Have been installing ceramic forever but have been getting more requests for "wood" floors lately, so have begun installing these for about a year every now and then. All floors so far have been glue down engineered or floating laminates. But now I have a customer who wants 1900 sq. ft. of pre finished Australian Cypress, 3/4" solid hardwood nailed down. Yeah!!! Great easy wood for the first nail down! So I have a few questions if someone doesn't mind answering.
1. House is offgrade with crawlspace. Walls are really thick brick with some missing at the base for ventilation of crawlspace. One part of floor is some kind of original wood floor that shows zero sign of damage (cupping, gaps, etc...) except for some dryrot at the 2 entries for this room. No standing water noticed on property at all except on a badly poured slab at rear of house approx. 3' below floor level of wood.
So I shouldn't be concerned about vapor transmission from the crawlspace?
2.Underlayment is a mix of different things. PT plywood, KD plywood, original hardwood floor. Subfloor I only saw in one area that used to be a bathroom. They had dimensional lumber on sleepers between the joists which were cut to a point for a mudfloor for the ceramic. I saw the original contractor replace this floor with new dimensional lumber, then 2 layers of ply to match up with the height of the rest of the floor. In this one room he installed 15 lb. felt under the underlayment. I would assume that there is also 15 lb felt under the original hardwood floor (?) (house was built in 1964).
Do I install 15 lb felt under all areas? Or will knowing/assuming that there is felt in those spaces cause moisture issues if there are 2 layers of felt seperated by ply/ hardwood?
3.Splines. I have to turn around in a few closets.
Just glue them in with Titebond 2?
4.How bad is Australian Cypress to nail in? Are tongue splits that bad? Wood came straight from the mill in NC and it looks really nice and problem free.
5.Any issues that you can see that I'm not aware of yet?
Thanks for any help.

ausssie cypress tends to be brittle so you need to keep an eye on the chance of it splitting too much. I would make sure there is 6 mil plastic down in the crawl space. Check the m/c of the wood and subfloor make sure there within the range for your particular local. I just nail the splines but if you want to glue and nail that would be fine just be sure to nail it. Splines like to dive down when you nail them so use a scrap block next to your nailer to keep that in check. If you are going over an existing floor it needs to run the other direction. Dont run it the same as the original. You can felt it, plastic would be a bad idea but with 15# felt it will still allow vapor transmission.

Thanks Kevin.
Anyone else?