Hello, <!—-><!—-><!—->
I’m in the process of upgrading my hardwood floors. In the family room I pulled out the old 3/4 oak hardwood floors and was shocked to find only 1/2 plywood for subfloor. Worst yet, in some places the seams don’t fall on the joists. I would like to know what is the minimum amount of plywood that I need to add to existing subfloor:<!—-><!—->
1) Would 3/8 plywood nailed down to the existing subfloor be enough? <!—-><!—->
2) To cut down on squeaks should I also use liquid nails subfloor adhesive? <!—-><!—->
I’m planning on installing either 3/4 solid wood or 1/2 engineered wood floors.<!—-><!—->
Replies
How did your 3/4" hardwood floor perform before you found out that it had 1/2" ply as a substrate?
The 3/4" single layer floor system only became popular in the late 70's. Before that, we always l/2" cdx as as subfloor. We did break all the vertical joints on joists however. To do otherwise would endanger the crew as they went about their business framing.
I can't say if they layed an additional subfloor for hardwood. I do know that they always layed a 3/4" mudbase for ceramic tile and layed 5/8" particleboard (underlayment grade) over felt and laid carpeting over that.
The oak hardwood had longer pieces though and it all probably was nailed into the joists.
Bob's next test date: 12/10/07
When we started as carpenters (about the same time as you), we used 5/8 cdx for subfloors, we added 1/2 underlayment for carpet, vinyl or tile. If we felt that the floor was not in the best shape because of water damage during the framing, we would add the same under hardwood. I have 5/8 cdx on my own house built in 1983. I notice a lot more squeaks than we now get with a 3/4 subfloor.
I would advise the OP to use 3/8, glue and screws.
Does your subfloor have a layer of red rosin paper to segregate the layers? I think it's main purpose was to silence the squeaks.The one floor system came into being and the main benefit that they pushed was it's silence. Bob's next test date: 12/10/07
15# felt. This may help but not much. I can live with it as it is still a good floor. Some could not. I wouldn't want this on a job and we don't get it now with a 3/4 subfloor.
When I started framing back in 1983, every sub-floor was 1/2" and every oak floor went on top of that. We put 1/2" underlaymnet in the rooms that were carpeted. We started using 3/4" t&g around 1987-88 and that's it, nothing else on top.Joe Carola
Every house I've ever pulled apart from 1900's to 80's had either 3/4" 1 x 6, 8 or 12 solid wood decking laid diagonally, 3/4" ship lap or 3/4" ply. In new construction (80's or so) we laid down 5/8" T & G.
Edited 12/19/2007 6:55 pm ET by ted
I was thinking the same thing. I've never worked on a house with 1/2" subfloor. Always 3/4".
you ain't lived till ya get a 1/2" - 3 ply 24"OC floor w/ 3/8 roof...
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The floor in the family room was not in a great shape. A lot of squeaking.
The house is located in suburbs of Washington DC and was built in 1964 by Pulte. I guess judging from people responses 1/2 subflooring was the norm back then. I still think i need to add at least 3/8" to the existing subfloor. Specially if I settle on 1/2 engineered wood.
Don't get your knickers in a wad. I worked ona 1924 or 1926 house that had no subfloor ... the oak was laid perpendicular to the joists, and directly on them. If your new floor is 3/4" solid and laid perpendicular to the joists, the subfloor you have now is fine. you just have to be careful to nail only on top of the joists. if you plan to lay diagonal or parallel to the joists, then you would want to put down a layer of 3/4" underlayment ply.
You know what ... now that I think about it ... you might have a problem with the 1/2" problem is that, even nailing over the joists, the nails won't penetrate far enough into the joists to hold properly.
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"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
1/2" CDX Subfloor + #15 roof felt + 5/8" BCX Underlayment + 3/4" oak surface = easy install and no bouncy/squeaky.
Don't even need glue... (just to piss off the over-builders)
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I work on houses from about 1830-1860. Many of the earlier ones are about 7/8 finish flooring only. Some are T&G w/ no sublfoor at all, some are not t&g, just planks laid over 1/2" dustboards laid so as to have backing behind the gaps between the boards. And the joists run anywhare from about 22" O/C up to 36" or more.
When doing repair work on these floors, I often use 1/2" ply to replace the dustboards w/o changing thickness. They seem to have held up pretty good for the last 180 yrs or so...
Steve
FYI. young whipper snapper. In the olden days it was not uncommon to lay 3/4" T&G oak, pine or other strip flooring directly to the floor joist 16' o.c.. It was not even necessary to break the end/butt joints over a joist. Some times however the end joints were end matched. We did it even as late as the mid 1960's. I am presently living in a house built in 1929 in one of the nicer areas of Ft. Worth, Texas which is floored in this manner.
In fact International Residential Code #R503.1.1 still allows this application.
We are in the process of doing a flip and the oak flooring is attached directly to the joists. We are going to treat it as our subfloor and lay a new floor over it. Should we do anything special to prevent problems? Bob's next test date: 12/10/07
Sorry Jim. I will have beg off on that. I have never done it nor seen it done, but by no means that it can't be done. I can think of some possible problems. You really want to make sure that the existing floor is very well fastened. Like ringshanked nails or screws which may be very labor intensive. I don't know how difficult it will be to nail into the hard old oak flooring which by now may be even harder. Are you going the run the new flooring the same direction as the old? If so, is there a danger of perpetuating any irregularities that are in the existing floor? What will be result if the new nailing falls into the joints of the existing floor. I wish I could be of help to you, but I just don't have any actual experience doing this. You might want to check with someone that installs oak flooring all the time as a profession. It may be just fine. I just don't know. Good Luck.
We were going to turn the direction and run perpindicular.I hope someone else has done this and will weigh in. Bob's next test date: 12/10/07
In the Kitchen with a Cathedral thread that I had going the floor sub laid his new Hickory over the old pine T&G floor.
Perpindicular to the old floor, 15# betweent the layers.
They sanded the old floor as flat as felt they needed to, then ran their new floor.
Then they sanded again after the new was laid and finished it.
We screwed off all the old flooring with my quik drive screw guns with the stand up attachments, almost 500 sq ft screwed to the old joists in under an hour including the time to snap lines for the joists. Woods favorite carpenter
FKA- Stilletto
So far. any squeaks? We don't see any reason that the existing oak will be bad but I'll defer to experience. Thanks for your input. Bob's next test date: 12/10/07
Theres not a single squeek in that entire floor.
But it has only been about 2 weeks since they put a second coat of finish on it. So far so good.
If you go this route field finish it, don't buy the prefinished.
Cleat nails were used, 6" OC for a nailing schedule. The pine floor had alot of squeeks until we screwed it back down to the joists. Now it's silent.
Woods favorite carpenter
FKA- Stilletto
Edited 12/21/2007 5:28 pm ET by MattSwanger
HRH
I started framing in the late sixties, and 1/2" plywood with red rosin paper, and 3/4" oak was the norm. We did 100's of houses that way, and they are still alive and well.
If your home performed well prior to your remodeling, why change? This may be a regional thing-I can't tell where your from.
Greg in Connecticut
As another poster said, 3/4" t&g flooring can be used without any subfloor. My own house has that on the second floor and I've seen it a lot in older homes. So I wouldn't worry too much about it. The only caveat is that you have to be careful to hit the joists when you're nailing. To cut down on squeaks, use a slipsheet of rosin paper or 15lb. felt. (I prefer the felt since rosin paper tends to turn to dust after, admittedly, a long time. Some say the felt will smell like tar forever, but I've never found that to be true. Prolly wouldn't risk it over a radiant floor, tho'.)
As for the engineered stuff, follow the mfgr's specs.
Mike Hennessy
Pittsburgh, PA
Funny how things change. Those 3/4" boards were the foundation forms to start (see if they look a little grey) and then were used as subfoors. First they were perpendicular to joists, later went on at an angle (much stronger but more waste). 1/2 plywood was stronger than the angle 1X's. If glue was added to the joists things were top notch. Then 3/4" T&G took over and if tile was being installed the subfloor was 1 1/4". Then nails gave way to screws. Really didn't make me worry about the 1/2" in my 1968, and the 3/4 oak was nailed anywhere (into the joist or the subfloor). The squeaks I took out with a 3/8" drill bit over the joist, glued a short piece of dowel over the screw--finished it with water based.
My cabin doesn't have any problems. Floor is dirt. Tyr