Sandpaper is a given – although the type will depend on the condition of your floors. Use 40-grit sandpaper for floors that need a lot of work, 60-grit to 80-grit grit for floors in reasonable condition. You will need a hammer and nail punch to tap in any loose nails, preventing your sander from snagging on them.
Your floor needs to be sanded in stages with progressively finer abrasives for the best finish. Starting with grit 40, then grit 60 and finally grit 100 is tipically a good procedure for most wood floors. The goal with the first coarse abrasive is to remove the old surface coating and to flatten the surface.
For a floor in better condition, you should get three P80 grit sheets. These numbers are for an average sized room, so if the room is exceptionally large, you should consider increasing the amount of sandpaper to four or five sheets.
Sanding your hardwood floors takes three sessions with progressively lighter grit sandpaper. To begin, use a coarse 30-40 grit, then a medium 50-60 grit, and finally a fine 80-100 grit.
You'll need two kinds of sanders for the process: A walk-behind sander, like a drum floor sander, and a floor edger, to get into the corners and smaller nooks and crannies. You can rent these from home improvement stores. Before you start sanding, remove everything from the room and vacuum the floor.
Orbital sander uses and advantages
Orbital sanders are best for floors that require a light to medium sanding. If you need to prep a floor for a new top coat of clear finish, an orbital sander is the right machine.
It is imperative not to skip more than one grit of abrasive at any time. Most contractors sanding sequences start at 36 grit; they skip the 40, 50, 60 grits, and go straight to 80 grit. This saves them lots of time, labor, and money, but to the detriment of your hardwood floors.
20 grit sandpaper is ultra coarse and mostly only used in industrial sanding projects. This type is good for the first step in removing old paint or varnish, or sanding old floors.
If a floor is flat throughout and the purpose is to rejuvenate the floor, then in effect the sanding process is just removing the coating and some consider only up to 0.5mm of timber is removed.
Once again, wet-sand the surface, starting with 1000-grit wet/dry sandpaper, proceeding to 1500-grit and then 2000-grit. Use a soft, clean cloth to buff.
The Golden Rule of Sanding
The golden rule for choosing your sequence is to never skip more than 1 grit. For example, if you start with P80, and need to finish at P240, rather than using every grit from P80 – P220, you can do P80 – P120 – P180 – P240. This sequence cuts out P100, P150 and P220.
You could use 120 as a medium, do all the things sandpaper, 80 grit if you want to really rough up a finish or do a little shaping and 220 grit for final sanding between coats of paint or poly. But if you want a little more flexibility, here is a fuller picture of the sandpaper grits and their uses.
The palm sander is definitely the most common tool for sanding a wooden floor by hand. Palm sanders also oscillate, however, unlike orbital random sanders, the pad of the palm sander is fixed straight.
If you're using both the electric sander and the edger in 140 square-foot floor space, it will take you roughly 5 hours to do three sanding passes. Another thing you must take into account is how old your house is. If yours is 50 years old or more, you'll need extra time to complete it.
Fine sandpapers range from 120- to 220-grit. For most home workshops, this sandpaper will suffice for final sanding before the work is finished. Extra fine sandpaper is often used between coats of paint or varnish.
These 500 grit fine-cut sandpaper discs are ideal for finish sanding on all types of surfaces. Use them to finish sand automotive paint, primers, and putties before painting or for removing light scratches and extra fine finish sanding on wood and paint.
Dresdner offers the following rule of thumb for grit progression: jump under 100 points with coarse papers, 100 or more with medium, and 200 or more with very fine papers. Example grit progressions: 80/120/220/400 or 100/180/280/400. When in doubt, better to have too many steps than not enough.
Avoid sanding too fast, or too slowly.
It's a bit of a “Goldilocks” issue – going too fast can lead to poor results, with sections not sanded enough or missed entirely, and going too slowly can lead to over-sanding or cut-through in some areas.
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Hardwood flooring can be re-sanded up to 10 times, depending on how bad the floor is and how skilled the person doing the sanding is. It costs about $2.50 per square foot to refinish a floor, plus $50 an hour for patching and thresholds.
The process for sanding a floor by hand would be, as a general rule, to start on a 40 grit sandpaper and work your way up to 100 or 120 grit paper to leave a fine finish. It is important to keep any sander moving so it does not dig into or burn the floor.
Generally, you should do sanding after 10, 15, or 20 years from the time of installation. After that, you can sand it after every 10 years. The number of times you can sand your hardwood floor in its lifetime depends on how thick the solid or top layer of the engineered flooring is.