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Old 03-23-2019, 10:57 PM   #1
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"Lowering" a section of my floor?

The wheel wells and the floor around it on my bus are tremendously rusted out, to the extent that I need to basically rebuild the entire floor from about two feet behind the wells to three or four feet in front of them. I have discussed this repair with my mechanic (a guy who also does a lot of custom vehicle modification) and we discussed the basic conventional way of rebuilding the floor, which would be to cut out the existing floor, weld in cross-members of some sort (3" high rectangular steel tube or something like that) running side-to-side from chair rail to chair rail and resting atop the chassis rails, and then a layer of 16 ga sheet steel on top of this, creating a replacement floor that is at the same level as the original factory floor (and joined with the existing wheel wells which are themselves OK other than the bottom 2" which is rusted away completely).

However, since I am planning on building a 3" deep insulated subfloor on top of the factory floor (2x4s with a half inch ripped off), I believe that there is a way to rebuild the floor section around the wheel wells so that the new sheet metal would be at the level of the top of the chassis rails (i.e. the bottom of the original floor structure) and the subfloor would be on top of this.

Basically, my idea is to run one cross-member beam behind the wheel wells (about where the fuel tank inlet is) and a second one about three feet in front (where the side exit door starts) and then remove all of the original factory floor in between. The removed flooring bears the weight of the rest of the body, so the two beams would need to be strong enough to bear the weight normally borne by the removed flooring (I'm thinking 3"x2" rectangular tube with 1/4" walls would do the trick, but I dunno).

I would then run two rails (possibly also 3"x2" tube but I think these don't need to be that strong) from the front beam to the rear beam, but these rails would be welded to the undersides of the beams (so that the tops of these longitudinal rails are at the same level as the tops of the chassis rails) and would run next to the chassis rails (on the left and right sides, respectively) in between them and the inside of the wheel wells. The new sheet metal would then be placed on top of these longitudinal rails (and also on top of the chassis rails), so when completed this section would be 3" below the original factory floor.

I would then build the wooden subfloor for this as a separate section on top of the new sheet metal, which would give me a fully-insulated floor section that would only come up to the level of the original factory floor (the front and back of the bus would also have the 3" subfloor but there it would be built on top of the original factory floor and thus be 3" higher). This might seem kind of not worth it, but I'm 6' and if I build a 3" subfloor and insulate the ceiling with furring strips, I'll end up with a ceiling that is an inch or two too low for me to stand up fully. With this "lowered" floor section, I would have an area for my kitchen, bathroom and dressing area that would allow me to stand up fully (these are the only things that I really need to be able to stand up for) and I would achieve this without having to do a roof raise.

Is there some reason this plan would not work?
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Old 03-23-2019, 11:18 PM   #2
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I’m a Fabricator professionally (just for background) I think you could do it,but I wouldn’t recommend it. Just thinking aloud I guess if the sheet metal only had two ribs running parallel with the chassis frame rails I don’t think it would be very ridgid. The span for the sheet metal would allow it to flex, now after you built the insulated subfloor you probably wouldn’t notice it as you walked on it. When driving though it would probably still vibrate and flex which is not great for your welds.
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Old 03-23-2019, 11:30 PM   #3
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I’m a Fabricator professionally (just for background) I think you could do it,but I wouldn’t recommend it. Just thinking aloud I guess if the sheet metal only had two ribs running parallel with the chassis frame rails I don’t think it would be very ridgid. The span for the sheet metal would allow it to flex, now after you built the insulated subfloor you probably wouldn’t notice it as you walked on it. When driving though it would probably still vibrate and flex which is not great for your welds.
My thought was that walking-around weight would be borne by the subfloor, which itself would be resting mainly on the chassis rails (with the sheet metal in between). I would also weld four plates onto the chair rails in front and behind the wells that extend down 3" and had a lip (this would support the sheet metal on the outer edge and also support the edges of my wooden subfloor. The joists of my subfloor would have L-clips screwed to the bottom, and these would be welded to the sheet metal.

So basically the sheet metal would not ever have to support any weight, and it would be held rigid because it's welded to the subfloor.

Also: I very much appreciate the opinion of a pro fabricator, since I've never done metal work like this myself. Do you have a rough idea of what this would cost? When looking at materials, there's a place locally where I can get 4'x8' sheets of 16 ga steel for about $40, so my rough estimate for this is that the material might be $500, and then it's just whatever my mechanic guy would charge for labor. I have a feeling my estimate is wildly low.
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Old 03-24-2019, 12:05 AM   #4
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I can see it working well how you are proposing. Basically the sheet metal is a shield and the rest of the framing takes the load. I don’t think I would do it for my own bus, I am planning on going the roof raise route, but if your set on not doing one. We charge 70 an hour plus materials for jobs like this and without seeing it I would guess it would take 6-8 hours $420-$560 for labor. I think your estimate for materials is Close maybe three sheets of 16ga one stick of 2x3 maybe two for the ribs too then odds and ends for the rest
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Old 03-24-2019, 06:16 AM   #5
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I can see it working well how you are proposing. Basically the sheet metal is a shield and the rest of the framing takes the load. I donít think I would do it for my own bus, I am planning on going the roof raise route, but if your set on not doing one. We charge 70 an hour plus materials for jobs like this and without seeing it I would guess it would take 6-8 hours $420-$560 for labor. I think your estimate for materials is Close maybe three sheets of 16ga one stick of 2x3 maybe two for the ribs too then odds and ends for the rest
Cool, glad to know this isn't 100% crazy. This is probably the crazy bit, though: I'm also thinking of keeping open a 2'x2' hole on one side of this section, between the back of the wheel well and the fuel tube (there is just enough room here for an opening this size) and then building a sheeted and insulated box that extends about 10" below the floor. Above this opening I would position a step tub like this one:

https://www.campingworld.com/sit-in-...ite-68806.html

such that the tub part is in the 2x2 hole and projecting below the floor level. This would give me a good bit of extra headroom in my shower (maybe an extra 6" or so) meaning I wouldn't have to position it in the middle of the bus, and then the gray water drain would be at the bottom of this box (the kitchen sink will be right next to the tub and will drain into the same outlet).

One thing that seems advantageous about the tub hole is that it would be a natural low point in this rebuilt section, and if any water got in it would drain down into this box and I could get it out via the tub drain opening.

Crazy idea 2 is to make a similar hole with recessed box on the opposite side of the bus and put a cat litter box in it, with my composting toilet placed above it (so all shitting on the bus would be in one place).

Any chance you're near Philly? I'm not totally sure I trust my mechanic - I took my bus to him because his shop is literally around the corner from my parking spot, and since I don't have the bus registered or insured yet I wouldn't feel good about trying to drive it any farther.
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Old 03-24-2019, 06:21 AM   #6
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I can see it working well how you are proposing. Basically the sheet metal is a shield and the rest of the framing takes the load. I donít think I would do it for my own bus, I am planning on going the roof raise route, but if your set on not doing one. We charge 70 an hour plus materials for jobs like this and without seeing it I would guess it would take 6-8 hours $420-$560 for labor. I think your estimate for materials is Close maybe three sheets of 16ga one stick of 2x3 maybe two for the ribs too then odds and ends for the rest
Sorry, one more question (ok, questions). When butt-welding the sheets for this, is it to be expected that the seams would be water-tight just from the welding? Or would it be necessary to also put seam sealant over the seams? Would this sealant go on the inside or outside? Is it necessary to have a joist over the seam (so that the two pieces break over it) or can it be sort of free-standing?
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Old 03-25-2019, 01:53 AM   #7
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I will answer part of your question(s): When two pieces of metal are welded together, they form one piece of metal. If you have a proper weld along the entire ength of the seam, it will be water-tight ... as if the two pieces were always the same piece of metal and never cut. You will still want to protect the metal by priming and painting, at least on the exposed surface.


As far as the resultant piece being "free-standing", that all depends on the thickness of the metal and the forces applied. In your case, the sheet metal is being used as a cover and the structural support is (mainly) coming from the length-wise and cross-wise 2"x3" rectangular stock you are planning to use to support the flooring.


P.S.: I like your idea of setting the tub down a bit. Please take care to make sure there is enough clearance for the other stuff that is already under the frame ... like your exhaust pipe. I believe there is a college girl (wendysdrivethrudude) that did a complete sunk-in bath tub on this site. The whole thread is a good read. The first post about the sunk-in bath tub is here: http://www.skoolie.net/forums/f11/co...tml#post199465
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Old 03-25-2019, 10:08 AM   #8
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Native is right on about a proper weld being %100 waterproof and airtight too. Think. Propane tanks air tanks etc The problem is getting that quality of a weld in the environment of the bus, using a 75 25 instead of straight co2 is going to help but there will be a lot of awekward welds to make and I would guess it will be worked on outside which is harder when there is some wind blowing the shielding gas away. My point is that if I was doing it I would not rely on the weld to be waterproof. I would use the welds for the structural part of the job and use an undercoating seam sealer or good paint to do the waterproofing. The welds need to be covered anyways.

I too like the idea of a sunken shower pan, it reminds me of the curbless ADA style showers people have started putting in higher end houses around here. I think it would be pretty easy to build an angle iron frame that fits the pan and sheet it with the same 16ga to protect the pan.

I am all the way over in California so probably a little too far to just get some welding done
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Old 03-25-2019, 10:58 AM   #9
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Quote:
Originally Posted by Native View Post
I will answer part of your question(s): When two pieces of metal are welded together, they form one piece of metal. If you have a proper weld along the entire ength of the seam, it will be water-tight ... as if the two pieces were always the same piece of metal and never cut. You will still want to protect the metal by priming and painting, at least on the exposed surface.


As far as the resultant piece being "free-standing", that all depends on the thickness of the metal and the forces applied. In your case, the sheet metal is being used as a cover and the structural support is (mainly) coming from the length-wise and cross-wise 2"x3" rectangular stock you are planning to use to support the flooring.


P.S.: I like your idea of setting the tub down a bit. Please take care to make sure there is enough clearance for the other stuff that is already under the frame ... like your exhaust pipe. I believe there is a college girl (wendysdrivethrudude) that did a complete sunk-in bath tub on this site. The whole thread is a good read. The first post about the sunk-in bath tub is here: http://www.skoolie.net/forums/f11/co...tml#post199465
Thanks for the link to the sunken shower post. It's reassuring to know that there is at least one other person with the same crazy idea going on.

I'm pretty sure I have sufficient clearance for this - it helps that I already have a big hole in the floor there. Although things will definitely be tight since I want this to be insulated.
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Old 03-25-2019, 11:01 AM   #10
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Originally Posted by FAC View Post
Native is right on about a proper weld being %100 waterproof and airtight too. Think. Propane tanks air tanks etc The problem is getting that quality of a weld in the environment of the bus, using a 75 25 instead of straight co2 is going to help but there will be a lot of awekward welds to make and I would guess it will be worked on outside which is harder when there is some wind blowing the shielding gas away. My point is that if I was doing it I would not rely on the weld to be waterproof. I would use the welds for the structural part of the job and use an undercoating seam sealer or good paint to do the waterproofing. The welds need to be covered anyways.

I too like the idea of a sunken shower pan, it reminds me of the curbless ADA style showers people have started putting in higher end houses around here. I think it would be pretty easy to build an angle iron frame that fits the pan and sheet it with the same 16ga to protect the pan.

I am all the way over in California so probably a little too far to just get some welding done
I'm going to have a local mechanic/fab guy do all the welding for this (I own a MIG welder but I've never used it or any other welder before) and it will be indoors. Is it reasonable for me to assume he can do a waterproof seam?
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