About 6 weeks after a 2nd floor naildown install of solid 5/8" bamboo over plywood, there began to appear a deep yellow stain that went partially accross the boards. It almost looks as though someone has swiped a paintbrush filled with yellow paint across the board. Within a couple of months, about 15 boards scattered randomly through 3 rooms changed. There is no obvious pattern to the locations of the boards: some see foot traffic, some have never been walked on, some are under area rugs, none really get direct sun. The floor is only dry-mopped, no water or cleaners have been used. Looking at the cut end of one of the discolored boards, it appears that the stain goes into the top layer of wood about 1/8". The importer, Greenwood, sent out an inspector who checked ambient conditions, board moisture and several other things and concluded that it was an installation related problem. He claimed that the staining was caused by asphalt contamination due to the 15# roofing felt used as an underlayment and/or residue from the resealed street outside the house. Since Greenwood requires the use of roofing felt with its installs and the street was resealed months after the problem occured, the installer brought in another inspector. The second inspector stated that the problem was clearly in the boards and had nothing to do with asphalt contamination. Unfortunately, he also believes that since Greenwood's warranty has an "as-is" clause, there is no basis for having the discolored boards replaced. Greenwood is sticking to the asphalt story in spite of the facts. Has anyone ever seen this type of strange discoloration? Does anyone have experience with Greenwood's "as-is" warranty? Thanks

I have approx 600 sf of 5/8 bamboo flooring from Home Depot. The flooring looks to be a 3 ply, although it was sold as solid. The subfloor is in a 2nd floor condo, 3/4 ply with 5/8 cement based backboard installed on top. The backerboard is required as a sound and fire barrier, installed when the condo was built in 1980. 2" hardwood nails or staples will not penetrate the bakerboard layer, so I was planning on gluing the bamboo, AND stapling it in place. Screwing additional ply on top of the backerboard is not really an option as there are 6 transitions into other rooms that would end up too high. What do you guys think, and can you recommend an adhesive? I am an experienced carpenter and have nailed plenty of hardwood floors, but have never run into this problem or glued down a floor. Thanks!