What to use for holding down underlayment?

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Old 12-30-11, 07:41 AM
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What to use for holding down underlayment?

I have to replace some flooring that has water damage. My floor is ¾” tongue & groove with .200” thick (13/64”?) underlayment over it. The original underlayment was nailed down with nails about 2” long and spaced about 18” apart. Those nails seem a little long to hold down something that thin.

What’s recommended to hold this down? Adhesive backed vinyl tile will be going over it.

Thanks.
 
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Old 12-30-11, 08:09 AM
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11/64ths? That seems like an odd dimension to me. The underlayment I'm accustomed to is normally 1/4 inch. 11/64ths is less than that. I've seen jobs where someone tried to use stuff thinner than 1/4, but it normally doesn't work all that well. In any case, I use an air stapler with a 7/16ths crown staple to put down underlayment. It can also be done with ring shank nails, but I don't like doing it for fear they will work out over time and cause problems with the new flooring. Sheet rock screws are a good alternative to staples if you don't have access to a stapler.
 
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Old 12-30-11, 04:16 PM
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Curious as to why fasteners are needed for a hardwood underlayment? I don't think I have ever had a need to do that.
 
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Old 12-31-11, 01:25 PM
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I may have misunderstood the original question. I thought this was a three quarter tongue and groove plank subfloor with underlayment over it with some sort of vinyl or something applied to it. Here in Oregon, I see LOTS of floors like that.
 
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Old 12-31-11, 02:03 PM
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Maybe I’m not being clear or am using the wrong terminology… Overlayment?

Anyway, my sub floor is ¾” tongue & groove, on top of that is thin plywood (underlayment/Overlayment?) that is less than 1/4” thick. I am going to put Peel & Stick tile on top of that. What is generally used to hold that thin plywood to the sub floor?
I think staples would be fine, my wife thinks staples will pull out and it needs to be screwed down.

I told her I would ask the experts.

 
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Old 12-31-11, 06:25 PM
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If you have access to an air stapler, that's my recomendation. The staples have glue on them that is melted by the friction of driving them in. When it sets up, which is right away, they are difficult to remove. I've never seen one work out like a nail will. With underlayment, (correct terminology as far as I know), as thin as that, be cautiouse about your air preassure setting. The staples can blow right through and not actually be holding anything at all. I would also advise more fasteners than normal. That thin stuff can actually bulge up between staples so literally sew it to the sub floor with staples.
 
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Old 01-01-12, 08:38 AM
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Right. I was thinking of an underlayment for 3/4" hardwood flooring, as in builder's felt or rosin paper. Narrow crown staples as Smokey said would be best.
 
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Old 01-01-12, 06:26 PM
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Screws will cause 1/4" underlayment to pucker which will show thru the vinyl. Staple every 4" to 6" in the field and every 1" to 2" on the edges. And don't use luan. It has voids in the plys which can lead to collapse. Use underlayment plywood. Ring shank nails were used for years but if you are not an expert at nailing them down you will have a lot of dimples to fill. Underlayment staples are divergent point, which means they lock in.
 
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Old 01-12-12, 08:01 AM
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I have couple of questions as this will be our very first underlayment work.
We have also ¾” sub-floor (some of it is 2” hardwood planks). We are planning of using ¼” plywood for new Tarkett sheet vinyl and will be using Rigid R150FSA stapler and Bostitch 7/8” 18ga staples to cover the 75-90% depth.
Would the 9/16” divergent point staples be long enough? Or is it because of the divergent point?
Thank you
 
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Old 01-12-12, 03:08 PM
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I have used 9/16" without problems but the 7/8" would be better.
 
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Old 01-13-12, 04:27 AM
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Where do you purchase the divergent point staples? I can't find them in local stores. I have Rigid R150FSA finish stapler.
I have also problem finding ring shank nails under 1" of length.
These two are recommended by Tarkett.
Thank you for any advice sam floor.
 
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Old 01-13-12, 09:52 AM
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What size staples does your Rigid use? Finish staples are normally a fairly narrow crown and insufficient for sheet vinyl underlayment installation. I use seven sixteenth inch crown staples. Narrower ones tend to blow right through the underlayment, ending up holding nothing down, and wider crown ones tend to bow up between the staple legs making it difficult to get them flush with the surface of the underlayment. I much prefer staples to nails. Ring shank nails will work OK, but they are too time consuming to install unless you have an air nailer. Most pneumatic staples on the market have hot melt glue applied to the leg of the staples that melts from friction heat as the staple is driven home, gluing it in place. Once installed they are difficult to pull out and I've never seen one back out as some nails can.

You say you are using 1/4 inch plywood as your underlayment. I never recommend 1/4 inch plywood as an adequate sheet vinyl underlayment. The issue is the voids between the plys. With full spread glued vinyl, the plys can come apart. As sheet vinyl glue dries, it shrinks. As it shrinks it draws the vinyl down tight to the surface it's glued to. In so doing, it also exerts an upward pressure to the underlayment and I have seen it pull the plys apart at the voids, creating bubbles in the new floor. When using felt backed, full spread glued sheet vinyl, this is a very real potential. An additional problem with the voids is potential crushing. The voids can be crushed by continual foot traffic or weight from appliances or furniture legs, causing indentations in the new floor. With no-glue, fiberglass backed vinyl, there is no glue to cause the potential bubbles issue, but the crushing issue is still there. There are several solid core 1/4 inch materials on the market that are rated as sufficient for sheet vinyl installation. Make sure you ask your material supplier to verify that the material you get is so rated.

Tarkett comes in either backing. The fiberglass backed has printing on it that specifically warns against perimeter gluing it, which is another installation method entirely. It can be full spread glued using pressure sensitive adhesive, but I rarely do it and, after installing miles of the stuff, have had very few issues with it.
 
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Old 01-13-12, 10:46 AM
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You would probably need to go the a flooring installer supply store to find divergent point staples. I have always used 18 guage. That is what most manufactuters ask for. And Joe is right, do not use luan. It is worth the extra money to use underlayment grade plywood. I have never had an underlayment failure in 40 years of installing.
 
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Old 01-13-12, 11:48 AM
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Thank you both for replies.
I have Bostitch 18ga 7/32” Narrow Crown Staples 7/8” long. I do not think it has a hot melt.
What size of staples and gun do you exactly recommend?
I'll check local flooring companies for the divergent point staples.
The 1/4” plywood is approved by Tarkett, it is IntegraPly. I will not use Luan for sure.
The Tarkett sheet vinyl is a solid foam, no paper underlayment. It has lifetime warranty. I can glue it or not, I am planning on gluing it.
Looking more at the subfloor and differences in the material and elevations I am thinking on putting another 1/4” plywood down on the sub-floor, staple it down with above mentioned Bostitch staples, than adding another IntegraPly 1/4” plywood. I realize nails would be too time consuming, however I am thinking of using 1-1/4” ring shank nails and than adding recommended latex reinforced cement compound (Henry 547 Unipro Universal Patch & Skimcoat together with Hendry 546 Patch Additive) over the nail heads as needed. I’ll let it dry and than roll on BioTect Universal Pressure sensitive Flooring Adhesive and roll down.
 
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Old 01-13-12, 08:56 PM
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The staples you have would be fine.
 
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