Sanding wood floors & refinishing yourself will definitely save money, and even an inexperienced homeowner can likely do a better job than the lowest bidding handyperson who quotes on it. Once you understand the basics, a quality final result on your wood floor is more about patience than anything else.
Ultimately though, once any ridges between boards are removed so you won't trip, it's all about aesthetics. Upon completion your floor will be a work of art to show off and be proud of, then your kids or your dog will come in and it will just be a wood floor again, something that you mop or vacuum once a week.
Floor preparation, the first step to the perfect wood floor
Before attempting the refinishing of a wood floor, know what you're tackling first. Is your floor old floorboards that have been covered with carpet? Are they good enough for sanding and finishing? Are you sure? Did you pull all the gripper rods off first that held the carpet in place - because sometimes they use no-nails AND nails, and that makes a mess as the planks often split when you try to get them off. There's little worse than slaving over the perfect finish to your wood floor only to be hobbling around very shortly after when you scuff the floor with your bare foot one evening after a couple of pints and drive a splinter under a toenail.
Is the floor a solid or engineered hardwood? Some engineered floors can be sanded and refinished but not all - generally speaking it needs a few thou of laminate before you should consider sanding and refinishing, maybe try a hidden area first, like inside the bottom of a closet. If the floor is a solid hardwood planks, congratulations, you should be good to go. But, one word of caution because I've seen someone try it, make sure your floor isn't a very realistic laminate before renting a sander for the weekend... that absolutely doesn't work.
After all that and moving everything off the whole floor to be sanded, sweep and vacuum everywhere, then mop it with a slightly moist cloth, then once dry, vacuum it again, particularly around the edges. Ban everyone from the room, because the worst thing is getting a big lump of grit stuck in your sanding pad, disc or belt and putting a huge gouge all over the precious wood floor you're supposed to be making beautiful.
Then, get down on hands and knees, and if it's an old planked floor, very carefully run your hand over the entire floor to check for protruding nail heads or bits of grit stuck in the joints.
Once you're convinced that your floor is suitable, that it's immaculately clean, and when you have nothing better to do on the weekend, it's time to decide what kind of sander to rent. But first, think safety!
Before even starting to sand the floor, safety first!
All these sanders are going to produce dust, and you're going to be using noisy machines - so ear protection is a must. Splinters are a definite probability, so wearing gloves are a good plan too. Eye protection is recommended, and a suitable facemask is essential unless you enjoy blocking sinuses with old toxic varnish and peppery wood dust that can also be pretty toxic depending on the type of hardwood.
While you're at it, you might as well get a couple of those disposable all-in-one's like on CSI, complete with the pull on booties for after the floor is all prepped to make sure you don't drag something all over it out of the garden. Once you've got all that on, you'll be too hot, and/or nature will call - so you'll probably end up doing the job without protection and suffer for weeks after with sinusitis. It's not big, and it's not clever to ignore safety warnings folks - and now you can't say I didn't warn you... so on your head's be it!
Floor sanding machines, what are the choices?
Buffer sanders work in a circular motion, it's the same machine that is often used to polish and clean industrial and commercial floors. If you've used one in any other application you could give it a try, but sanding floors might not be the best place to learn. They have a very sensitive balance and will take off across the floor spinning wildly and wrapping the cable around your legs as they go if you don't yet have the magic touch. And if you even have to ask "do I?" - you don't.
If you decide you are brave enough anyhow, (really?) you will need to buy several different grits of paper and some cushioning pads. These are available at the rental counter, someone there can likely help you determine how many of each you will need based on the square footage of your job, but buy a few extra as they can usually go back. This is a common practice, and you will be going back to return the machine anyway so there is no inconvenience or wasted trip - better to have too many pads than not enough - and catching just one proud nail in an old floorboard you didn't notice before very quickly rips up a pad - which goes straight into the bin.
The pad acts essentially as a shock absorber, giving the sander a smooth ride and ensuring even removal of material. After a while (a couple of hours or so) the pad will become compressed and worn out and need to be replaced.
Installing paper and pads is quite easy. The paper sticks to the pad, you then just drop it on the floor (yes that's right, paper side down) then sit the sander on the pad which will stay simply due to friction and the weight of the machine.
Old sanding pads can be cut up and re-purposed into excellent floor scrubbers.
Square vibrating sanders are the easiest to use and the hardest to screw up with. You can rent one at most major home building stores, and like with buffers, you'll need to purchase pads and paper. This is really you're best option if you haven't sanded floors before, but here's hoping it's just a powder room floor - seriously, it needs to be small for this option to work.
Both buffers and square sanders will come quite close to the walls, but you'll also need a small orbital hand sander to do around the edges. For new floors, keep in mind your baseboards will likely cover a good 1/2 to 3/4 inches away from the wall.
For using a buffer or square sander, the process is the same. You start with a really rough paper that will smooth out any ridges between boards and give you a uniform surface. From there each different grit of paper is designed to remove the ridges from the paper before so don't worry if the first pass leaves all swirly lines everywhere, they'll progressively disappear.
Papers will go in sequence starting at 36 or 40, then to 60 grit, 80 grit, 100 grit, and 120 grit. You can go up to 180 or 220, but before you do that, I'd think about hand sanding 2 sample pieces and putting some oil on. If you can really tell the difference between a 120 and 180 then go for it. I'd do it for a paying client simply because there will be an initial nose to the floor inspection, but for my own floors I stop at 120.
Drum sanders - oh boy, this is where things get a little different, and the stakes go right up. If sanding a floor for the first time was like learning to drive, choosing a drum sander would be like choosing a stick shift instead of an automatic. With lots of hill starts. Blindfolded and with Metallica blasting on volume 12.
Drum sanders have a rotating belt, and do a quick and relatively clean job in experienced hands. But they can be quite tricky to learn, and have a lot more potential for causing damage if you do it wrong. Like huge furrows, everywhere. Nightmare! If this is the machine you choose, make sure you start out in a place that won't be highly visible. Like the dark side of the moon.
There are two types of drum sanders; tip sanders and lever sanders, both of which operate with sandpaper belts. Of the two you are most likely to encounter a tip sander, as they are the easier of the two to learn and use, relatively speaking. They have two wheels that you tilt the machine back onto to change directions, whereas a level sander mechanically lifts and lowers the drum.
It's important to start the machine with the paper OFF the floor. Once you tilt it down and the sandpaper touches the wood, it will instantly start pulling you.This forces the operator to switch actions from pushing to pulling - usually eyes popping as you strain every muscle in your arms tring to stop it hurtling across the floor and through the wall opposite. These things are brutal, and pull your arms out of their sockets.
For all types of sanders (especially drum sanders), if you're hoping for any kind of a decent finish to your wood floor it's important to keep the machine moving. If you stick around in one spot you will start to dig yourself a bit of a hole (literally) that will be hard to fix with the next grit. Very, very hard if it's a laminate and you grind right through it!
Techniques for sanding wood floors
Firstly, go with the grain, alwyas, secondly after ever stage, do a quick look around to see that you've got all the scratches from the pass before. Once you've done a 120 grit pass, for a really smooth surface you can wet it (that brings up all the fibers) then wait for it to dry and do a quick pass with a 120 screen. The golden rule is that if you can see marks, swirls and scratches, keep going, move a grade finer, keep going again. Because if you can see it before it's finished, it will look ten times worse after...
Skipping a step might seem like a time and material saver, but it isn't. If you go from 60 to 100 grit and don't do 80, you will spend a long time trying to wear down ridges with a paper that is just too fine for the job and often clogs before it cuts the surface.
Really the only step you can feasibly skip is the initial paper you choose. If the newly installed floor is quite uniform, you may be able to start right at 60. How long you spend on a floor is really determined by how well it is installed and how long it takes on your first pass to get it to a point where you are happy.
The one thing that can really expose cut corners, will be if you choose to stain the floor. Floor stain will make any scratches and flaws a lot more visible.
And as I said, be sure to wear proper protection from breathing dust particles, especially if you are repairing old floors with a finish on them. Small paper masks protect you a little, but not much. Despite being a sweaty pain to wear in hot weather, wearing a respirator is a really smart idea to protect your lungs.
Be ready with a broom and dust pan, and ideally a shop vac. Be sure to use vacuum attachements with soft bristles, hard plasic can leave lines across the floor. Also, if you vacuum with the grain, there is less chance of leaving any visible marks. Get as much of the dust off as possible, if your floor is nailed planks make sure any nail heads are under the surface (as otherwise they tend to rust over time and leave stains.
So, the floor is sanded and clean, the weekend is over, your arms and back throb and ache, and you're half deaf, but hey - at the very least you now have a fun dinner party story to share and you'll really appreciate the professional you pay to do it next time!