YOu need to figure out the source of your problem, not the bandaid for the symptom. Wood floors usually have gapping in the winter due to the lower humidity. Cupping usually occurs in the summer with the higher humidity. So, your home has some form of humidity issue that is causing this problem. Do you have a whole home humidifier hooked up? What is the home's relative humidty? What does a moisture probe tell you about the humidity of the wood? What about the humidity of the slab? When you say you put down a moisture barrier and then glued down the bamboo, exactly what products did you use and how did you use them? Does your plumbing run in slab in copper and have you looked for leaks? What about laundry, refrigerators, dishwashers, sinks, tubs? Have you checked around these for leaks? You've got a lot of sleuthing ahead of you to fix the problem. Sanding down the cupping only addresses the symptom, and will not at all address what moisture issue your home is having.

With the risks involved you'd be better off gluing it down but if you insist on nailing, pay close attention to the size of the staple being used or if possible, use a nailer with a cleat like a PowerNailer rather than a stapler.

FWIW, Lumber Liquidators insists all their flooring exceeds all regulatory standards in the EU and California. SEE LINK BELOW... The one bad "report" that is floating around out there causing a stir, seems to focus on one product, and one sample only - not everything they sell. hmmm That said, it's enough to make me wonder. But there is the other side of me that is a cynic. Some old school sellers of flooring I've talked to are accustomed to gouging customers with massive profit margins and price fixing. Their world is crashing down in the new reality of a global economy and big box retailers that get better margins than they can ever see. They are vehemently outspoken against all big box stores - particularly LL. I've been in several of these types of stores and they are so much higher in price they cannot compete IMHO. Besides these particular ones being smug, arrogant and slightly shady - talking trash about other sellers and installers of flooring outside of their tiny realm, came off as disingenuous to me, if not outright bitter. This is enough to make me wonder too - who is fooling who? In fact, it's almost having the opposite effect for me - we're shopping for 1600sqft of flooring, and I just want to run away from those guys. As a result I'm just completely confused about what the truth really is. Anyone can launch a campaign of vitriol on the web - it doesn't necessarily make it 100% true. It's also the "squeaky wheel" syndrome. How many tens of millions of people have wonderful experiences buying big box flooring that aren't making noise? Yup, totally confused. Maybe that was their goal. EDIT: I went into another local non big-box flooring store today and they were very good - no trash talk - just helpful, nice and competitive in the market with many products and fair prices. It was a welcome ray of sunshine! So not all of the local stores may be as difficult as the few I went to before I wrote the original reply. YMMV Here is a link that might be useful: http://www.lumberliquidators.com/ll/flooring/Flooring101-formaldehyde-what-is-it This post was edited by karyn on Sat, Jul 20, 13 at 17:31

Is there a reason nail down is preferred on floors with a wood subfloor? The flooring subcontractor will do whatever method we want, but he advised against nailing down bamboo. He said he occasionally sees dimpling of the nails visible on the surface of the wood and prefers glue or floating.