I prefer 90 days, but try telling a builder that. Naturally with higher end or homes with more square footage they'll get past that 90 days easily. There's a calcium chloride (CaCl) test that somebody mentioned here recently, but I don't see it used very often, although it should be. Can be expensive. I've talked to adhesive reps that mention using a concrete moisture meter, then if there are signs of questionable moisture levels, bring in the CaCl test. A few of the concrete moisture testing leaders. Not inexpensive either, but any good installer should have at least one. https://www.tramexmeters.com/store/moisture-meters-flooring/Tramex-Concrete-Encounter-CME4-Moisture-meter-for-concrete http://www.wagnermeters.com/shop/rapidrh4/c575-analog-concrete-moisture-meter/ "he's mentioned a plywood subfloor" Is there a reason here since you mentioned engineered? Perhaps the engineered has to be brought up to meet a different level? Vapor barrier. Yup, more than likely under the slab.

"Does this sound right, or crazy? Crazy, because most guys don't have a clue in how to do it right. I've known enough experimenters. I don't get why when there are other very good options today, particularly 3/4 inch engineered. However, many are either still unfamiliar it actually exists or still feel engineered has that fake stigma. Some markets are also stuck to old habits that die very hard, as solid 3/4 inch hardwoods are king in many areas. In actuality, 3/4 inch engineered offers more benefits opposed to older methods of hardwood on concrete. Unique also has good points. I've handled some 3/4" by gluing but they were herringbone and chevron designs. IE: shorter lengths For others that may be facing the older plywood on concrete application, I put together an analysis compared to 3/4 inch engineered. This is one of the graphics. Naturally costs will vary depending on where you live. More info here Ken Fisher

As Greendesigns points out, laying hardwood over concrete is tricky. A permanent hardwood (glue/nail/staple) on slab is more likely to go wrong than right. To be crystal clear, you can GLUE DOWN hardwood STRAIGHT to the slab. Adding plywood is a step used to NAIL down (or cleat/staple) hardwood into place over slab. You can SKIP this part if you GLUE DOWN the wood. But....and this is a MASSIVE 'but'....the professional must be SUPER EDUCATED as to glue down technique, glues, trowel size, coverage, moisture mitigation, etc, etc, etc! Gluing down hardwood is no different than gluing down plywood. Both are wood. Both require the same adhesives...and both have the same failure rates (ie the 'rotten plywood' comment above). The next issue would be height variation. I would expect a transition. Even a small one. And the reason: the townhouse subfloors were BUILT to accommodate cork glue down tiles (probably 4mm) in the kitchen and then another floor in the living space (???original floor???). And this BUILT IN floor height variation will never go away. Not unless you go back in time and make all of your decisions based on the inclusion of the hardwood running into the kitchen. I personally would find out if the engineered hardwood (with the 4mm wear layer) can be FLOATED - most are allowed to float...but not all so it is best to be super prepared. If it can be, your situation has been solved....remove the old vinyl/cork and FLOAT the new hardwood in the kitchen. A thin sheet of plastic will be laid down over the concrete and the wood will be floated over top. You will have a small transition ANYWAY (floor height variation = transition) so you might as well change the type of install to MATCH your slab = floating hardwood = MOST APPROPRIATE form of wood flooring install over slab. Also be aware that the finish might have a slight colour/gloss variation. Again, that's where a well prepared transition strip/area can be SUPER helpful in hiding these slight variations.

Bamboo is a tricky duck. It requires HIGH END production to get the 'cast iron' finish people claim it to have. A high-end product starts around $10/sf and moves (quickly) into the $15/sf range. The link you showed is $2.70/sf. If you MUST float a bamboo floor (or any solid wood-like product) please use the 'glue edge' approach. And please work with something in the 3/4" range. And please work with something CERTIFIED as 'old growth bamboo' (which is classified as grass poles 9 years or older). I can pretty much guarantee the $2.69/sf click together bamboo is not going to give you the easy life nor the 'cast iron' wear touted by bamboo lovers. Bamboo lovers will have purchased the $12 - $15/sf stuff that is solid strand old growth product in a natural colour. And it was probably installed with a glue down system (the really tough bamboo is horrible to puncture with a nail or staple gun!). If $3/sf is your budget and you are looking at a click together floor, you can purchase a VERY VERY nice laminate for that range. As in 'European Grade' product with off-gassing that is LESS than a jar of pickles!