When it comes to sanding a hardwood floor, grit sequence is everything.
You want to start with a more abrasive grit and then use successively finer grits. The first grit is meant to take off any finish, the next is to smooth out the pattern of the first grit, and the final grit is meant to smooth out any remaining sander marks and provide the finishing touches.
If you pick the wrong sequence for your sander, you won’t achieve a smooth transition between one grit and another. Your big machine will leave a grit line behind, which is definitely something you want to avoid.
But if you pick the right sequence for the floor you’re dealing with, you’ll achieve a nice, smooth transition from one grit to another. The floor will accept the finish evenly and look great.
Sometimes it takes more than just three grits to achieve a smoothly sanded floor. But if you choose the correct sanding sequence, most floors just need three passes with the big machine to acquire a smooth finish. Click here to browse our selection of sanding abrasives.
How do you choose the correct sanding sequence? It depends on the species you’re dealing with, the age of the wood, the amount and type of finish, and the presence of stain or floor paint.
Available grits and when to use them
12-16-20-24: very coarse
120-150: extra fine
12 grit: This is one of the coarsest grits available. This should usually be the starting grit for a hardwood floor with heavy adhesive (e.g. a floor that was underneath carpet) or several coats of paint.
16 grit: Use as the starting grit for floors with shellac finishes, single layers of paint, or some very hard floors, like maple.
20 grit: Use when there is a good deal of flattening of the floor needed. You will remove a lot of wood stock even when sanding the hardest of wood floor species.
24 grit: Use 24-grit sandpaper if there are sander flaws (e.g. swirl marks) in the wood, or if the finish has worn down to the wood in certain areas. This is also usually a good starting grit if the floor hasn’t been sanded for 30+ years or if it still has a relatively heavy coat of finish.
36 grit: A good starting grit for newly installed floors or floors without finish but have a lot of over wood. This grit should remove all over wood and make the floor flat.
60 grit: Not intended to be used as a starting grit. This grit takes out the scratch from 36-grit sandpaper, but does not remove much wood .
80 grit: Takes out the scratch from 60-grit sandpaper. This is usually the final grit for most standard hardwood floors.
100 grit: Takes out 60 or 80 grit scratch. This is usually the final grit for maple, birch, or other particularly hard woods, and for any floor that you would like to stain.
150 grit: Extremely fine sandpaper. Can take out the scratch from 120-grit or 100-grit sandpaper if necessary.
Note that there are other grits available, including 30, 40, 50, and 120.
Remember to sweep and clean the floor before you start sanding AND in between each grit. This will ensure the smoothest results possible.
Deciding on a sequence
When sanding a new floor, you’ll often want to define the finest grade you want to use and then work backwards, skipping a grade of grit between each sanding. For example, if you’d like the finish grit to be 80, your sequence can be 36-50-80.
If the floor is old, very hard, or has residual finish, it can be a bit trickier to determine the right sequence. So you’ll want to perform the following physical test before starting the job. Make sure to do this in an inconspicuous location.
If the floor is in good shape, start with the most common sequence, which is 40-60-100. Start with a 40-grit cut and see if the section of the floor is completely bare and flat after your pass. If it is, that means that you can sand the floor with the 40-60-100 sequence. If it’s not completely bare and flat, try progressively more aggressive cuts in different inconspicuous areas of the floor until you find the cut that leaves it bare and clean.
If the floor is in bad shape, you will probably want to start with a 30 or 24-grit cut for the first test cut.
Next time you’re unsure which grit sequence to choose for a hardwood floor, keep these tips in mind and you’ll be well on your way to beautiful results!
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