Hi
I’m wondering if there is a proper way to lay new sub-floor over old or if I’m just over-thinking things again.
House currently has 3/4″ x 6″ wide planks running diagonally across the floor joists. I have screwed all of the old sub-floor planking back into the joists below. I now want to add a layer of 3/4 T&G Sturdifloor over the top. One small area is receiving ditra and tile and the rest of the room is getting 7/16 solid wood flooring (installed with 18 gauge 1 1/4 staples).
If the joists are running north south and I want the flooring to run east/west what is the correct/best orientation for the the new sheets of T&G? Do I run the 8′ lengths north south or east west or does it even matter?
Thought I would check before I start in case anyone has some input (other than I’m being to anal about the whole deal).
Thanks!
Replies
Run your plywood perpendicular to your joists. That is all that really matters.
With a double layer of subfloor, you can run your flooring in any direction you want.
EDIT to add: Be sure to glue down your plywood to the T&G with a PL like adhesive, and nail/screw through to each joist.
J. D. Reynolds
Home Improvements
Pp, Qq
Edited 3/19/2008 12:46 pm ET by JDRHI
if your old flooring is tite u probably dont need the xtra 3/4 on there
Not sure if your post was intended for me, or if you just responded to the most recent...
But I'll respond anywho. While the original 3/4" T&G subfloor may well be structurally sound, I don't always trust it. I did in the second hall floor on my own home....an area with moderate traffic....but I don't know the condition nor the circumstances of the floor of the OPs T&G.
He could certainly get away with 1/2"....but if he's already planed on 3/4", all the better and no harm done.
J. D. Reynolds
Home Improvements
Pp, Qq
What JD said.
"Doubt is not a pleasant condition, but certainty is absurd."
~ Voltaire
Do you have stairs in the area you are re-flooring? If so, you may mess up the rise on the first step.
Mike Hennessy
Pittsburgh, PA
Thanks everyone.I do have stairs to the basement at the very end corner of the room. I think I will be ok because the old flooring was 3/4. That leaves me about 7/16 high at the transition which I think will be ok if I just match the transition piece (it's already there) to be flush with the new flooring. I'm open to other suggestions though.
I'd go 1/2 ply for the tiled area skip the ditra) and full 3/4 flooring directly over the existing subfloor for the rest.
[email protected]
Why do you think you need an additional 3/4" underlayment?
I would use 1/2" cementitious tile backer under the tile and install the hardood over existing subfloor with rosin paper or 15# felt membrane.
Solar & Super-Insulated Healthy Homes
Rs,
While cbu would probably be ok in this situation, considering the stiffness of the existing underlayment, the cbu lacks the structural integrity of glued and screwed plywood. That sandwich of existing subfloor and glued up ply is hard to beat for stiffness.
Eric[email protected]
the cbu lacks the structural integrity of glued and screwed plywood.
I beg to differ. Cement tile backer board is stiffer than the equivalent thickness of plywood, and should also be screwed to joists as well as to subfloor 8" oc.
It also makes a far better substrate for tile since it is far more dimensionally stable than plywood.
I'm not talking about Hardibacker, but fiberglass reinforced cement board.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 3/19/2008 11:50 pm ET by Riversong
I beg to differ. Cement tile backer board is stiffer than the equivalent thickness of plywood, and should also be screwed to joists as well as to subfloor 8" oc.
I'm not going to go into a protracted debate on this but you are wrong on two counts.
Lets put a sheet of cbu and a sheet of 1/2 ply across some floor joists 16oc. You can even fasten your cbu if you want. Now, lets start jumping up and down on our sheets. Make sure you are landing with your feet between the joists........I'll bet you a jelly donut who is going to end up in the basement.
Now; go purchase a sheet of Wonder Board or maybe find the install on the www. Last time I looked it stated rather specifically to NOT fasten on joists only in between.
You should know better.
Eric[email protected]
I'm not going to go into a protracted debate on this but you are wrong on two counts.
No, just state that I'm wrong and run off?
Lets put a sheet of cbu and a sheet of 1/2 ply across some floor joists 16oc. You can even fasten your cbu if you want. Now, lets start jumping up and down on our sheets. Make sure you are landing with your feet between the joists........I'll bet you a jelly donut who is going to end up in the basement.
And you should know the difference between stiffness (modulus of elasticity) and structural strength). And, we're talking about installation on top of existing sublfoor which should be designed for structural strength.
Now; go purchase a sheet of Wonder Board or maybe find the install on the www. Last time I looked it stated rather specifically to NOT fasten on joists only in between.
Nothing in the installation manual indicates NOT to fasten into joists. But it's a moot point since the correct screws are only 1-1/4" long.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
And you should know the difference between stiffness (modulus of elasticity) and structural strength). And, we're talking about installation on top of existing sublfoor which should be designed for structural strength.
Then why did you make the point about it's "stiffness" at all? Based on your above definition I would say that plywood has both more stiffness and structural strength than cbu.
Nothing in the installation manual indicates NOT to fasten into joists. But it's a moot point since the correct screws are only 1-1/4" long.
And why then did you state that it should be screwed to the joists?
You cannot make an argument then attempt to back-pedal to the middle to regain some ground.
I looked on the Wonder Board web site this morning ang yes; it does not state that it should not be attatched to the floor joists. It used to say that before Custom became the producer of WB. Or at least it used to state that on the label attatched to the product.
We all know what happens to sheetrock when studs dry out or are subject to seasonal movement. I don't want one of those big screws under a tile when it decides to rear it's ugly head up!
You stated that it should be attatched to the joists, then I point out that you are incorrect then you tell me it's a moot point...............do you see why some folks here are having issues with you?
[email protected]
Edited 3/20/2008 8:01 pm ET by EricPaulson
You stated that it should be attatched to the joists, then I point out that you are incorrect then you tell me it's a moot point...............do you see why some folks here are having issues with you?
You tell me it said no screws in joists and then you tell me it doesn't say no screws in joists (and if you read the installation instructions, it says to screw into studs for wall applications).
Sounds like backpeddling to me.
But I'm not going to personalize this like you choose to do.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
You tell me it said no screws in joists and then you tell me it doesn't say no screws in joists (and if you read the installation instructions, it says to screw into studs for wall applications).
Wrong again...I stated that it once DID state that. I corrected myself and stand corrected as to what the installation instructions stse.
You just keep rolling along right as rain, at least you think so..............[email protected]
Thanks to everyone for their input. Here is some reasoning behind my decision to put 3/4 t&G over the original sub-floor. First, there was a previous tile install that showed a lot of cracked grout and tiles. This was done on cement backer board that was glued and nailed to the floor. I know this because I tore it out and it was not easy work for a pretty small area.Second, there are areas of the original sub floor that have been cut out and hacked away at over the years. While I have patched these parts, I still have some concern about the overall rigidity of the original floor. However, now that I have screwed all of the original sub floor to the joists it is much more solid that it was before and no creaks or groans whatsoever from popped nails. I would say that about 80% of the nails in the original sub floor had popped to some degree.Third, the areas where I will be placing the new sub floor material and new tile/hardwood are high traffic areas.Fourth, I'm willing to overdo it. We are spending a substantial amount of money (to us anyway) and time to renovate these 3 areas and the flooring materials are not inexpensive materials. When I do it I want to make sure that I am not going to have to "redo" it for a long time. Because the wood floor is warranted with a "proper" sub floor and other installation factors I assumed it would be in my best interest, if the need ever arises, to be able to show the rigidity of the sub floor.So I guess my thoughts are that unless there is some reason (other than time and expense) not to use 3/4 T&G over the old sub floor and a reason not to use Ditra membrane I'm going to move forward this way. Now if someone can tell me that there is something detrimental about my plan I am all ears!Thanks again everyone. I like reading the differing views and experiences of the posts on here.
Nope...proceed as planned.
J. D. Reynolds
Home Improvements
Pp, Qq
What are your joist size and spacing? Check out this handy calculator: http://www.johnbridge.com/vbulletin/deflecto.pl
The awful thing is that beauty is mysterious as well as terrible. God and the devil are fighting there, and the battlefield is the heart of man.- Fyodor Dostoyevski
If you are putting down tile, the CBU probably should NOT be screwed to the joists, only the subfloor. At least that is what the instructions generally say. I know Hardi board does. The idea being to allow the wood joist movement independent of the tile subsurface.
And me plumb outta Jiffy Pop.
Be dang me, dang me, oughta take a rope and hang me
Spheramid Enterprises Architectural Woodworks
"Success is not spontaneous combustion, you have to set yourself on Fire"