Floor framing and attachement

[QueticoBill]

My usual Google fu is not helping me with the search here on what must be a common topic. I'm starting with an Ironton 5X8. Putting axle on top of springs, preserving an option to upsize wheels later, moving axle back - probably 3' from rear of 8' frame as many suggest or if it saves a few holes, within an inch of that.

So, with the Ironton frame with cross members every 2', why shouldn't I just attach floor to frame without the 2x 2 or similar I see in so many builds? My thought is to lay down a bead of glue - more for cushioning than adhering and might use a butyl caulk, and Tek screwing the 3/4" ply down. (I'll use a router to hog off the flange thickness of side rails so it all sits flat to sides and cross rails, and plunge route for bolt heads.) I plan to get the Tek screws that drill and tap the steel, as well as have a little edge to cut countersink in wood. Not sure if I'm using 2 5x5s or 2 4x8s, but will probably undercoat ply before install, attach foam to bottom inside frame, and undercoat all.

If it matters, I plan to have most or all the stressed skin wall sit on top of the floor. With a woody style in mind, I might let the outer ply extend down, or just the wood (trim) strip, or leave frame exposed. To be figured out soon before I attach floor. And just to put things in the bigger picture, I just got notice trailer is in store as of yesterday so will pick up next week.

[les45]

I bolted my 5/8 floor ply directly to the frame using carriage bolts and the holes that are already drilled in the frame. I used wood strips to shim the tops of the cross members. I applied two coats of Zinsser primer and two coats of Henry's 107 to the bottom before bolting it down. (I used the primer because the Henry's can said it could cause de-lamination of plywood).

[djohnsonnv]

Thank you for asking the question. I have been wondering that myself. The reasons I have figured are that it makes it easy to create an insulated floor system by building up the frame, makes it possible to remove the box from the trailer if needed as a dual purpose, or most builders are just more comfortable with working with a wood structure than a metal one.

I have seen a few builds that do what you are suggesting. A lot of the steel fabricators on this forum seem to go that route.

I haven't yet built or done any serious planning but I have given this a lot of thought since I have concerns with overall height and the difference of a couple inches in the floor system could be a an issue.

[QueticoBill]

To Don - I'm not seeing that this prevents insulation - just lowers it. Plus I think I saw it done this way on some youtube and it made sense. I do have some concern about the foam and stones and gravel - may warrant a hard covering.

Les - I'm failing in finding Henry's #7. Is it [url]Henry's #700 Gel Seal Canister Grade[/url]?

Thanks.

[greygoos]

On my next build I am planning to bolt a sheet of 3/4 to the frame, build the walls on top of that, then drop in a sheet of insulation followed with a floating floor. My inspiration is the Northern light. Eliminates framing and doubling the plywood.

[les45]

Les - I'm failing in finding Henry's #7. Is it [url]Henry's #700 Gel Seal Canister Grade[/url]?

Thanks.

My mistake. I should have said Henry's 107 asphaltic coating. It was the coating of choice when I built my weekender.

[Don L.]

I had the same idea screwing the 3/4" plywood to the frame with Tek screws but I put a fender washer on the screw first. The treated plywood I used would compress easily with the screw, in fact a screw head could go all the way through it.

I had a tube of asphalt sealant laying around so I put that between the plywood and the frame.

I coated the under side of the plywood with aluminum/asphalt paint and the edges with titebond II before that, just to harden and help it resist any water penetration.

You can see the center section is screwed to the underside of the frame (took a cross member out) to give me a little more headroom in the areas where you stand.

This was an old camper chassis and has steel brackets welded on the rectangular frame that extend outwards. The extended parts are where cabinets, benches and bed are.

Oh yeah, the wooden rails that run along the outer sides give stiffness to the plywood there, but I found out the hard way that they were too close to the tires, which didn't have enough clearance to come off, so I had to make a cutout in that area, pita!

[QueticoBill]

Glad to see I'm not the only one to think of this. I'm surprised you need washers though because I've seen plywood attached to steel tubes and some beefy angles with Tek screws and they countersunk fine. Maybe larger - like 12 or 14 - would work well without washers.

[Don L.]

This was some treated plywood from Lowes and was kinda fresh/damp and soft wood to boot. I think their regular yellow pine plywood , well I know their regular plywood is much harder. And drier.
On this stuff the screws even pulled the washers down flush with the ply.

Greygoose, we think alike , I did the same thing with my floor. FWIW I have been using an electric rubber heated floor mat to warm the camper and I'm sure the insulation under the floor helps some.