I haven't been able to find the answer for this by searching.

I am installing a 3/4 thick prefinished brazilian cherry floor in a large part of my house. The house was built in 1963, and has what appears to be a 2" thick T&G subfloor on 16" joists.

It previously had carpet, and had a 3/8" particle board underlayment nailed down under the carpet. I've removed all the underlayment and resecured the subfloor to the joists...

I decided to go with 1/2" CDX plywood over the subfloor, mostly because height isn't an issue and I wanted more stability (though the thick subfloor is pretty stable).

Now I'm trying to figure out if I am about to fasten the underlayment incorrectly

I've borrowed a pneumatic framing nailer and purchased 2 1/2" 8d ringshank nails. I've yet to be find any FAQ or other resource (including this one) that mentions the best way to fasten underlayment in this case. I did read a post by Gary where he mentions stapling the underlayment...but would using a framing nail be a really bad idea?

Thanks,

T

You can use 1/4" crown staples 1 1/4" long. Place staples 1/2" in from edge of the sheet and 1 1/2" to 2" spacing from each other, space field staples on a 6" grid. Use sub floor adhesive to glue the underlayment to sub floor.

You are good to go. You need to be sure you are doing it right, though. Just make sure the plywood is in contact with the subfloor before you pull the trigger. I am a qwick-drive guy, so I don't have to bother with that.


p.s. Leave gaps between panels and never force any panel against a wall. You can be pretty sloppy if ya want. Just don't lock anything in.

p.p.s. Buy a roll of felt and use it to make patterns for the more troublesome pieces. It will save you an awful lot of grief.

A 2" thick subfloor??????????? Are you sure?????????? Perhaps you meant a 1/2" thick subfloor.

Stapling is best, IMO. Because it is FAST, CHEAP and hold very well. Chuck's method of screwing it down is SUPERIOR in terms pure holding power and sucking the underlayment down but for the novice and professional alike, it takes more time and costs more. Just my 2 cents worth. I am not a fan of gluing down underlayments due to the fact that IF it ever needs to be removed (house flooded for example), you will be tearing up the subflooring as well. Framing nailers work OK. I used to do it that way but found staples to be way better. If stapling, I recommend a general construction staple size. 16 gauge, 1/2" crown with a 1" to 1&1/4" leg for 1/2" CDX plywood.

Thanks for the help folks!

Ok, I was guessing at 2"...now that I have taken another look, its more like 1" to 1 1/2"...keep in mind, its not plywood, its solid board, about 4" wide, T&G. This house is weird anyhow...I even have wall hung toilets, those were fun to source when I needed a new one!

I think I'm going to stick with the framing nailer, as that's what I already have on site...what sort of pattern should I stick to? How many nails around the board edges, and how many inside the boards?

Also, when I am putting down the floors, do I need to secure the 15# felt to the underlayment? Or does it float underneath?

Thanks again,

T

Either diagonally from corner to corner of from the center out like you are putting on a cylinder head.

nail 4-6" on all edges and 10-12" in the field. Line up field nails with the joists.

Glue can be a 2 edged sword. If you have to go backwards later, it sucks. I ALWAYS use it as insurance against squeaks....and i'm with chuck, I screw floors, unless it's a giant project.

Just remember nails will promote squeaks, as over time, the wood starts sliding against the nail, ever so slightly. I've chased squeaky nails with screws when I did warranty work, and the builder had squeaks, under the carpets. It was always framing nails used to put the decking down.

If you screw it down, do you use just regular 2" deck screws countersunk?

Also, what's the best way to secure the felt under the floor?

Thanks!

Roll it out and flip it , it will lay flat .. lay one sheet at a time , put the next one down a board or two from the edge of the previous one ..

Awsome, thanks for the help...should be a fun 3 day weekend!

I'm doing the hallway and master bedroom (we've been in the house a year and haven't lived in the master yet! can't wait to get it finished)

As far as nailers go...I am putting down prefinished 3/4" brazilian cherry...from researching here, it looks like a 2" stapler is the preferred method...I have only been able to find a local place that rents the Powernailer 445...the guy said this takes staples, but I'm wondering if its actually taking cleats...would this be sufficiant?

Use the staples

Home depo rents the stapler ..