I have 1500 sq ft of marble (on a concrete slab) that I am replacing with 5/8" bamboo. The manufacturer says you can nail or glue down. I've had 2 contractors come out with 2 completely different opinions. One says he can go right over the marble (sand it down a bit, do some leveling) with a moisture seal and Bostik best glue. the other says we should remove the slab lay a 5/8" plywood subfloor and staple the bamboo to it. (their prices aren't that much different).

Which is a better solution... I need help!

Either will work.

Weigh the pros and cons of each, and make a choice.
Have you checked references and done a background check, on both contractors.
Will these contractors, actually be doing the work, or are they just the estimate guy?

Bad idea all im going to say.

I'm no flooring expert, just a guy doing his own install.

Here's something to think about re bamboo - and why I decided not to go with it.

No one seems to manufacture it in North America. It's all made in China, imported by some importer, and sold to distributor who brands it as their own or to a box retailer who does the same. I've never found a single bamboo retailer who actually make their own products, and I've looked pretty hard.

This wouldn't be a problem if this was managed well by the retailers, but I got a bad feeling when I'd questions retailers about:

1 - warranty. What happens when the importer chooses a new manufacturer in China? Who provides the warranty? The importer, distributor, or retailer? What if one of them goes out of business?

2 - consistency. The importers are choosing the cheap manufacturer of the month to increase their profit margins. Products I examined differed from crate to crate, even though they were re-branded to the same brand. If you're doing a large area, will the product be the same for the entire area?

3 - quality. I immediately noticed a big difference between a nice hardwood like say Pollmeier beech and all of the bamboo I inspected. They're just not made as well. I noticed the bamboo felt rougher, almost splintery at some places. The tongue/groove are not as nicely cut, and edges are not as nicely beveled.

4 - installation. I have never installed a floor, but I can tell you bamboo is DAMN hard. I took some samples and tried to drive a nail into them. Concrete is softer. Bamboo has so much glue (particularly stranded) it's insanely hard. A retailer told me it must be glued down, nails/staples just bend. I don't know if this guy is right, but I couldn't put a nail in it by hand. It just bent. I could hardly dent the stranded with the claw of my hammer, and I beat the heck out of it.

5 - formaldehyde. All the adhesives and finishes contain known carcinogens. Hardwood has trace amounts in the finish, bamboo has lots more, in both the adhesive and the finish. Many are now compliant with E1 European standards, but still.. I don't want my kids crawling on something which off-gases cancer.. Wood is natural, glue isn't.

That's it.. that's my anti-bamboo rant.

John