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Sunday, December 21, 2014

Question

Recently, I instructed 24 students who were required to perform top scrubbing/stripping & waxing for certification with the options of using "floor models" built on plywood w/cement boards for stability...I opted against it - my overall concern was the subsequent rotting of the underfloor which could possibly cause a cave-in and therefore injury. Given that this was a rotating class that conclude with approximately 40 plus students with a time frame of 10-11 months, what is the probability of such an incident happening?


Answer

I probably should have written back for clarification, but since I did not, I'll qualify my judgment.
First off, I would picture the "floor model" you describe as some sort of elevated platform within an existing building. It is framed and then covered with 4 x 8 plywood sheets and cement board on top of that. Then VCT or sheet goods have been glued down on the subsurface so that it looks like a floor, but elevated.
Since you can't teach VCT maintenance on bare cement board, this picture should be accurate.
Now, your question is whether or not you need to be concerned with this "model" rotting, and my judgment is NO. Both the VCT and the sheet goods will prove to be quite water resistant if installed properly and if sound procedures are used during training.
It is never good practice to flood a floor and let it just sit there. Even stripper solutions are placed with a mop or pad, not by dumping a bucket, and the dwell time is only a few minutes before agitation and removal with a wet vac. The opportunity for water remaining long enough to soak into lower levels of plywood is not there.
Even if the underlayment were to be weakened by water over time, the spongy feel of the floor would indicate the damage long before a collapse took place.
If this is the situation you describe, I believe you are safe to use the "model floor" for your class.
The other possibility is that you are concerned about the actual floor under this platform getting wet from the activities above it and rotting. This is, of course, possible, but with minimum effort the water can be controlled to keep this from happening. Water or solution control is of great importance in floor work and here is a great place to learn that.
In either case, I doubt you face any risk of a sudden floor collapse.

Lynn E. Krafft, ICAN/ATEX Editor
lekrafft@juno.com