Discovered rotted out subfloor - am I overengineering the new one?

[iamatesla]

My bus had "coin pattern" black rubber flooring so I picked out some nice LVP at Lowe's to install in its place only to discover that the entire wood subfloor under the original rubber flooring was rotted out. Spent the last 2 days ripping all the old wood subfloor out and cleaning it up. luckily the galvanized steel floor pan is mostly ok with some rust but not too bad.

Now, I've come up with a pretty elaborate stackup for the new flooring. I'm trying to balance adding more insulation to the floor, making it waterproof so it doesn't rot again, keeping it thin enough (no roof raise), making it quiet, and strong enough.

Is this overkill? any adjustments to this stackup you'd change?

I'm still worried if water makes it back into the floorpan even with this new stack. I should probably check for small leaks first... I didn't think I had any leaks from above, but the old wood was pretty moist and growing mold under the original rubber flooring so maybe I do.

Pics of the rotten subfloor

Also - just want to say it was a massive pain removing the old subfloor. The original builders had both screwed and nailed down the wood to the metal floor pan and covered the screw heads with wood paste / glue stuff to make the heads flush & hidden - so a few hundred screws were invisible and buried inside the wood making it like trying to excavate the damn pyramids trying to remove the wood.

 

[s2mikon]

My only question is what happens when not if, the next water leak happens. Are you leaving some way for it to drain out?

 

[iamatesla]

Yea there are already quote a few holes in the metal floorpan from previous old subsystems i removed. I could just leave them open? or even add a few more in key locations?

In my stackup, the XPS foam will be resting at the lowest level, so if it gets wet occasionally i doubt that will be a problem. just don't want any wood above it to get or stay wet.

Is there a more standard way to accomplish drainage of inside floor-pan?

 

[TheHubbardBus]

Consider yourself lucky you ended up pulling it and finding that rust. I imagine if it had continued for very much longer you might have had some places eat through. Our floor was similar, though not as bad excepting a couple areas.

If I were you I'd put some real effort into knocking all that rust down physically. If you leave the rust scale, nothing you coat it with will stick to it long-term, and moisture will remain trapped allowing rust to continue. We spent days w/ an angle grinder equipped with a wire wheel to remove all the scale, followed up by ospho, followed up by a plain water rinse, then a good dry, and finally KBS rust seal (a moisture-cured urethane which I'm VERY pleased with).

Note that what caused your problem was moisture trapped against the steel with no way to get out. While wood is really good at that, there's no reason the exact same thing can't happen with water getting trapped between the XPS and the steel if conditions/construction allow it. The how and if of that I can't comment on, as we didn't do a floating floor.

 

[nikitis]

Prime example of why we should always rip up the floor. I was lucky and didn't need it at all, but still glad I did just so I "KNOW" it's in good shape and can have peace of mind.

If you do as your plan suggests, it's gonna be air tight on the floor, and likely water tight as well. I have a similar plan on mine but with 4inch of xps. I did close up all of my holes except for ones on the edge corners of the bus where the foam wouldn't quite reach or water could roll off into. I poked a couple of small holes there, but there's no way water will get to the rest of my floor and yours either. It'll work it's way to the edges of the bus so if you do strategically poke holes that's where you'll want them IMO.

 

[iamatesla]

ah that makes sense - if i get everything glued and tight enough the chassis saver + xps foam should be watertight. I like the idea of then having basically wheep holes around the perimeter in case water does get in.

I think once things are cleaned really well & rust removed inside, ill also spray / pressure wash all over the top & outside - and see if i have any leaks pulling water in before i go further with the flooring. I need to wash this thing anyway.

I'd like to do thicker XPS, but i'd rather add thicker insulation to the ceiling. I definitely don't have room for 4 inches - that's probably really nice though!

Tomorrow starts the angle grinder wire wheelin...

 

[Bjorkinman]

Since you're doing the vinyl flooring that could be installed and then built directly on top of, you could just install a single roll wall to wall. I wish I had done it that way. I think you'll be in good shape with your plan.

 

[Cannabus]

Since you're doing the vinyl flooring that could be installed and then built directly on top of, you could just install a single roll wall to wall. I wish I had done it that way. I think you'll be in good shape with your plan.

He’s using vinyl boards not rolled vinyl.

It’s not recommended to lay a vinyl floor board or vinyl sheets down before you add walls and cabinets. Also I would an adhesive like loctite premium PL on your plate and studs as well as your fastener screws for a more secure bond. Vinyl at the stage will just add a joint that’s slippery.

Laying down the vinyl should be the second to last stage before you add the trim and moulding. The vinyl floorboards needs about a quarter inch space next to walls and cabinets to allow for expansion otherwise those boards will pop up and then add the moulding last over the gaps.

 

[Cannabus]

ah that makes sense - if i get everything glued and tight enough the chassis saver + xps foam should be watertight. I like the idea of then having basically wheep holes around the perimeter in case water does get in.

I think once things are cleaned really well & rust removed inside, ill also spray / pressure wash all over the top & outside - and see if i have any leaks pulling water in before i go further with the flooring. I need to wash this thing anyway.

I'd like to do thicker XPS, but i'd rather add thicker insulation to the ceiling. I definitely don't have room for 4 inches - that's probably really nice though!

Tomorrow starts the angle grinder wire wheelin...

Are you spray foaming the walls. If so you want to install the floor first sans vinyl in and foam in the gap between the wall and plywood. if you do have a leak it stay above those layers and off your foam and pan. If you’re worried about condensation or leaks along the wall if not foaming I wouldn’t be too concerned about adding holes. The bus isn’t sealed up where the outer wall meets the floor pan just for this purpose and the skid guards on the outside has drains built in. Little holes in your pan makes a perfect passage for ants to nest. If you live in a rainy wet area they will sure love to set up home under your floor.

What ever paint you use if it recommends a primer then use some after ospho treatment. Primer bonds the paint securely. Your floorboard presently has a felt layer. I would switch to an a vinyl board that already has non absorbent rubber layers bonded to the board. It’s more expensive but the cost of eliminating the felt should compensate it. Also you may want to paint both side of your plywood flooring. Be sure to get a premium quality exterior board. Deck paint or a similar product does the trick.

Best of Luck!

 

[iamatesla]

Considering it, but not planning to spray foam the walls. Currently planning to glue XPS foam sheets up between internal wood framing and spray foaming the gaps with a can myself. I might get spray foam quoted though we'll see.

@Cannabus your correct - planning Vinyl planks - currently the "Smartcore Ultra" flooring from Lowes. It's pretty thick (~7mm i think) and does have a rubber pad already on the bottom - it is unfortunately one of the more pricy options. you think i can avoid the felt layer if I stick with this product?

I've made a bunch of progress the past week. I wire brushed every inch of the metal pan and removed all surface rust I could. Cleaned floor well and pained a thick coat of Chassis Saver directly on (used entire gallon). I've also glued down 1 inch XPS foam with tons of loctite PL3X. FYI Amazon Hot Knife Foam Cutter was extremely useful for the foam cutting - highly recommend.

I've got roughly 1/4 inch to 1/2inch gaps all around the edges where the foam wasn't exact up to the metal walls. planning to go back and fill in any gaps with canned spray foam & cutting level once dry. Still considering adding "wheep holes" in select spots or not - i do believe the chassis saver has made the inside floor pan quite watertight - that stuff is no joke.

Next step is to go buy the plywood sheets for the floor and glue them to the top of the foam. Leaning toward 5/8 BC Pine Exterior Plywood (my local lumber shop has these options Plywood and hardwood plywood price list - Intercity Lumber Tampa, Fl). I was planning to screw these plywood sheets down with tons of wood to metal self tapping screws (through the foam) but after some reading, it seems that may cause other issues (tons of new holes in floorpan is bad). So, my current plan is simply to glue the wood sheets down on top of the XPS foam with tons of PL3X glue and then paint the top / sides with Zinsser B-I-N to seal.

Then, i'll probably do my walls and ceiling completely, and maybe more of the buildout - walls, cabinets, and whatnot - then lay down the vinyl planks near end of total buildout as @Cannabus recommends.

 

[Cannabus]

I think you’re on the right track. Hope to meet you in the outback sometime

 

[Bjorkinman]

Looking good!

 

[Cannabus]

Considering it, but not planning to spray foam the walls. Currently planning to glue XPS foam sheets up between internal wood framing and spray foaming the gaps with a can myself. I might get spray foam quoted though we'll see.

@Cannabus your correct - planning Vinyl planks - currently the "Smartcore Ultra" flooring from Lowes. It's pretty thick (~7mm i think) and does have a rubber pad already on the bottom - it is unfortunately one of the more pricy options. you think i can avoid the felt layer if I stick with this product?

I've made a bunch of progress the past week. I wire brushed every inch of the metal pan and removed all surface rust I could. Cleaned floor well and pained a thick coat of Chassis Saver directly on (used entire gallon). I've also glued down 1 inch XPS foam with tons of loctite PL3X. FYI Amazon Hot Knife Foam Cutter was extremely useful for the foam cutting - highly recommend.

I've got roughly 1/4 inch to 1/2inch gaps all around the edges where the foam wasn't exact up to the metal walls. planning to go back and fill in any gaps with canned spray foam & cutting level once dry. Still considering adding "wheep holes" in select spots or not - i do believe the chassis saver has made the inside floor pan quite watertight - that stuff is no joke.

Next step is to go buy the plywood sheets for the floor and glue them to the top of the foam. Leaning toward 5/8 BC Pine Exterior Plywood (my local lumber shop has these options Plywood and hardwood plywood price list - Intercity Lumber Tampa, Fl). I was planning to screw these plywood sheets down with tons of wood to metal self tapping screws (through the foam) but after some reading, it seems that may cause other issues (tons of new holes in floorpan is bad). So, my current plan is simply to glue the wood sheets down on top of the XPS foam with tons of PL3X glue and then paint the top / sides with Zinsser B-I-N to seal.

Then, i'll probably do my walls and ceiling completely, and maybe more of the buildout - walls, cabinets, and whatnot - then lay down the vinyl planks near end of total buildout as @Cannabus recommends.

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I wouldn’t screw down the plywood. Glue it to the foam as foam is glued to float. Don’t worry about it flying off in a roll over. Once you put in walls, cabinets and closets it ain’t going anywhere and you’re not putting more holes into your pan. I use loctite premium PL. it doesn’t dry so hard it loses flexing properties to allow for expansion and floats somewhat. It’s also great for repairing shoes and boots separated soles and other great applications.

Sorry I didn’t reply sooner