framing

[straydog]

This may seem like an obvious question, but what has everybody done to secure your framing to the floor? We have 1" of insulation covered by 1/2" particle board. Trying to secure 2x4s to the floor for framing. The longest Tek screws I have found are 2 3/4". Not long enough for the job.

[nat_ster]

Read through Jake C's build thread. He did a fine job of securing his floor, without compromising his thermal brake.

http://www.skoolie.net/forums/f11/pr...utus-5059.html

Nat

[ponyracer1]

Shouldn't be much transfer through a 2x4. I'd use a circular saw to cut slots into the plywood/insulation and screw the 2x4 to the floor of the bus. The roof might be more sensitive to heat transfer.

[nat_ster]

Originally Posted by ponyracer1

Shouldn't be much transfer through a 2x4. I'd use a circular saw to cut slots into the plywood/insulation and screw the 2x4 to the floor of the bus. The roof might be more sensitive to heat transfer.

IMO
You my fellow skoolie need to lean about thermal transfer and proper thermal breaks before giving advice.

A 2x4 has massive thermal transfer, but the screws have far more.

That's why Jake C left is floor "Floating", with no screws from the surface to the metal floor.

Nat

[Guy&Mary]

We used liquid nails to hold the bottom in our old bus.

[ponyracer1]

Originally Posted by nat_ster

IMO
You my fellow skoolie need to lean about thermal transfer and proper thermal breaks before giving advice.

A 2x4 has massive thermal transfer, but the screws have far more.

That's why Jake C left is floor "Floating", with no screws from the surface to the metal floor.

Nat

Sorry Nat Ster, I'm not an overly educated man. Nor do I have a degree in thermo dynamics, engineering, or physics.

What I do have is 25yrs exp in construction and a good deal of common sense. People on this site seem to get "wrapped around the axle" about stuff that doesn't really matter. In the end do what makes sense. To me notching the floor for the lower wall stud to sit directly on the bus floor makes sense but to each his own.

But according to the posters info, 1" insulation and 1/2" plywood. I can only assume it's hard board insulation and if it's Rtech then it really wont matter. If it's higher quality Rtech then the difference will be larger but I still doubt it will be noticeable.

Rtech R3.85
1/2 plywood .63
Combined=R4.48

R value of a 2x4=R4.38


So his floor is probably R4.48. 2x4 Lumber is R4.38 or a difference of R0.10.

ColoradoENERGY.org - R-Value Table

[family wagon]

Originally Posted by ponyracer1

R value of a 2x4=R4.38

So his floor is probably R4.48. 2x4 Lumber is R4.38 or a difference of R0.10.

ColoradoENERGY.org - R-Value Table

Keep in mind that R value is for heat conducted in the 3-1/2" direction, as a vertical 2x4 stud would be in a wall assembly. When laid flat on the floor as in a bottom plate of a wall, heat is conducting through the thinner 1-1/2" direction of the 2x4, and the cross-section is wider to boot. Farther down in the linked table there's a line for 2" nominal lumber that calls out 1.88 in the "R/Thickness" column. I think that's the value that would apply in this scenario.

Even though the thermal performance of the 2x4 laid flat on the floor rather than up on top of the foam is worse, it may still make sense to do for other reasons. And if there isn't much surface area installed this way, then its lower thermal performance will be negligible in the overall thermal performance of the floor.

[ponyracer1]

True! Although even at the lower number I don't see it mattering but I guess every bit helps and adds to the overall finished product.

[nat_ster]

Originally Posted by Guy&Mary

We used liquid nails to hold the bottom in our old bus.

That stuff will not hold to the metal vary long when the bus starts moving down the road.

Nat

[aaronsb]

If it helps, I cut pressure treated 2x4's down to a true 2" wide strip, then laid the uncut face on the metal side, countersunk 3/4" or so into the top side with a forstner bit, then attached with galvanized self tapping screws into the steel floor deck every 16"

I used approximately 18 to 24 inch spacing for these runners which were parallel to the bus body, and laid 2" rtech foam between them.

On top of that I primed and painted plywood which was then cut to fit and screwed into the runners. It seems to stay comfortable with bare feet even in winter (pacific northwest)

[nat_ster]

Using pressure treated wood inside your bus is asking to poison yourself and loved ones.

That stuff is deadly. Please guys don't use it inside habituated spaces.

Nat

[aaronsb]

Arsenic based pressure treatments are unhealthy, and not commonly available anymore.

I used Copper Azole treated wood, which isn't terribly bad for you and is the type of treatment most pressure treated wood you buy at the big box stores sell now. I have more concern about toxic exhaust stink stuck on the highway at this point than any type of gassing or emission from the wood strips buried under plywood and vinyl flooring.

Originally Posted by nat_ster

Using pressure treated wood inside your bus is asking to poison yourself and loved ones.

That stuff is deadly. Please guys don't use it inside habituated spaces.

Nat

[nat_ster]

Glad to hear you chose the least toxic of the bunch.

Nat

[Tango]

One important note regarding the "new" copper treated wood products...

...make absolutely certain to use only fasteners approved for that treat. Regular "old style" fasteners will basically dissolve after maybe a year. When they made the change, the industry did not put the word out and a bunch of construction projects fell apart. No idea how it plays when in contact with galvanized but might be worth some research.

[nat_ster]

This also means isolating the treated wood from the bus steel, as it will also attack and corrode it too.

Best is to just not use treated wood in your bus. There is no reason to use it if your building your bus properly.

Nat

[CaptainInsaneo]

I don't think there is a good reason to use treated wood. Seriously if you fear bugs/rot in your bus use red wood sure it will be expensive, but how much framing are you really doing in a bus?

It is far more important to never burn treated wood so don't burn pallets.

[Tango]

If you are in fear of ply going to rot in a bus...look at marine grade. No nasty chems. Just good wood.

[EastCoastCB]

certified Okoume is awesome if one can afford it. I may just have to save up for some. Very resilient and stiff stuff.
Always make sure to seal up the edges real well and it will last nearly forever.

[Tango]

Thinned out silicone is great for sealing the edges of ply.

[REDD]

I've used fiberglass resin on both sides of the plywood and the edges when I built wind break walls in the back of service trucks. Used a paint roller. It's lasted four years so far and it's in the weather all the time.