to renail or screw down the plywood subfloor. If you have a pneumatic frame nailer, you can use 2 1/2 inch threaded, ring nails (never use common nails), or alternately use 1 5/8 inch drywall screws. Install your nails or screws every 8 to 10 inches apart along each joist line with special attention to seams of the plywood. The importance of securing the subfloor well cannot be understated. The major cause of squeaky floors is drying or aging wood loosening around the nails, allowing them to move.

The second step is to lay a layer of building felt or rosin paper between the subfloor and new hardwood. Simply roll it out and staple it enough to hold it in place. This will assure that there is no wood on wood contact which can also result in squeaks.

I hate to be the one to tell you this, but there is really no magic putty or filler for shallow scratches and gouges in hardwood flooring. Even though there are a lot of colored wood fillers on the market, they are not designed for high traffic flooring or nuclear dogs. If it was just a couple of scratches you might be able to sneak by with a filler, but not for a refinishing job in a larger area as you describe. Most engineered flooring has 3/16" to 1/4" of hardwood veneer over a plywood base. If the scratches have not gone through the veneer, then you can sand the scratches smooth, stain to match, and refinish with 3 to 4 coats of urethane. I would recommend an oil based urethane. Apply 3 to 4 thin coats rather than 1 or 2 thick coats. Remember, the veneer is fairly thin and usually can only be sanded and refinished 2 or 3 times at best. Once the scratching penetrates the plywood base, your floor is unrepairable.

My advise would be to protect the floors with area rugs, runners, etc or keep the dog's nails cut short, or better yet, train them to behave in the house.