Old House, New Floor: Sanding A New Hardwood Floor With A Rental Drum Sander

By Bruce W. Maki, Editor

Of all the steps in hardwood floor installation, sanding is by far the least favorite, and not because it's boring. I can't imagine doing this for a living, but some people do it.

I should note that the rental floor sanders are very noisy and hearing protection should be worn, as well as dust masks.

The beginning of the sanding ordeal, I mean... project.

Note the fan in the window. We found that by blowing the air out we could expel almost all of the dust that the sanders didn't catch with their dust bags.

We covered the ceiling fan with an old bed sheet to keep the sanding dust off.

This is The Beast: The Silver Line drum sander. The first time we installed a floor, in a second-story bedroom, my back ached for days from carrying this monster up the stairs. And that was with a helper.

 

And this is The Battle: What looks like a gap between two boards is actually a difference in height of about 1/32" (about 1 mm).

The Brute Force Starts Here:

As with any sanding task, the first sanding is done with the coarsest sandpaper, in this case 20 grit.

If you've ever used one of these machines, you can see we are cheating. The dust bags are inflated when in use, not limp. We just posed with the machine turned off because it was easier to communicate that way.

The initial step in sanding a new floor with uneven board heights is to sand at a 45 degree angle to the grain.   In the photo at right you can see some diagonal scratches. This shot was taken after just a few passes, and the height difference is still clearly visible.

It can take quite a few passes of the sander to remove these small peaks. The diagonal sanding was by far the longest procedure. The precision of the tongue-and-groove milling will determine how much of this sanding is required.

There is a pattern that must be followed with drum sanders: successive passes working from right to left. The sanding drum is tapered slightly, and it cuts deeper on the left (where the diameter is larger) and the right side feathers out the deeper scratches. For this reason the right-to-left pattern must be followed. The commonly recommended method is to advance 2 to 4 inches each pass.

If you think about it, 2 inches of advancing each pass isn't very much. The work progresses very slowly. This is just plain old labor, and tedious labor at that. 

To make matters worse, we found that the only way to make serious progress was to lift up on the handle as the sander was pulled backwards. This takes weight off the back rollers and puts more weight on the drum (you can hear the motor working harder). But this puts a lot of strain on the forearms. My arms ached for days afterwards.

Some people recommend pushing and pulling the sander. We would let the sander pull itself forward, until it bumped the wall, and then pull it back. On the forward stroke the machine was barely pressing down, but on the back stroke we would lift up to apply pressure. This allows a brief moment to rest one's muscles.

After going over the floor the first time, we found many high spots, so we had to do another complete diagonal sanding.

After the diagonal sanding had removed all the height differences between the boards, we sanded the floor again using the coarsest sandpaper, 20 grit. This sanding must be continued until no more diagonal scratches are visible.

As the sander is dragged backwards, the operator eventually hits the wall with several feet of floor remaining. The approach is to work right-to-left across the room, then turn around and sand the missed section, from right to left, back to the starting point.

A fundamental problem of this unavoidable approach is that when the sander is stopped, it digs into the floor slightly. So in the middle of the room we had a sea of slight waves. These can barely be seen... until the floor is finished with a coat of urethane. Then the waves show up great.

Changing The Sandpaper:

Changing the sandpaper on the Silver Line drum sander is kind of a pain in the neck. The front housing tilts up to provide access to the drum.

The drum is rotated until the seam in the paper is up front. Of course, unplugging the sander is critical. If this machine were to accidentally start, it will sand your fingers down to little tiny stubs.

We used a pair of wrenches to turn the clamping devices.

On the front of the machine, above the rubber bumper, there is a long tray, which looks sort of like that map pocket on the door of your big 'ol SUV.  This is used as a folding guide, to make the proper end fold in the sandpaper sheets so they fit into the drum just right.

These are not the ordinary 9" x 11" sandpaper sheets that you buy at your local hardware store. They are specifically made for floor sanders, and all rental shops should have a supply of sheets that they will sell you. Our shop sent us home with a couple of each grit, and they gave us a refund for the sheets we didn't use. 

Which brings up an important point: There is a good chance that a sheet will get ripped during sanding, so having extra sheets on hand is a good idea. In our case, the house is 15 miles out in the country, and we did this job starting on a Friday afternoon and wrapping up on Saturday morning. It would be a real disaster to have the sandpaper rip into shreds just after the rental shop closed. So we got extras of all the grits: 20, 36, 60, 80 and 100.

To install the new sheet, one end was placed into the slot and the drum turned by hand to wrap the sheet around.

The other end was pushed into the slot.

That shiny metal piece with the arrow... that is the end of the clamping device. There is another one on the opposite side of the drum. When those square shafts are turned in the direction of the arrows, they pull the paper into the drum.

A wrench is used to tighten the clamping mechanisms. I believe it required a 1/2" wrench. Sometimes we were able to tighten the paper by turning one clamp at a time, sometimes we had to turn both simultaneously.

We did have some difficulty getting the paper installed tight. It often took several attempts, and sometimes the paper would be loose on one end of the drum, which I figured would lead to premature ripping.

Cleaning Up The Perimeter: 

After sanding with two grades of sandpaper, it was quite evident where the drum sander's work ended... a very distinct line about 4 inches from the wall.

The power edge sander is necessary to sand down this edge strip. This tool is basically a very beefy 7 inch disc sander, and the same grits as the drum sander are used. We found that a circular looping motion worked better than simply running the machine along the wall.

We used the edger for the entire closet, because the boards were oriented the wrong way for the drum sander. Sanding the closet didn't take very long.

We developed a routine, one of us running the drum sander, and the other going around the room with the edge sander. Luckily the room had outlets on two separate circuits, because each of these machines has a motor rated at 15 amps.

Many motors rarely draw their rated current, but the drum sander does. Several times when I started the machine it tripped the 15 amp circuit breaker. I found that I could roll the drum a little by hand and try starting again, and it would work just fine, after I reset the breaker. 

Some Thoughts On This Puzzling Behavior:
Humans Voluntarily Sanding Floors

This was the only the second time we have used the rental floor sanders. I didn't really remember anything negative about floor sanding until we started this second room. And then it all came back to me. This is really a form of punishment. This is not a hobby... nobody would do this if they knew what they were getting themselves into.

Or maybe I'm just not a big enough guy. I'll admit I'm smaller than the average bear, maybe smaller than the average adult male too, at only 165 pounds. The drum sander is certainly made for a much larger species. Maybe it is intended for the Cro Magnons among us, or maybe some people have trained gorillas to run these drum sanders.

After running the drum sander for about 8 hours, I went to bed sore and tired. The next morning I ached all over. I should have followed the advice on the TV commercial: Take some Advil and use those stiff aching muscles.

By noon on Saturday I was ready to return the beast to the rental shop. We stopped sanding at 80 grit. We never touched the 100 grit paper. There were still some high spots around the door that were hard to reach with the edge sander. We had left the door in place to keep the dust out of the rest of the house, which worked well.

Saved By... The Inexpensive Power Tool

Owning a 5 inch random orbital sander, I figured I could use this tool to touch up some problems areas. The 5 holes in the disc allow the sander to pick up much of the dust.

There were several problem areas:

• The wave zone in the middle of the room, caused by stopping the sander momentarily to reverse directions.
• The edges. The power edger does a poor job of blending in with the drum sander's work. The result is a definite hump a few inches from the wall, all around the room.
• The corners. The 7 inch disc cannot get close to the corners.
• The area around the door that was hard to reach with the power edger.

The 5 inch random orbit sander solved all of these problems. I started by purchasing a large quantity of 60 grit hook-and-loop (a.k.a. Velcro) discs, as well as some 100 and 150 grit discs.

I began with 60 grit, which meant that our earlier 80 grit sanding was essentially wasted.

• For the wave zone, I sanded in large blocks, about 2 feet square. I ran the sander over and over, side-to-side and up-and-down, randomly and in uniform patterns. Since the small sander can be run with one hand, I could feel the floor with my other hand. After about an hour of sanding I had the wave zone pretty much flattened out.
• Along the edges I ran the orbital sander in loops and circles, feeling the smoothness as I progressed. In about an hour I was able to vastly improve on the results of Cro-Mag rental tools.
• While sanding the edges I spent a few minutes getting into each corner. Since the random orbit sander is round, it too cannot get all the way into the corner. But it made a big improvement over the power edger. The remaining high spots in the corners can be scraped out with a chisel or paint scraper, and hand-sanded smooth.
• The high spot around the hinged side of the door. For this I removed the door (the fan drew the air into the bedroom, keeping almost all of the dust from the dining room) and attacked the hump. At first I thought it would take an hour for this hump, because it felt like it was 1/4" high. But after maybe fifteen minutes I had the hump evened out.

So this little $60 Porter-Cable random orbit sander ended up being the hero of the story. Sort of a "David fixes Goliath's shortcomings" tale. This tool is worth it's weight in gold. Porter-Cable deserves a "Golden Hammer Award" for their fine product.

Then I went over the entire floor with 100 grit sandpaper. I was considering doing a pass with 150 grit, but decided that would be overkill. For fine furniture, yes. For a floor, no.

I read recently in The Journal Of Light Construction about a large 4-head random orbital floor sander that costs about $3,000. Of course, do-it-yourselfers aren't going to buy such machines, but tool rental shops would. This machine might be just the ticket it you can find it. But I have to wonder if it can handle the boards with the height differences?

I would describe the rental drum sander and power edger as the Brute Force And Ignorance approach to flooring. I guess it really is a statement to the lack of precision that is standard in the flooring industry. But then, we bought our flooring from a small local sawmill. What can anybody expect? When dealing with wood, precision is hard to achieve.

Or is it?

In the past two years I have installed three rooms of pre-finished flooring, some normal 3/4" thick, some thin 3/8" thick. This material is just like installing normal flooring, but when the boards are installed the floor is done. It really hastens the pace of a project.

Most pre-finished hardwood flooring has a coating of aluminum oxide, which is the same material that most sandpaper is made from. These floors resist scratching very well, but they are still prone to denting and water damage. One possible drawback is that when it comes time to refinish the floor, you can't simply sand down the surface because the coating is just as hard as the sandpaper. Supposedly there are special chemicals available that soften the aluminum oxide coating and allow for refinishing, presumably with a conventional urethane.

Was all this labor worth it?

Continue To: Finishing A Hardwood Floor With Urethane

Additional Reading:

Floor Sanding, by Don Bollinger, Fine Homebuilding's Builder's Library series, Taunton Press.
Originally published in Fine Homebuilding magazine, April 1983

Wood Flooring Web Links

Copyright © 2001, 2005  HammerZone.com

Written September 7, 2001
Revised January 11, 2005