Question:
Hi. I just bought and read your article on how to sand a floor without leaving machine marks. I am in the final stages of having a new, solid 3/4 inch white oak floor installed throughout the main floor of my house. I am not attempting to do any of it myself, and have hired someone who came very highly recommended and who does many high-end homes in this area (San Diego, CA).
My house is just an ordinary one but of course I want a nice floor. This guy has been doing floors for 25 years, and his father and grandfather before him; but it surprised me that he used circular sanders for every stage of the process, finishing with a 120-grit screen, and I can clearly see millions of circular scratch marks over the entire surface of the floor when the light is at an angle. I mentioned this to him and he was very surprised, and said everyone does floors with this type of sander and no one had complained about it before. I notice in your article you assume a drum sander will be used; but for the final stages you do mention “screening”. In your method is this screening also done with a drum sander or with a circular sander? In your opinion when is it OK to use circular equipment, and even in the final stages how would you avoid the circular scratches?
My floor now has the second coat of oil-based polyurethane applied (there was no stain used) and the scratches are everywhere. How is that possible with 120-grit? Thanks Debbie
Answer:
Dear Debbie, I know of NO professional floor sander in my area (Greater Toronto-about 6 million people) that uses a buffer (also called floor maintenance machines) to intially sand the floor. We will ALWAYS use a drum (or a belt) sander to level the floor and take it down to the final polishing of the wood. This is because, as you can see in the article’s pics the sandpaper travels WITH the grain of the wood. A well tuned drum sander leaves no marks in the wood.
And as the article goes on to suggest, we only use the buffer with screen (100 grit) to do a final light polishing of the wood surface. In fact this is mostly done to blend in the edger marks with the middle of the floor. Or to remove any egder marks in a cross laid hallway. In the extreme case when there are severe chatter marks in the floor would we consider using a large sandpaper disk (100 grit also) to remove these errant marks. Then we return to the screen to remove even the sanding disks marks.
A screen is simply an arbrasive nylon mesh disk that fits under the buffer. I’m including pics of the buffer in use and the screen. The buffer and screen are also used to smooth out the finish between coats. And even then we use fine screen, somewhat worn, so no circular marks show in EVEN in the finish.
Here is the URL of a fairly new machine that some pros are going to be tempted to use to sand floors. The have their place when doing the final wood polishing of parquet floors. But others will want to use these machines for sanding (and creating circular marks) in strip floors. Go figure. http://www.laegler.com/html_e/p_trio_te.htm
The finished wood floor should look as good (better really no “over-wood”) as a prefinished floor. No machine marks should be visible at all if the floor mechanic is doing his job correctly with the proper equipment. I hate to say this, but I’ve seen guys doing floors the wrong way ALL thier lives, with no improvement. I’ll bet you didn’t go over to see some of his “custom jobs” like I suggested in my article How to Choose a Flooring Contractor” free in the How To section of this site.
If he has sanded the floor with aggressive screen or sandpaper disks, no fine sanding with these same disks will remove the marks. The marks are just too random and embedded into the wood surface. I hate to say this, but you’ll have to have the floor done all over again, by someone that does know what they are doing, and has the proper equipment.
Before you ask, no, there is no one I can recommend in your area, I only talk about products and methods. People change (or not). Find the guys who will use the best methods, and the job will go swimmingly this time. Oh, and good for you for reading what is a really technical article, just to find out how the work is really supposed to be done. I hope this has helped.