greetings all!

i've been reading the posts - lots of great information and some very gracious and helpful people out there!

i'm laying 3.25" brazillian cherry in my living room. i'm concerned about the subfloor. i read in a book (bollinger's) that if you're laying the strips PARALLEL to the joists, that your subfloor must be at least 1 & 1/8" thick. good enough. i have no problem with that.

now my questions:

can i have ONE monolithic layer of 1 & 1/8" plywood down for the subfloor, OR would it be better (cost-wise, structurally, or whatever) to have TWO layers (laid @ 90 deg to each other) as long as they add up to the requisite 1 & 1/8 inches? IF the two layer approach is ok, should they be the same thickness? one thicker than the other? if one thicker than the other, WHICH layer should be the thicker one - top or bottom?

also, what KIND of plywood is best in terms of cost / structural considerations?

thank you all in advance. i really appreciate it.

G

Well, if the house is already built, you do not have a choice unless you are adding on. I don't recommend anyone tear out their subfloor. Read this:
particle-board-osb-subfloors-underlayment-types-t385.html
If you are building a new home, you can buy 1&1/8" T&G plywood subflooring and span it over joists/trusses 2' OC. This would make a very stout subfloor. Georgia Pacific makes Plytanium subfloors, also called SturdiFloor. IF your house is already built and you have a subfloor already, simply add CDX plywood to it. If you have a 3/4", then add 3/8". If yours is 5/8", then add 1/2". If it is 1/2", add 5/8"; you get the picture. The single plywood system( 1&1/8" subflooring over joists 2' OC) is superior to say 3/4" + 3/8" over joists 2" OC.

thank you for the good (and timely!) advice. we decided to bite the bullet and scrape the adhesive/particleboard off and save the subfloor. we'll put down a 3/4" plywood underlayment over the top of our 3/8" subfloor. no worries.

one additional question has arisen: we have a fireplace on one end of the room. it has a lip of concrete about two inches wide that sticks above the level of the subfloor by anywhere from 1/8" to 1/4" in any given place. now, in order to get my underlayment to lay flat, i'm going to either have to 1) cut a rabbet into my plywood to accommodate it OR chisel the lip of concrete flush with the subfloor.

what do you recommend? i would think the rabbet method would be less desireable, since you're robbing the hardwood flooring of plywood for its nails to bite into.... but then the notion of all that chiseling doesn't look terribly appetizing, either.

An air chisel or electric demo hammer will make short work of the concrete with minimal mess. Another possibility is use a grinder with a diamond cup wheel but I wouldn't seriously consider that if you're living in the house unless you use a very good vacuum grinder system.

Don

Don,

Thank you very much for your reply!! I'll give my local tool rental house a call and see what they've got.

thanks again!

...and thanks to all who've taken the time to read my posts so far!

G

the link above is broken

If the concrete merely projects 2 inches into the space, then I wouldn't worry too much about losing nailing surface, you wouldn't be nailing that close to the end anyway.
Save yourself the effort and clean-up and merely rabbet the bottom of the plywood as you had planned. Suppliment the install by gluing this section of plywood down to prevent movement of the new floor system