Solid Hardwood, Engineered and Laminate Flooring - Nails & pet stains in HW - what do to?

We just removed the carpet covering the hardwood floors in our old house to discover several problems. There are LOTS of nails in the floor - a nail every 12" (yes, inches) on every board throughout the floor (the boards are very narrow). Several places have been patched where there used to be floor heat vents. There are also some urine stains in the floor. What should we do with this floor? Should we replace the boards where the pet stains are? Is it worth doing anything considering the thousands of nails that are in the floor? What would you do? Help!!! Thanks for the advice!

You can remove old wood floor and replace with new, or you can do like previous owners and cover with new. Perhaps one of the new floating engineered wood products would be to your liking. If height issues and extra weight on joists are not problems, then installing new solid hardwood over old can be done. Or, you can recover with carpet.

Nails can be countesunk and holes filled. Stained boards and boards over vent holes would have to be removed and replaced from inconspicuous areas such as in closet. This can be quite involved and still give you a less than perfect floor.

When you say your house is old, just how old is it? Narrow strips, say 1 1/4 inch, all face nailed sounds like a style from a century ago. If that's what you've got then you should look into refinishing.

The house was built in 1918. The floor boards are 1-1/4" wide. We think the nail were put in some time after the floor was installed, because they are only in the living and dining rooms. Other rooms in the house are not nailed. Diagonal lines were drawn every 12" or so throughout the rooms and a nail is in every board along those lines, plus a nail at the end of each board where they join together. Because we don't know why all the nails were put in, is it questionable to refinish the floor or even install a floor over it? Could all the nailing be hiding a bigger problem?

Thanks so much for the advice!

Previous owner could have done face nailing in areas where there were squeaks.