Sanding a New Floor
If you're installing new flooring, it may come prefinished, meaning the stain and topcoat are already in place. If this is the case, no sanding is necessary.
If you're installing unfinished planks, you'll have to sand the wood before you apply the wood stain and must sand afterward in addition to sanding between each finished coat.
You may complete the initial sanding, before applying wood stain, with a walk-behind random orbital sander that rotates at high speed while the entire sanding head revolves to reduce the risk of cross-sanding marks on the wood. You may also use a belt sander on the floor, but use only a fine-grit sanding belt to reduce the risk of sanding away too much of the wood surface.
Fine sanding is necessary after you apply wood stain that tends to raise the grain of the wood. Hand sanding produces the best results at this stage. Using a regular 120-grit regular sanding paper or a foam sanding block, sand lightly only in the direction of the wood grain.
Sanding to Remove Old Floor Finish
A walk-behind drum sander comes in handy if you're sanding off floor finish before refinishing the floor. A drum sander features a spinning cylinder that grinds away hardened varnish or lacquer that are difficult to remove by hand. This type of sander can quickly dig a chunk out of your floor, however, so practice using it on scrap wood before sanding the floor, and never let it sit in one position when the sanding drum is spinning.
Sanding Different Wood Types
Soft flooring woods, like pine and cedar, sand quickly, but there is also a greater risk of damaging the wood when using a power sander. Hardwoods, like oak, ash and maple, require more sanding to make them smooth enough to apply wood stain and wood finish.
When It's Advisable to Hand Sand
For all sanding steps after the wood stain is on you should sand by hand. A 220-grit foam sanding block works well to smooth down the wood grain after staining.
The final sanding requires very find sandpaper, such as 400 microgrit, just to buff away any bits of dust that settle onto the wet floor finish between topcoats.