Half of floor is missing?!

[midazzler]

2003 Collin’s 6 window F450 with 7.3 power stroke…I just started demo and planning to put in a floating subfloor with 4” XPS, 3/4” advantech and 1/2” rubber gym mats as the finished floor (we use the bus for hauling dogs as we run a dog rescue)…but when I pulled up the 26 gauge layer of “foil” there’s only half of an actual floor underneath! My guess is that it appears to be 18g…
Is this a known thing? Do I need to be calling in a welder to patch the spaces or is the layer of “foil” and subfloor good enough to spread the weight out appropriately to span those gaps (17” and 21” gaps)?
My plan had been to put chassis saver on the interior side of the floor but now am wondering if I should treat both sides of the “foil” before putting it in? My husband wants to step up to 22g for the new foil layer but I am wondering if we need to go to 18g or higher?
Has anyone run into this before? Should I not be alarmed?

 

[nikitis]

It's your floor, there's a lot of re-enforced beams but if you step in the middle of one of those on a 18g, it's gonna flex. I'd probably go 16g if it were me for the floor. 18g for walls if needed. Definitely not 22g.

 

[ewo1]

22ga is tooo thin. Yes you can use it but remember this, it's about as thick as a pepsi can.
Most all bus bodies are made with 16ga. 16ga is sturdy and will support the weight just fine between the gaps you are concerned about. On top of the sheet metal I see you'll add insulation and a rubber mat?

On my bus I put insulation and then 1/2 plywood.

Believe it or not, from the picture of the floor, it looks like your in great shape to do a nice restoration.
I would pressure wash and wire brush all the loose rust and dirt, spray all the metal with Ospho to kill/stop any rust, then seal it all with some good paint.

Me personally, I would put in 2 new pieces of 4x10 16ga sheet metal on the floor, leaving the two strips in the middle in place.
I wouldn't go welding in new patches, use complete sheets!

I can't see if that fuel tank has lift pump inside of it. If it does then take measures for future access. I used a marine floor 8" access plate, like this one...

 

[midazzler]

Thank you so much folks! We plan to grind down the little existing rust and coat everything with chassis saver. I appreciate yall weighing in on the appropriate gauge thickness. Our problem is that, locally, we can only procure 48” wide sheets which would put the seam right down the aisle where there is a 21” wide gap…so we were thinking to weld a crossbeam down the aisle to rivet the new floor pan to.

 

[Slapdash]

Double what ewo1 said about clean up and the like. Might want to replace the fuel pump, sending unit, etc., whilst it's all open. Dropping the tank on my '05 GMC 5-window was a nightmare.

 

[Neurotaffy]

Remember...the higher the Gauge number the THINNER the metal is. FYI traditional automotive body panels circa 1970's -1980's are 19 gauge steel. Structural aspects of a car body are 14 gauge steel for stronger spots

 

[AlphaHare]

IMO 18 gauge is more than enough - the strength will come from the 3/4" OSB you put on top of it. Don't over-metal the skin. Do use galvanized or Galvaneal, and consider painting and then undercoating it before you put it down. Ditto the exposed elements - clean them and undercoat while they're exposed.

 

[midazzler]

Thank you so much for all of the thoughtful advice! I put in full sheets of 18g galvanized with several coats of chassis saver both top and bottom, with a marine floor access plate. The 2” of XPS followed by 3/4” Advantech primed with Kilz mold and mildew resistant and a waterproof paint came out beautifully! Better yet, the sound and vibration reduction have been huge and we are still waiting for our rubber mats to arrive so it will be even better soon. Time to get started on the hatch patch and Maxxair install.