All of the hardwood flooring contractors who contribute to this website recommend hiring a professional for hardwood floor sanding. They do not benefit from this recommendation as the chances of you hiring them is miniscule. Hardwood floor sanding is a skilled job that takes practice and experience. There are more ways to ruin a hardwood floor than there are to sand it properly.
You may come across much information giving you instruction, and encouragement, to save money and do it yourself. However ... we suggest strongly that you consider doing the clean up and finishing work yourself to save money, and hire a professional for the sand itself.
That being said ... for those stubborn do-it-yourselfers and those with related or beginning skills, below are some tips and basic instructions for hardwood floor sanding.
There's really no such thing as 'dust free sanding'. You are gonna make dust no matter how much you are able to trap and capture. The key is doing an excellent job of protecting the project area and its property - and doing a very thorough job of cleanup upon completion. But there is equipment available that specializes in dramatically reducing the dust. Many of our hardwood flooring contractors recommend simply using a good old vacuum for dustless floor sanding - before AND after the project!
There are many grits of sand paper. You can consider that the number of the grit equals how many sharp pieces of sand per square inch. Therefore, smaller numbers (i.e. 24 grit) are rougher and larger numbers (i.e. 100 grit) are finer, producing a smoother result.
Step 1: Prepare the Area
Cupboards, doorways, closets and any other areas or items where you are working should be protected from dust with plastic. Remove wall hangings, light fixtures, window coverings and anything else in the area that could be dirtied or damaged by your work. Putty nail holes from carpet (tack strip). This step also helps you find any metal staples or nails left over from carpet removal and such. Use a wood filler that is stainable and is the color of the floor. Prior to rough-cutting, remove quarter-round and/or baseboards.
Step 2: Start with the Rough Cut
On older floors, the first step when sanding is to choose an aggressive grit (like 24 grit per square inch) to level the boards one to another and remove imperfections if possible. The result is a fresh, new-looking wood floor. We call this process rough-cutting. Don't be afraid to use new belts, and more than one. Some waxy, older floors will gunk up your belt and make it dull and useless. And with new belts, don't hesitate to hit areas again that aren't new enough looking.
On a newer floor, you might start with a less aggressive 50 grit. In handling the belt sander, the machine MUST be moving when you gently set the drum down into action to avoid digging holes in the floor that won't come out. As you near the wall, be extremely careful to pull up the drum BEFORE you hit the wall. You will be sanding forward and backward. Use care in your backward motion so you pull up the drum before you run into the wall. DO NOT RUN OVER YOUR ELECTRIC CORD.Step 3: Rough Cut the Edges
Now you will sand along the walls, in the closets, and anywhere else the belt sander could not reach, using an Edge Sander. Start with a 24 grit on your Edge Sander and change your disc often. Level the floor and go over imperfections as needed. Work the machine in circles or figure eights and with the grain as much as possible. Don't allow the machine to dig into the corners. Use extra care in those areas. Level sand out any drum marks.Step 4: Medium Cut with Belt Sander and Edge Sander
Use the same procedure as above with 50 or 60 grit. The purpose of this step is to remove the deep cuts and grooves from the rough cut.Step 5: Fine Cut with Belt Sander and Edge Sander
Use the same procedure as above with 80 or 100 grit. The purpose of this step is to smooth the floor in preparation for buffing.Step 6: Scrape Corners
The goal to scraping a corner is to remove old finish and level corner with the rest of the floor. The best way to achieve this is by having a very sharp scraper. We achieve this with a good, metal, inch-wide file you can find at a hardware store. Or you can flip your edge sander over, turn it on with 100 grit sand paper on, and gently grind the scraper to produce a sharp edge. Watch to keep the scraper level, not angled, and not to remove too much metal. Sharpen often, after every corner if needed. We liken it to sharpening a pencil, shaving the wood in the corners. You will have shavings. You can hand sand corners with 100 grit to blend.Step 7: Buffing
Use 100 grit screen under your buffer pad to blend the edges with the rest of the floor to get the surface as smooth as possible. Remember, there is two sides to a screen - so flip mid-way through - and use more than one screen for a larger area. Buff slowly and thoroughly. This machine does not dig like a sander, so don't worry about going over areas too much. The more you go over it, the smoother it gets.Step 8: Vacuum and Cleanup
Thoroughly vacuum the floor and other areas with wand and crevice device. We recommend a hair bristle or felt-bottomed wand to protect the floor. Use care if you use a plastic wand ... three layers of blue tape recommended on the edges. Your floor is now ready for staining, sanding sealer, or a first coat of polyurethane.