# Securing plank subfloor to joists?



## duffman56 (Mar 9, 2012)

I have purchased some #10 2" screws to attach our t&g plank subfloor before tiling.

How often do I need to screw the planks into the floor joists? Joists are 16" oc and planks are 3-1/4" wide. So, screwing every other plank would mean a screw every 6-1/2". Is this adequate, overkill, or a good plan?

1/2" ply to go over t&g, attached with #8 1-1/4" screws, then Ditra, then the tile. I've received advice on amount/spacing of the 1-1/4" screws, but not the 2". 

Oh yes, I consulted the Ditra handbook, which was helpful regarding the method, but said nothing about how often to screw the t&g. 

Thanks to everybody for your help!


----------



## joecaption (Nov 30, 2011)

Why in the world would you ever use planks and not Just use T & G Advantec subflooring? Far smoother, 0 chance of it cupping, far easer to install, 50 year warrenty.
I use ceramic coated decking screws installed with an impact screw gun with constrution adhesive on the joist and install the screws every 6".


----------



## shazapple (Jun 30, 2011)

I did basically the same installation about a month ago (my boards are 4.5" wide and 3/4" thick). I put two screws in every board at each joists. Overkill? maybe, but I bought a bucket of 4300 screws so I was going to use them! I screwed the plywood (also 3/4") down 6" oc, sometimes 4" oc if it was a high traffic area using the same screws as the subfloor (1 1/4"). 

Be sure to buy extra thinset, as filling in those waffles in the ditra takes a lot!


----------



## JazMan (Feb 17, 2007)

Duffman,

It would have been better if you had added this question to your original thread concerning this project. All the info is there, but OK.

Absolutely, you need 2 screws at every joists and it's not overkill. I have not idea either why you'd consider skipping a plank. :no:

Shazapple, 

The 1 1/4" screws you used to fasten the subfloor to the joists are too short. Good luck with that.

Jaz


----------



## duffman56 (Mar 9, 2012)

Joecaption - I didn't choose this flooring, it's what was there. 


Am I getting this right? Two screws per plank, per joist? Basically one screw every 1-3/4" along the joist? Never would have dreamed I needed TWO per plank, and yes, every other plank seemed like it could be a bad idea... Glad I asked!


----------



## JazMan (Feb 17, 2007)

See...........


> Joecaption - I didn't choose this flooring, it's what was there.


Exactly the reason not to start a new thread. That info is in the original and Joe would have known. :wink: 



> Two screws per plank, per joist? Basically one screw every 1-3/4" along the joist?


1 3/4" is not relevant, if the boards were 2", the screw might be 3/4" apart. You need two per plank to help prevent the boards from cupping. With wider boards I have used 3 screws at times.

Jaz


----------



## Gary in WA (Mar 11, 2009)

"Oh yes, I consulted the Ditra handbook, which was helpful regarding the method, but said nothing about how often to screw the t&g."---- because sub-flooring should be *nailed, per minimum code*: 
24 1" × 6" subfloor or less to each joist, face nail 2-8d (21/2" × 0.113") 
2 staples 13/4"
From: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_6_sec002_par005.htm

Underlayment: http://www.apawood.org/pablog/index...tion-of-Plywood-Underlayment-in-Floor-Systems

http://www.apa-europe.org/Languages/English/PDF/R340G.pdf

Gary


----------



## mnp13 (Jan 16, 2007)

duffman56 said:


> 1/2" ply to go over t&g, attached with #8 1-1/4" screws, then Ditra, then the tile. I've received advice on amount/spacing of the 1-1/4" screws, but not the 2".


Plywood is 1/2 inch, t&g is 3/4 inch, that means that the screws that you're planning to use will barely make it through _to_ the joists, if they even break out the back at all.

I wouldn't use anything shorter than 2"


----------



## JetSwet (Jan 21, 2012)

It sounds like the op meant using 1 1/4 screws for tile spacing?.....


----------



## mnp13 (Jan 16, 2007)

JetSwet said:


> It sounds like the op meant using 1 1/4 screws for tile spacing?.....


Maybe, but that's not how I read it:


> 1/2" ply to go over t&g, attached with #8 1-1/4" screws, then Ditra, then the tile.


I understood that to mean that the 1/2 inch ply was to be attached to the t&g with the 1 1/4 screws. But it sounds like there are two threads on the same topic (not that I've ever been guilty of that. :whistling2 so you may be reading with other info that I don't have. 

When I did the kitchen floor in my last house, I screwed the t&g to the joists with 2 inch screws, then screwed the ply through the T&G with 2 1/2 inch screws. I used shorter screws for the hardi backer layer, but at that point I had raised the level of the floor close to an inch (ply, SLU, hardi backer) so I figured that if it was still going to shift/bounce there was nothing I could do about it.


----------



## shazapple (Jun 30, 2011)

You are not supposed to screw the plywood through the t&g to the joists. I don't remember the reason but that was one of the things mentioned in the TCA underlayment document. 

I'm not too worried about the length of screws I used for my planks, but longer probably would be better.


----------



## mnp13 (Jan 16, 2007)

shazapple said:


> You are not supposed to screw the plywood through the t&g to the joists. I don't remember the reason but that was one of the things mentioned in the TCA underlayment document.


Huh, I wonder why. We'll have to wait for an expert to answer that one. 

I was told specifically to do it the way I did it by a floor contractor. :laughing:


----------



## duffman56 (Mar 9, 2012)

Yes, I am guilty of starting a new thread on the same topic. I only did so to generate some answers, as the other thread seemed to of died before my questions regarding the joist screws were answered, and I am wanting to have the floor ready for tile this weekend (working on it every night after work). For that I am sorry. 

The #8 1-1/4" screws are not intended to go into the joists, only to secure 1/2" ply to the t&g. 

The #10 2" screws are to go through the t&g and joists only. Given that I will be putting the screws so close together, and two per plank, are these screws too beefy? Should I use #8s instead? 

I had looked for "flooring screws" but couldn't find anything by that name. The screws I did purchase are #10 2" Spax Construction screws ("For Multiple Materials"). I thought the fact that no pre-drilling was required would be beneficial. 

Is there another size/type of screw that would work better, or should I go ahead and purchase more of these? Thank you all for your help (obviously I am very green at this), and again - sorry for starting a new thread.


----------



## JetSwet (Jan 21, 2012)

The 1 1/4 screws won't hold your ply to the plank floor use 2 1/2 or 2 5/8 either deckmate screws or very corse sheetrock screws but galvanized screws would be better to use for these sizes for both 1st and 2nd layers.

I don't think screwing in the t&g will be a good idea as its a week spot in the wood your also putting 1/2 on top so any chances of it cupping are very slim.


----------



## Ed911 (Oct 15, 2011)

Not that I'm an expert, but as I've seen on DIYTV...you screw the subfloor to the floor joists...then the sheeting over that does not get screwed to the floor joists, but to the subfloor. What I've been told is 6" on perimeter and 8" in the field should be good. 

So, 2 inch screws will work for the TG subfloor, and then 1-1/4" will work for the half inch sheeting. The 1-1/4" screws that you are using will penetrate the TG subfloor to the full thickness of the TG, especially if you drive them in so that the heads are countersunk slightly. 

The reason that you don't want to skip boards is that you will essentially have a floating floor where you don't have any screws...and movement, and squeeking...not good. So, like was said, 2 screws per board...and I'd also consider gluing them to the floor joists. And, don't forget to block around the edges for support. The old TG or whatever the subflooring was, extended over the rim joist and under the wall's and on top of the floor joists. When you cut out the subfloor, you need to block the edges so that you will have a nailer around the perimeter of your new TG subfloor for support. Sometime this little bit of information is overlooked. 

I did some research in a couple of other DIY forums...it appears that it's not recommended that underlayment, like plywood, be glued to the subfloor...your TG. 

Never scrimp on things that will be hidden and that can only be fixed by a tear out.


----------



## duffman56 (Mar 9, 2012)

Seems to be general consensus that the 1-1/4" screws I have will do the job. 

Mostly asking about the #10 2" screws: Will the ones I've purchased (see above post) work well?


----------



## JetSwet (Jan 21, 2012)

I was taught 1 1/4 screws are never used for any flooring except luon and hanging sheet rock and butting cabinets together. 
Be on the safe side and go higher up on the size.


----------



## JetSwet (Jan 21, 2012)

duffman56 said:


> Seems to be general consensus that the 1-1/4" screws I have will do the job.
> 
> Mostly asking about the #10 2" screws: Will the ones I've purchased (see above post) work well?


Just because you have 1/2 ply doesn't mean that you exceeded your screw size, I'm just saying that you have to take in consideration that you need to make shore that ply doesnt go anywhere
The more the screw holds on to the underneath the less Likely it's will move. Use your 2" that you have for a piece of mind.


----------



## duffman56 (Mar 9, 2012)

JetSwet
Actually I'm asking if the #10 2" screws are a good size for attaching the t&g to the joists (two per t&g plank, each place it sits on joist).


----------



## JetSwet (Jan 21, 2012)

duffman56 said:


> JetSwet
> Actually I'm asking if the #10 2" screws are a good size for attaching the t&g to the joists (two per t&g plank, each place it sits on joist).


Yes they are good sorry about that.


----------



## duffman56 (Mar 9, 2012)

Very good. 

These screws claim no pre-drilling is required. If I were to purchase some more (and I'm going to need A LOT more) #10 2" screws that don't advertise this, I'm guessing I would need to drill a pilot hole for each screw to avoid splitting the wood. What size bit is recommended for this?


----------



## mnp13 (Jan 16, 2007)

Aren't you putting the screw in the center of the boards?


----------



## JetSwet (Jan 21, 2012)

The only spax I have used are masonry type, try to screw it in the board and if you inbed the screw like a 16th inside the board you should be good with out having to predrill.


----------



## duffman56 (Mar 9, 2012)

mnp13:
No, I am putting TWO screws, per plank, per joist. I realize this will be a lot of screws, but I'm told this will minimize cupping. 

I was planning on putting a screw about 3/4" in from each edge of each plank. Given this distance would this minimize the chance of #10 screws splitting the planks? 

Just wanting to make sure I'm doin the little things right. I am very grateful to everyone for being so patient with such a newb.


----------



## mnp13 (Jan 16, 2007)

Well I'm not at your house with you to see the boards, but i would guess at that distance pre-drilling wouldn't be necessary


----------



## shazapple (Jun 30, 2011)

I didn't pre drill, except at the butt joist because they had a tendancy to split.


----------



## duffman56 (Mar 9, 2012)

Just put the first screw in (3/4" in from edge) and yep, it split the plank. Guess I'll have to drill pilot holes to avoid this?


----------



## framer52 (Jul 17, 2009)

Get a nail gun and shoot ring shanked 8d nails into the subfloor. Screws are not necessary.


----------



## JazMan (Feb 17, 2007)

Duff,

Just in case you're not in the mood to spending several hundred on a nail gun and a compressor, you can easily hammer 8D deck nails and be done. It's common for the planks to split near the ends. So just drill does, 1/8" should be good. 

Jaz


----------



## duffman56 (Mar 9, 2012)

Ok, so ringshank 8d nails will do just as well as the screws? I may switch to them, although the pilot holes/screws went pretty quick tonight. 

However, we ran into another problem... :furious: After we secured all the planks to the joists I had my wife jump up and down. She is not a big girl... There was noticeable deflection. I went down to the basement to investigate. She was actually only a foot or two away from a steel I-beam which runs perpendicular to the joists. This I-beam has a piece of wood (2x4 maybe) running across the top. The particular joist that was below her is not quite making full contact with the wood on top of the I-beam. 

Do I need to put some kind of shims between the wood on top of the I-beam and the bottom of the joists so they are making good contact? Any suggestions on how to do this? I was thinking about trying to pry the joist up so that I could get the shims in. Do you guys think this would work?


----------



## JazMan (Feb 17, 2007)

You need to check why. Something is warped or has sagged. The joists and subfloor need to be fully supported and everything must be flat. A shim might be in order if it doesn't raise the joist. 

I don't remember what joists you have. They were 2x8 right? Did we check the deflection ratings for the intended purpose? 

Jaz


----------



## Ed911 (Oct 15, 2011)

You can get some pretty thin shims...wood or other materials...at the big box stores...you shouldn't have to move anything to use them...unless you are talking about a very small gap.

The non-wood shims don't shrink...and may be your best bet...however, I like the wooden ones.


----------



## JetSwet (Jan 21, 2012)

Duffman, how thick are your boards? I saw u mentioned there very narrow these sizes may play a good part on why you still have movement.


----------



## framer52 (Jul 17, 2009)

Yes you can and must shim the joists.


----------



## duffman56 (Mar 9, 2012)

The joists are 1 5/8" x 5 5/8" with 16" span o.c. We're using a snap line to mark where the joists so we know where to screw. When doing this the line was tight and I noticed that the center (basically where there was movement before) was about 1/4" lower than the edges where we had the chalk line. 

Do I need to try and raise the joist to counter this, or should I only try to add enough shim to establish contact between the I-beam and the joists? 

While in the hardware store I noticed some metal straps maybe 1/16" to 1/8" thick, 1.5" wide. Would these work well to shim under the joists?


----------



## mnp13 (Jan 16, 2007)

I would just get shims regular wood or plastic shims. One in from one side, one in from the other. Tap into place, secure. And also take a look and see if you can see why the joist settled that much. It may need a vertical support under it.


----------



## JazMan (Feb 17, 2007)

> The joists are 1 5/8" x 5 5/8" with 16" span o.c.


What?  We need to discuss this.:yes:

Jaz


----------



## mnp13 (Jan 16, 2007)

> For joists that are SYP or Douglas Fir, in good condition, 5.5 inches tall, 1.5 inches wide, 16 inches on center, and 10 feet long between supports, the deflection calculated is 0.510 inches.
> 
> This translates to a deflection of L / 235.
> 
> Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Sheet Vinyl or wood.


How far is your joist span?


----------



## duffman56 (Mar 9, 2012)

Jaz, you have me worried! 

The span is 6' 10" from foundation to first I-beam, and 6' 3" from first I-beam to the second one. I entered all this info into a deflection calculator (on John Bridge's forum) and it said the deflection was suitable for ceramic (but not stone) tile. 

I have already purchased all the materials thinking we could tile and based on this deflection calculator. Please tell me we can still tile?


----------



## JetSwet (Jan 21, 2012)

Plywood for subfloor relies on how far apart your joists are and how big they are not how long they are from footing to footing.

I think we might all be confused on the height And with I think you put down the exact is would be like 2x6 2x8 2x 10 or 12's.


----------



## mnp13 (Jan 16, 2007)

The measurements he put down are generally the true measurements for a 2x6. Aren't they? That seems small for a floor, but I'm used to the beefy construction of old houses. 

And plywood or not, doesn't the underlying structural strength of the joists determine the floors stability? Yes, of course the plywood will add stability, but the joists still ultimately carry the load. I have cracked joists in my attic, it does happen.


----------



## duffman56 (Mar 9, 2012)

According to John Bridge's "Deflect-o-lator" (http://www.johnbridge.com/vbulletin/deflecto.pl), they are 2x6s. I used a generous 7' for joist span, and entered all other information exactly. I hope this deflection calculator is accurate, and that we can still tile.


----------



## duffman56 (Mar 9, 2012)

mnp13 said:


> Tap into place, secure.


Mnp13, you are referring to shimming between the underlying I-beam and the joist, correct? How would you secure them?



mnp13 said:


> And also take a look and see if you can see why the joist settled that much.


I'm guessing the joist settled because of all the added weight that was not originally there. The floor had the original 3/4" t&g (which we are keeping), 1/4" ply on top of this, a layer of linoleum, *1/2" particle board*, and another layer of linoleum on top all of this. Perhaps this is why the steel I-beams were added? 



mnp13 said:


> It may need a vertical support under it.


What do you mean by this? Wouldn't the shims provide support under the joists?


----------



## JazMan (Feb 17, 2007)

Duffman,

OK, sorry that clears it up.


> The span is 6' 10" from foundation to first I-beam, and 6' 3" from first I-beam to the second one.


I didn't see where you had ever said the joists were 2x6 spanning only under 7'. 

Jaz


----------



## duffman56 (Mar 9, 2012)

Yeah I don't know that I had ever specified the span, I should have. Good to know we can still tile!

Regarding the shims, would metal perhaps be ideal?

Prying up the joist just barely enough to get the strips under the joist?

I guess for some reason this sounds better to me than going in from each side with wood shims, but I don't want to argue with the experts (I'm just not sure how to get the wedge shaped wooden shims to stay).


----------



## JazMan (Feb 17, 2007)

Use the type that are closer to you. I don't know which will fit better. I also don't know whether you should/need to pry anything. I'd evaluate how flat the floor is before you create a high spot.

Jaz


----------



## duffman56 (Mar 9, 2012)

I know at least in the one area that had the bounce the center is about 1/4" lower than the edges (discovered this when using snap line). I guess we'll try to raise that joist a 1/4" and evaluate/raise the others accordingly.


----------



## mnp13 (Jan 16, 2007)

When I shimmed my old kitchen floor, I put my 6 foot level on the floor across the low spot. Then I had someone sit in the doorway across the room to watch while I shimmed the floor from the basement. I put a little glue on the top and bottom of both shims, then tapped them into place and they told me when the floor hit the level. After that, I screwed the floor to the joist next to the shims (the second time... the first time I put the screw through the shims which splintered them into toothpicks... oops!)

But when I did my bathroom, I just screwed the floor to the joists, then leveled the worst places, then plywood, then leveled the whole thing - which was waaaay easier, but rather pricy. However, it was well worth it for the simplicity of tiling a perfectly flat floor.


----------



## duffman56 (Mar 9, 2012)

*We did it - But...*

It was a little scary, but we successfully (I think) raised the joists so that the floor is flat (or at least flatter than it was). 

It was a little scary - using a 7' post and a automobile jack to raise the joists, but it worked amazingly well. We shimmed with 1/8" sheet metal pieces, cut to about 2"x4" pieces. 

It seems to me that the floor is more secure. However - jumping on the floor still shows noticeable movement in the floor. Inspecting from below shows that the joists are flexing BETWEEN their support (I-beams). 

I guess right now we will just plan on counting on the information on the "Deflecto-lator" being correct, and hoping for the best. :whistling2:

Thoughts?


----------



## mnp13 (Jan 16, 2007)

In my opinion? No. 

If your floor is flexing with you on it, it will flex more with all that additional weight on it. The deflectolater assumes that your joists are in good shape. A joist that flexes when the span is only 6 feet is not what I would consider "good shape"

It will stiffen up when you do the plywood layer, BUT the underlying support is still your joists. It would really suck to do all that work just to have the tiles crack and/or come loose


----------



## Big Stud (Jul 3, 2011)

:wallbash:


----------



## mnp13 (Jan 16, 2007)

I'm not sure if "Big Stud's" head banging is to me or the OP. :wink:

However, I'm now that I have re-read, I'm confused by the post from earlier.

You jacked up the joist using a car jack and a post, and then shimmed _what_ to _where_???

When you shim something, you put a wedge between the secure item and the moving item. I'm not following what you shimmed with these 1/8 inch pieces of metal. You jacked up the joist, then... what? And did you leave the post in place? Because if you didn't, what is holding joist that you moved? 

In MichelleLand, a shim is a wedge shaped piece of wood/ plastic/ whatever. It is not flat. You tap a shim into place and it is held by the tension between the secure item and the non-secure item. Yes, I secure them afterwards, but they should be held by the pressure. 

Can you post pictures? 

Oh, and this:


> and hoping for the best.


is a recipe for a very very disappointing outcome.


----------



## duffman56 (Mar 9, 2012)

I placed the pieces of metal under the joists, where they rest on the I-beam. I guess we will secure the 1/2" ply and see how much that helps, then go from there. 

On DIY I saw them screwing and gluing plywood to either side of the joists. Would something like this strengthen the joists significantly? Would the best option be to screw and glue another 2x6 to the current joists? 

I've actually started securing the plywood in the utility room, which didn't have as much flex as the kitchen. We've run into another problem. :furious:

As I said before, we're using #8 x 1-1/4" screws. I'm not sure what the problem is... some of the screws are counter-sinking, but some are not. I tried moving these over an inch, thinking I may have hit the seam of the t&g on the ones that aren't going in. This doesn't seem to be helping. 

Do I need to try #10 screws? Pilot holes? I have no idea how to fix this problem, or why it is occurring to begin with.


----------



## mnp13 (Jan 16, 2007)

At this point, I think you need to have a professional come in and look at this. Yes it will cost you some money, but doing this install on inadequate support the entire thing is going to be a disaster.


----------



## Ed911 (Oct 15, 2011)

duffman56 said:


> I've actually started securing the plywood in the utility room, which didn't have as much flex as the kitchen. We've run into another problem. :furious:
> 
> As I said before, we're using #8 x 1-1/4" screws. I'm not sure what the problem is... some of the screws are counter-sinking, but some are not. I tried moving these over an inch, thinking I may have hit the seam of the t&g on the ones that aren't going in. This doesn't seem to be helping.
> 
> Do I need to try #10 screws? Pilot holes? I have no idea how to fix this problem, or why it is occurring to begin with.


I'm guessing that you didn't strip out the screws, that they just stopped and you couldn't get them in any deeper.

Or, are they spinning in place and not going any any deeper? Is this the reason that you asked about the #10's...you think that the 8's don't have enough bite, so they are spinning in place. Question: Are you using fine threaded screws, because you should be using coarse threaded screws...fine threads do not have enough bite in wood.

As far as buying bigger screws, that will only increase the amount of energy it takes to drive them in. So, if you're having trouble driving #8's, then you'll have more trouble driving #10's and you'll have more splitting.

As far as hitting the TG...after you moved the screws, did they then counter sink?

Based on your post, this is about as good as I can suggest.


----------



## duffman56 (Mar 9, 2012)

I'm wondering if the screws aren't stripping out. They will continue to turn, but aren't going any deeper. This surprises me, as the t&g planks they're going into are in good shape. 

As far as the technique - those are a lot of helpful tips. Based off of what you said I think I'm doing it correctly. When I run into one that doesn't countersink I've just been moving it (usually 2-3 times) until I find a spot it will countersink. 

The Ditra Handbook said to space the ply sheets 1/8" for expansion joints. Just curious - won't these fill in with thin set when I go to put in the Ditra? I'm sure it will work, as this is what they suggest, just wondering how the joints will expand if thin set gets into the gap.


----------



## Ed911 (Oct 15, 2011)

Are you using fine threaded screws...if so, you need coarse threaded screws...other than that...you may occasionally hit a space...like the T&G, but moving the screw over should have taken care of this, as long as you're not moving them along the line of the T&G.

Fine threaded screws don't have enough bite in wood...and can strip out...


----------



## Ed911 (Oct 15, 2011)

duffman56 said:


> The Ditra Handbook said to space the ply sheets 1/8" for expansion joints. Just curious - won't these fill in with thin set when I go to put in the Ditra? I'm sure it will work, as this is what they suggest, just wondering how the joints will expand if thin set gets into the gap.


Good question...I'd like to hear the answer to that myself...never thought much about it.


----------



## JetSwet (Jan 21, 2012)

I think we will have to wait until JazMan comes back to answer that question.
Can't wait to learn about how that will work


----------



## Big Stud (Jul 3, 2011)

You may need to get Mike Holmes to come in and raze the whole house and start over from scratch :no: ........ I'm sorry, couldn't help myself,


----------



## duffman56 (Mar 9, 2012)

Ha! I would LOVE to have Holmes come in and redo everything, as long as DIY was paying for it... 

Given the fact that I am worried, should I go ahead and sister the joists (at least every other one)? Would it take a special grade of 2x6s to accomplish this? Would this be extremely pricey? 

Or would bridging be a better option?


----------



## JetSwet (Jan 21, 2012)

duffman56 said:


> Ha! I would LOVE to have Holmes come in and redo everything, as long as DIY was paying for it...
> 
> Given the fact that I am worried, should I go ahead and sister the joists (at least every other one)? Would it take a special grade of 2x6s to accomplish this? Would this be extremely pricey?
> 
> Or would bridging be a better option?


If I was in your position I would sister the joists,
A 2x4 or 2x6 perpendicular between the joists will stiffen up the play you have.


----------



## duffman56 (Mar 9, 2012)

JetSwet said:


> If I was in your position I would sister the joists,
> A 2x4 or 2x6 perpendicular between the joists will stiffen up the play you have.


Is this "sistering" or "bridging"? I thought sistering was basically attaching another joist alongside the pre-existing joist (parallel, not perpendicular)? 

Just took a look and there is a lot of stuff to work around down there (ducts, electrical, gas lines), so installing boards perpendicular may be easier in some places. I was under the impression that attaching boards to the joists provided more strength than perpendicular.


----------



## duffman56 (Mar 9, 2012)

Just looking into bridging - Anyone heard of "IBS Engineered Bridging"? Their site claims it provides significantly more floor stiffness than standard bridging options. Just wondering if there's any truth to their claims.

Looks like it's a product from Canada - it looks like minimum joist height for them may be 7.25" though. Also, I'm not sure but it looks like they may be designed specifically for engineered I-beam joists, and not 2-by's?


----------



## JetSwet (Jan 21, 2012)

I meant to say I wouldnt sister the joist I would but "cats" in yes bridge them if you want but thats the x effect of the joists not slanting on you,
Running cats is a straight run from joist to joist not angled.


----------



## duffman56 (Mar 9, 2012)

JetSwet - everything I've read states that the described method is the least effective in reducing deflection. Please tell me this is wrong, as this would likely be the easiest method to use. 

Yet another couple methods I just saw - gluing and screwing a 2x4 to the underside of the joist. The main disadvantage of this is reduced headroom, but since that I-beam is under the joists anyway this wouldn't be a problem. 

Also, Ideas 5 at the link below, which I have never seen nor heard of. It's a very interesting idea, but I wonder about effectiveness:
http://www.finehomebuilding.com/PDF/Free/021184090.pdf

I'm starting to wonder if securing the joists (though I don't know how) to the I-beam may be beneficial? Any tips on how to accomplish this? Will try and post a photo or at least detailed description tonight. 

Thoughts?


----------



## JazMan (Feb 17, 2007)

Geee, lots of catching up for me to do with this thread. :wink:

In post # 56, Duffman, you said.



> I'm wondering if the screws aren't stripping out. They will continue to turn, but aren't going any deeper. This surprises me, as the t&g planks they're going into are in good shape.


Are you telling us you can't tell if the screw is just spinning? 

ED911 asked;



> Are you using fine threaded screws...if so, you need coarse threaded screws..


I hope you're using coarse, that's elementary for soft woods.:thumbsup:



> The Ditra Handbook said to space the ply sheets 1/8" for expansion joints. Just curious - won't these fill in with thin set when I go to put in the Ditra? I'm sure it will work, as this is what they suggest, just wondering how the joints will expand if thin set gets into the gap.


Several theories about that. The latex modified mortar will bond the ply together while still compressing a bit. You want a monolithic substrate otherwise you will get movement causing cracks in the tile work. Some people on the other hand will tape over the joint or apply some caulking in it to keep the gap free. 

I suggest you follow the direction based on the method you're using. I believe most, if not all bags of thin set tells you fill the space. I have always filled the gap. :thumbsup:

Jet said;



> If I was in your position I would sister the joists,
> A 2x4 or 2x6 perpendicular between the joists will stiffen up the play you have.


Ahhhhhhhh, What? :no: again........:whistling2:



> I meant to say I wouldnt sister the joist I would but "cats" in yes bridge them if you want but thats the x effect of the joists not slanting on you,
> Running cats is a straight run from joist to joist not angled.


Please pay no attention to the above on the long shot that anyone understood what was said. 

I see OH Mike's advice in #33 of another thread didn't help. :laughing: http://www.diychatroom.com/f5/enough-subflooring-support-137052/index3/

Jaz


----------



## JetSwet (Jan 21, 2012)

Jaz, really?!?... You just just put all the so far advice for this op and threw it right out the window.
Stop criticizing every one Jaz!..not cool man
Now I'm whistling and laughing..... Lol

Course screws for flooring is not Elementry for a DIYer. 

This really shouldn't be a issue, if all planks are screwed in then ply on top staggered right and screwed in correctly there shouldn't be any play.
Not shore what the issue is I think it's still the screw size.


----------



## duffman56 (Mar 9, 2012)

I've attached the first photo. This shows the 2x6 joists resting on the board (2x4 I believe?) which rests atop the I-beam. 

What it doesn't show is all of the other electrical and plumbing that would get in the way were I to try and sister the joists...


----------



## duffman56 (Mar 9, 2012)

Having trouble uploading the second photo. We are having someone come look at the floor, hopefully this week. He installs tile for a living, and is probably the best in town (though our town is quite small). Regardless, the fact that he's still in business hopefully means he can give us some answers, and I hope the answer is :thumbsup:


----------



## duffman56 (Mar 9, 2012)

I wish there were a simple way to TEST the deflection... Is there?

Should I hold off on securing 1/2" ply until we've figured out the joist issue? I believe I took the majority of the sag out of them. I just want to keep this project's minimal momentum going...


----------



## JetSwet (Jan 21, 2012)

duffman56 said:


> I wish there were a simple way to TEST the deflection... Is there?
> 
> Should I hold off on securing 1/2" ply until we've figured out the joist issue? I believe I took the majority of the sag out of them. I just want to keep this project's minimal momentum going...


http://www.johnbridge.com/vbulletin/deflecto.pl


----------



## duffman56 (Mar 9, 2012)

I've used the deflecto-meter to enter my specs, but to me this isn't truly testing my floor. The fact that the deflecto says I'm ok but there is still a noticeable bounce means there must be another variable involved. I meant more a way to truly MEASURE the deflection in my floor.


----------



## JetSwet (Jan 21, 2012)

duffman56 said:


> I've used the deflecto-meter to enter my specs, but to me this isn't truly testing my floor. The fact that the deflecto says I'm ok but there is still a noticeable bounce means there must be another variable involved. I meant more a way to truly MEASURE the deflection in my floor.


Do you have room in the budget to replace your planks with ply? If I was to guess I would say that the reason you still have so much play or bounce is that your planks are to narrow.


----------



## shazapple (Jun 30, 2011)

Simple way? Screw a board to the middle of the joist and let it hang down towards the floor, attach a marker to something sitting on the basement floor (chair, bucket, etc). The board will move when the joist flexes and the marker will show that distance. It is not going to be much though!


----------



## duffman56 (Mar 9, 2012)

JetSwet - I had thought about replacing the t&g with 3/4" ply, but would like to avoid that if at all possible (we spent a lot of time and maybe 100 bucks putting over 1000 screws trough the planks into the joists). 

If I HAVE to do this, I will. I'd just like to avoid it if possible. It may get tricky, as there are a lot of cabinets to work around, but hopefully leaving the t&g under them and putting the ply UP TO the cabinets would suffice (again, if I have no other option)? 

So based on ceramic tile's requirement of L/360, am I doing this (see below) right? 

Joists are a little over 13' long, with foundation support on one end, I-beam on the other and I-beam in-between. Foundation to I-beam is 6'-3" (to edge, not center of I-beam), I-beam to I-beam is I think 6'-10", or 82". 82"/360 = .2278", or just under a quarter inch (closer to 7/32"). 

So based off of the longest span (6'-10"), the floor is allowed to sag a maximum of 7/32"? What is a realistic weight to expect this to hold up to? I'd read a good test is to stand on your toes and drop to your heels, but I only weigh about 160 lbs. If I perform this test and the joist sage is <7/32" can I assume it meets the L/360 requirement? What about heavy appliances and moving them across the floor? (I'm sure we'll want to replace our fridge before too long). 

Also - could this test be done _after _the plywood is secure, as this will undoubtedly strengthen the floor and provide for less deflection?


----------



## shazapple (Jun 30, 2011)

The deflecto-meter tells you the deflection. Realistic weight is your fatass cousin jumping off a chair after changing a lightbulb.


----------



## duffman56 (Mar 9, 2012)

So in Other words, if the deflection is <7/32" when I do one thing (for example run across the floor) but >7/32" when I do another (e.g, jump as high as I can and land) the tile will hold up to the first, but not the second activity. It sounds like although there is a standard deflection requirement for tile there is not a standard weight-to-achieve-this-deflection requirement?


----------



## JetSwet (Jan 21, 2012)

How about going with 3/4" ply instead of 1/2" you will notice a big difference. Will that option end up to high for you?


----------



## duffman56 (Mar 9, 2012)

Yeah I had wondered if three-quarter would work better. The thing is I already have all the half inch and I've started to attach it (though over a small area). I got the half inch at Home Depot for 12 bucks a sheet. Any idea how much more three-quarter inch would cost?


----------



## JetSwet (Jan 21, 2012)

duffman56 said:


> Yeah I had wondered if three-quarter would work better. The thing is I already have all the half inch and I've started to attach it (though over a small area). I got the half inch at Home Depot for 12 bucks a sheet. Any idea how much more three-quarter inch would cost?


Probably 18 bucks or so, I would go with that.


----------



## JazMan (Feb 17, 2007)

Duffman,

Have you confirmed that the movement is because of the joists and not the planks? If the joists are deflecting too much they must be a poor quality in poor condition. 2x6 spanning such a short span should be fine. 

Adding the plywood is not gonna improve the joists, just the subfloor. You need to figure out where and how much deflection there is.

When you add the new plywood underlayment make sure you do not buy sheathing. You were just referring to $12 a sheet ply which is the wrong stuff.

Jaz


----------



## JetSwet (Jan 21, 2012)

JazMan said:


> Duffman,
> 
> Have you confirmed that the movement is because of the joists and not the planks? If the joists are deflecting too much they must be a poor quality in poor condition. 2x6 spanning such a short span should be fine.
> 
> ...


Jaz, there is nothing wrong with plywood you want to drag it through the mud by naming it sheathing it's meant for what it does and it works. 
I always use unsanded cdx and then sanded to tile on
for subflooring. Hasn't failed me yet 

He has steal I beam that holds up the joists he's as good as sound, your going to have bounce with 1/2 on old planking.

Raising to 3/4 will tighten up the deflection believe me I have been down this road so many times.


----------



## duffman56 (Mar 9, 2012)

Had the pro come over tonight. He said we are doing things right and we should be fine. I showed him that the things atop the deep freeze jiggled somewhat when I jumped from a few feet away. He told me this was normal and that every floor will have some give to it. What a relief!


----------

