Day 188: Grinding

We had decided early on that we were going to try to refinish many of the original wood floors in the house.  The entirety of the main house was constructed out of yellow pine and the floor boards have this really neat knotty quality to them.  In the 19th century, yellow pine was the timber of choice for basically all construction from wooden ships to houses to tables.  It was abundant, which made it cheap, and it’s reasonably hard.

Raw Yellow Pine

Raw Yellow Pine

A floor finish is basically a combination of coloring and a weather sealer.  In most cases this means a stain or paint plus polyurethane.  If your floor is just scuffed or scratched, then you can usually save yourself a lot of trouble by just refinishing the protective layer.  If you want to change the color or if your floor is more deeply scratched or damaged, then you have to remove enough wood to take out the stain and poly.  Most hardwood floors are 3/4″ thick tongue and grove boards.  They’re assembled by tapping one board into the next and then driving nails into the tongue section.  The rule of thumb is that you can sand floors until you reveal the nail head.  That’s about as far as the floor can go.  Unless your particularly agressive with your sanding, this means you should get quite a few iterations of refinishing the floors before their worn out and should be replaced.

Once we stripped off everything that was on top of the floors we wanted, the next step was the patch holes.  It’s interesting how people appreciate things over time.  We really care about these floors and are working to make them usable again.  At some point, people got tired of these floors and covered them up.  It’s clear that as the mechanical technology of a house increased over time, new installers disregarded the floors in order to get the latest and greatest in pipes, ducts, and wires from point A to point B.  As a result, there are a number of places where the floor was patched prior to us and a few places where we needed to patch it ourselves.  This job pretty much sucked.  For several of the small areas, we were able to use some reclaimed floor boards from upstairs.  For others, I had to use a contemporary floor board.  Unfortunately for my sanity, “three quarters inch” today means something different than it did a hundred years ago.  A quick aside about structural wood, we use nominal measurement references like “2×4″ to suggest 2 inches wide by 4 inches long”  However, this measurement refers to the rough hew of the board when it’s cut down at the mill.  After that point, it’s sanded and cured, which reduces the size of the board.  As the technology at the lumber mill changes, the actual measurements of it’s end product changes.  This is one of the reasons why it’s tough to fix old framing with new boards.

Em runs the drum sander

Em runs the drum sander

Back to the floors, once patched, we started sanding.  The main part of the floors were ground down with a drum sander.  A drum sander is a really cool machine.  It’s basically just a motor with a belt that turns a small drum.  The drum has rubber fins.  You slip a sand paper tube over the drum.  When you turn the machine on, it spins the drum.  The centrifugal force, tightens the tube via the rubber fins and away you go.  It has a leaver that you use to raise and lower the drum to make contact with your floor.  I read a lot about sanding floors and watched several videos in preparation for the project.  To tell you the truth, they actually had me concerned about my ability to do this.  The biggest fear that everything I saw instilled is that you can grind a hole in your floor.  Specifically, if you drop the drum and hold the machine in place, the sand paper will dig straight down.  You always have to keep the machine in motion while the drum is down to prevent damaging your floor.  The analogy that I think makes the most sense is it’s kind of like working a manual transmission.  You have to move forward slowly and drop the drum fluidly to start sanding.  Then move slowly across the floor, pulling the drum up in the same motion.  What the videos don’t explain is that when you drop the drum, the machine is going to drag you forward.  It actually makes it very difficult to burn a hole in your floor.  The knack is much more in leaning back and moving at a steady pace to get a consistent sanding pattern.

2014-04-01 13.24.57The drum sanding process uses three levels of grit.  The first on gouges the wood through the finish and stain and right down to the raw wood.  The middle grit smooths out the deep gouges and the finishing grit brings the floor back to a nice, but stainable finish.  For our project we used 32, 60, and 120 grits.  For one section, I even had to go down to a 26.  After sanding the main part of the room, you’ll have about a 4 to 6 inch band around the outside that needs to be edge sanded.  You can rent an edging machine (we rented the drum sander from Home Depot) or use a random orbital sander.  An edge sander is basically just a more powerful orbital.  At this point in the project, my time was a bit spotty, so I used my 5″ orbital over the course of several days of sanding work.  The toughest part was finding course enough pads for the machine.  Home Depot doesn’t stock anything courser than 60 grit.  Lowe’s stocks a 40 grit.

2014-04-02 10.28.38The last step in sanding floors is to screening.  Screening involves using a buffing machine and a screen (literally, like what you have in your windows).  The rough metal sands down your floor.  Screening serves a few purposes.  It helps even and sand your floors.  It blends the two sanding strokes you’ve been using so far (circular from your edger and straight from your drum).  And it opens the grain of the wood to allow the stain to penetrate.  I’ve never run a buffing machine before.  I’m not sure I’d recommend running one with a sanding disk as a first time out.  The first couple of times I turned the machine on, it shot across the room and crashed into the wall.  It was equal parts comical and frustrating.  I’d get it set up, turn it on, it would shoot across the room uncontrollably.  What was particularly frustrating was that the machine isn’t that complicated.  It just has an on/off switch and a handle.  That’s it.  After a handful of tries, I gave up and called Em for advice.  We read the internet until we came up a rough description of how to run a buffing machine.  In case you ever have to run one, here’s what I learned:

2014-04-02 16.07.15A buffing machine is just a motor on a stick.  The stick can be adjusted.  It has a trigger and a safety to turn the motor on.  There’s not really a way to adjust the motor speed.  The best way to think about it is to imagine you’re controlling a top.  The top is spinning clockwise.  If you push the top away from you, it’ll go right.  If you pull it towards you, it’ll go left.  With a buffing machine, this analogy is in terms of pushing down or pulling up.  Set the handle somewhere between your navel and your groin so that you can use your core muscles as leverage.  Ideally, you want to balance the machine in the middle of this up/down spectrum.  At that point, it’ll stay in place when you turn it on.  Then you can ease it on direction or another and push or pull it in the direction you desire.  What you want to try to avoid is wildly swinging back and forth from between up and down.  This will cause the machine to swing back and forth like a cartoon janitor waxing the floors.  You want a controlled movement so that you can cover the floor evenly.

After screening, we stained and sealed the dining room and living room floors.  The upstairs bedrooms still have yet to be done.  The downstairs got a dark coffee stain and 4 coats of poly.  They came out looking fantastic.

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About Nathan

Originally from central Florida (near Orlando), I've lived in the Cleveland area since 2008. When I'm not caught up in the life project de jure, I paint, sculpt, play games (mostly board games and video games), and run a small hobby import/export business.

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