Sanding a wood floor is a multi-step process.
That way you’ll get a heads-up on, and hopefully the knowledge to avoid, some of the problems you might encounter and some of the mistakes beginners make.
Knowledge is power. You’ve got this!
The 13 steps to sanding your floors:
Step 1: Determine your grit sequence.
You’ll sand your floor multiple times with multiple grits of sandpaper. You can also read our How to determine your grit sequence article.
Sand multiple times
Did you know that refinishing a floor means that you’ll sand over your floor multiple times?
Some first-time sanders believe that they’ll just use one grit of sandpaper and sand over their floors one time and, voila!, the floors will be clean, flat and smooth.
But the sad truth is that sanding is not like renting a Rug Doctor—it will take at least four passes, each with a progressively finer level of sandpaper, to truly refinish most old floors. And the hardest thing you’re going to do on the project is to determine the perfect grit starting pass for your floor. But we can help you figure it out.
Most people who have never sanded a floor before assume that every floor is sanded with the same grit sequence.
If we had a dollar for every customer who insisted that all floors only three grit passes we would have lots of dollars. But every floor is different and the condition of your floor will determine how you sand it.
And you can’t start sanding until you figure out the right starting grit.
Pete’s carries SEVEN different sanding grits for sanding floors, but not every floor needs all seven grits.
The more damaged your floor and the harder the wood species, the coarser your first grit pass will be.
Here is a rough guideline for what the various grits do:
12-grit (available for edgers only)
Starting grit for floors with heavy adhesive or multiple coats of floor paint.
Starting grit for floors with heavy shellac finishes or single layers of paint and sometimes for very old, hard maple floors (this is an unfortunate but common starting grit here in the Minneapolis/St. Paul MN area.
Starting grit for floors that still have finish or haven’t been sanded for 30 years or more. 24-grit is the recommended starting grit if there is sander flaw in the floor from previous sandings or obvious foot-soiled areas where old finishes have worn through to wood.
Starting grit for floors that are newly installed or have very minimal finish. Every trace of finish should be gone from your floor by the time you finish with this grit.
Never a starting grit – 60-grit takes out 36-grit scratch, but it does not remove wood or finish.
Takes out 60-grit scratch, but does not remove wood or finish –Final grit pass for most American hardwood floors.
Takes out 60- or 80-grit scratch. Final grit for birch and maple floors and any floor that will be stained.
Assess honestly, sand appropriately
The most common mistake we see in floors done by do-it-yourselfers is timid sanding: a floor that still looks dingy because it wasn’t sanded aggressively enough.
So, the more honest your assessment of the condition of your floor, the more willing you will to accept how much work it will take to renew your floor.
36grit is your testing grit
36-grit is your testing grit – it will help you determine the finest starting grit that will work for your floor
If you think your floor is in pretty good shape, put a 36-grit belt on the drum sander and sand a small test area, about 4’ x 4’ (pick an area of the floor that is in rough shape, not one of the spots that still looks good).
Stop the sander and carefully inspect the area you just sanded.
If that section of floor looks completely bare and clean, even at the edges of the boards, then you have successfully determined that the grit sequence for sanding your floor is 36-grit, 60-grit and 80-grit.
If the area you tested is not completely clean, then you have determined that your floor will need MORE than just that 36-60-80grit formula.
So, pick a new spot on the floor (again, preferably a spot in bad shape) and try a more aggressive test. For example, if the first test left just small amounts of finish at the very edges or centers of the boards, then your next test might be to cross-cut at 36grit followed by a straight pass at 36-grit (read our “Magical Exception of Cross-Cutting” below).
Look at your sanded test area. Is it bare and clean? If yes, then yay! You’ve determined that your sanding sequence is 36grit cross-cut, 36-grit straight, 60-grit and 80-grit.
Most floors in the Minneapolis/St. Paul area were installed prior to 1950 and will need a 24grit start when using a 110v sander.
Think your floor is in bad shape? Don’t bother with the 36grit test – begin testing with a 24-grit – 36-grit combination.
What if it fails that test? Keep testing with more aggressive combinations until you find one that gives you clean wood by the time you reach 36-grit.
Don’t bother testing 60-grit or 80-grit – they are not designed to remove finish or wood fiber. We already know that they will adequately remove scratch from 36-grit, so limit your testing to figuring out your starting point.
The magical exception of cross-cutting
If you have the reverse—a severely scarred, uneven, water-damaged or painted floor—then you may want to consider not only starting with a coarse grit, but sanding at an angle to the grain.
This is an important exception to the rule of always sanding with the grain of the wood. It only applies during the rough sand stage, but it is a very efficient way to speed the process of cleaning and leveling an old floor.
Because of wood’s natural tendency to shred and splinter when it is sanded off-grain, the sander can remove more wood with the same amount of effort when positioned at an angle. The angle does not need to be drastic; sanding just 10-15° off parallel is enough.
The downside of using this procedure is that, after you make an entire pass at an angle, you must follow it with another pass parallel to the grain at the same grit. So, if you do a 24-grit cross-cut pass, your sanding sequence would be 24 diagonal > 24 straight > 36 > 60 > 80.
Newly installed floors can be rough-sanded with 36-grit parallel to the grain.
The rule to remember is that, no matter what grit you choose as your starting point, you must sand, in order, with every grit that is finer than your starting point.
So, if you start with 16-grit, you cannot jump to 36grit; you must go 16 > 24 > 36 > 60 > 80 on both machines.
If you start at 24-grit, you cannot jump to 60; you must go 24 > 36 > 60 > 80 on both machines
Step 2: Sand all the main field areas with the drum sander using your pre-determined starting grit.
For each grit pass you make on your floor, you will begin with the drum sander. Make sure you read Working with Sanders and Edgers.
Don’t just sand one room at a time – sand everywhere the drum can reach in every room in your project.
If you’re sanding floors on two different storeys, do everything on the upper level first and then sand downstairs; you only want to haul those machines upstairs one time.
If you have the luxury of having two people on the project—one on the drum and one on the edger—do not use both machines in the same room at the same time!
This is a safety issue; it is much too easy to be focused on your machine and not see the cord of your partner’s edger.
It is better for the drum sander to go first, finish that grit in the first room and proceed to the second, and then let the edger begin, alone, in the first room once the drum sander has moved on.
Step 3: Use the edger (using the same grit you just used on the drum) to sand all the areas that the drum couldn’t reach.
For every grit you do, drum first and edge second. This is largely because the edger can sand out drum marks that you might leave during the transition at the wall edge.
In older homes, where there has been significant foot traffic in the main field of each room, but no wear at all around the perimeter, you may find that there is a whole lot more finish around the edge. So, don’t be distressed when you switch to the edger and use the grit that was working just fine in the middle of the floor and find it clogging up and glazing almost immediately.
Just drop down to the next coarser grit on the edger only. Move quickly and use that coarse grit to remove about half of the finish. Then continue with the grit you were supposed to use that matches the drum sander pass you just finished –now the condition of the edge area matches the condition of the field and you can proceed with your planned grit sequence.
Step 4: Sweep or vacuum all sanded rooms.
Every time you finish a grit you need to vacuum, or at least sweep all the surfaces you just sanded. This is because the pieces of sanding mineral fall off the abrasive and litter the floor after every grit pass.
Even though you may have moved on to a finer grit, those big, coarse particles from previous passes are still being driven into the floor by your drum and edger. Even under your fine paper, they continue to grind their 16-grit cat-scratch into the floor, and you will wonder where all those big, deep gouges are coming from.
Step 6: Sand all the areas that the drum couldn’t reach
Use the edger (using the same grit you just used on the drum) to sand all the areas that the drum couldn’t reach. Hopefully, this is self-explanatory by now.
Step 7: Repeat steps 4 through 6 until you have sanded the entire floor through 80-grit.
So, now you’ve established your pattern, it’s just a matter of sanding without skipping grits until you reach either 80- or 100-grit. 100-grit is the recommended finishing grit if you plan to stain your floors, or if you are sanding a maple floor.
In both those cases, particularly on the edger, you need to work harder to make sure that all evidence of your sanding is removed, which is easier to do when you can sand to a finer grit.
Why is maple different?
Maple is so hard and dense that any scratch left in the wood is held cleanly and crisply. Those crisp incisions make a snug little crevice for stain, or even natural finishes to accumulate.
Once you have pigment or product built up in that scratch, it becomes twice as visible, particularly the curved scratch from the edger. Sanding through 100-grit makes the scratches smaller which means they can’t hold as much color and are easier to camouflage.
As your floor gets progressively cleaner, it gets harder and harder to tell where the sanders have been. Remember, you’ll have at least TWO sanding passes (60-grit and 80-grit) where you will just be polishing out scratches – there will be no finish to serve as a tracer.
So, we recommend using a series of light pencil lines drawn directly on the floor before you begin 60-grit and again before you begin 80-grit. The drum sander will erase any pencil lines it touches and the lines that remain will show you exactly where you need to edge.
When all the pencil lines are gone, you’ll know you haven’t accidently skipped any areas of the floor with your big machines.
Step 8: Use a radiator edger to sand under all radiators or toe-kicks if you have them.
You’ll get a better blend with the cut from the drum sander and edger if you sand your radiators or under your toe-kicks after all the other sanding is done.
This also keeps your rental of that extra sander down to an absolute minimum.
Step 9: Scrape or sand all corners and around radiator feet or pipes.
Edgers are round, but rooms are square, so you’ll need to do something in the four corners of every room, closet or stair tread In your project. Carbide scrapers are great, but can be expensive. Carbon steel scrapers are cheap and work well, but you’ll have to keep sharpening (often once for every corner) because carbon steel dulls quickly when you’re scraping finish.
Multi-tools (like the Fein or Bosch) have small, triangular sanding heads that also work well. If you scrape your corners, sometimes you can leave them too smooth; take a folded piece of 80-grit sandpaper and lightly sand over where you’ve scraped to reopen the wood grain so it matches what you did with your other sanders.
Step 10: Examine perimeter of all rooms and remove any visible edger swirl by hand-sanding.
No matter how long you have been sanding floors, no matter how skilled you are with the edger, there will still be edger swirl left around the perimeter of your room, even after you finished sanding through 100-grit. And even if you didn’t skip any grits!
After you finish your final edger pass, you should inspect the entire perimeter of your project on hands and knees and with a flashlight if necessary to locate every last bit of visible sanding scratch from the edger. When you find it, remove it by hand-sanding with 80-grit.
Don’t be tempted to go get your palm sander!
A palm or orbital sander is more powerful than your hand and will so over-polish the floor that, while the swirls will be gone, the texture of that area will be much smoother and more closed than the areas that were done with either the drum or the edger.
These areas will not allow finish to absorb as easily or deeply and will have a distinctly different tone than the surrounding floor.
Step 11: Blend cuts
Use a pole sander or a buffer over the entire floor at 100- or 120-grit to blend the straight sanding cut from the drum with the circular sanding cut from the edger.
Do you know how, when you look at the outfield at a baseball game, they stripe the field just by mowing adjacent areas in different directions? Unfortunately you can get the same effect on your sanded floor, only it doesn’t look quite so cool.
The place where the straight scratch from the drum sander meets the circular scratch from the edger can show up as a line, just as distinct as one of those outfield mowing lines. And what’s worse, you won’t see it on the freshly sanded floor; it only becomes visible AFTER you’ve applied a coat of finish.
Once that coat of finish is down, it takes a lot of work to fix this problem, so the idea is to prevent it from happening in the first place. And prevention is easy, but it needs to happen just as you are at your most exhausted. But before you begin your final cleanup, you need to use a pole sander or a buffer to do one final, blend-sand over your entire floor.
Using 100- or 120-grit, you will put a shallow, but most importantly uniform scratch pattern over the entire floor. This will fool your finish into believing that only one machine left its mark on your floor and it will absorb uniformly into the wood and will look consistent and blotch-free everywhere.
Step 12: Vacuum the entire area thoroughly.
Vacuuming twice never hurts and usually helps.
Getting all the dust off is more important than we can ever say. Pay particular attention to the dust in the cracks between the boards and at the very edges of the room, especially the gap under the baseboards. Finish has a way of finding little hidden pockets of dust and pulling it up and spreading it along with your mop head.
Try not to use the plastic wand on your shop vac – it can leave plastic residue marks where it scrapes on the floor. Find a vacuum wand with strong, soft bristles.
Step 13: Remove remaining dust
Use a dry microfiber cloth or other clean, lint-free textile to remove all remaining dust from the floor.
Many people would use a commercial tack cloth for this step, but we don’t recommend it. Read “But the guy in the hardware store said…” about the danger of using tack cloths.
Pete’s Bonus Tips
You actually use 12-grit sandpaper on floors?
Most first-time sanders are horrified when they see the sheer aggression of the sandpapers we use for floor sanding. And many of them flat-out refuse to use anything coarser than a 36-grit sandpaper on their floors.
They're worried about taking off too much wood and ruining their floor.
Stop worrying. That floor is 3/4" thick. It was designed to undergo four or five complete refinishing events—removing 1/32nd" or 1/16th" of wood—in its lifetime. So those horrifyingly rough grits are necessary because wood is hard and old wood floors are scratched and damaged and usually still coated in some sort of low-melting-point finish.
Removing all that old finish and damaged wood requires big guns.
Don't worry; we promise to advise you on the best grit sequence to use and we won't let you grind your floor down to the nubbins!
Be careful when you remove carpet. Utility knives are the devil’s tool.
You can damage your floors just taking out the carpet! Never let your knife cut into the wood itself - it digs deeper than you think, and leaves cuts that are almost impossible to sand out. Instead, tear up enough carpet to fold over a section and cut on the fold.
80-grit as final grit?
80-grit seems way too coarse a grit for the final sand. In shop class, 80-grit is barely considered a medium grade of sandpaper. Shouldn't I be sanding my floors to at least 150-grit?
80-grit will be fine enough to remove all visible traces of all our other sanding passes, but it will also leave enough texture or "tooth" in the wood to give the finish coat a good surface to bond to. Remember we're sanding floors here, not making a fine piece of furniture.
Obviously you don't want to leave sander marks, but worrying about leaving a mirror-smooth finish is overkill.
You'll be putting so much finish on that floor that the actual texture of the wood fiber should not be detectable through it.
If I come to your house in the winter, I'll be bringing gritty particles in on my boots and I weigh more than the drum sander, so I'll be literally sanding your floor with every step. You better have a substantial, well-adhered coat of finish or I'll grind it right off!
Can I call for free advice, for free?
Yes and no.
We love educating people, but it's expensive. And we're uncomfortable taking questions about products you bought on Amazon.
So, calls are free and unlimited if you:
- bought product from Pete's
- are shopping in Pete's online shop and need help choosing between products
- currently have equipment rented from us and need advice
- are planning to rent from Pete's
But please use our cheap and splendid Help Hotline consulting service if you:
- bought a product we sell, but from a different supplier
- have a complex flooring problem you don't see addressed on the website
- have questions about products we don't carry
The rights and wrongs of drum sanding.
Incorrect drum sanding looks like this.
When you first start sanding an old floor, you can tell exactly where the sander has been and how effective your feathering technique is, just by looking at your sander mark.
The photo above illustrates what happens when you are using the drum sander incorrectly – you can tell that the drum was still touching the floor when the sander stopped at the wall to change direction.
Correct drum sanding looks like this.
But in this photo, it is clear that the operator was smoothly lifting the drum off the floor as she prepared to stop at the wall to change direction.
The photo also shows that the drum was correctly feathered onto the floor as she began her backward pass.
Learn on the equipment you rent.
Pete’s is the only shop that offers a free, hands-on, personal lesson (though in this time of Covid, we require that you schedule all lessons in advance - no walk-in lessons) with every equipment rental.
Our lesson is not just reviewing the low-budget training video that came with the sander, no.
Available only at Pete's storefront in the Minneapolis/St. Paul area, this training takes place on a real hardwood floor with the actual machine you are renting. Taught by an actual hardwood flooring contractor, it will address the particular floor project that you are facing. Bring photos of your project.