1. Floor Refinishing - demolition
In a fit of loathing for polyester flooring, I ripped up the carpet in my room and found a blackened wood floor, with 3" boards (tongue-and-grooved together), held down by about 20 hand-made nails for the entire room. Unable to resist the urge to destroy, I recruited a friend for the weekend, and we went to town on the floor with a 100# floor square buff sander (Flecto's vintage 1990s Squar Buff Sander, to be exact) and started with a series of 35-60-100 grit papers. I polished it off by hand with 200 grit. Once we got the top 1/16" off of the floor, we realised it was 100+ year-old New England heart pine.
Fig 1. Colonel Burne Sanders
So, to begin at the beginning -- as to what equipment to use, I prefer the orbital sander to a drum sander because you're less likely to hurt yourself or irreparably destroy your floor out of mechanical ineptitude or sheer inexperience. The trade-off is that the vibration is like a free trip to augmented physical therapy. You'll get blisters through gloves and will need to take frequent breaks. Most square buff sanders run on 120V, whereas more industrial floor refinishing equipment (and contractors) require 220V service. If you hire a contractor to refinish your floors, do not, under any circumstances, allow them to clip in to your mains to get 200V service up to the work area. Your homeowner's insurance will probably count such stupidity as "Act of God getting down to business and doing something he should have done to smite you a long time ago." Check to see if a contractor requires 220V before hiring them. Run the following: if ((req? 220V) and !(220V installed)) then hire(electrician) else open(beer). Also, as an aside, you will likely not save time or money by refinishing the floor yourself, unless you value your time at $2/hr. I broke even on my room (in cost, not time) because it was small. If I were refinishing my entire upstairs, however, it would have only cost about twice as much to have a contractor come in and do it for me.
I edge-sanded my floor with a hand pulse sander. This was woefully inadequate. I will use a belt sander with a feather-light touch in the future.
Once the grain appeared, I began to realize I might not have a hardwood floor after all. Once this happens to you... as soon as you realize you're not refinishing hardwood (or fir), tone down your methods (and the grit of sandpaper) and try working cross-grain. Normally, you always want to go with the grain, but pine likes to de-laminate and separate along grain lines in large, splintered pieces. This effect is amplified with age. And if you think you can patch a floor with the chunk of board that just came off in your hand... think again.
2. Floor Refinishing - renewal
When refinishing floors of any age, condition the wood before applying urethane. It will a) improve the condition of old and dry wood, b) show you the final color of the wood once you urethane it, and c) produce an even finish in the event that you either stain the floor or add stain to your urethane.
High-build poly-urethane does not do what you would expect it to do. If you're short on coffee and picking out materials in the hardware store, it seems like a good idea. Two coats and you're done! Durable! Shiny! What you will not notice is that while the marketing materials say that it's meant for interior wood surfaces, it does not say "floors." If the ad copy doesn't say, "for floors," do not try to use it on floors. The high-build poly provides a relatively soft (antithesis of durable) finish, but even worse - it never dries. It smells like double-plus death (even with brand-new organic solvent respirator cartridges). In my case, I put one coat on after the wood conditioner (following directions), it promptly soaked very deeply into the wood (you would also be porous and dry after 100 years of solitude). I waited two days (due to humidity) and did a second coat. The second coat refused to dry despite ventilation and time. I later used a paint scraper to clean up the floor and switched over to the more traditional Fast Drying Poly-Urethane For Floors. Ask for it by name.
For a roughly 100 square foot room, I went through one gallon of wood conditioner and 1.5 gallons of polyurethane for 4 coats. I went for a semi-gloss finish. The most difficult things involved in cleanly polyurethaning a floor were.
- Getting (and keeping) the room dust-, hair- and junk-free during application and drying.
- Applying the urethane slowly and evenly enough to avoid creating bubbles.
- Being patient enough to wait for ample time in-between coats of poly (sanding).
- Being humble enough to avoid extemporaneous re-interpretation of the directions.
This section will be obscure without accompanying photographs, but there are a lot of entries up on Yahoo! Questions asking how to invisibly patch a wood floor and there aren't a lot of good answers. It turns out there isn't a good way to do it. Rather than documenting all of the different ways I screwed up...
Start with High Performance Wood Filler. Anything else is Weak Sauce and not worth your time. Use it to fill any large and profound gouges, splits and cracks - but be careful to get it on as little of the surface as possible. If necessary, mask off the floor adjacent to the crack you're filling. Once you get this material into the grain of the wood, it's very difficult to cover up or sand away and it leaves a nasty grey color. Aesthetics aside, this two-part filler can't be beaten on strength and durability. Like epoxy, it hardens faster in higher temperatures. If you can, under-fill your cracks to leave yourself room to sand down the filler and work on how you're going to blend it in with your floor. Use a metal application tool - it perma-bonds to plastic.
You can try to stain the wood filler, but it will be touch-and-go on color matching. If you match the filler to the pre-urethaned raw wood, it will not match after you apply the first coat of poly (even for clear poly). Use a test-piece of finished wood as your color reference. I ultimately layered stain on top of the filler and adjacent wood (because I was messy with my patching) in-between coats of urethane. It looks like I have a restored, water-damaged floor as opposed to a restored floor full of wood putty. I consider it a pyrrhic victory.
Another method you can use to "match" filled areas to the rest of the floor is to save some very high-grade sawdust from your refinishing stage. I recommend sawdust generated with 200 grit paper or finer - sieved to remove any detritus. Mix the sawdust with fast-drying polyurethane and apply to your (preferably sunken) patch job on the first coat. Build up additional layers if necessary. Once you feel you've got good opacity, sand the area smooth and feather it into adjacent areas (without removing the sawdust-impregnated poly entirely) and polyurethane over it normally in subsequent layers. The color will match, but the texture will not. This will be more apparent under semi-gloss and flat urethane finishes.
Finally, buy kneepads. You'll need them.