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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 900 sq. ft. 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.

FIRST How big is your job? Measure the rooms and get the actual square footage. A 500 square foot 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 500 square feet in a big living room is easier to sand than 500 square feet in three bedrooms, three closets and a hall. The more edges a job has, the longer and harder it will be to sand.


example 3 of not recoatableSECOND 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 at right is an example of exactly what you should be worried about.


cuppingTHIRD 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. Minnesota's 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.


bad floor smallcrosscut flawFOURTH 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.


FIFTH Old adhesive? Paint? Water stains? They'll take more time and more abrasive than you think.


SIXTH  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. 


overwood - worst everSEVENTH  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.


EIGHTH   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.


pet stain 2AND FINALLY Pet stains? Fuggeddaboutit. 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 thoughts here) 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.

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 that 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.

pet stain 1Accept 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.

Have you decided to move forward with your project? Click over to Floor sanding 101 for the next stage of instruction.