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Sanding Old Floors

What's the best machine for safely bringing old hardwood back to life?

Ask This Old House Crew
Photo by Matt Kalinowski

In the process of remodeling my house, built in 1904, I uncovered Douglas fir flooring that appears to be in good shape after being hidden for nearly 40 years under red shag carpeting. But I have received conflicting advice about how to refinish the floors. One contractor told me to rent a commercial floor sander, then finish with a rotary sander. Another contractor said the big machine has a tendency to damage a floor, so I should work only with the rotary sander. What do you think?
— Marty, Colfax, CA


Tom Silva replies: Why would you want to get rid of red shag? It's a great conversation starter. Seriously, I bet the Doug fir will be beautiful. Flooring that old is bound to have tighter grain than anything that's affordable these days. But if you have a whole room to refinish, the fastest way to tackle this is with a commercial floor sander, often called a drum sander. These high-powered sanders, widely available at rental centers, are also quick to destroy a wood floor, particularly one as soft as fir. So be very careful — or turn the job over to a professional.
Or, Instead of a drum sander, rent a disk sander, a relatively new type of floor sander with four separate sanding heads. It's not as aggressive as a drum sander and so takes longer to get the job done, but that makes it more forgiving of inexperienced operators, particularly when a floor is uneven. The homeowner of the Salem, Mass., TOH TV project used this kind of machine on his old pine plank floors, and they came out looking great.
I suspect the rotary sander you refer to is actually a floor buffing machine, a single head fitted with an abrasive screen. A "screening,"as it's called, is much too slow to remove a finish. It's for smoothing bare wood, or roughing up the finish on slightly worn floors before applying a new coat of finish.
For an overview of what's involved in refinishing a floor, see Refinishing School, or check the Web site of the Wood Flooring Manufacturers Association (


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