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Old 11-21-2023, 02:16 PM   #1
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Join Date: Jan 2020
Location: North Carolina
Posts: 2
Year: 1997
Coachwork: Collins
Engine: 6.5 Diesel
Question Light-weight flooring thoughts?

Hi Folks,

New poster here. Got my Chevy Express 3500 demo complete, now about to start the build. I've got a 10K GVWR on this. Totally stripped, it weighs abt. 8500 lbs., so I've got to stay under 1500 lbs for the build weight. I'll be living in the bus full time, so it will be my work/living space. I'm a woodworking artist, and all the equipment I'll have to have with me comes in just under 600 lbs., I need to do as lightweight a build as possible and also as sustainable as possible (yes I know - it's a diesel, but my footprint will still be considerably less than house living). So for flooring, I am considering a simple layer of R-10 Kingspan Greenguard rigid insulation directly on the floor with 3/4" plywood over that, which I intend to seal with AFM Safecoat, EXT Exterior Polyureseal. Since it's such a small vehicle, there will only be at most 8' x 3' of walking space, and I'll probably put a rug runner down over that as well. From what I've read, I can lay the rigid GreenGuard down with no adhesive and lay the plywood over and then build on top. I'd like to NOT put an adhesive down if possible, because if I want to change it down the line I don't want to have to go through what I did when removing all the adhesives that kept the rubber matting and rugs in place. And it'll be just me - not 16 kids in the bus. Has anyone in the forum done a*similar*flooring option? Any input and/or thoughts would be appreciated!

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Old 11-21-2023, 05:04 PM   #2
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Join Date: Oct 2017
Location: Bellingham Washington
Posts: 105
Year: 2005
Coachwork: Thomas
Chassis: Freightliner
Engine: 6.4 liter Mercedes MBE 900
Rated Cap: 48 passenger
I've done pretty much what you're considering. I have no weight considerations - my bus NEEDS weight - but in the interest of simplicity, cost, and height, I put down one inch of pink board and 3/4 in t&g plywood, originally thinking it would just be subfloor under some "nicer" flooring. I did glue the foam down to the steel floor and glue the plywood to the foam board with Loctite "foam friendly" glue.

We use the bus for traveling and camping, and have been using it all along through the build. The plywood has been unfinished for the last 3 years, so I needed to sand it thoroughly to clean it up.

The cabinets I built are accented with doors that are stained blue, and I wanted the floor to be pretty much a wine color. I just put the first coat of polyurethane over General Finishes "Merlot" dye stain yesterday.
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Old 11-21-2023, 06:11 PM   #3
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Join Date: Oct 2021
Location: Jacksonville, FL
Posts: 672
Year: 2003
Coachwork: BlueBird
Chassis: TC2000 28ft
Engine: Cummins ISB 5.9 24v, MD3060
Rated Cap: 14
Going to be tough to keep a final build under 900lb. I would highly suggest to get a little 6x10 enclosed trailer to haul your tools, bikes, and extra stuff that accumulates. That said, for the problem at hand...

The insulation weighs nothing. Use whatever thickness you want. I wouldnt skip gluing it down. You are going to build your floor on top. For what future reason would you want to demo down to the steel again.. Sure maybe the plywood, but you built walls couches and beds on top. The glue really helps to keep the vibrations from the diesel from humming the steel like a kazoo. Sure, you could skip it if you wanted, but make sure you put some self tapers from the wood to steel all the way down..

Unless you use furniture grade plywood like maple, birch or oak, it will want to cup and bow on you unless glued and screwed very well. Even then, you will want to t&G them. If you are going for lightweight, I would recommend to lay down a 7/16 Huber ZIP sheathing. Its made of more glues than wood and I have a few pieces that have been laying in my Florida yard out in the rain for 3 years and just beginning to delaminate (still pretty straight). Its a lot more rigid than 7/16 OSB or 1/2 pine plywood. It will be about 60% of the weight of 3/4 subfloor. Then over the top you can lay vinyl sheet flooring. That comes in 12ft wide rolls that you buy by the foot. Its waterproof and very lightweight and durable. Then you can build walls on top of it. If you ever want to change it, you can just lay another on top or use 1/4 clicklock vinyl floor.
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Old 11-21-2023, 06:52 PM   #4
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Join Date: Sep 2018
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Year: 2007
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Chassis: Minotour
Engine: Chevy Express 3500 6.6l
3/8 underlayment from a pro flooring supply house
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Old 12-06-2023, 02:34 AM   #5
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Location: pa
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Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford 1998 e350 4x4 7.3 2 mercedes 2004
Engine: 7.3 powerstroke & MBE906
Can you post a picture of what you have , an empty 3500 is 6600 lbs or so according the web.
If you are demoed then it should be less.

In our city low floor we went with 5/8 tongue and groove over the 2" foam with hydronic floor heating. It for weight but for better heat transfer.

I would not worry about going a bit over the gvwr if you are using the proper tires.

Good luck,

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Old 12-06-2023, 03:21 PM   #6
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Join Date: May 2018
Location: topeka kansas
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Year: 1954
Coachwork: wayne
Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
Light weight and water resistant

Thermo-lite Board…….. this is I believe the trade marked name.

Fiberglass outer skin, structural foam core. Light weight, strong. Down side, burns toxic. Expensive. Has reasonable R value. No need to paint, coat or other wise. Used in the boat industry as decking.

I think you can buy in 4x10 sheets = reduced number of seams.

Down side… does not come groove and tongue. You have to devise method for holding edges flush.

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Old 12-07-2023, 02:26 AM   #7
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Join Date: Jun 2021
Location: Baja often, Oregon frequently
Posts: 426
Year: 1996
Coachwork: Our hot little grubbies...
Chassis: Ford CF8000 ExpeditionVehicle
Engine: Cummins 505ci mechanical
Rated Cap: Five Heelers
2003, for our new floor, I scraped the original floor, scrapping an abundance of chewing gum etcetera.
Chalked it, painted it, primarily to close those gaps and gapes.
On top of the original floor, I laid one-inch pink-board... directly on top, no glues, no laser-bonding, nor other fussiness.
Over the pink-board, I laid a sheet of marine plywood, painted on all surfaces to seal.
If you stop there, your floor would fit my definition of 'light-weight'.
Our GVWR : 29,000#.
Weight across the scale : 14,000#.
Cargo capacity : about seven ton.
As you might guess, we are prone to over-due it.
So, as you might imagine, we shot the wad, waddled all the way over to the dark-side of feeding the fuel pump.
Our visual floor is SLATE! TILES!.
Tons and tons of the stuff.
No, really, literally tons of it.
I am literally shaking at just the literal memory of that.
We like these tiles because:
* sizes include 2x2, 4x4, 6x6, and 12x12 (measurements in fUSA inches).
* tiles can be swapped for creating different patterns.
* tiles can be lifted and stacked to sweep.
* we can arrange tiles for sunlight and other lights reflections.
q : so, LM, how is your one-inch pink-board floor holding up?
a : over two decades full-time live-aboard, as-new in appearance and function.
An aside:
We experimented with vinyl tiles, 16x16, inter-locking, and engineered for supporting the weight of vehicles.
In our rig, they pooled condensation.
Sometime early the second week, we noticed a swampy, slimy, squishy humidity in our fine unmentionables.
Investigating an unusually alarming amount of 'popping-followed-by-a-gurgle' 'neath our vinyls, we a curled-up few to discover vast pools of freshly-recycled watery goodness!..
... except the minor issue of breathability...
... and except the other issue of everything on the floor is edible to somebody.
And so, our very-own Primordial Ooze swang by to see if we were open to adoption.
We mopped as much of that muck as we could tolerate, bleached it, scrubbed then sanded it.
Tilted the Wave 3 catalytic heater for a direct-hit on the dampish innerds, pulled the fan around to help extradite any more of those shenanigans.
For sale:
Twelve 16x16 inter-locking vinyl tiles.
* black stains on the under side do not respond to any combination of cleansers in the known universe.
* substantial 'abandoned fridge in meth-house' fragrance, but most of that should dissipate in a few decades.
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flooring, light-weight, sustainable

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