Ceiling and floor in 1 inch total?

[Grasswaiting]

I have a 2007 Thomas C2 5 window and I’m 6’5” so I have 1” total of clearance to the metal ceiling ribs standing barefoot on the bare metal floor. I want to maintain standing height at all costs. The entire bus is sprayed with closed cell foam level with the ribs and underneath the floor for maximum insulation, given my situation. The ceiling will be fully shaded by solar panels.

Is it reasonable to do the following with my 1” of clearance height or would you guys have a better idea (other than a roof raise)?

1) 1/2 inch T&G ceiling : Use 1/4 inch foam thermal break tape on the ceiling ribs, then countersink flat trim screws directly into the ribs in 1/4 inch cedar T&G and wood putty the holes (1 per board per rib)

2) 1/2 inch waterproof cork floor : Use 1/4 inch XPS foam underlay thermal break, then float the 1/4 inch waterproof cork flooring over top (the underlay does not void the warranty without a subfloor).

Happy holidays all!

[rossvtaylor]

Hi and thanks for the holiday wishes.

"Reasonable" really depends upon your plans and intended uses. Will you be full-time or vacationing? Are you stuck somewhere with hot or cold extremes...or will you be chasing the moderate weather? Those will all have an impact on the effectiveness of your plan. But, without knowing those yet, I'd say that my recommendation for something 1/4-inch thick to create a thermal break would be either EHP Rollboard or Ceratex ceramic felt or paper.

On a side note, because solar panels are black...or dark blue...I wouldn't plan on counting them as shade for your roof unless they're installed quite a bit above the roof. Generally, with solar panels mounted pretty low, they actually act more as a heat source than shade.

[Grasswaiting]

Thank you Ross!!! Home run sir, Ceratex 1/4” is perfect for the floor and ribs in my situation.

I will be vacationing and chasing moderate weather, with a Minisplit for heating and cooling but a solid 1/4” thermal break supposedly makes a huge difference on metal studs for houses by like 15% average R value. I don’t know much about thermal break products but solar is my day job; solar panels on the longer Z roof clips reduce roof temps by 40%.

[HamSkoolie]

Originally Posted by Grasswaiting

1) 1/2 inch T&G ceiling : Use 1/4 inch foam thermal break tape on the ceiling ribs, then countersink flat trim screws directly into the ribs in 1/4 inch cedar T&G and wood putty the holes (1 per board per rib)

Every one of the screws in such an installation will create a thermal bridge to the head of the screw. Multiply how many screws you will have going into the ribs and you'll have a lot of thermal bridging. You'll also, in cooler weather, find that condensation forms on the cooler screw heads due to the humidity that WILL be inside your bus.
If you hadn't already spray foamed you could have attached 1x or 2x wood to the sides of the ribs then attached your 1/4" cedar to those boards. With the foam already in, that would be a difficult operation to perform and likely an expensive one.

[Grasswaiting]

Thanks sir! Appreciate the comments. I think this is a make it work moment due to the clearance issues and the choices I already made. I’m aware of the condensation and bridging issue on the screws, so I am resigned to counter-syncing the smallest finish screws and wood puttying them, unless someone has a better idea that’s not a massive amount of work. I am semi concerned about counter-syncing in 1/4 cedar, but there’s no weight on it and I’ll give it a test. Honestly, far more concerned about some fuel system issues with my MBE906 and the mystery alarm going off when I turn the key to on, as the bus cranks but won’t start.

I looked as these tongue and groove hidden clips that would have worked nicely but they don’t make them for 1/4” T&G. I just didn’t ever consider putting the furring strips on the sides as I jumped on a great price ($1000) on a really good complete spray foam from a guy going out of business.

Happy holidays!

[DeMac]

Originally Posted by Grasswaiting

Thanks sir! Appreciate the comments. I think this is a make it work moment due to the clearance issues and the choices I already made. I’m aware of the condensation and bridging issue on the screws, so I am resigned to counter-syncing the smallest finish screws and wood puttying them, unless someone has a better idea that’s not a massive amount of work. I am semi concerned about counter-syncing in 1/4 cedar, but there’s no weight on it and I’ll give it a test. Honestly, far more concerned about some fuel system issues with my MBE906 and the mystery alarm going off when I turn the key to on, as the bus cranks but won’t start.

I looked as these tongue and groove hidden clips that would have worked nicely but they don’t make them for 1/4” T&G. I just didn’t ever consider putting the furring strips on the sides as I jumped on a great price ($1000) on a really good complete spray foam from a guy going out of business.

Happy holidays!

------------------------

Are you using 1/4" thick lumber? Finish size actually 0.250"? Reaching flush may prove difficult. The screwheads, themselves have a thickness.
See Head Height in the table below.


Any screw larger than #8 will likely have a head-height exceeding 3/16" (0.1875") leaving 1/16" of lumber in the grip, zero recess. #8 won't hold your pants up.



Have you located the hardware you intend to use? Thread per inch count will also determine the griping force.


The screws I used are made to hold wood to metal. The head height is greater than 1/4" thick, #12 w/ 24 threads per inch.


Measure the distance from the end of the thread to the top of the head. That is your minimum thickness to flush.


I was able to recess the screw heads nearly a 1/2", into 2"x3" thick lumber, inch-&-a-half actual, leaving only 3/4" of meat under the 1/4" thick heads.

EDIT:
Though OP read 1/4" T&G

[BarnYardCamp]

I used 1/4" tonge and groove pine. To attach, I used wood to metal, self drilling flat head screws. These have a broad head (23/64") to better support the flimsy wood.
I pre-drilled each hole in the wood, then used a counter sink bit before installing the screws. (I did not pre-drill into the metal ribs)
Using 1/4" wood on the ceiling, I don't think you will have enough material to bury the screw heads deep enough to fill over the screw heads.
So, I may have some thermal bridging, my bus will be used for vacations. No extreme temps ( I hope)

Since I haven't finished my build yet, I can't say how well the ceiling will hold up over time.
edit; I thought the original post said using 1/4" t & G.

[mmoore6856]

why not insulate outside and roll new tin over it?

[mmoore6856]

got down to 3 degrees last nite. we did a roof raise of 18 inche and got a good 3 inches of insulation in the ceiling and the walls. 2 in the floor . i installed a new rv furnace when i was building and last nite it only came on 5 times in a 12 hour period

[musigenesis]

Originally Posted by DeMac

#8 won't hold your pants up.

Hey now! You just need a lot of them to hold your pants up.

[mmoore6856]

everyhere where wood touched metal i used sill insulation that helps stop the cunduction

[Grasswaiting]

I think these wafer head screws in stainless (low heat transfer) are the answers, good call. I’m going to try to countersink these in 1/4” T&G with a forstner bit and bondo. Between this and the Ceratex 1/4” over the ribs and floor, you all got me home, great community! Odds of pants retainage is high. I’ll post results to close out the thread.

[musigenesis]

Early on in my project I bought some ceramic screws with the idea that I'd be using them to attach my ceiling panels directly to the ribs (or "bows" as it seems they're actually called in the industry lol). They have about the same thermal conductivity as wood so condensation should not have been a major problem with them. No way they're a practical solution, though - they're very expensive, pretty ugly since they have raised cylindrical heads (and they're kind of a greenish-yellow tinted off-white), and you'd have to drill and tap all the holes for them (and you'd need a lot of them since they're not as strong as steel or even brass).

[turf]

to save headroom, how about using more of a headliner type ceiling?

i think that a foam backed suede glued to the sprayfoam could be a nice ceiling. i did some pieces glued to polyiso that worked well.

good luck

[Grasswaiting]

I don’t think I am nimble or patient enough to try a sprayed in headliner. But it would definitely work for my situation. I did a sprayed in headliner on a 66 mustang with my dad growing up, that was when I learned how to Swear.

Someone mentioned ceramic screws, which I appreciate for the out of the box vibe. Stainless is way cheaper and stronger with similar low conduction (3.5 worse than regular screws.)

Last question folks: I’m going to be starting this part of the build and the new dash in a couple weeks. The water tanks (2x40-50 gal) are going under beds in the back. Should I continue the flooring in that area, leave it primed and painted metal or do something else for the “Garage” area?

[Jolly Roger bus 223]

on both of my buses one in progress now on the holding takes.
i like to use linoleum or heavy rubber sheet and build a wet area floor pan with 1-1/2" or 2" high sides for just in case.
the second bus my wife found by accident some silicone rubber sheet that seems like it will work well and was alot easier to form into pan style in the corners than other sheets of rubber or linoleum i have used.