How to Sand A Subfloor


The world of floor sanding can be a very discouraging world for the following reasons:

*It’s a dusty job.

*It’s a loud job.

*It’s a job that requires you to move furniture.

*It’s a job that requires skill.

*If you do not have skills, you could wind up ruining your floors.

*People groan (loudly) when you tell them that you will be sanding floors.

Nevertheless, if you are stubborn and diligent, then none of the above will matter because you are sick and TIRED of having nasty floors and are ready to have BREATHTAKING floors.

For crying out loud.

As eager as I was to get started, however, I did a little online research first.  Unfortunately, there was a disappointing amount of information on floor sanding and most of it was of poor quality: written instructions were not accompanied by photos, videos had poor sound quality, etc.

In the end, Dave and I stepped out on faith and survived the project with such surprisingly good results that I have assembled my own step-by-step floor sanding tutorial:

How to Sand Your Floors Using A Drum Sander

1. Remove all current flooring. 

Warning: Carpet rolls are HEAVY!!

We cut our carpet into thirds with a razor blade before rolling it up.  This made carpet removal a breeze.

Removing our carpet and padding was easy.

Removing our linoleum, however, was a big pain in the arse…and the arms…and the back…

…and the wrists…and the fingers..

…and I think you get the picture.

What was worse, our nasty linoleum left large patches of nasty paper backing which had to be scraped up.  Ugh!

2. Take Time to Create As Smooth A Floor Surface As Possible

The occasional paint splotch is permissible, but scrape away any globs of plaster, carpet padding, etc.  Also remove any bent nails, carpet tack stripping, etc.  Fill nail holes and cracks with wood putty.

If your floorboards are uneven, you might need to use a leveling compound.  When using a floor leveling compound, apply in thin layers and allow to dry thoroughly.  Otherwise, the compound will crack.  (Spoken from experience!)

Finally and MOST importantly, hammer down any loose or raised nails.

Using a nail set will allow you to hammer nails below the surface of the wood.

3. Cover/Seal All Ceiling Fans, Fixtures, Vents, Electrical Outlets

These are the LAST places you want sawdust flying into!

Also, while you sand,  open every window!

4. Determine Which Sander You Will Need

Visit this useful website to learn about all the types of sanders and their purposes.

In the end, we decided that a drum sander would best meet our needs.  You can rent drum sanders from local hardware shops or equipment rental shops.  Lowe’s did not offer drum sanders for rent so we went with a local business called Templeton’s.

5. Determine The Grit Of Sandpaper You Will Need

Another mystifying aspect of floor sanding for me was the sand paper.  Which grits did I need?  Where would I find this paper?  How much would I need?

Fortunately, Templeton’s carried the sandpaper we needed and had a buy-back policy for any leftover and undamaged paper we didn’t use.

As for the sandpaper itself, the lower the number, the coarser the grit.  Most rental places offer grits from 20 to 100 with 20 being the coarsest and best for removing tough finishes first and 100 being softer and best for buffing last.

Pre-stained hardwood floors typically require at least 4 descending grit sizes, but since we were only sanding unfinished plywood, we just used 40 and 60-grit sandpapers.

6. Gear Up

Protecting your eyes, ears and lungs is NOT a step you want to skip, either.  (Spoken from a minimalist who usually goes without goggles, masks and earplugs on other projects.)

7. Sanding Your Floors

For those of you wishing to stain your floors, you will need to make sure that you follow the grain of the wood with the sander.

For those of you who are painting your floors, it doesn’t matter (as much) which direction you move in.  (Nevertheless, for efficiency’s sake, I moved in a methodical down-left-back direction.)

Turn the machine on, and slowly lower the drum to the floor.  If you lower it too quickly, the drum will bounce against the floor causing “waves” in the wood.

I must admit, I allowed the machine to bounce a few times, but our sandpaper wasn’t coarse enough to make much of a difference.

But still, don’t go crazy!

The machine will naturally pull you forward at a quick rate.  Control the speed by steadily holding the bars.

Walk behind the machine using small, quick steps…almost like you were a member of a marching band.  (Minus the tuba and dorky outfit, of course.)

It is okay to allow the machine to bump into the wall, but once it does so, IMMEDIATELY pull the drum up. Otherwise, the drum will keep running in that same place and sand a dip into your wood!

Some machines I saw online had special gears on the handle bar that lifted the drum up and down.  Thankfully, our sander had no such complications; if we wanted to move the drum off the floor, all we had to do was tilt the machine back.

Our sander also allowed us to pull the machine back and sand in a backwards direction:

8. Vacuum Between Grit Sizes

Once again, this is a step you do not want to skip.  If you do not vacuum the sawdust up (we used a shop vac) between each sanding, the dust will clog the paper preventing the floor from being properly and efficiently sanded.  Excess sawdust means you will also have to change the sandpaper more frequently and more sandpaper used = more money spent!

So vacuum already!

Oops!  Guess I missed a nail!  Time to change the paper!

9. Changing The Sandpaper

Eventually, the paper in the dadgum machine will need to be changed.

But no worries, life could be worse.  🙂

How often do you need to change the sandpaper?

The answer to this question depends on the surface.  Overall, we sanded roughly 1300 square feet and only needed 5 sheets of 40-grit and 5 sheets of 60-grit.  Halfway through a room, I would turn the machine off and touch the sandpaper to determine how rough it was.  The floor leveling compound that I used had a tendency to clog the sandpaper very quickly, but, luckily, there weren’t too many leveled places to sand.

Okay, let’s change the paper!

First, make sure machine is unplugged!  Then, flip machine all the way onto its back.

Locate the slot at the top of the sander and slide in a sheet of sandpaper with the grit facing away from you.

Pull the paper taught towards you…

…to create a sharp right angle:

Lift the metal flap that covers the drum…

…rotate the drum until you find the gap…

…and loosen the left bolt to open the gap.

Remove the old paper…

…and slip one tab of the new sandpaper into the slot:

Tightly roll the paper around the drum…

…and tuck in the second flap.

Make sure the paper is tight and snug in the slot before tightening the bolt.

If you cannot get the bolt to tighten any further, you are ready to rock n’ roll!

If the bolt will NOT tighten, check the paper for gaping.  You don’t want to see ANY gaps between the paper and the drum.  Otherwise, the paper will rip when you start to sand.

If there are no gaps and you STILL cannot tighten the bolt scream into a paper bag, and then find a piece of thick cardstock or cardboard, loosen the bolt, and wedge the paper into the slot.  This may take some shimmying, but in the end that bolt will get tight!

Now you are ready to resume sanding!

10. Conclusion

Overall, floor sanding turned out to be a not-so-bad project.  It helped that most of our rooms were bare of furniture and decorations to begin with.

The actual sanding went pretty quickly, and we were able to knock out about 1300 square feet in 8 hours!  Not too shabby!

Of course, as with any painting job, the majority of the work is in the prep work.  Prepping the floors took me a good 2 weeks.  Bleh!

Our next step is to sand the edges of the floor that the sander could not reach, as well as the two staircases.

In the meantime, the progress we are making on this project is exhilarating, and the incentive of seeing the final product spurs us ever forward!

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8 thoughts on “How to Sand A Subfloor

  1. Very nice! It brings back my memories if “floor sanding” and staining…I am almost tempted to find out what’s under my linoleum in the kitchen. If we find wood we might paint the floors too!!!!! ;D
    Great job y’all!

  2. I did the same thing in my house (pre move-in) with the help of my parents. You can see my posts about it here: http://heathert.blogspot.com/2010/05/floors-part-1.html and here: http://heathert.blogspot.com/2010/05/floors-part-two.html

    It was definitely a dirty, dusty, messy, time-consuming job, but I am in LOVE with my floors. And I’m so proud that I tackled them myself, instead of spending $2K and up to have them done. It’s been about 15 months since I did that, methinks it’s time to pull up all the crappy tile in my kitchen and hallway and uncover (hopefully) more beautiful wood floors.

    Great job on your step-by-step. I actually found this one that helped me tremendously (including info on staining): http://www.russetstreetreno.com/2010/03/refinishing-upstairs-hardwoods.html

    • I felt so empowered the minute I realized I didn’t have to spend a fortune on floors, too! I will totally look at your results! 🙂

  3. Pingback: Floor Painting Update: We’re ALMOST THERE!! « Tales of a Clyde Woman

  4. Pingback: Tackling the Small Stuff |

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