Using a floor sander to finish your stairs might seem a bit scary but hiring a professional to do the job done can be quite an expensive proposition. All it will take for you to do it yourself is a bit of time, some instructions and some practice. Running the sander is the most difficult part of the operation because you can damage the stairs if you do not properly operate the sander.
The best type sander for stairs is an edge sander, which you can rent at a local tool rental center. The following suggestions will, hopefully, make the job easier.
Step 1 - A Little Knowledge
Once you learn the basics, sanding is a fairly easy chore. The secret to a good finish on your stairway is learning to get a “feel” for the equipment. Although sanders can be loud and messy, they are easy to operate. Keep the machine moving at all times while employing pressure on the surface of the stairs. Moving the sander constantly is like ironing clothes--if you leave the iron in one spot, you will ruin the item. The same is true for the sander. If you leave it in one spot, it will either burn or dent the floor.
Step 2 - Practice First
Take some time to practice on an extra piece of wood. Keep a firm grip on the sander, making several passes--following the grain. Practice for as long as it takes to get the proper feel for the machine.
Step 3 - Remove the Old Finish
It may be necessary to remove an old finish on your stairs before completing the sanding process. Use a coarse grit sandpaper to remove any existing finish. Once the stain or paint has been removed, follow up with a finer grade of sandpaper to remove any remains. Vacuum each tread as you sand individually so all dust is thoroughly removed. Once you have all the stain or paint removed, proceed.
Step 4 - Sand for New Finish
If you are re-finishing the stairways, change back to a coarser grit to remove the top layer of wood. Work each tread carefully, keeping the edge sander moving at all times. Once you have made one pass on all treads using a coarse sandpaper grit, replace it with a finer grit. You may need to do this several times to remove any scratches you create removing the top layer or layers from each stair tread.
Step 5 - Re-vacuum
If you are satisfied with the sanded surface, vacuum all the treads and then repeat again a few hours later to make sure you have removed all the dust. Make sure you rent a newer machine that will have an attached dust adapter because the sanding of the stairs will create quite a bit of dust. It will be a good idea to wipe the treads down with white mineral spirits and allow this to evaporate before applying a new stain.
When renting a sander, purchase several breathing masks to wear while operating the machine.