96' GMC Vandura 3500 - Floor prep question

cooliebus · 04-15-2018, 06:13 PM

I recently bought this short bus and the previous owner already gutted it to its base and started prepping the floor. According to them they used a grinder on the rust and then added a coating of Rustoleum. The floor appears to be in good shape aside from two minor rust holes and all the bolt holes scattered throughout.

Question 1:

What is my next course of action on the floor?

My plan: I planned on welding up the rust holes and gluing pennies to the bolt holes as I have read here on the forums. After that I'm assuming I need some additional protective coating over the Rustoleum, I just haven't been able to nail down exactly what I should be using.

The floor is a bit flimsy in the areas where the seats used to be (along by the windows and in front of the emergency exit in the back of the bus).

Question 2:

Should I weld additional supports underneath the floor in those areas? Or would the wood in my constructed floor provide enough support?

The previous owner also appeared to have made some cuts in the base floor as you can see from my photos. The four cuts toward the front of the bus expose the frame and bolts and the one in the back expose some type of lines (perhaps pump lines?).

Question 3:

How should I cover these up? The ruffle pattern of the base flooring in these areas would make it difficult to weld. I'm assuming the access to the lines is important seeing as how they went through all the trouble to cut a hole in the floor to get at them. I planned on making a trap door of sorts in my constructed floor just in case I ever have to get at those.

shilohsbus · 04-16-2018, 12:13 PM

I am glad to see someone in close to the same spot as me, I just got my floor ripped up and have been cleaning rust. I was surprised also to see the corrugated section and flat section, I hadn't seen this in any other pics. I am planning on putting foam board down and then plywood, everyone says to go ahead and do it, I didn't know if I needed to put sheet metal down over center section or not. I also have a sponge floor on my lower step at door, plus all the ones you mentioned. interested to follow your progress, sorry not much help since I am slightly behind your progress.

cooliebus · 04-16-2018, 06:24 PM

^shilohbus

Do you have the same make/model bus as me? Are the flat sections of your floor flimsy as well? Are there any cuts in your buses metal floor like mine? I'm assuming the ex-owner made those cuts but maybe its just manufactured that way. Thanks for the reply though at least it might help to get more eyes on this thread.

I think my plan is to clean the floor real good, glue plastic grommets inside all the bolt holes, have the rust holes welded, aluminum tape the open cut holes, add a layer of Ospho (let dry 24 hrs), add a layer of POR-15 and let dry.

Twigg · 04-16-2018, 06:34 PM

Personally I wouldn't use POR15 in this application. It's horribly expensive and formulated to line tanks, filling pin-holes, etc.

Most grind off any loose rust. roll on some Ospho and prime with Rustoleum primer. That should be good for the next 20 years.

shilohsbus · 04-16-2018, 07:16 PM

yes my flat sections are a little flimsy but I think when I get plywood on it will be ok. and yes I have the 4 holes that access the bolts in the same spots, but don't have the center hole (actually wish I did) for fuel tank sender I think. My bus is the same body style but a 90. I have a thread on short bus build under 90 short bus

cooliebus · 04-17-2018, 05:25 PM

^Twigg

Thanks for the advice especially when it comes it saving money. My floor already has a layer of Rustoleum. Do you see any problem with adding the Ospho over the current layer and adding an additional layer of Rustoleum primer?

^shilohsbus

Yes I think the floor will be ok with the plywood. I also figure those wont be the areas where people will be walking over anyway. Were those 4 holes that access the bolts used to bolt down anything inside the bus? Were the seats secured with those? I've been thinking of covering them with carbon fiber.

Twigg · 04-17-2018, 05:27 PM

Quote:

Originally Posted by cooliebus

^Twigg

Thanks for the advice especially when it comes it saving money. My floor already has a layer of Rustoleum. Do you see any problem with adding the Ospho over the current layer and adding an additional layer of Rustoleum primer?

^shilohsbus

Yes I think the floor will be ok with the plywood. I also figure those wont be the areas where people will be walking over anyway. Were those 4 holes that access the bolts used to bolt down anything inside the bus? Were the seats secured with those? I've been thinking of covering them with carbon fiber.

Ospho needs access to the rust to work.

If your floor is sound, and has a coat of Rustoleum Primer already applied, it should be good to go.

If there is any rust breaking through the primer, grind the primer away and re-apply the Ospho.

shilohsbus · 06-04-2018, 05:38 AM

did you ever do anything with your flimsy floor sections I have been sidetracked for a couple weeks and just getting back to it. I am debating some supports underneath or something???

cooliebus · 06-04-2018, 06:06 AM

shilohsbus

No I havent reinforced it at all. My plan is to build the subfloor over it and sorta feel it out. But I think the sub floor should be good enough.

I have since prepped and sealed the floor. I ended up using silicone caulk in the cracks and corners, fiberglass over the big holes, expandable foam and silicone caulk in the smaller open bolt holes, and flex seal over the entire floor.

Mr4btTahoe · 06-04-2018, 08:39 AM

If you've got the head room... I'd subfloor it.. go over the metal with 3/4 or 1" blue board... then over that with 5/8 plywood.

It will make the floor very solid/stable.

Good progress

cooliebus · 06-04-2018, 04:54 PM

Mr4btTahoe

Thanks man!

The blue board you mentioned is that board insulation right?

Would you use 2 x 2's to build the subfloor?

Mr4btTahoe · 06-05-2018, 12:37 PM

I didn't frame mine out... however my original floor is wood.

Go with what ever thickness the foam insulation you choose is.

For instance.. if you go with 3/4 blue board... frame it with 1x2s (as they measure 3/4 thick).

The foam is very dense so it will support weight.. the framing is only needed to give something to screw to. You could always just skip the framing and shoot through the metal floor with pan head (or anything you can countersink into the flooring) self tapping screws long enough to go through the decking/insulation/metal floor. Just be sure you wont hit anything such as brake/fuel lines or wiring.

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