Gleaming, beautiful, rustic hardwood floors — it doesn't get much better than that. But one of the keys to having the quality floor you envisioned, as most things are in life, is the quality of the foundation. You can't get around it. No matter how top-dollar or high quality your flooring is, if the sub-flooring isn't prepped correctly, the end result could be something you have to fight for years to come.
And it's really pretty simple: you need your sub-floor to be clean and dry and stable and level. You're investing a good deal of money on quality hardwood flooring, it only makes sense to enable the product to serve its purpose beautifully. And nothing can disable a floor more than a poorly prepared sub-floor.
You can install hardwood over most existing flooring materials, but it's important to make sure the moisture content of the flooring material and the sub-floor are compatible. This can be done with moisture meters. They come basically in two versions, one each for porous and nonporous materials.
And one type does not fit all. If you use a meter for concrete on plywood, your readings will not be accurate, and that could cause problems in your installation. Also be sure and measure the moisture content in several different places on the expanse of the sub-floor. Moisture content can be drastically different from area to area based on foundation issues, placement near windows and doors, and so on. It's important everything is dry and proper moisture barrier products are used.
Not only does the sub-floor need to be dry, but it also needs to be clean — very clean — especially when doing a glued installation. Debris or dirt can make it impossible for the adhesive to adhere to the sub-floor properly. And any glue or debris under a nailed down or floating floor can cause uneven pressure that can, over time, cause damage. You also have to make sure, if installing over concrete, that the base material of the floor doesn't have a coating or compound that makes it nonporous because the adhesive needs a slightly porous or at least roughed surface to be able to truly meld with the material and hold.
Last but not least, which should be no surprise to anyone, your sub-floor must be level, flat, and of course stable. With the unforgiving nature of some flooring products, your floor absolutely must be level, which can entail some extra work — but very worth it if you want your floor to last its full life cycle.
And if the underpinning of the floor has gaps between joists that are not up to code, then the wood can start resembling a diving board, or at the least you can get rid of the unending "squeak" that every teenager dreads when they're sneaking in late. On second thought, maybe the squeak is a good thing.