The most common mistake from beginners when sanding a floor is to sand too timidly. The more honest your assessment of the condition of your floor before you begin sanding, the better you will accept the amount of work required to restore it. Many newbies are horrified when they see the menacing look of 36 grit sandpaper in the rental center to get the necessary equipment. These very aggressive papers are often necessary because hardwood is, well, hard (!) and old wooden floors are scratched, damaged and are often stained, oiled, or covered with an old varnish, which are difficult to remove. In these situations, you have to pull out the heavy guns to get the job done effectively. Keep in mind that hardwood floors are at least 3/4 of an inch thick, and a proper sanding will remove between 1/32 and 1/16 of an inch. A hardwood floor can therefore undergo 4 or 5 successive restorations before having to be replaced.
The three stages of floor sanding
1
The first step of sanding has two important functions. First, it is about leveling the floor as much as possible (if the wood has moved/warped over time). The second function is the removal of the original finish using aggressive sandpaper, between 16 and 36 grit. Regardless of the grit used initially, the old finish on the floor should be completely removed once the surface has been sanded to 36 grit.
2
The second phase of sanding is carried out to correct the surface and level it using 60 to 80 grit abrasives. While the first step removes the old finish and larger defects, the 60 and / or 80 grit sanding will remove the grooves and sand marks left by the first, more aggressive sanding that was done during the first step.
3
The final step aims at closing the wood grain with a 100 or 120 grit paper, depending on the type of finishing product that will be used to protect the freshly sanded floor. Once the floor has been sanded with 80 grit, the floor may look good, and some will be tempted to skip the final step, but that would be a mistake. 80 grit sanding will leave the wood fiber very exposed and the wood will absorb too much of the finish that will be used. This is why we use 100 or 120 grit sandpaper before applying stain, oil or varnish.
Every step should be carried out starting with the drum and belt sander or orbital sander, followed by the edger with the same type of abrasive paper, while making sure to blend in the areas sanded with the two tools. Once that's done, you'll work on wall corners and other areas the edger can't reach, using a paint scraper and a sanding block with the appropriate sandpaper. Finally, a meticulous visual inspection of the entire surface should be carried out and any defects corrected manually with either a hand or electric sander, making sure once again to use the same grit as the one used for the whole floor. Then, it's back to the drum and belt or orbital sander with a finer grain, followed once again by the edger, and the scraper, and so on, until the 3 steps above are completed and the floor is ready to be finished with an appropriate product.
4 things to always keep in mind: clean, inspect, manage the dust and change abrasive
Between each grit progression, e.g. between 40 to 60 grit, 60 to 80 grit or 80 to 100 grit, it's extremely important to vacuum the floor thoroughly in order to eliminate all the dust and abrasive particles that will have been left on the freshly sanded floor. Even the best sandpapers will reject a few granules during the sanding process. And a 36 grit pellet that slips under a sander equipped with a 60 grit abrasive will leave ugly grooves in the floor. It is recommended that you wrap sticky paper around the nozzle of the vacuum cleaner if it does not have soft bristles to avoid scratching the wood with a plastic nozzle during this important step. Vacuuming following the wood grain will minimize the chances of leaving visible marks on the floor.
Furthermore, it is also essential to always do a good visual inspection after each sanding step to ensure that the grooves and other previous sanding marks have been completely removed before switching to a finer sandpaper, as they will be extremely difficult and long to eliminate them with finer grit.
Another thing to keep in mind throughout the sanding process is the importance of regularly emptying the dust collection bag on the electric sanders you use. A good rule of thumb is to empty it when it is at a third of its capacity, to ensure good air circulation and that the appliance operates optimally, without the risk of overheating. In some rare but possible cases, the combination of wood dust and old finish (varnish or oil) could cause spontaneous self-combustion. It is therefore very important to empty the dust bag regularly and always empty it when the job is finished or when you take a break. It is also recommended to leave the empty bag outside or at least far from any source of heat or flammable or combustible products.
Finally, remember that fresh sanding belts and discs will work much faster and produce better results. Do not hesitate to change them regularly, based on the information provided by the equipment manufacturer and your rental center. Stretching the life of abrasives for too long is a strategy you will quickly regret, because once the old finish is removed (usually after sanding with 36 grit abrasives), it is difficult to see with the naked eye if the sander is doing the job well unless you carefully inspect the surface. So you might be encouraged to keep sanding, as the sander raises the dust and the job seems to be going well. But used abrasives fail to remove scratches left by the previous, coarser grit. Another risk when using stuffed sandpaper is that you might end up polishing the wood rather than sanding it, which will seal the surface and prevent a uniform finish across the entire floor.
This problem can be difficult to identify, until you've applied the finish of our choice and it is too late. This problem can surface while using both drum and belt sanders and edgers. In short, while the sandpaper may still look sharp, it may not be at its best anymore. Therefore, the best way to avoid this problem is to rely on the data provided by the manufacturer or the rental center and to estimate as accurately as possible the area you sanded with your abrasive. If in doubt, do not hesitate to replace it. It makes sense, then, to purchase a little more sandpaper than you need just in case, especially if the rental center allows you to return unused items. This will save you unnecessary travel in some situations. Remember that hitting a nail head or a small rock on the floor is enough to tear or ruin a sheet of sandpaper. So plan accordingly!
