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langless28 12-05-2012 11:09 AM

is this subfloor adequate for tile?
i have 2x10 rafters on 16"OC on a late 50's ranch. there is 3/4"x6" boards as the subfloor in which we re-hammered down the nails to the rafters. we then glued + nailed 1/2" Douglas fir plywood to this subfloor every ~4" and then screwed inbetween the rafters the plywood to the subfloor every ~4". it still squeaks a little but feels solid. is this ok for directly laying tile down onto?

zakany 12-05-2012 02:26 PM

What do you mean by "directly"?

I would not skip the concrete board or better yet the DITRA layer. Unless you're talking about vinyl tile or some such.

langless28 12-05-2012 04:03 PM

sorry by directly i mean thinset then tiles (probably 16" porcelain), no other substrates. this would better match the thickness of the hardwood surrounding the kitchen but also because my father said that is all that is needed. the douglas fir plywood was chosen because apparently thinset has a hard time sticking to the other big box store plywood i have up my way (maybe spruce?)

has it been done this way is all i am asking? i have been reading up on the ditra stuff and it appears to be a thin layer for "troublesome subfoors" when and when is it not needed? im sure i can find a bunch of threads on the ditra... if its a very redundant question on here.

joecaption 12-05-2012 04:09 PM

If it's squecking then it's still moving, attacing it directly to the plywood is a sure way for it to fail.

DannyT 12-05-2012 04:22 PM

like zakany said you need either 1/4 cement board or ditra which is an 1/8 of an inch. what is the unsupported span of your floor joists?
you should have a couple of screws to each joist through the subfloor into the joists and not glued the plywood to it.

langless28 12-05-2012 05:14 PM

The span which happens to be the room width is 11'.

zakany 12-06-2012 12:36 PM

I hate to disagree with your father, but I disagree with your father. Wood is not a suitable substrate for tile. And DITRA is not for troublesome floors.

Wood expands and contracts. Period. It is in its nature. Ceramic tile does not (or at least at a much different rate). Adhering ceramic to wood will cause the former to break - either the tiles or the grout will fail.

Keep in mind that I am an absolute amateur at this. Several posters here are experienced experts, but I'm giving you the perspective of a simple home owner.

I don't care if it's a tool for only professional, high-end use, I still recommend using DITRA rather than concrete boards and similar products. I found it very easy to use.

I'm sure that you will find people who tile directly to wood. And I'm sure it looks okay for awhile, too. But that's not how I would tile a room in my house, nor would I ever suggest it to anyone else.

ToolSeeker 12-06-2012 02:04 PM

The first mistake was re-hammering the nails back in if they were loose. To hammer them back in means they are by now loose again that is why you have squeaks whice means movement you should have used screws they won't come loose. I think this problem will continue to get worse until you get everything solid and I would sure address it now before you tile, because I'm pretty sure if you don't at some point will end up with some cracked tile and grout. Just my opinion.

langless28 12-06-2012 03:53 PM

i re hammered the original nails back into joists through the subfoor (3/4" planks) then glued, nailed, and screwed 1/2" ply over all of that. i used 2.5" ring shank nails in a nail gun along the joists and 1-1/4" screws in between the joists to secure the plywood to the original structure. i see what you are saying about the old nails. i guess i can go back and use 2.5" nails along the joists in between the nails and see if i can eliminate the squeak.

langless28 12-19-2012 08:37 PM

I went back and used 2-1/2" screws through the plywood,subfloor, and joists. I still have one sections that squeaks.... Someone in the basement verifies the joists move under when someone jumps but its slight.

JazMan 12-20-2012 04:25 PM


Someone in the basement verifies the joists move under when someone jumps but its slight.
Well then any cracking of the grout or tile will likely be slight too. :whistling2:

If the movement is only in one area, you may have a weak joist or two. Easily fixed if the ceiling is open.

I recommend installing a 1/4" tile backer or Ditra like everyone else. Tiling directly on wood is not smart.


langless28 12-21-2012 02:20 PM

i measured with a tape measure the deflection to be around 1/16" with my fiancee jumping up and down.

i do have some other concerns. in the ditra manual i read its good practice to leave 1/8" gap between sheets of plywood and to also not have a plywood edge on the actual joist. well i didn't do either of those. i figure i can use a circular saw to put the gap between the plywood sheets but i cant really do anything for the plywood sheets joining over the joists. is this a major no no or can it will it not cause major harm?

JazMan 12-21-2012 03:12 PM


i measured with a tape measure the deflection to be around 1/16" with my fiancee jumping up and down.
That is not how deflection is measured. No way any human can measure it that way. But you're probably alright unless a joist is cracked or has been compromised some how. Is there any damage? The deflection between the joists is actually more critical and with your plank subfloor and 1/2" ply you should be fine, as long as it's installed correctly.

Next time offset the underlayment both ways, do not glue the underlayment, do not fasten underlayment into the joists, just the subfloor, gap the sheets, no need for 2 1/2" screws.

The squeak; Often a stubborn squeak after fastening the area is caused by a subfloor nail the just barely hit a joist but may have splintered an edge. Look for such a culprit from below.


langless28 12-21-2012 03:28 PM

thank you for the helpful information. im more of a teach a man to fish guy so why do you suggest not gluing the 1/2" underlayment and not going into the joists? all i ever hear is glue and screw. none of the joists show obvious damage. i was thinking of adding some blocking under the section that sweaks, and bring it out 3 joists on each side of the "squeak" zone. there are a few nails (from the nail gun) that barely missed the joists so i can take a look at those tonight. i also did offset the underlayment length wize so no two ends butt across 2 sheets. i attached a photo of the subfloor.

again i appreciate the information especially before the holidays. i am sure i will have more questions after i lay the ditra down and start planning the layout. i will be using 16x16 porcelain tiles. i need to make sure the floor is flat as well before laying the ditra down, any suggestions for that? i was going to use string across block and measure down.

if i don't hear from you have a good holiday!

JazMan 12-21-2012 04:12 PM

The idea of not fastening an underlayment into the joists is to provide a little more isolation so stresses do not as easily transfer to the finished flooring.

We recommend not glueing the underlayment to the subfloor cuz most people use construction adhesive from a tube and therefore it's kinda thick. This thick bead creates voids where there is no glue causing a slight deflection. Glueing would only be helpful if you could do a 100% lamination using thin wood glue. Hard to do, you'd have to have help and work fast.

Figure out where to floor is not flat and by how much. Also check how the flatness issue relates to level. In other words, flat is mandatory, level is not. But if you choose Self Leveling Cement to make the floor flat, it's gonna run to the low areas first. You need to know so you can go with patching material instead, maybe.


Merry Christmas everyone.

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