NEED HELP with weird hardwood strip floor - 1921 house

pictures to illustrate: http://silvercrayon.com/floor /
I am planning to install a new 3/4" thick hardwood strip (unfinished) floor in my living room. (the old school kind) and i have a couple of questions.
The house is in baltimore and was built in 1921. a fairly typical 13 foot wide baltimore rowhouse (that's baltimoreese for cheap townhouse)
There is no true subfloor, there is an existing tounge and groove 2 3/4" hardwood strip floor nailed directly to the joists and joist extenders. this floor is a little thicker than 3/4" and has been carpeted most of the time. the floor has been carpeted for 50 years i imagine.
Anyway, I pulled up the carpet and pad, and replaced the rotten and deteriorated sections with shimmed up 3/4 ply nailed to the joists.
The floor is uneven by 1/8" variance i would say (slight buckleing, wear, slight sag and old radiator holes) and also what appears to be tile grout or some kind of honeycomb patterned adhesive gunk on some strips (old bath location). these appear to have been sanded down enough so that 1/8 inch or so above the surface is the most uneveness.
is this an acceptable "subfloor" for what i am doing?
the flooring will be installed by a floor installer, not a full-blown contractor.
pictures to illustrate: http://silvercrayon.com/floor /
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see what the floor installer says will they guarantee the floor?
They should be experienced and they have seen the floor. The most experienced of us here cannot really see the unevenness and where it is.
Wayne

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hank wrote:

Dunno but to me 1/8 is a lot depending on how much distance...1/8 over all? 1/8 in one foot? Easy answer is that anything that precludes laying the new floor flat with each board flush to its neighbors needs to be fixed.
Then there is the direction of the boards...planning on laying the new ones parallel to old? Can't say for sure but I don't believe that would be a good idea. Neither would be laying them perpendicular to the old (parallel to joists).
Seems to me that you need a new, proper subfloor.

IOW, he puts what you tell him where and how you tell him to put it and has no other responsibility.
-- dadiOH _____________________________
dadiOH's dandies v3.0... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at http://mysite.verizon.net/xico ____________________________
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i am now planning on installing a second subfloor directly on top of the original wood floor (There is no true subfloor, there is an existing tongue and groove 2 1/2" hardwood strip floor nailed directly to the joists)
I will use 3/4 plywood and just nail it directly down - any suggestions/pitfalls?

all?
new
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hank mitchell wrote:

1. Use tongue and groove ply
2. Stagger the ply joints. Take a 12x16 room for example... 4x4, 4x8 4x8, 4x4 4x4, 4x8 4x8, 4x4
3. Fasten securely. a. Try to get ply edges over joists and fasten through ply and strip floor into joist. b. Fasten other areas of ply to strip floor c. Don't skimp on fastenings
4. Do a good job on the sub-floor...it will make the laying finish floor go much better and help avoid potential problems with it later.
-- dadiOH _____________________________
dadiOH's dandies v3.0... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at http://mysite.verizon.net/xico ____________________________
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would you suggest 2" or bigger ring shanked underlayment nails? in order to get down to the joists? how about also using a liquid nails type glue (in additionn to RS nails)

strip
go
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hank mitchell wrote:

Let's see...3/4 ply + 3/4(?) strips = 1 1/2. Two inch would give 1/2" in joists. I'd want another inch. For field nails (just into the existing strips) 1 1/4.
Can't advise you re ring shanks, only used them decking my boat. Worked fine. Mostly I use square drive screws, #8 & #10, for the general wood hobby stuff I do now. ________________________

Dunno, don't see how it could hurt.
dadiOH ________________________
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Just a thought but don't forget about your friendly neighborhood flooring installer. He will be laying through the tounge of the new wood into the ply & hopefully getting into the original flooring. Not much chance of actually nailing into the joist. Nailing the new flooring into the joist isn't required but it sure makes me feel better.
Adam
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I had a similar situation at the other end of Chesapeake Bay from you. I found a flooring firm who did lots of old houses. One section of house they floated a floor on top without problems, the other section they said "do you realize how much this old floor is worth?!?!?!"
Before you do anything irreversible ask a dozen of your rowhouse neighbors who did their floors. Bet there are two or three firms commonly used.
In my situation I carefully pulled up the old tongue and grove, a regular carpenter repaired the subfloor, and the flooring guys then deployed.
Good luck! Your friends in new houses in the suburbs will have sagging floors sooner than you will.
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