Here are 9 tips you must read before sanding your hardwood floor.

There are some hardwood jobs that you just shouldn’t do yourself.

Of course we think you’re capable, but success depends on understanding the full scope of your job.

Sanding projects are not all the same! The size and condition of the floor and the orientation of the rooms really do make a difference.

Use the following list to evaluate your floor before you sand your floors.

Having just one or two of these conditions shouldn’t scare you away from the project, but if you have 900sqft of shellac-covered, water-damaged 1915 maple that also has old sander flaw in it, we urge you to seek professional help. Or, at least eat a really big breakfast.

Smiling customer sits cross-legged on old unfinished wood floor
Tip 1: How big is your job?

Measure the rooms and get the actual square footage. A 500sqft job is about as about as big as a first-time do-it-yourselfer, working alone, can possibly expect to sand in one weekend.

Keep in mind that 500sqft in a big living room is easier to sand than 500sqft in three bedrooms, three closets and a hall. The more edges a job has, the longer and harder it will be to sand.

High gloss dark wood floor with bad stain
Tip 2: The more finish that is left on a floor, the more work it will take you to remove it.

When customers tell us that they’re floors are in “pretty good shape” this usually means that there is significant product left on the floor. Unfortunately, this makes your job harder, not easier!

Floors with shellac or still-thick layers of wax can be especially challenging. The photo above is an example of exactly what you should be worried about.

Wood floor with uneven finish shows cupping after sanding
Tip 3: The longer it has been since the floor was last sanded, the more distorted the boards will be.

The more distorted the boards, the more work it will take to get them flat and level. Pete’s is located in Minnesota, and seasonal changes are especially tough on hardwood and any floor that hasn’t been sanded in 20 years or more will have significant areas that are cupped, crowned or simply skewed.

And while you think you don’t care if the floor is really flat, you actually do because you can’t get the floor really clean until you get it flat. This photo shows cupping that was revealed by sanding.

Maple wood floor shows dark lines from inexperienced drum sanding
Tip 4: Have you inherited sander flaw from somebody else’s well-intentioned but horrifying refinishing job?

You don’t want those left in your floor, but it will take additional time and effort to make them go away. Sanding this floor revealed damage from drum marks.

Hardwood floors damaged coated with adhesive and paint
Tip 5: Old adhesive? Paint? Water stains?

They’ll take more time and more abrasive than you think.

Sanded maple wood floor
Tip 6: Do you have a maple floor in a house that was built before 1920?

Maple is hard to begin with, but older growth maple is particularly dense and mineralized and it will take a lot of grinding to get through it.

Closeup of wood floor boards with uneven height, overwood is the thickness of a penny
Tip 7: Overwood?

Sanding is the only way to level out all the the highs and lows of each individual board, but sometimes that lippage is enormous. More wood means more grinding time.

The floor in this photo—which is easily the worst we have ever seen—took seven passes and five different grits to finally become level again.

Hand holding 3M Lead Check to test for lead paint on old window
Tip 8: Check for lead in homes built before 1978.

If your home was built prior to 1978 you should test your finish for lead. If the test is positive, strongly consider hiring a lead-certified professional to sand your home (all floor refinishers have been required to carry this certification since 2005 – but always check before you hire).

Homeowners are not legally required to follow lead-safe practices when they sand, even when lead is present, but sanding will spread enough lead throughout your home to permanently harm your children.

When in doubt about lead, don’t sand it yourself.

Read this helpful brochure from the EPA.

Dark cat urine stains on hardwood floors
Tip 9: Pet stains? Fuggedaboutit. They don’t sand out and bleaching is an unpredictable, last ditch alternative.

If you are willing to go through the headache of staining your floor (and staining is never a cakewalk; read our Let me talk you out of staining your floors info) and are willing to stain to a dark ebony, this can make the dark pet-damaged areas less noticeable.

Unless the black stains are concentrated in a small area that you can patch, think about getting a new floor.

You can also read Pete’s Cat pee and dog toenails: Are pets always a deal-breaker for hardwood floors?

Learn more about pet stains

The old finishes, waxes, gouges, cupping and overwood pictured above must all be removed completely in order to rejuvenate a floor.

Of course you’ll be removing all that old, ugly finish, but understand that old finish is embedded in the wood of your floor, so you can’t avoid removing the top layer of wood when you sand off unwanted finish. But this is how newly refinished hardwood floors are born!

We get customers all the time who speak of a “light sanding” – they seem to believe that you can remove old coatings without touching the wood itself. This is impossible and would leave a lot of ugly floor behind.

Accept that you will be removing at least 1/16th of an inch from your floor, plus whatever nastiness is on top of the wood.

Understand and embrace the full scale of how much old finish AND damaged wood must be removed from your floor before you begin and you will do a much better job overall.

pet stain 2

Have you decided to move forward with your project?

Click over to Pete’s Hardwood Floor Techniques 101 for the next stage of instruction.

Pete’s Bonus Tips

Wood floor with long utility knife scraches

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.

If you are in the Minneapolis/St. Paul area, we rent sanders for your projects, and will give you a free lesson on the equipment at our storefront.

Badly stained wood floor with prominent dark marks

A stain catastrophe?

Our website is like a lightning rod for citizens all around the country with flooring problems. Unfortunately, most people come to us after the catastrophe has happened.

Ray from Pittsburgh, who very generously allowed us to use this photo, wrote to ask advice about his staining "disaster" (his word, not ours). His photo illustrates why we have such disdain for stain manufacturers who make it sound easy to stain wood floors.

This is a vivid illustration of how important it is that the texture of your wood floor be absolutely uniform and consistent before you apply your stain.

This floor was sanded correctly, but was aggressively mopped with water against the grain, probably in an attempt to remove all the dust.

The scrubbing motion, combined with the water, left irregular lap lines that trapped stain in that same irregular pattern. The takeaway here is to never use liquids to remove dust from a freshly sanded raw floor! Vacuum, then use a dry microfiber cloth to wipe up the dust the vacuum couldn't get. Yes, it will take a little longer, but you won't risk problems like the one poor Ray had.

Side note: If you are deliberately wetting your floor to water-pop it prior to stain or Rubio to intensify your color (read our water-popping philosophy) make sure you wipe with the grain.

Or better still, use a pesticide sprayer to mist the water evenly and uniformly over the floor.

Woman showing how to use a floor sander

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.