I had the exact same issue. Initially they thought they could do it. But my house is old and when they did the demo they said the way they did the spacing of the supports under the wood on the older section cannot be duplicated today and the floor would never look even and the old section would always be a little higher and "squeaky". Ended up doing the whole floor. However, the hallways are old hardwood as well and the transition (via a doorway) seems fine.

Sigh...sounds like you have someone who isn't willing to jack out 1200sf of tile (back breaking but do able) and then grind down the thinset and then fill the low areas (aka 'subfloor prep). Of course the COST is something most homeowners don't like to see on a 'job cost' proposal. Many a contractor has lost a job because s/he quoted the cost of the BEST PRACTICES option. So the installers have gotten smart and started quoting 'low ball' work. This is just to get them the job (so they can feed their families). But what that means is they are forced into the 'not great' practices. I always recommend the homeowners get a full quote for the job. That includes flooring REMOVAL and SUBFLOOR PREP (two different costs) and then the installation costs (a third cost). If they are purchasing the materials then material costs are another cost to be added. To jack out tile = $2-$3/sf. The subfloor prep can be another $2-3/sf (these quotes will always be a 'range' of cost because the installer won't know the amount of TIME it takes to do the work...some tile is SUPER STUBBORN and other tile pops off like Pezz candies. With a situation like yours, that would have added as much as $5/sf = $6,000 MORE than what you have already been quoted (I'm assuming some things here). My question to you is: would you have hired the person if they had quoted you $6K more than what you were offered? Now onto what is usually the best option: Remove the tile and prepare the subfloor for the new porcelain tile. Please ask your installer to draw up a NEW quote for those two jobs to be ADDED to your job and ask for a new time line estimate (could be 2 days or it could be 5 days...we don't know). And ask him/her if s/he has the ability (in their schedule) to revamp your job to suit the new requirements = remove tile, prep subfloor, install new porcelain tile. In other words ask for a new quote using 'Best practices' which include removing old tile and subfloor prep. You will want to see their reaction to this. They will either jump at the chance to earn another $5-$6K or they will scowl at all the 'work' ahead of them.

Kim,,,it's very solid. just make sure the glue is spread to completely cover the plank. I have a few spots (like under the kitchen sink) where they missed the corner and it squeaks. They've held up great. I don't have dogs, but I have cats and have heard their nails burning rubber across the floor they go off on their tangents. I've spilled water, cleaned up their barf, spilled food, whatever, it all cleans up very well. as for dents, only if you drop something very heavy. but any wood floor will dent. I vacuum w/a Dyson, and then I use Bona wood floor cleaner on a mop. in the kitchen, i'll often take the scrubby brush and watered down Dawn to clean up spills or oil stains. no problem. no, I don't baby them. I don't wear shoes in my house though. I love my floors. just make sure on install they clean up all the glue residue. my guys were messy and lazy. had to call them back w/special glue remover and rag and go over the entire floor.

Generally it’s preferred for a house to have one continuous flooring material (obviously excluding baths). The house will look larger and more harmonious. If you want something fun buy a rug for over the hardwoods. Grey hardwoods on one level and warm wood tones on another sound discordant.