Subfloor Questions

Schluter Ditra is the way to go. No cracking. I would contact them directly and give them an idea of what you have as far as the floor is concerned. They have guidelines for just about every situation. They would be able to tell you if your subfloor, joists, and joist spacing is adequate. They are professionals and they know this stuff in and out.

Side note: make sure you use the proper thinset under the tiles if you use Ditra. It is different than if you went directly to a cement board or on the plywood itself. Again, Schluter will be able to better guide you on that.

That's my 2 cents worth.

 

Correct me if I'm wrong but I believe
Ditra to subfloor = modified thinset
Tile to Ditra = Un-modified thinet

 

Hollow core doors and I was playing with different total heights of the floor in relation to the door clearance.

 

For hollow core doors, you can remove the blocking from the bottom, then trim the door, then re-glue the blocking back in.

 

OP , is the area under the floor crawlspace , or will the ceiling receive a finish like drywall ?

Can you apply strapping to the underside of the joists without affecting your future plans for the room below ?

 

Oz by strapping are you refering to something similar to what is already there. If that is the case then yes I can install more strapping. Eventually that ceiling will get finished however right now it is just a basement. Would the strapping be a better idea?

 

The metal straps you have in the joist cavities are known as crossbridging , what I am referring to is 2x4 strapping nailed flat to the underside of the joists on 16" or 24" centres . This tremedously stiffens the floor assembly by virtually eliminating independent joist movement which leads to the floor " rolling " as you walk on it .

If strapping is not an option , I would solid block the floor with 2x8 .

 

So strapping doesnt seem like the best options since we plan on finishing the basement eventually. so it seems like 2x8 blocking will happen. In places where a 2x8 wont fit due to plumbing should I use a 2x4 block in those spaces.

Also if I glue and screw from the top should I stagger the blocks so I can nail in from the side. In addition how far apart should I space the blocks under the floor to be tiled? Thier is 11" or so that I can get to should I run 2 rows of blocking In that space to stiffen the floor?

In addition, I just got off the phone with shluter and they said ditra will work with the floor as it is but I want to add additional support just in case.

 

On your roughly 12' span , I would do 2 rows of blocking , approx 4' apart . It is OK to stagger them for nailing , make sure to add subfloor adhesive to the tops of the blocks as you install them so you don't create a new squeak at the plywood .

Using 2x6 or 2x4 where there is plumbing is fine , whatever will fit .

Keep the blocking from directly touching any pipes , at least 1/4" away , this will help eliminate any noises in the floor .

Your floor joists have probably shrunk some since they were installed so do yourself a favour and rip your blocking to an 1/8" undersize and make it tight to the plywood , it doesn't matter if it is flush to the bottoms of the joists .

Finally , run screws through the subfloor and into your block while the glue is still wet , this will complete the connection .

 

Metal bridging.
We stopped using it a long time ago to reduce call-backs for squeaks, etc (if it is not installed correctly)
If you're leaving it, make there is no contact at each intersection and of course that it's nailed properly.
We use blocking made from the same material as the joists, in this case it would be 2x8 blocking in lieu of the above.

Your area is not that large so you can beef this up without too much expense or effort.
Looks like this floor framing assembly may be right at the bottom of the acceptable range to carry the tile system.
Also looks like you have a basement judging from the stairs in one of those pics. This eliminates some floor stiffening techniques.

If it were mine I could walk it and decide what I wanted to do, if anything, for additional stiffening of the floor.
Get in the middle of the and shift your weight, you can feel the deflection if present.
If the deflection was unacceptable my first opportunity to stiffen that floor would be to utilize the 7-1/2" joist space and double (sister) the joists below.
I say first opportunity because any additional blocking beforehand would nix the "doubler" option.

So, if you're going to double the joists you have to get rid of the metal bridging and pull/ reinstall that Romex (electrical wire).
If pulling the Romex is not an option, then you could use 2x6 (I would try to use 2x8) instead of 2x8 and run above the Romex. Identify the "crown" on each joist to be added and position it "up".

After your doublers are done you can solid block the assembly, either in halves (one row) or thirds (two rows). If your existing 5/8" decking is in fact square edged, you may be able to place these block lines in "smart" locations.

So, to recap, if any doubt about that floor assembly's stiffness, I would double joist and then solid block if it were mine.
I have some broken 8x8 tile on an inadequate, wood frame substrate, done by someone else and it's a bit of an eyesore.

 

jflan , have you ever used Schluter Ditra ?

 

Exellent info oz I feel as though I can pull this off. One more question. I have a seam that I can see from the basement. Going every 4 ft will put me right on the seam. Should I stay away from the seam? if so by how much or should I go right down the seam?

 

Holy shit jflan, sistering every joist and blocking solid is way overkill! I know it was said earlier that you can't overdo it but at some point it just becomes ridiculous. Solid blocking the floor like OZ-T said at third spans and the ditra system would be well more than sufficient for a residential application.

 

Are you able to tell if it is square edge plywood or t+g ?

ie , can you see between the sheets or is the " seam " you are seeing actually the shoulder of the t+g joint ?

 

No not really.
It's a very small area we're talking about and it's wide open....done it lots of times.
More benefit than just blocks.

It would be easy for a weekend warrior to sister 2x6's in that space although I would use 2x8 but that would take more effort.
As I said previously, this is a small area easily beefed up.


In reality, what happens, and this happens in residential and commercial settings alike....
One day someone decides to move (fill in the blank, refrigerator, gun safe, etc.).
That's what you have to prepare for as well.

 

jflan you are old school , like me .

I am old school , I trust old school , old school works .

However , every once in a while a product or technique comes along that changes the equation , and Schluter Ditra is one of those products . If you haven't used it , you owe it to yourself to try it out .

While your sistered joist solution absolutely will work , the solid blocking / Ditra combo will work as well , and the cost of the additional lumber for joists could go towards the Ditra .

 

Oz Im not sure if its t&g I need to rip up more of the flooring to find out I will check back. Also there is one joist span that I can only fit a flat 2x4 under due to well pump line and heat pump lines. That span is very close to the foundation.

Also is 2 1/2" deck screws right for this application?

 

Fit whatever you can

They will work , pretty much anything but drywall screws will work .

 

Your house looks new enough to where I would predict that T&G was used.
To check...
Go upstairs and find an 8' joint. Put your foot on one side.
If you can move one side independently you have square-edged decking.

For joist blocking in difficult areas, the simple solution is to do a flat block above and a flat block below. Then block pressure is carried through the block line, top and bottom.
Use construction adhesive where practical and get a minimum 1" penetration to your substrate(backing) with your screws. Preferably more, but no benefit if you blow through.

Edit:
Pretty certain that one of my sheet notes on the remodel planset would be to double those joists.
Just sayin.

 

jflan , you got me on ignore now ?

Lol