Navigation Menu+
Commercial Flooring News

Floor Sanding

Terry Guilford with advice on floor sanding
AS most people know, wood is hygroscopic. In other words, it likes water. The little wood cells sit around for months doing nothing and not getting to meet anyone outside of their own circle of friends (i.e. other wood cells). So you can imagine how excited they get when the circus makes its annual trip to town.
The new kid on the block (excuse the expression) is not in this case Billy Smart, but HUMIDITY. OK, I know it’s mid-winter as you read this, but when I wrote it the weather was humid and sticky.
Now let’s get back to Cedric Cell and Hubert Humidity (I told you it would get worse). Once the formal introductions are over, Cedric, being a very hospitable type immediately offers the newly arrived Hubert board and lodging until the heating goes on (winter, in other words, making the article topical right now, after all). And in winter it’s time for Hubert to make his annual migration.
So once ensconced in his snug little cell, Hubert does what every new young arrival does and invites his mates over to stay (okay I won’t give them names, I do have some shame!).
Now, of course, you can imagine that it’s all getting a little bit cramped inside Cedric, so he puffs his little walls out to make room for all these new arrivals (To be honest he is a little bit too accommodating in my opinion but hey it’s his business). The real problem is that all Cedric’s neighbours have been equally obliging and they are all doing the same thing, making themselves bigger.
I am now going to come out of the ‘childrens author’ mode and spell out technically what is happening. It is technically possible for a hardwood floor in an average size sitting room to expand by 25mm over its width if installed at factory moisture content with no acclimatisation during the summer. But add also moisture in the form of floor lacquer and it gets worse still. And if you think that just sanding old floors means you are safe, forget it!
A great many hardwood floors are installed by people who have absolutely no training or experience in hardwood floorlaying. So they do not allow the necessary space around the perimeter of the floor. These floors may have been down for years and are just about remaining flat even though they are touching the walls, door frames or other obstructions.
However, then you come along and sand and lacquer the floor when there is humidity around and you are lighting the blue touch paper. The floor will go one way and that way is UP! Now the spotlight falls on you. You come along visiting a client, offering your services to re-sand and finish their wood floors.
Before you quote a price, be sure to look for the following warning signals.
1. Any gaps at all between the staves;
2. Any slight buckling appearance to the wood;
3. A slight springing in the floor;
4. Bulging wood near door frames or walls;
5. Signs of the floor pushing against pipework or other obstructions; and
6. The lacquer cracking due to pressure.
If you spot any of the above, you should investigate further by removing skirting boards or scotia and checking for expansion gaps. Note that it is very tricky to create expansion gaps if they are not there, especially around pipes and under door frames.
Whatever work you do from here on in, you WILL be blamed by the client if that floor rises! So you may choose to walk away, or to advise them to get someone to put the problem right; or, if you have the skill, you can offer to do it yourself. But you MUST do one of these three things.
The scientific relationships between moisture, temperature and humidity are way beyond my feeble brain (hence the Thomas the Tank stuff). But if you need to understand or measure this stuff I would highly recommend the excellent gentleman at Tramex.

T: 00353 (0)94 9048284
T: 0161 818 2582 (for training courses)
Terry Guilford is technical director of The Ultimate Floor Sanding Co, a corporate member of the National Carpet Cleaners Association (NCCA).

This article has been reproduced from the Contract Flooring Journal. You can find them at