Wide-plank, floating, doug fir floor???

[Paul Macias]

Not sure if I'm crazy, but here she goes:

Me and my family will be moving into a new manufactured home in August. I was all set to do a face-screwed-and-plugged wide-plank, doug fir floor . . . until I found out that flooring in a manufactured home has to be floating. So I wonder, could I lay down 1/2-inch ply on the sub-floor and not attach it, essentially creating another floating subfloor, then screw 1X6 doug fir into it?? Of course I would use a vapor barrier, maybe adhesive, and sand and finish as normal for wood flooring. I guess I'm wondering if I can successfully build my own floating wood floor rather than use a laminate or engineered product.

Important facts:

1) Northern California foothills, so it's not what you'd call a humid climate.
2) The doug fir is NOT an engineered flooring product (with t-and-g or releif cuts), but rather it's kiln dried, 2X6, "structural select" (some knots) that is resawn at the mill (NOT vertical grain, but rather mixed).
3) Largest open area would be the family/dinning room/kitchen, 24X22.

I have never installed a wood floor, but my woodworking skills are fairly good and I understand the basic process; nevertheless, I would appreciate any feedback on this.

[Mike Wilkins]

Not sure why flooring in a manufactured home has to be floating, unless you have something like OSB or particleboard subfloor. The only concern with the your method of using 1/2" ply then the wood flooring would be the increased height of the floor. If you can live with that, there is no reason not to use that method.

[Mark Bolton]

As Mike has said I dont know why you have to float the floor anyway? Im assuming you mean because there is a metal frame below? I dont see why this would mean you'd have to float all the floors in the house provided you had enough subfloor to fasten the floor to.

That said, I dont see anyway you could float a subfloor over the existing. There would be no way to keep the ply flat, flush joints, and so on.

Could definitely be wrong but I would guess with a little more investigating you may find that you can install non-floating floors.

[Richard Coers]

You bought any 1/2" plywood lately? That stuff stays flat about as long as it takes to get it out or the rack. It would be like walking around on a spring. Also they cut the faces on real engineered floor so it acts more like veneer than solid wood. Solid fir, 22' wide, is going to move a ton! I'd look for a different option if it was mine.

[Kevin Bourque]

My understanding is that the floor is floating because it would be damaged in transport if it wasn't. As long as you aren't moving I think it's okay to install the wood flooring the conventional way.

[Paul Macias]

Just talked to the contractor I'll be working with (manufactured housing specialist), and he says the issue with fixed hardwood in a manufactured home is the subfloor material, which is basically particle board; it's not that the subfloor of a manufactured home moves any differently. So, the necessity to float seems off the table. Therefore, I guess I could screw my 1/2 inch ply to floor joists and then glue/screw the doug fir planks to it. Anybody see a major problem with using the doug fir product I'm talking about (see original post)? I'm thinking that gluing and screwing this wood is going to stabilize it.

[Richard Coers]

All solid wood moves from season to season in width. Is it kiln dried like furniture grade material, 10%, or like construction grade fir, 19%? And how wide is wide plank? 7" or 12"? Anyone that decides to glue and screw solid wood to plywood, also wonders why the wood splits, or it wants to curl up? Wood moves, plywood doesn't.

[Jay Jolliffe]

We put 1x10 t&g pine down on our floor. We have radiant heat so it was set on 2x4's on the flat. Reason being between the 2x4's is cement with pex tubing. We used polyurethane adhesive & screws. Bad Idea. The wood couldn't move with the seasons so some of the boards cracked down the middle. If I was to do it over I wouldn't use the adhesive. There were a lot of bungs to put in & trim off. Router worked great.

[Kevin Stricker]

While a screwed and plugged Fir floor sounds like it could be amazing, I would personally choose something else for your first flooring project. For starters Fir is a fickle wood, prone to splintering and likes to move when not Vert. grain. If you are set on the fir, I do not think you should be concerned about a PB subfloor if you are screw/plugging. It is more of a problem when using a cleat nailer. Use a good construction adhesive ( one line per course) to help keep things quiet and make sure you test the moisture content of the flooring and subfloor before install. Ideally you want to sticker the flooring in the room to be installed in for at least a week prior to install. Use parallel clamps as spreaders against a cleat to get the boards nice and tight before screwing. Also remember that T&G is meant to be blind nailed at the tongue so that each plank can move with the seasons. By face screwing you are restricting this movement so maintaining a somewhat constant humidity is more critical.

[Peter Quinn]

Is the fir truly KD? I'd be concerned it shrinks after install. Most "structural" lumber is not dried to millwork standards, even KD framing lumber is only required to be something like "average below 15%", but for flooring in climate controlled space, you need something more like 8%-10% MC. Being on the east coast we don't have the widest selection of fir products available, but almost none of what arrives here is ready for millwork, it all seems to come wet, even clear grade vertical grain material. Luckily it air dries pretty quickly, unfortunately if it does that after you install it the gaps can be rather troubling. PDAMHIK. As far as the glue down, consider your glue carefully. They make adhesives for for gluing down flooring, bostik is one brand that comes to mind. Some of your general purpose "construction adhesives" like PL 400 or such dry with a rather rigid glue line and expand as they cure (like most urethane adhesives), neither of these are great features in a flooring glue IMO. The actual flooring adhesive I've used cures like rubber cement, so it holds a floor board like a monkey holding a banana, never lets go, but it allows some movement. Its elastometric moisture cure urethane, its not cheap, but neither is replacing botched flooring in a whole house.

http://www.lowes.com/pd_245393-68935...ductId=1269115

As far as the floating thing, I'd be disinclined to start reengineering the whole project in an experimental ad hoc sort of way. If you had the capacity to have the fir re-sawn and glued to plywood as engineered flooring, I'm thinking that would make a great but very expensive soft wood floor. I've made some engineered flooring on a limited basis, would not want to do a whole house that way, not a great DIY project on a whole house basis. We make it where I work, its fairly stable but most people are surprised to learn that in all but the most expensive species of lumber engineered is MORE expensive than solids, not less, for premium plank flooring. Sure the lumber liquidators type stuff may be cheaper, but its all shorts and chopped up.

I've seen some beautiful square edge plank floors laid down at different job sites, the term "rustic elegance" is usually applied, because there are almost always gaps between boards here and there, they almost never have a perfect elevation like strip flooring where edges meet, they move a round a bit more than standard toe nailed t&g floors. This can be a beautiful accent to some, it would drive others crazy, just make sure if you go that route you are in the former category. I have no info about prefab housing construction, but I have seen plenty of stick built homes built with OSB decking that have floors nailed to them, scratching my head on that explanation, also not quick to discount the experience of the guy that does this for a living, but have also heard the "bs contractor explanation that amounts to please don't inconvenience us with your special requests" enough times to know not every warning is legitimate. I added drawer pull outs to an island once for a lady whose builder had given here 9 different reasons why she couldn't have drawers in an island...everything from safety issues to code violations......hog wash all for them, truth, like a good chinese lunch menu, no substitutions, they slow down production!

[Paul Macias]

First of all, thank you all so much for this discussion; I know it's helping because I can see my plan getting simpler.

I'm starting to reconsider the KD fir product--just seems like good "insurance" to go with, if I can, something that's been milled to be flooring. So, upon browsing the Lumber Liquidators website, the 3/4 X 5" Southern Yellow Pine product is starting to appeal. Questions:

1. Do I need underlayment for this?
2. Would it be sufficient to screw/plug the pine to the OSB subfloor (through the underlayment)?
3. Would I need adhesive (probably one that allows movement)?
4. Or, easiest yet, could I face nail the floor through OSB to the joists? Nail gun??

[Mark Bolton]

Why wouldn't you just install it as designed? Rent a nailer and smack it down?

As for subfloor, no one can tell you whether you need an additional subfloor until you specify what the subfloor in the home is. Beyond that the manufacturer (or lumber liquidators) should tell you specifically what is required below their floor to meet spec and warranty.