Hello to all,

Great site! I've searched for an answer in previous posts but I can't find one. I'm hoping you all can set me straight. I intended to lay a 1/2" layer of homesote (440 Sound barrier) beneath 2 layers of 3/8" plywood glued & screwed (to each other. Not through to the actual sub-floor) plywood laid at 45 degrees from each other, and then install 1/2" ARK oak engineered flooring to the new floating under-layment. As it turns out, doing so would put the new finished floor at 1/8" above the existing patio door threshhold so I've changed the plan and I'm screwing a single 3/8" layer of plywood through the homesote to the 3/4" t&G actual sub-floor with the intention of nailing the 1/2" engineered flooring to that. So I'm left with the following dilemma...

----My research is telling me that 18 gauge staples do not come in lengths greater than 1 1/2".
----Math tells me that a 1.5 inch staple installed at 45 degrees will not reach the actual sub-floor (which leaves the new finished floor attached to only the 3/8" plywood and the homesote) which is not enough for the staple to bite into from what I've read.

So what's the solution? Do I:
a) use a 2" - 15 1/2"ga staple on 1/2" engineered flooring to reach the sub-floor?
b) use the 18 gauge 1 1/2" staple and add a poly adhesive between the finish and the 3/8" plywood, together to make up for the lack of "staple bite"?
c) abandon my hopes of accomplishing some sound abatement and eliminate the 3/8" plywood under-layment altogether, and staple the 1/2" engineered flooring straight through the homesote to the T&G?

I know quite a bit about sound proofing and I get that screwing the 3/8" ply into the actual sub-floor reduces the result but then again stapling a wood floor straight into the sub-floor is just as bad and has less mass overall.

so, the question is ; bigger gauge and longer staple or normal gauge and glue?

Thanks in advance for your thoughts!
Sean

I would screw down the 3/8 and use the 18 gauge on the 1/2 inch flooring. The 1/2 is most likely a throw away prefinished that will be torn out in 7 years anyway.

Thanks for the reply Cottonwood,

i understand what you're saying but the engineered flooring is some decent stuff with a 4mm top level. Its got a 25 year warranty and I'd hoped it would last longer that 7 years especially with the sub prep I'm trying to do.

let's assume it was going to last for a while and if so, what's the best approach?

Thanks again.

Can you sand down the homesote back a ways so it it a flat plane?

hey Tucson,

That wouldn't work out well. The Homesote is a compressed cellulose fiber board. Sanding it would make a huge mess.

What about just using more staples? I've got a bostich 1838K with 1 1/2" x7/32" staples. Would it be stable if I just stapled into the 3/8" ply every 6" or so instead of the recommended 8"?

Thanks in advance for your thoughts.

Sandings always messy. Then sand out the top 3/8 plywood sheet. Its only an eighth inch.