bobjones00

Hi,

We had some remodeling done and I disccovered that the existing flooring was particle board that had gotten wet and was deteriorating so I decided I would replace it with 3/4" Advantech. I pulled up the particle board and found what looks like the original Oak T+G 3/4"x6" "sub-flooring". I'm going to leave the "sub-flooring" in place as it is in pretty good condition and it only helps to make the floor that much stiffer. A friend suggested that I put tar-paper between the original "sub-flooring" and the new Advantech as a vapor barrier and to help eliminate any noise issues (there was tar-paper between the "sub-floor" and the particle board that I pulled up). Also, the makers of Advantech suggest that you glue it down where it lays over a joist. So because of these two recommendations I layed out the tar paper in strips so that where the Advantech would lay across a joist I could glue it (see attached photo). I'm guessing that when Huber Mfg. suggested gluing the Advantech down they probably had in mind the Advantech laying directly on the joist. So, my case is a little different. Laying out this tar-paper was time consuming and I had a fair amount of tar-paper "waste". So, I have a couple of quetions:

1.) Do you think that it is really necessary to put the tar-paper between the old Oak T+G and the new Advantech? Wouldn't the Oak T+G act as a vapor barrier for the Advantech? Will the tar-paper help in other ways (e.g. noise)? Also, the joists do have insulation between them.

2.) Should I even worry about gluing the Advantech down to the Oak "subflooring" at the points where the Advantech lays across a joist? I'm nailing the Advantech usining an air-gun with 3" 10d ring-shank nails at the joist and 2" 8d ring-shank nails at non-joist locations. Lastly, is there a reason I *shouldn't* glue the Advantech down?

3.) Should I just keep doing it as I am, laying out the tar-paper in "strips"?

Thanks

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bobjones00

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CookeCarpentry

1) No need for tar paper. That should be installed under hardwood floor between that and the new subfloor (advantech).

2) First and foremost, go around and use ring-shank gun nails and nail all the t&g subfloor into the joists.

3) Why are you using 3/4" advantech? Is it for a height issue between rooms?

4) With existing 3/4" t&g, you could easily skin over it with 1/2" plywood, glued and nailed down.

bobjones00

Thanks for your response.

I don't quite follow you. Could you rephrase for my novice understanding?

The particle board I pulled up was 5/8" so I went ahead with the 3/4"
mostly for strength reasons but yes, height was a consideration because
of thresholds and adjacent floors.

I'm glad you brought plywood up because I would like your experienced
opinion. I talked to 3 or 4 builders / remodelers all of which seem to
go on about Advantech. Mostly I think because it tends to warp less if
at all. I ended up buying some Advantech based on their opinions but
when I look at Advantech I just see glorified OSB with a lot of water-
resistant resing baked into it. Maybe it's just me but I don't like OSB.
It's kind of like particle board in that onces it gets "damaged" it has
a tendency to just start deteriorating. I noticed that OSB just likes to
start flaking away which strikes me as very cheap and problematic.
Plywood doesn't seem to flake and "fall-apart" like OSB and if it has been
sanded a little from the factory handles very well. Am I way off base
here? I'm just a novice and my opinions may not even be close to
reality.

I'd really like to know your opinion of good quality plywood versus
Advantech. Is Advantech just a lot of hype and the trendy thing to
use?

CookeCarpentry

After your subfloor is installed, be it one layer of 3/4 over joists, or whatever, and IF you are installing a nail or staple down tongue and groove hardwood floor, that is when tar paper comes in handy. You roll out 15 lb tar paper or rosin paper over the subfloor, then nail or staple the hardwood ontop of it. This layer prevents the hardwood flooring from rubbing and eventually causing squeeks against the subfloor.



1/2" plywood over 3/4" t&g subfloor is going to be sufficient in strengthening any diflection in the floor without it being overkill. 3/8" would also work (unless you are tiling on top of it). 3/4" over 3/4" could be considered overkill given the fact that 1 1/2" of subfloor is excessive, and it is going to wreak havoc on room thresholds/transitions. So 3/8" would be fine, 1/2" would be preferred.



Bob, Advantech has it's applications, like all products. Do I like it? Yes. Do I use it? Yes. But not in the application you are.

If you were building a new addition and needed a subfloor recommendation, I would say Advantech because it has some extended weatherproofing technology in it. Meaning that the time between you installing the subfloor and drying the addition in, it can get wet without cupping, warping, exploding, flaking, etc, etc...within reason, of course.

If you want my professional opinion, as to what to use in your situation, I would say plywood. You already are weathertight and just need a product to stiffen up the existing subfloor, why pay for a waterproofing feature you don't need? Also, like I mention above, 3/4" is somewhat overkill. Additionally, a bit of "old school" mentality on my part, but I think plywood holds nails/staples better - so if your new flooring is hardwood, a plywood subfloor would be ideal.

I use advantech and commodity brand OSB - basically whatever the lumber yard has in stock. I use OSB for wall and roof sheathing and like it, but do agree about it damaging. I also use commodity brand plywood for wall, roof and floor sheathing. Multiple manufacturers out there - for your particular application, any 1/2" CDX plywood sheathing would work well.

If you have any other questions, or I need to explain myself better, let me know. Otherwise, go to it, and let us know what you selected.