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Old 08-29-2015, 07:52 PM   #1
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framing

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.
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Old 08-29-2015, 09:21 PM   #2
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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
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Old 08-31-2015, 11:08 PM   #3
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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.
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Old 08-31-2015, 11:48 PM   #4
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Quote:
Originally Posted by ponyracer1 View Post
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
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Old 09-01-2015, 01:40 PM   #5
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We used liquid nails to hold the bottom in our old bus.
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Old 09-01-2015, 03:37 PM   #6
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Quote:
Originally Posted by nat_ster View Post
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
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Old 09-01-2015, 06:18 PM   #7
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Quote:
Originally Posted by ponyracer1 View Post
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.
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Old 09-01-2015, 11:55 PM   #8
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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.
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Old 09-02-2015, 12:01 PM   #9
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Quote:
Originally Posted by Guy&Mary View Post
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
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Old 09-04-2015, 10:13 AM   #10
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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)
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