Floor Sanding Basics – Part 1

Floor Sanding Basics!

Here I am going to outline some of the basics of floor sanding with regards to the process. Unfortunately I can’t go into detail regarding the use of different floor sanding machines, at least not at this stage. It may be something I can get into at a later date. For now I will be discussing how to remove certain substances or previous finishes as well as how to get the floor flat and smooth: what grits to use when where and how.

So first of all I’m going to cover floor prep.

Make sure all furniture is out, this includes picture frames and other things you can catch yourself on. With years of experience behind me I still knock paintings, clocks among other things. If you have a low hanging lamp you will walk into it… a few times. If you have a chandelier or you are working in a kitchen and you are using hired machines, you should put plastic sheets up. Preferably don’t sheet anything within 3 feet of the floor(vertically) as it just tends to get in the way or get sucked up against the machine. Fireplaces tend to suck the sheets in so they are out of the way so its fine.

Remove all tacs, staples and sweep/hoover the floor. Repairs will be covered later, for now I’m just covering the basics.

How to flatten and clean
Generally speaking you start with a rough grit, 36 grit or 40 grit. This course sandpaper is designed to level the floor and remove the previous finish along with any dents and scratches. Levelling the floor involves sanding across the grain in some way. If there is a setting on the sander for coarse, medium or fine grit sanding, set it to coarse. Now, rough grit sanding tends to be the toughest part of the job, especially for DIY enthusiasts. Even for us professional folk it is occasionally the most painful and sometimes a very substantial part of the job. Here’s why: The sandpaper is made to sand wood NOT paint, varnish, wax, oils, bitumen, screed, carpet glue or nails. This means that the effectiveness of the sandpaper can be severely hindered by these materials. Often these substances heat up with the sanding and stick to the sand paper, if this happens, you’re done. You have to change papers. If you have a floor with paint, for example, AND nails, the nails will smooth the belt which means the surface heats up more and quicker. OK, so how can we go about getting the most out of the sandpaper and our time under these circumstances?

1. If the floor is nailed down you can get a nail punch and punch the nails in 3 to 5mm. This can help to fasten loose boards as well as provide a better environment for sanding.

2. Sanding against the grain. Exactly how to do this specifically for the floor you are sanding will be explained in other articles but basically if the wood and thus the grain is all running in one direction, you want to be sanding diagonally across the grain’s direction. Sanding with the grain produces a smoother surface because it doesn’t effect the micro-structure of the wood the way sanding across the grain does. Sanding across the grain really tears the fibres of the wood and helps to remove the worn surface very quickly. This will get the floor flat and clean (though very rough looking) quickly.

3. Only sand the floor when walking backwards! This sounded utterly bizarre to me the first time I heard it but I have tried it many times and have found it to help immeasurably on some floors, so let me explain. When you are walking forward with the sander and the drum is down, any material that is sanded off at the front of the drum-floor contact area has to pass under and through the whole contact area before its then free to be extracted or whatever. Whereas when you are walking backwards, the material will pass under then immediately get sanded off released to be extracted. Other than that you are halving the time that the drum is in contact with the floor which means less heat and less caking on the sand paper. Give it a try.

In some cases despite all this it can still be a slog cleaning and flattening the floor, you just have to keep going until its done.

Once you have sanded the floor diagonally with the rough grit, you should then go over the whole area again with the same grit but going with the grain of the wood. If the floor is flat and clean it should be fairly easy and fast, just keep your eyes open to remove all diagonal scratches in the main body of the floor.

You can now start rough edging. This means using the 6 or 7 inch disk sander you should have rented or borrowed along with the belt or drum sander. This machine is used for sanding the rest of the floor where the main belt sander cant reach; around the edges of the floor, in bay window areas or hallways. For now we will just assume we are sanding 1 square area. Rough edging is pretty much the same as any other edge sanding it just takes a little longer. You should be using the same grit as you used with the main sanding machine. You want to be flattening and cleaning any one given area before you move on. If the floor is flat you just want to remove the previous finish and/or scratches and dents and MOVE ON. Don’t sand off too much or leave dents in the floor.

The rough edging should leave only the very corners of the room un-sanded. You can clean these with a scraper before using a delta/triangular/detail sander to get it down level with the rest of the floor as much as possible.

At this point all you should see is flat and clean wood, if a little rough.

See also: How To Stain A Floor LIKE A PRO