House Truck Conversion

[tinyhousetruck7]

Hi all,
I am converting a box truck into a shepherds hut style home; I realize this is not a skoolie but it is in a similar vein, especially when it comes to the body of the box that I am using (steel construction, see photos). I have some questions I thought skoolie builders might have good answers to. To give you a quick run-down of the project, I am keeping the 20' box on my truck but removing the roof and welding on arched rafters, so it will have a nice and cozy shepherds hut appearance. After that, the interior conversion will resemble a skoolie with a roof raise; framing windows, insulating, etc.

The question I'm stuck on right now is this: subfloor. I know that skoolies have a metal pan floor that they build their subfloor atop. I, however, have 1" tongue and groove planks of wood that sit on top of the crossmembers of the steel bed that is the foundation of the box (see photos). This has served as the only floor of the truck throughout it's life moving furniture and the wood is in good condition. However, I am worried about building my subfloor atop this for the foundation of my home for several reasons: it is unprotected on the bottom side, so I worry that over the years (especially through snowy winters) the wood could rot... compromising my home foundation. I also worry about its ability to keep out insects and rodents as there are some gaps in the corners. Here are options I've thought of to solve this problem:

A) Cheapest/easiest: Leave wood, go on the underside of the truck and coat the bottom of my steel frame and all visible wood with some kind of water resistant paint... not sure what so any recommendations would help. Fill gaps where critters could get in (recommendations??)

Unscrew and pull up all the wood, give it a few coats of a heavy duty primer, then screw it all back in. This would use the wood that's already there but would be tedious (probably 70 screws into steel). Fill any gaps in corners where critters could get up with spray foam or something else?

C) Take out all the wood (could use it for something else) and lay down sheets of 3/4" painted ply. Recommendations on what to use to prime this to protect it welcome.

D) Most expensive/most difficult: And lastly, remove all the existing wood and lay down metal sheeting on top of the steel bed crossmembers, I could wrap up the walls just a couple inches so I would have a true pan--like a skoolie.

Let me know what you think I should do. Of course, would love to use the wood that is already there because like I said, it's already there. But, willing to spend money to fix this if it could be a long term issue. Taking all advice!!!

 

[Albatross]

I would go with something like a tar paint on the underside.


You could fill the gaps with new wood, and coat the underside with a Pine Tar paint, and then brush on some bituminous/coal-tar paint for any metal on the underside. Once the paint(s) have cured (I would give it a couple of weeks), I would go over both with something like Spar Varnish, a marine urethane epoxy designed for yachts.


Going this route would probably mean that you would want to reapply the finish in 3-5 years, and then every 5-10 after that, but it would give you a solid and stable "undercoat" that should resist pretty much everything you have to throw at it, water, salty muck, and oil like very little else will. It should also still let the wood breathe a bit, and I personally like the smell of pine tar once it's dissipated a bit.


Wood is a better feeling floor to me, and it's likely a better insulator than metal or plywood, assuming that you've properly filled any gaps.



The only other thing I would caution you on is to be sure to keep your height under about 12'6" if you want to clear most overhangs on the roadways. That, and to wear a respirator if/when you bust out the bituminous paint and urethane. Probably wouldn't hurt to keep it on with the pine tar paint, especially if you've got to thin it out.

 

[nikitis]

I'd honestly buy some galvanized steel sheets and remove the existing wood carefully to reuse it after laying down steel sheet for protection.

 

[tinyhousetruck7]

Thank you so much! This is a good idea too. I have plenty of ways I could repurpose the wood even if I didn't use it in the floor system.

 

[tinyhousetruck7]

@Albatross Thank you so much! I appreciate that advice; it seems like your method would give the wood the longevity I'm hoping for. One thing I'll note is I will be insulating above the wood, so the existing wood plank floor will be underneath my insulated subfloor.

 

[sportyrick]

those floors are built to last the life of the truck so I wouldn't worry about it that much. A coat of some kind of sealer on the underside would be smart. I think the problems with wood floors in a truck start from the top not the bottom.

 

[Timeline]

I think Rick is right, that floor is probably going to be fine, is the wood solid if you poke around? Any holes could be covered with tin.


Check out this method for insulating the floor:

Good Luck!
John

 

[Rucker]

Agree with SportyRick. My shuttle bus has a plywood floor open to the bottom, 25 years on in California, still not a problem except as described below.

Spot replace the deck where needed, and you can build on top of it with a rigid foam/plywood floor system.

I'm assuming you're not a perfectionist and don't need the job to be perfect. I had a soft spot in one corner of my bus from a leaky window. I fixed the leak, and just left the plywood in place. In my case, the plywood failed because that area of the bus had sheet metal shielding around the gas tank fill pipe, and the water was unable to drain/evaporate. It's under the bed in a corner, and it's just a bus, after all.

 

[Ronnie-SKO]

What kind of wood is it? Some woods are nearly indistructable and very weather proof. The flooring in sea containers is often Ipe, sometimes called iron wood. Very hard and very rot resistant.

 

[tinyhousetruck7]

@sportyrick I've talked with a few people who've shared the same sentiment; these floors are built to last and I've met some folks with skoolies who've had wood plank subfloors for over 30 years. If I seal the bottom of the wood and leave the top open, I'm wondering if this would be problematic if I had a leak at some point and the wood got saturated; would having an underlayer coat prevent the wood from naturally drying out? When I think about that, then I wonder if I should either a) seal top and bottom of planks or b) don't seal at all so wood can dry out if ever needed

 

[tinyhousetruck7]

@Ronnie I wish I knew what type of wood it was. It doesn't look like any north american species to me so my best guess based on color and grain would be a tropical or african hardwood. I might give a call to metro box manufacturers just to see what they use. If it is one of those very water resistant woods I will worry much less.

 

[Ronnie-SKO]

@sportyrick I've talked with a few people who've shared the same sentiment; these floors are built to last and I've met some folks with skoolies who've had wood plank subfloors for over 30 years. If I seal the bottom of the wood and leave the top open, I'm wondering if this would be problematic if I had a leak at some point and the wood got saturated; would having an underlayer coat prevent the wood from naturally drying out? When I think about that, then I wonder if I should either a) seal top and bottom of planks or b) don't seal at all so wood can dry out if ever needed

From my perspective as a boat builder I would seal the top. But not the bottom to allow it to dry, as the bottom will be exposed to air.

 

[LargeMarge-TC]

That commercial-rated wood floorboard is pretty tough.
.
a)
We plugged major gaps with expanding spray-foam.
The label claimed it resists vermin and bugs.
That was over a decade ago... we will post the results after a quarter-century of full-time live-aboard testing.
Twenty-five years should convince anybody.
.
.
b)
For the wood floor on our ExpeditionVehicle plus the wood floor in the toy-hauler I fabricated on a similar commercial chassis, we poured exterior house-paint on the floors, then rolled the puddle into spaces between boards.
.
The next step in stand-up 'lazy', we used long handles for standard paint-rollers.
.
Paint-filling the gaps took a couple coats, but what's time to a hog.
.
.
[edited to add]
As a dramatic illustration of inflammation at work, drop a random spark on bare wood floorboard.
You might need a magnifying-glass to see, but you will probably notice a tiny smoke-less crater forming.
.
After a few seconds, the crater might turn into a shockingly-rapidly expanding hole.
.
In a minute or so, you can probably put your fist down through to the outside.
.
Note the lack of neither flames nor smoke.
.
For this demonstration, you probably want a handy garden-hose turned 'Full-Blast' someplace in the vicinity.

 

[LargeMarge-TC]

Here is all the Disaster Class you need to insulate the floor:
a -- lay at least one one-inch pink-board on your freshly-painted original floor.
b -- after painting all surfaces to seal, lay half-inch plywood on the insulation.
c -- install your visible floor (our ExpeditionVehicle has slate in the center, bamboo around the perimeter).
.
2003, we built our ExpeditionVehicle using this floor build-up.
Over two decades full-time live-aboard, zero issues.
The pink-board has zero indication of crumbling, because weight is spread by the plywood.
.
An aside:
We are also founding members of the No! Holes! In! The! Roof! club.