Subfloor replacement?

[slapthecat]

Has anyone replaced the subfloor in the B190?
What started as a replacement tub has developed into a backend redesign. It appears the brake light above the back doors was not sealed - all the wood around the back (underneath the vinyl shower walls) and the back closet were waterlogged. That all came out fairly easily.
The majority of the floor in the back has been reduced to dust. How do I go about laying a new subfloor?!?

Questions I'm having but not finding any definitive answers to:
Pressure treated plywood with an epoxy coating? Or marine grade plywood? With epoxy coating?!?
How to attach the plywood to the van? 3M 4200 sealant adhesive?
Is a barrier of any kind necessary between the van floor and the plywood?

Then there's the brake light that caused the problem. Anyone know of a direct replacement for that fixture?

[FoCoKCCO]

I recently have redone the bath and noticed that there was a leak from the third brake light as well. I was lucky enough that the floor was not damaged. When redoing the rear I noticed there was not anything between the subfloor and the van body. I'm not sure what type of wood to use though.

[skater]

Mine had regular chipboard, just like a house would have. I wouldn't use pressure treated lumber.

I don't know what was holding the chipboard down, if anything - mine was in good shape when we put in tile, so I didn't go farther down. I'd be tempted to simply glue it down or tape it down like you said.

The light fixture might be a major headache. You could try calling Airstream and asking them about it, but I wouldn't be surprised if they can't get them any more. I'd look into finding a way to seal it.

[lido14co]

Anyone taken the brake light out to see if there's a serial number of some kind? I'll take a look at mine since the frame around it is cracked and will post any info.


Cliff

[slapthecat]

Ok - to follow up:

I sent an email to AIrstream about the brake light. The part number is 510809. You can order from any Airstream dealer. Need to call on monday...

As for the floor - what I've found is strips of a hard board - Luann? - running lengthwise under the wood in the grooves of the van floor. On top of that is a foil insulated board (1/8" with foil on both sides) - this is stapled to the strips. On top of that is 3/4" MDF - which doesn't appear to be connected to the foil board underneath at all?!? It's really the pressure of everything stuffed in there.

The foil board I found at Home Depot - $10 for a 4x8 sheet. Am going to use marine grade plywood for the floor - will be worth it should I have any other water incidents.

[EricZ]

The third brake light on my 1993 Airstream 190 is marked:
"SIERRA PRODUCTS, INC.
LIVERMORE, CA."

The red lens includes the marking "SAE-U-88 DOT". I don't see any manufacturer part numbers.
(I tell where to get a replacement at the end of this posting.)

The cutout in the fiberglass for the fixture measures 6.5"x1.5" (with radiused corners).
The outer flange of the fixture measures 7.25"x2".
The fixture body measures 1.5" deep.
The fixture is mounted with screws through the back of the bulb chamber extending into brackets in the van (not through the flange in the front; that's a different fixture).
The light has two black wires exiting the bottom center back of the fixture.
The fixture has two sockets, each holding a #912 incandescent lamp (specs: 1 amp, so about 13 watts each).

Even when the light fixture was sealed to the fiberglass at the factory, it wasn't very water resistant:
- The red lens is held in with screws, but there's nothing around the edge to keep water from entering the bulb chamber.
- The fixture was clearly designed to be vertical or slightly down-tilting. Our vans mount them slightly up-tilting.
- If (WHEN!) water gets into the bulb chamber, it can easily leak past the wires into the van.
- Water in the bulb chamber also rusts the fixture mounting screws, rusts the socket mounting hardware, and corrodes the bulb sockets.

Worse, after many years the caulking sealing the flange against the fiberglass can dry up, allowing water running off the roof to directly enter the van (i.e., without having to go through the bulb chamber).

Despite these problems, I'll probably clean and reuse my fixture or replace it with the same model. I'll probably make the following changes:
- Cut the wires and install a disconnect plug (for easier future maintenance).
- Seal the opening in the fixture where the wires exit (at the bottom back).
- Seal the flange to the fiberglass with marine-grade butyl tape (the "butyl" tape sold for RVs is sometimes not even butyl, let alone high-grade).
- Replace the fixture-mounting screws with stainless steel screws.
- Replace the screws retaining the red lens with stainless steel screws.
- Use silicone dieletric grease in the bulb sockets to reduce corrosion.
- (Perhaps) Substitute LED bulbs for the two #912 incandescent bulbs.

Here's the company that made the fixture:
http://sierraproductsinc.com/

And I believe this is the fixture used in my 1993 Airstream 190:
http://www.1vshop.com/esierra/Qstore.cg ... 1374008322

This is described as "Item: #403 0° (Vertical) Flange Mount (small flange)."
Ours would be "Two 72 inch leads" (as opposed to the three-lead version).
Cost: $18.44 + $10.75 shipping = $29.19

(Search terms: 3rd brake light, high-mounted stop lamp, center high mounted stop lamp, CHMSL.)

[lido14co]

Thanks for the research. I noticed on the description that the lens can be tilted down 20 degrees. Don't know how that will work since the mounting surface tilts the other way!


Cliff

[EricZ]

Yes; the fixture is designed for anywhere from vertical to 20° down.
Our application has them tilted about 5° up.

[Planck]

Yep - that's it. Sierra Products

[Saprophyte]

I've done a lot of work on the floor in my B190 lately. It's a '96. The original subfloor is 1/2" plywood. It's not strongly attached to the body of the van at all. Taking out the entire kitchen cabinet and couch, I noticed only one screw which actually went all the way through the plywood into the van body. That was under the black plastic stair cover by the double side doors.

Adhesive would probably not be a bad idea for fixing the new subfloor, since it will presumably be in smaller pieces than the original, which might creek when you walk on them.

Avoid pressure treated in all interior applications. The stuff lasts against bugs and fungus by virtue of being very toxic. The modern stuff has less arsenic in it than older pressure treated lumber, but it's still not nice stuff. Marine plywood might be better.

Insulation is something else to be careful about; not for toxicity so much as water retention. Polyisocyanate foam has the best R-value-per-inch, but it also absorbs and holds water. Extruded polystyrene, XPS, like the Owens Corning pink boards is better for applications which might get wet, and you can get versions of it with good crush strength, so it won't get destroyed in light load-bearing applications. Better still, I think, would be something like Roxul rigid mineral wool boards. They have good crush strength, fire resistance, and they're not hydroscopic ( they don't soak up and hold moisture. I wanted to use Roxul boards, but couldn't find a supplier. I used Owens Corning XPS-250 boards, about $20 per 2ft x 8ft board, 2/4 inch thickness. I'm going to make a big post about my project with good pictures when it's done, soon I hope.

You might consider making a sandwich of rigid foam (not Polyisocyanate) between two layers of hard 1/4 inch plywood. One layer of reflective foil for radiant heat insulation would be good. Beware of adding multiple layers of vapor bariers (such as foils), though, because you don't want water to ever be trapped inside your floor. Spills and leaks happen as you've seen all to well, so you want to allow that moisture to get out again when that happens.