Subflooring as decking

[Pappy]

My plywood workdeck is in serious need of a rework. I am off this next week and that is my main objective.

One mistake was to screw through the perimeter boards into the ends of the joists instead of using joist hangers. After stripping the 3/4 PT plywood that will be fixed. I also plan to put the joists at 12" on center and sister a 2x4 at the 8' joint, giving me a full 1 1/2' under the end of each section of plywood.

The plan now is to use 3/4 (23/32) tongue and groove subfloor as the new decking. The placard on the display say weather protected applications but I am going to paint the bottom side with an oil based floor paint. The edges will get 2 coats before putting the sheets down and then the top will also get 2 coats. This should give me several years of good serviceable life. I used the moisture barrier OSB as a floor in a metal garden shed. With the foil side on the ground and the top painted with the same paint, it has held up to lawn equipment (Mowers, tractor, tiller, as well as a few gas spills) for 3-4 years.

I considered glueing down cheap sheet linoleum but was a bit worried about it getting too slick with sawdust on it. Also the plan is to eventually move the Playen to the back yard and convert it to a finishing room. The linoleum would make it difficult, if not impossible, to detach the deck from the building without detroying the plywood.

Once the work deck is done I will rent a jamb saw and cut the floor out along the walls inside to adjust joists and fix some uneven areas in there. The floor framing was covered with plywood and the walls built on top of it so I can't remove the plywood in full sheets. Haven't decided yet if I am going to go with the T&G inside or reuse some of the existing plywood. Either way, it has to be basically a one day job to get the tools back under lock and key. (Either that or I camp out one night with my girl....)

[gerti]

Can't comment much due to lack of experience, but what peaked my interest: One mistake was to screw through the perimeter boards into the ends of the joists instead of using joist hangers. Why was that a mistake?

BTW quite the girl you got there. She's the work supervisor I presume?

[chopnhack]

I think Pappy is saying that because he wants to change his joist centers from 16" to 12" o.c.

Pappy, this may be a little unorthodox but, why not use the cheap sheet lin. and fasten with washer head screws at one end and then stretch the sheet to the other side and fasten again? That way you can remove the covering and remove the deck as necessary. A dab of silicone before fastening or after should make it watertight.

This is not the new workshop you built is it?

[Pappy]

I think Pappy is saying that because he wants to change his joist centers from 16" to 12" o.c.

Pappy, this may be a little unorthodox but, why not use the cheap sheet lin. and fasten with washer head screws at one end and then stretch the sheet to the other side and fasten again? That way you can remove the covering and remove the deck as necessary. A dab of silicone before fastening or after should make it watertight.

This is not the new workshop you built is it?

Over time the ends of a couple of the joists have cracked, allowing them to move under the weight of tools. Joist hangers should give me a more stable base.

I thought about a perimeter glue down but was still concerned with water getting under the linoleum and rotting out the plywood. Even thought about something similar to your idea of screws, using drip rail along the outside edges. Part of my concern with an edge fastening of any kind is how well the sheet linoleun/vinyl would hold up under the Texas sun. The roof only covers 2/3 of the deck.

No, this isn't the new building. That is still waiting for the $$$ to have the slab poured. I don't want to tackle that job myself and it's going to run about $6 K to have it poured. Probably another year away. When that happens the current Playpen will be moved near the new building and converted to a finishing booth. (Wider door opening, filtered air inlet and exhaust, insulated, drywalled, multiple level lights to reduce shadowing of the project)

[pelligrini]

I thought about a perimeter glue down but was still concerned with water getting under the linoleum and rotting out the plywood. Even thought about something similar to your idea of screws, using drip rail along the outside edges. Part of my concern with an edge fastening of any kind is how well the sheet linoleun/vinyl would hold up under the Texas sun. The roof only covers 2/3 of the deck.

OK, you're thinking of using the T&G on your whole deck, not just inside the shed? I'm assuming the T&G subfloor you're talking about is an OSB product.

If it is a strand board product, I don't think it's a good idea for outside use, even with a paint coating. My shed has an OSB floor. I don't think it was flooring OSB though. It's been in there for a couple decades, but it has issues. The dogs piled up some dirt underneath against the subfloor in one corner a few years ago and it wicked up a lot of moisture. I put my foot through that corner last summer. It is also delaminating and breaking apart in areas, mostly in high traffic areas like; at the door and under the paths where I roll some of my tools. I used to get splinters in my feet often before I put down some foam floor mats.

The paint on top might get you a few years, but I think it will degrade fairly quickly. The top coating will be compromised when the strands delaminate and chip off from tools moving across it and from foot traffic. I also think that the coatings on both sides will trap moisture and rot the panel quicker.

[Pappy]

OK, you're thinking of using the T&G on your whole deck, not just inside the shed? I'm assuming the T&G subfloor you're talking about is an OSB product.

Wouldn't even consider OSB for this application. What I am looking too use is a plywood T&G. It is available in both 3/4 and 1 1/8. The thicker would be nice but, at almost 2x the price, I can't justify it.

[pelligrini]

Cool, OSB products have their places and outside isn't it, unless engineered for it. Although, I used some T1-11 siding for a small awning above the doors on my shed. The prefinished side is down and I finished the top and edges with some elastomeric paint. It's been up for a few years now and appears to be working well.

The only problem I see with the plywood subfloor would be the glues that were used on it. When I first moved into this house the previous owner had a small plywood deck in the front topped with 3/4" marine grade. It probably lasted at least 8 years or maybe more. I probably would have gotten a couple more but the dogs chased a couple rats under it and really tore it up trying to get at it. I used some regular 3/4 PT plywood from the blue borg and it it seriously delaminating now. It only took a year to start falling apart and getting some high ripples. Someday I'll get around to pouring a concrete pad. As I understand it, the glues for marine grade are designed to hold up longer. The subfloor product might hold up with a finish on both sides.

[wardprobst]

Don,
I've used the pressure treated 3/4 ply outdoors and it's not bad if you set the drainage correctly and treat it annually with deck protector. I didn't find any T&G so I used the router bit set you can buy (best done outside IMO). If you make sure to edge the laminated ends, it will last even in the oven/freezer up here.
DP
"Don't worry about the weather, it'll be different tomorrow!"

[gerti]

Over time the ends of a couple of the joists have cracked, allowing them to move under the weight of tools. Joist hangers should give me a more stable base.

Makes sense. Thanks for the info!