Hi,
Hoping someone on here can give me some advice before tomorrow. I have an old barn style coop that measures 5m x 4m. Have built a sub floor (approx 2 feet up from ground) and ready to lay the boards tomorrow. Which boards should I purchase? I’m confused with difference between hardwood plywood, softwood plywood and OSB? Will either cover with vinyl or ideally would like to seal it with a paint so I can mop/disinfect after clearing bedding away each week? Thank you.
I'm not fond of raised floors - more material costs, more framing, eventually it WILL fail (even though I built my first coop with a raised floor - just throwing that out there, so you know my biases.
OK, here goes. OSB is cheap, its made from chips of wood, oriented in a direction, pressed together with much pressure heat, and some rather decent glues. It is MUCH better than particle board (which is really glue and sawdust), and is better suited for outdoor use (but not exposure) than the old products. Its also only strong in one axis, and it tends to warp/bow easily. Typically, OSB is oriented longways (look at the chips, see which direction they generally point), that's the strong axis. You want your joists framing it to run perpendicular to that, in effort to compensate for its relative weakness in that axis. I don't like it, but it is a popular building product, and if protected from the elements, can last a long time.
Plywoods - Hardwoods/Softwood. Unless you are doing finish cabinetry or putting a new floor in a boat or an RV, there is no need for hardwood plywood. Typically its much more expensive (since its made from slower growing, more densely grained "hard" woods) and somewhat heavier. If you look at the edge of the plywood, you can see each layer is perpendicular to the one next to it. It doesn't have a "weak" direction like OSB, and is less prone to warpage or splitting. (OSB tries to correct that in the middle layers, but its just not the same, its more like an oreo cookie sandwich).
Plywood can usually be purchased in three major grades at the typical big box:
Interior. This $#!+ is worthless for high humidity environments like chicken coops, I've seen it swell, twist, warp, and delaminate in garage shelving, cheap cabinetry, and a host of other sometimes damp locations. Do not recommend.
Exposure 1 - this is what you are looking for. Different glues are used, its a little more moisture resistant. With care, it should be all you need. Exposure 1 basically means its allowed to get wet during construction - it can take brief and infrequent moisture contact of a serious and pervasive nature. Its not designed to be a primary water barrier, however, this isn't the stuff you want to wrap your house with, or leave exposed all the time, paint or not. Under a vinyl flo0or, however? Just fine
True Exterior / Pressure Treated - this crap is HEAVY. Its also very difficult to destroy. I purchased a 3/4" sheet of it for the bed of my trailer, rather than bolting down 2x4s or 5/4" decking as many tend to do. Probably more than you will need. Pricing MAY be comparable right now - in my area a 4x8 sheet of the thin stuff can be had for $44, while Exposure 1 in the same thickness is $41&change. If its that close, and you don't need a lot of it, I'd spend the extra $ and consider it insurance. I'm used to seeing a $10/sheet difference in pricing.
There are also "finish" grades which have a thin, sanded, veneer on one side or both for use one cabinets and the like. You won't be looking at it, it doesn't add strength, don't pay the extra cost. There are also marine grades (they make the Pressure treated, or "PT" stuff feel light) which tend to have more layers for the same thickness and some incredible epoxies holding them together. and true cabinet grade stuff, which like the marine grade, has lots of layers sandwiched together, but not the special glues. Chances are, you won't find either of those in the big box.
Note that you can buy "subfloor" sheets, designed specifically for your application - but because they are for human floors, they are likely 3/4" thick or thicker, and they usually have a tongue/.groove edge profile, to make fitting them together tightly easier on a large job. Whether plywood or OSB, these are going to be heavy, because they are thicker than what you need. and that tongue/groove my inconvenience you during assembly.
Hope that helps.
/Edit - and full disclosure, I built mine out of Hardieboard, its basically fiberglass reinforced concrete. Near indestructible, heavy, hard on tools. Water resistance at least as good as Exterior plywood, but no layers to delaminate, or edges to draw water up like a straw.
Thank you again for your responses. I was thinking of a paint to help with keeping the boards as waterproof as possible but think vinyl may be the way to go. Good luck with the pond!
