Laying down a new subfloor......in what was a barn

I have a machine shop in what was a barn. I use the first floor for nmy shop and the second floor for storage. The second forr is 2 x 6 T & G planks over 2 x 12 joists. The 2 x 6's maeasure about 1-3/4" thick. They are in poor shape, big gaps on some of them. Well, I landed a deal, what was listed in the auction catalog as 250 sheets of plywood, assorted sizes. Turns out to be closer to 500. About 1/2 of it OSB and the other half plywood. all 1/2" thick and about 39 x 87"
So my plan is to trim them to 35 x 87 to clean up the busted up edges, and then lay down one layer of OSB then a layer of the plywood crossways to that. Sound good?
I have a 20 degree full head framing nailer. I'm thinking ring shank nails about 2-1/2". When shopping for nails I see tham listed as "coated" but never a mention of coated with what? Anyone know the secret?
Nail down first layer with about 6 or 8 nails each, then fully nail down top layer with a nail every 6-8 inches.
Can anyone improve my plan?
Thanks Randy Remove 333 to reply via email
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Sounds like a working plan. I like HDG nails.....hot dipped galvanized. I know staples work real good also. I use the 1/2" crown and then 2" or 2 1/2" HDG staples also.
As long as the floor does not "work" it sounds good. (no movement) up or down. squeeky. Did you think about glueing? Not sure if that is necessary either. john

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Hot dipped galvanized for an interior subfloor? Why?
R
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They grip.
wrote:

Hot dipped galvanized for an interior subfloor? Why?
R
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On May 15, 2:25 pm, snipped-for-privacy@enter.net wrote:

Sure I can. First things first. You don't say what spacing the joists are set on - 16"? More? Anything more than 16" I'd be leery. 1/2" plywood or OSB does not make a good subfloor, and two layers do not make a good floor. You mention the machine shop on the first floor, but not what will be stored on the second. I understand you're happy about the sheetgoods bargain, but we're more concerned about loads and existing to get started.
Two layers of 1/2" will deflect more than one layer of 3/4". The two layers will not act in concert unless you make them do so, by gluing and screwing the two layers together. If you are planning on having any substantial storage, it's almost a must that you do so.
As far as the nailing and sheet orientation, don't lay the sheets crosswise. Plywood and OSB have a stronger orientation that runs the length of the sheet, so all sheets should be running in the same direction with the long edge perpendicular to the joists.
I am not sure where you came up with 87" for the cut length, but if you want full strength from the flooring the ends should land on a joist, and you should cut the sheets so that they do. Since you have 500 sheets I don't think this will be a problem.
You're nailing plan is fine. Coated nails, aka cement coated, just have some type of thermoplastic adhesive that heats up as the nail is driven and sets once the nail is embedded. Ring shanks and/or cement coated sinkers/commons would be fine, and you may want to think about gluing down the subfloor, but personally I wouldn't use glue unless you have plans to convert the barn/shop into a residence where squeaking floors might be objectionable.
The only other thing to do is to figure out what to do with the offcut plywood parts. Maybe you could cut them and donate them to a school for woodshop projects, or cut them into set sizes and sell them as birdhouse kits or something.
R
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On Sun, 15 May 2011 23:05:35 -0700 (PDT), RicodJour

20 to 24 " random joist spacing, they did not build them better in the old days.
2 X 6 flooring will not be removed, I'm going over it.
2 x12 Joist are rough cut and measure a full 2 x12"
joists rest on 18 and 24" steel I beams.
Currently store cars, boats and lots of other stuff up there. It's a"bank barn" built into the side of a hill with an overhead door access to the second floor.

Looking to smmoth things out and just cover the cracks and gaps.

Not worried about ending on Joists as I am going over the existing floor. 87" is 1" cut off all side just to clean up the edges.
I might need to rent a floor sander to even out a few buckles and warps.

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A barn with deep steel beams...hmmm. I think most people had a different idea of what was meant when you said barn.

You store cars on ~2' OC 2x12s? Huh? What's the span for those 2x12s?

Do you need two layers to do that?

That's a pretty oddball size of plywood. What were they used for where you got them?

As you see fit. Watch out for nails. They'll tear up the drum sander paper right quick and drive up your costs.
R
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On Tue, 17 May 2011 22:04:37 -0700 (PDT), RicodJour

About 9 feet, the beams are about 9'8" apart, but they vary a little too. This was the stable to a brewery, and I think the brewery was up and running as they built the barn.
I do not beleive the steel I beams are original, there are signs like they were added later. I have no idea what they replaced.

I was going to do 1 layer of 3/4" t & g. But I got a deal on the 1/2" and have plenty to do 2. And think it will get much nicer with 2. The old floor is worn.

They wer used at a place that made door. They were cut just larger than your standard door 3-0 x 6-8 so they would cover it while it was in the press, I guess for gluing.

Only screws that are through the top are ones I put in. I will deal with them as needed. ( remove or grind off)
Remove 333 to reply. Randy
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.com> wrote:

Hopefully it smells more like beer than horse piss. ;)

Probably old big wood beams that were meant to take hay and wagon loads as opposed to barrel loads and the like. Post some pictures on a free hosting site and post the link back here. I'm sure we're all curious what the place looks like...and jealous!

I could see it either way - one layer or two, depending on how much sanding you do on the existing, and what exactly is going to be rolling around up there. The two layers would be smoother, but whether it would be worth the time and effort, and whether point loads sitting in place for a period would cause things to conform to the underlying undulations is an open question. If you really want smooth, you smooth the stuff underneath unless the top layer as significant structural strength on its own to take the loads.

Got it. Thanks - I was curious.

I'm not sure I follow you. You're going to be hitting the existing 2x T&G with the belt sander, right? That's why I mentioned the nails. From the above it almost sounds like you're planning on sanding the new stuff.
R
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On Wed, 18 May 2011 12:26:09 -0700 (PDT), RicodJour

The old T&G is nailed through the toungues, so the nails are not near the top. I did fix a few boards with screws straight down thru the top, those will be the problem.
I'll see what I can do for a pic or 2.
Remove 333 to reply. Randy
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On 5/15/2011 2:25 PM, snipped-for-privacy@enter.net wrote:

Basically sounds good, but make sure your supporting structure can handle the additional weight. Look at the joists, and whatever holds the joists up and figure out what they can carry for weight. You don't want that floor falling down on you when done.
Of course stagger the seams, as best possible.
Coated is usually a hot-melt adhesive that melts from the friction of the nail being driven and helps keep the nail in place.
--
I'm never going to grow up.

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Layering 1/2" plywood sheets will do little to stiffen the floor, so I am assuming the existing floor structure is sound (you didn't mention joist spans or spacing). If that's the case, the plywood layer will primarily provide a smooth surface and cover the gaps in the planks below. In other words, a subfloor, not a structural floor.
I would lay the plywood perpendicular to the floor planks, and stagger the sheets so you don't end up with the corners of four sheets meeting in one spot. I would skip the second layer as this will only add dead weight to the floor reducing what you can store on the upper floor.
I would also use screws (decking screws, not drywall screws) instead of nails. This will prevent nail pops in the future if the floor does flex, will help pull the plywood and planks tightly together, and will allow you to easily replace that sheet in the future if it should get dinged up.
Maybe you could use the extra sheets on the walls. Unlike drywall, this will let you mount shelves, tools, etc. anywhere on the wall and worry less about stud spacing.
If you are really trying to use the sheets to add strength to the floor, I would probably screw one layer to the top of the planks, and the second layer to the bottom of the floor joists, using construction adhesive for both. In effect, you would be building a basic torsion box.
Good luck,
Anthony
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