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How to Sand a Wooden Floor

Sanding a wooden floor is one of those jobs that looks easy, but is actually surprisingly difficult and time consuming. If you want to get a smooth and even finish you will need to use the right equipment and work carefully and efficiently. It can be tempting to simply purchase a sanding machine and rush over the floor as if you were using a vacuum cleaner, but this will ruin the patination on the floor, and could leave you with unsightly gap too. This handy how-to guide will help you to pick the right equipment and achieve the best possible results.

Tools Needed

You will need:

  • An appropriately sized belt sander (the Lagler Hummel is a good choice)floor sander
  • An edge sander (such as the Lagler Unico or Flip)
  • Finishing sander (such as the bona buffer)
  • Dust extractor
  • An appropriate selection of abrasives
  • Scraper and sandpaper
  • Extension leads
  • Protective mask / respirator
  • Goggles
  • Ear defenders
  • Gloves

Step By Step Instructions

The first thing you need to do is choose the right abrasive for the floor. The type of abrasive you use will depend on the type of wood you are working with.

  • Aluminium oxide abrasive is inexpensive, but the belts and discs will wear down quickly if you are sanding a hardwood floor. They will also go blunt if they encounter unpunched nails. Aluminium oxide belts are best used to remove paint or glue, but for proper sanding you should choose a different material.
  • Silicon carbide belts are stronger and longer lasting, and are a good choice for oak floors and pine floors that have a lot of tacks or nails in them. They are a good general purpose abrasive.
  • Zirconia is the toughest type of abrasive, but also the most expensive. It is overkill for a pine floor, but it is a good choice if you want fast sanding or need to work with a very hard floor.

Before you start sanding the floor, try to clean it up as much as possible by hand. Remove rusty, old screws, pull up unpunched nails, or hammer slightly loose ones back into place. Scrape up large chunks of glue or anything else visible left on the floor, and manually sand any hard-to-reach areas such as underneath radiators, in tight corners, or around pipes.  If you notice any gaps in floorboards, or knot holes, fill them in using a mixture of wood filler and sawdust. Let them dry before you start sanding. Check your floor for any cables or wires that are running along the skirting boards, and make sure that they are taped up and out of the way. Check your floor again to make sure that it is smooth and clean and that there are no nails or screws showing.

You are now ready to operate the sander:

  1. Check that the clutch is UP and that the drum is not touching the floor.
  2. Open the sanding drum door and check that the tensioning lever is in the right position and the sanding belt is fixed firmly in place.
  3. Check that the dust bag is correctly attached to the sander. Use tape or cable ties if necessary to keep it totally secure.
  4. Make sure that all nuts and clips are tight – they can come loose easily during operation because of all of the vibration.
  5. Check that the clutch moves smoothly.

The sander should work in all directions (forward, backward, left, and right) however you can expect to feel some resistance if you are moving it backwards because you are pulling against the natural movement of the drum. For a thorough sanding job you should do a full “pass” going both forwards and backwards on each part of the floor. Start with a fine sanding belt and “feather” the clutch while you walk around the room. This will ensure that if you make any mistakes they won’t be too noticeable and you’ll be able to fix them when you start sanding with a rougher abrasive.

Once you are confident, you can attach a rougher abrasive and start sanding for real. Sand in a straight line (this is safer for the floor), and work methodically. Don’t take chances around pipes or skirting boards – use a hand-held sander for those if necessary.

The first pass with a rough sander is to remove any existing coatings and damage, and leave a level floor. After that you can do some more filling and spot repairs, and then sand with a finer abrasive (P80 or P100 are good choices) to leave a nice finish, which is ready for varnishing or other treatments.

floor sanding - before and after

Tips and Hints

  • If you aren’t sure which type of sander to hire, measure your room and take a photograph of the floor. Show that to the hire company; they will be able to tell you exactly what type of sander you should rent from them.
  • Always wear protective equipment when sanding. Some people may feel that wearing a respirator is overkill, but it is not worth taking that risk. Sanding a floor produces a lot of very fine dust which could cause some serious damage to your lungs. In addition, if you are using a solvent based filler or coating, you do not want to inhale the fumes from it.  Goggles will protect your eyes, and ear defenders will prevent any hearing loss from the noise of the belt and the engine.
  • It is a good idea to practice moving with the sander, operating the clutch, and keeping the cable out of the way, before you actually start sanding for real. Don’t actually turn the sander on until you are confident that you can use it properly. If you get distracted and stop without operating the clutch of the sander, you could sand a large divot into the floor by accident, and it will be incredibly difficult to cover it up. A few minutes of practice could save you from a costly mistake!

As you can see, it takes several passes with different abrasives to get good results, but it is worth the effort! Do not cut corners, because if you make a mistake it could be very difficult, time consuming and expensive to fix.