Yes. When you want to stain or change the color of your hardwood floors, you MUST fully sand and refinish the floors. If you don’t sand the floors first, the stain won’t properly penetrate the hardwood nor will the polyurethane properly adhere.
This is the ONLY way to change the color of your hardwood floors. If you attempt to add stain on top of floor without sanding it, expect it to peel off. The floors need to be sanded 3 times, with finer and finer grits, so that all polyurethane and all stain is removed. You must be starting with fresh (or raw) hardwood floors. This process opens up the pores so that the stain will penetrate…and penetrate evenly.
The sanding process will also remove all oils and waxes on your floor (including residual waxes from cleaning products, oils from your feet, etc.). All of these items will also prevent both stain and poly from properly penetrating as they clog up the pores.
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Do I need to sand hardwood before applying polyurethane?
Many people wonder if there is a simpler (and less expensive) way to refinish the floors. And, the answer is yes…sometimes…it depends. If your floors are in good condition, you have the option to do a screen and recoat.
A screen and recoat is when you buff the floors and add a coat of polyurethane. Note that you can’t just add the poly on top…you need to do a light screening (or buffing) on the floors). Some people call buffing a light sanding, but technically it is just scuffing up the top layer of polyurethane (in the same way you might buff your finger nails).
This buffing both cleans the surface and allow the polyurethane to stick on better. Without it, the polyurethane will not adhere properly.
A screen and recoat is really a preventative maintenance step and is not meant for floors that are really beat up. The polyurethane will not change the color. So, if you have scratched through the color or if you have sections of the floor where the poly has worn off (and you can see gray or black sections), it’s too late. You will still have those gray and/or black scratches after the screen and recoat.
And, importantly, if you have ever waxed the floors, or used cleaners that have waxes or oils in there, a screen and recoat won’t work as the poly won’t adhere. If you’ve ever used a product that promises to add shine or restore the sheen in your floors, then you’ve used one of these products and you will need to do a full sanding if you want to improve your floors. A screening just won’t work in these circumstances. (By the way, the cleaner I always recommend for hardwood is Bona and you can buy it here.
Related article: What is a screen and recoat?
Do you need to buff between coats of polyurethane?
Buffing smooths the poly out, and roughs it up a bit so that the next layer of polyurethane will adhere better. Buffing also eliminates (or at least camouflages) sanding flaws such as brush strokes, bubbles, rough spots. It’s especially important with water borne polyurethane as it’s a bit thinner.
Water borne polyurethane is more challenging to apply, especially for Do-it-yourselfers, handymen and less experienced refinishers as it’s less forgiving. If you are planning to use water based poly, it’s even more important to hire a professional.
Usually, you would buff between the 1st and 2nd coat of poly and 2nd and 3rd coats.
Screen and recoat video
This video from Ken Fisher shows you how to do a screen and recoat. This is what you would do if you are doing a simple screening to maintain and protect your hardwood floors. It can also be used when you are buffing the floors between coats of poly.
Determine the condition of your floors first and your objective before you choose your method. Many people search for short cuts and ways to save money, but sometimes this is a big mistake. If you want to change the color of your floors, you need a full sand and refinish. If you are happy with the color of your hardwood and they are in good condition, a screen and recoat is a great option to maintain and protect your floors. But be honest with yourself (and your floors); if they are too worn down, a screen and recoat will not do much for you. It’s like putting lipstick on a pig. It will only slightly improve the look of your floors and won’t last that long.
Related polyurethane and sanding articles:
- What is a screen and recoat? When does it make sense to do screening?
- Best brands of polyurethane?
- Which brands of poly do not turn yellow
- Can you change the color of your hardwood floors?
- Hardwood flooring trends
- Review of Loba WS 2K Supra Waterborne Polyurethane
4 thoughts on “Do I Need to Sand Hardwood Floors Before Applying Stain or Polyurethane?”
What do waxes and cleaners that add sheen do to the polyurethane? Do they break it down somehow?
So, if you are refinishing a floor, you need to sand in order for the wood to absorb the stain? I always thought sanding was mainly to remove the previous stain.
How many years of use do you get from hardwood floors that have been properly sanded, stained and have 3 layers of polyurethane? Particularly if you treat them kindly.
Margaret -When you floors have been sanded properly and you use a high grade polyurethane they will typically be good for 7 to 10 years. For people that take outstanding care of their floors, including removing shoes, I have seen them last as long as 15 years, but for a typical household, usually it’s 7 to 10 years.