Installing new hardwood questions

Redsail

I am getting ready to have 5" red oak flooring installed and site finished.
I live in the Seattle area on the shore of a small lake, so there is some humidity. In retrosect I should have probably gone for engineered, but instead I opted for rift and quarter sawn boards. Hurst Hardwoods assured me that they were much more stable and cupping would probably not be an issue in this part of the country. For the most part they will be installed over plywood subfloors, on the 2nd story, above a heated basement. My problem is:

A small portion of the living room has a 30 deg. prow shape and the triangle of the prow extends beyond the daylight basement and therefore has greater exposure to the outside. It has insulation, is covered with exterior plywood, and is protected from direct rain. There is a small (1/2")gap on 1/4 of the prow which probably allows it to breathe. Does anyone have experience with this type of construction and hardwood floors? I'm worried that the very different temperatures and possible humidity levels between the two areas of the living room will cause problems. Unfortunately, I didn't notice this before I ordered the wood!
The installer recommends putting down a liquid sealer on the prow to keep out any moisture. Is this a good idea?

2nd question: I would like to mitigate the noise from the floors to the basement. I've heard conflicting reports about underlayment. Several distributors have told me that underlayment will not mitigate noise under naildown floors. Does anyone have opinions or experience with noise abatement under naildown floors? I'd like the option of converting the basement to an apartment in the future, if possible.

Thank you for you for your opinions/help with these questions.

Redsail

woodman58

Rift and 1/4 sawn wood is the most stable (not cup easily) solid wood. In five inch wide wood I zig-zag a bead of liquid nail under each plank. It is not nessesary for wood 5" or under. But, It is for wood over 5". As for sound proofing, !/4" cork will help a lot. Make sure and glue it down with a wood glue.

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tacomafloor

The sound proof I have seen is hardwood nailed to sleepers over the sub floor with saw dust , I mean saw mill sized saw dust ,That was in apartments. as far as moisture,, thats usually dealt with by putting moisture barrier under the hardwood , The house should be insulated on any exposed exterior , and a moisture barrier under the siding , Never seen moisture barrier under a cantelever .
But i have installed hardwood over cantelever before , never got a call back !Never heard or was told anything would happen , i doubt you will have any problems , i have installed in houses built over a back filled marsh , I have a had problems when a genius had me install a floor in a house that floods underneath in the winter , but didn't tell me when i installed in the summer , the floor cupped a little
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