3/8" underlayment


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Old 04-15-15, 06:38 AM
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3/8" underlayment

Hello. I put down 3/8 ply underlayment over 23/32 osb subfloor. I already stapled down the underlayment with some porter cable 1/4" narrow crown 1" staples. I put the staples appx 2" apart on the edges and 4" apart in the field.

After I stapled down the underlayment i saw in the ditra installation book that they say not to use staples. Someone else suggested I add screws or ring shank nails to the underlayment but the problem is I cannot find ring shank underlayment nails or screws that are short enough to not go through the osb subfloor.

Any thoughts or suggestions? Do i need to tear up the ply i already stapled down?

Porcelein tile will be going over the ditra.

As always...Thanks
 
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Old 04-15-15, 07:29 AM
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Maybe Jaz will come along. I would be surprised if that floor will work.
 
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Old 04-15-15, 08:29 AM
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I have very little experience with tiled floors but in my opinion anything less than 1/2 inch added to a subfloor is a waste of time and money.

Staples, if they are driven at varying angles, will hold BUT the small section of the "top" will have minimal holding power and will be subject to corrosion if they ever get wet. I would recommend either the proper screws or ring-shank nails always be used rather than staples.

It is common for the screws or nails to go completely through the subfloor in my experience, especially when minimal thickness materials are used.
 
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Old 04-15-15, 08:49 AM
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I used the 3/8 because that is what the tiler at a tile shop recommended. I am worried that anything thicker + ditra + mortar + tile will have the floor too high to meet with the carpet in the adjoining room.
I have a box of 1.25" deckmate screws I can screw into the underlayment if that would help. I just read in several places that the fastener should not go through the subfloor.
Thanks
 
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Old 04-15-15, 09:04 AM
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I just read in several places that the fastener should not go through the subfloor.
Well, they shouldn't, but far too often do go all the way through.

I have nothing more but I wish you well with your project.
 
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Old 04-15-15, 11:39 AM
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A single layer of " subfloor grade ply or OSB is stiff enough to meet any manufacturer's specs that I've ever seen, with all the normal *'s. Actually, many say ⅝" @ 16" oc is stiff enough, but that scares me. When an underlayment is needed/desired, a full ⅜" underlayment grade ply is the min. recommended, thicker is always better. So, your floor should be good as long as everything else is in good shape and installed correctly.

I've installed ⅜" with " divergent staples under Ditra with no issues of any kind. I think Schluter believes ring-shank nails hold better cuz of the head. Maybe. But when you staple every 2-3" on the perimeter and 4-5" in the field, you should be fine. No floor is expected to survive a flood, but who knows what might happen. It wouldn't hurt to add some nails now just to make you feel better.

As for the length of the nails; They should be long enough to slightly peek through the subfloor. Ideally 1/16" would be good, I believe. Two reasons; 1. the first ⅛" of a nail or screw has no holding power. 2. Manufacturers want a way to confirm that enough fasteners were used in case of a warranty call. Nothing would be under warranty anyway, but just for info. Try to find 1 ' since I doubt you'l find 1 ⅛" ring shank. The idea to not use long fasteners is so you do not go into the joists unintentionally.

I just read in several places that the fastener should not go through the subfloor.
I wonder where. Schluter says; Fasteners must pass through entire thickness of underlayment and subfloor panels with minimal penetration into joists

Do you have your thinsets selected? Care to share?

Jaz
 
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Old 04-15-15, 11:44 AM
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Thanks for the info. I had some 1 1/4" deckmate screws so i tried using a few of those. Many of the were just spinning so i gave up on the screws. I will pick up some 1 1/4" ring shank and try a few of those. I am probably fine with just the staples but I was trying to do this "right" (whatever that may mean).

For the schluter to the plywood underlayment I will be using Laticrete 254.

For the porcelein to the ditra I will be using the Bostik Ditra-Set.

Thanks
 
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Old 04-15-15, 12:01 PM
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Why would the screws be spinning? How many did you try? Did you hit a void?

For the schluter (Ditra) to the plywood underlayment I will be using Laticrete 254.

For the porcelein to the ditra I will be using the Bostik Ditra-Set.
Perfect! How about trowels? What size are the tiles? Is the floor flat? Did you check?

Jaz
 
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Old 04-15-15, 01:45 PM
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i dont know why they were spinning.
For the mortar under the ditra i will be using what they recommend. I believe it is 1/4 x 3/16.
for the tile i will be using 1/2 x 1/2.
The tile is 30cm x 60cm. I will backbutter each tile before laying onto the troweled thinset.
the floor is flat.
Thanks
 
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Old 04-15-15, 04:01 PM
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OK then, sounds like you've got it covered.

Jaz
 
 

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