Questions on side walls and insulation?

[mlsa]

Good Morning Everybody

After reading more of your building reviews I have a few questions if you don't mind. I've used the search but didn't find answers to these questions.

Side Walls: I see where some use a sheet of plywood without a frame and some build a frame and then skin on both sides.
What's the end difference in the two?
Which way would end up being lighter if any?
If I went with plain plywood instead of framing/skinning, would I use 1/2" or 3/4" plywood?

Insulation: I see everybody is using block insulation. Why could you not use regular bat insulation like in the walls of a house? Seems like it would be easier to install.

Thanks for any replies and suggestions.

David

[starleen2]

Bat insulation gets it insulating properties from the air space between the glass fibers. Usually its about 4 to 8 inches thick. If you compress the bat insulation then you loss a lot of R- value (insulating properties). Also Bat insulation tends to hold water should a leak occur. Foam insulation virtually eliminated the above two situations with out sacrificing its r- value. I have found the rigid foam easier to install + minus the “itch “ factor

[RichAFix]

This does bring a question I am about to face (sorry I don't intend to hijack your tread).

I plan to use a .25"/.75"/.25" plywood sandwich for my wall construction, with intention to cut away as much of the .75" plywood in the center to save weight and have the ability to add rigid insulation.

Here's the problem, .75" exterior plywood is closer to .7" and pink .75" rigid insulation is closer to .8". Do people not put insulation in the walls? Is the white styrofoam insulation closer to .7"?

I am certainly not spending the extra money on Baltic Birch plywood which is .75".

[bobhenry]

Bat insulation gets it insulating properties from the air space between the glass fibers. Usually its about 4 to 8 inches thick. If you compress the bat insulation then you loss a lot of R- value (insulating properties). Also Bat insulation tends to hold water should a leak occur. Foam insulation virtually eliminated the above two situations with out sacrificing its r- value. I have found the rigid foam easier to install + minus the “itch “ factor

AND

Anyone who has ever opened up a bat filled wall on an old camper can tell ya that the stuff has settled to the bottom 1/3 of the wall. The bouncing down the road just promotes the setteling. So now the heat you are trying to keep out near the roof has a direct path in and the heat you are making to stay warm in the cool months has a direct path out as it rises.

[Mauleskinner]

Side Walls: I see where some use a sheet of plywood without a frame and some build a frame and then skin on both sides.
What's the end difference in the two?
Which way would end up being lighter if any?
If I went with plain plywood instead of framing/skinning, would I use 1/2" or 3/4" plywood?

The primary difference is that you can insulate a framed wall.

As to the weight, it CAN be built lighter as a framed wall. I used 1/4" ply inside and out, with 1x2 framing. The major portion of the weight is the ply, and two sheets of 1/4" are lighter than 1 sheet of 3/4", but about the same as 1 sheet of 1/2" (the framing will make it heavier). That's the basic mathematical calculation.

Here's the problem, .75" exterior plywood is closer to .7" and pink .75" rigid insulation is closer to .8". Do people not put insulation in the walls? Is the white styrofoam insulation closer to .7"?

I am certainly not spending the extra money on Baltic Birch plywood which is .75".

I got a sureform plane and worked the insulation down to the thickness of my framing. Doesn't take long.

David

[madjack]

...I just use 3/4ply for the sidewalls...no insulation...if you do a stick framed wall with 1/8plyx3/4framingx1/4ply you can insulate and reduce the wall weight by around a third...this weight savings CAN knock off upto 50#s(combined) weight from your walls.............
madjack

[kennyrayandersen]

...I just use 3/4ply for the sidewalls...no insulation...if you do a stick framed wall with 1/8plyx3/4framingx1/4ply you can insulate and reduce the wall weight by around a third...this weight savings CAN knock off upto 50#s(combined) weight from your walls.............
madjack

Also, if, rather than using the .7 inch plywood in the middle you frame it in fir/pine/whatnot, you could plane those boards down from rough to match the rigid foam and save all of the foam work. Lots of guys have planes, so even if you don’t have one you can probably ask around and use someone’s. If you can’t find rough pine/fire, you could use poplar which isn’t too heavy.

[greekspeedoman]

David,

I chose to insulate my walls for two reasons: 1. It would make the trailer lighter. 2. I live in Washington State.

In a cooler climate, like mine, it isn't unusual to have 100+ degree days and then 40 degree nights. I used rigid foam as insulation in my walls. In the heat, it knocks out about 6 degrees and keeps things warmer in winter.

Be forewarned though. It is much more work to do an insulated wall than just plywood. Plus you'll have to be careful to keep your walls square & from warping as you build.

[aggie79]

Here's the problem, .75" exterior plywood is closer to .7" and pink .75" rigid insulation is closer to .8". Do people not put insulation in the walls? Is the white styrofoam insulation closer to .7"? I am certainly not spending the extra money on Baltic Birch plywood which is .75".

Grant Whipp gave me the tip that the "white" insulation will compress more than the pink or blue. That is what he uses in his insulated walls constructed with nominal 3/4" plywood.

Tom

[Rock]

I framed my walls with 1" nominal ("1X") white wood, which actually varied in thickness. And because I'm uptight I actually hand planed everything smooth.



I ended up with significantly less than .75". I wanted to use blueboard, but that actually measured .79" I believe. I thought about ways to shave it down including getting some Ni-chrome wire to build a hot knife, but that was too much work.

Instead I used a heat gun judiciously to shrink the insulation flush or slightly sub-flush with the framing.

I didn't want to try and force or compress the insulation to be thinner and risk bulges on my plywood skins.

Eric