I self installed my bamboo flooring about 4 months ago and haven't had any major issues with it until today. It is 5/8in thick solid engineered bamboo glued onto concrete with bostik best. Checked for level, and moisture. Never found moisture problems, fixed some low spots.

The problem I am having is I noticed the floor was cupped. Now I have noticed this previously, but not nearly this bad. However, it is always localized to only a small section where the floor span is the greatest. The room it is in is about 30ft long and has varying widths upto 15ft or so. The place where it is 15ft is where it is cupped pretty much across the entire width, however the cupping stops as the width goes down by about 1ft on each side.

Now the cupping isn't visible unless you have the light hit it just right, or you drag your bare feet over it. Should this go away over time? There has been an unusual amount of rain recently. Usually here in south texas it is fairly dry, but we have been getting hit with rain quite regularly recently. The current humidity in my house is around 55%, the regular humidity is around 40% inside. Is it wise to invest in a dehumidifier for this room?

Finally, on an unrelated matter. I have a few squeeking spots where some of the boards have a small section not glued all the way down. I weighted them, I rolled the floor numerous times, I follow instructions, I don't know how these came about. Is there anyway to fix these? I was tempted to drill a small hole in the hollow spot and use a syringe with glue to force more down in there, and then patch it up. Is there anything wrong with doing this? Or should I just leave it be? There are probably 2-3 small spots in the 800ft I layed that have this problem.

Anyways, thanks for you guys help, this website has been very helpful.

Cupping is a sure sign moisture is coming from the bottom, underneath the bamboo. If it were humidity related, you would see it throughout the entire installation.

Bamboo is a grass, not a hardwood. It does funky things with moisture.
Ask Bostiks if there adhesive is waterproof, and how to go about fixing the cupping problem.

Since you checked for moisture, what were the 3 calcium chloride test, results? Did you map the concrete with a Tramex Moisture Encounter, before placing your calcium chloride tests, to determine a trouble spot?

They make adhesive injection kits, just for your problem of hollow spots. It is just as you describe. Drill a small 1/16 " hole and inject adhesive. Colored wood filler and your set. It is caused from a high orlow spot in the slab. Even the best of us, have these in traffic areas from time to time. I can walk into any gluedown over concrete installation and find a hollow spot. Only if they are making noise(popping) or flexing as you walk on it, or a whole lot in a small area, do I consider it an installation defect, when doing inspections.

Hmm.. guess I should have clarified a little better. I actually did the ghetto plastic & ducttape squares test. Did about 5 of them. Unfortunately none of them where in the location the problem is in.

The problem locations is about 1ft x 15ft. I would actually be very suprised if the water is seeping through the foundation. Here we have floating concrete foundations 3ft+ thick. Also the location with the problem is at its worst smack dab in the middle of my house. Bostik best is a waterproof polyurethane based adhesive so it should guard against some moisture.

Since this problem just showed up and it has been raining on and off for weeks upon weeks, I'm going to let it sit and see if it corrects itself. If it does I plan on patching my squeeking spots, and buying a dehumidifier.

Now atleast I know why professional installation on concrete is suggested. However, around here (san antonio) there isn't too many experience professionals. Neighbors had bamboo "professionally" installed. They never checked for moisture or level. They also used liquid nail to glue it down. I did find some very professional installers, but it would be cheaper for me to replace the entire floor twice over before going with them. They wanted 2x the price of materials & over 5k for install. My total bill was 5k & that included a table saw, misc tools, and doing the stairs. They wanted that much just to do my staircase.

Anyways, I appreciate your help and suggestions. I'm going to wait this thing out until it dries out a little more. After that I will see what the full extent of the problem is. I hear bamboo is very resilient, and I'm hoping it will return to its regular shape. Hopefully it is still all adhered to the concrete.

San Antonio is in my coverage area. It is about as far as I go. I go to Seguin, Gonzales, Columbus, and other small communities where finding a professional is unheard of. I have been as far as Lake Medina, to install, for a client.


Fuel and trip charges would kill you though!