RV wood framing, types of lumber used

The few times I've repaired a TT frame, the framing has been typical S-P-F, an inclusive rating of lumber (Spruce, Pine, Fir).

My old Starcraft has 1" x 2" (nominal) studs. Actual dimensions are 1 1/4" x 1 5/8".

All the ones I've torn apart or repaired over the years have been constructed with KD spruce. And when I worked at a trailer factory in the early 70's, we built with spruce.

No fir as it weighs a lot more than spruce. Spruce is strong enough yet a lot lighter than fir. Once it is all fastened together, glued, stapled together etc it makes for a strong lightweight unit.
Fir gets very hard with age and is more prone to splitting with flexing and movement. That's one of the reasons fir is not suitable for RV application.

When they KD (kiln dried) the spruce, the moisture content is largely gone and it does preshrink somewhat, but it is very prone to twisting warping etc. More so than fir. So it's important to buy it straight, store it out of the sunlight and use it ASAP. Once in place in a wall or whatever, it is held in place by the structure it is being used for and will stay there with minimum warping.

But it will fly to pieces in a serious collision or rollover.

Northwood MFG (Nash) and Jayco (Jay Flight) each make a wood framed TT with fiberglass sides. That wood (pun) seem to make it stronger than the old school corrugated aluminum. Not sure on the wood type though.

Go to the lumberyard and ask for #2 pine 2x whatever,rip it to size, (you need a table saw anyway ;-) that's all it is and can be found everywhere.

Dan

I used Doug Fir when I rebuilt the front and back of my TT some years ago. Doug Fir is stronger and more decay resistant than most of the softwoods. I saw Doug Fir studs at Home Depot in Chicago a week ago and that's a pretty long way from where it was grown.

Hammerboy wrote:
Go to the lumberyard and ask for #2 pine 2x whatever,rip it to size, (you need a table saw anyway ;-) that's all it is and can be found everywhere.

Dan

Except on the west coast where Fir reigns supreme. All we have out here are 1x's in pine.

NMDriver wrote:

Ivylog wrote:
The cheapest soft wood they can buy...rarely is it pine and never pressure treated.

X2 and luan for the roof decking.

I suspect cardboard would be used if they could get it to last until the warranty expired.

Watch what you say about cardboard. I have a friend who works for a cardboard manufacturer and he showed me where they are working on cardboard studs. He claims they will be stronger than a normal 2x4.
So who knows!:E

goducks10 wrote:

Hammerboy wrote:
Go to the lumberyard and ask for #2 pine 2x whatever,rip it to size, (you need a table saw anyway ;-) that's all it is and can be found everywhere.

Dan

Except on the west coast where Fir reigns supreme. All we have out here are 1x's in pine.

Actually, I see a lot more hemlock and douglas fir as structural lumber (Oregon and Washington), and it's usually hemlock. True fir is usually reserved for millwork.

BobsYourUncle wrote:

Fir gets very hard with age and is more prone to splitting with flexing and movement. That's one of the reasons fir is not suitable for RV application.

I have a house built in 1895 out of old growth fir. I've been doing some remodeling, and if I want to reliably sink a nail or screw into a stud without breaking the fastener, I have to either use a nail gun, an impact driver, or predrill.

bartlettj wrote:

BobsYourUncle wrote:

Fir gets very hard with age and is more prone to splitting with flexing and movement. That's one of the reasons fir is not suitable for RV application.

I have a house built in 1895 out of old growth fir. I've been doing some remodeling, and if I want to reliably sink a nail or screw into a stud without breaking the fastener, I have to either use a nail gun, an impact driver, or predrill.

I've reworked some really old fir over the years too. Remember when 2X4's were 2" X4"?
Yeah it can get pretty hard alright! Even with my Bostitch N80 coiler set at 120 PSI it still won't run the nail all the way in. Gotta follow it with a 28oz Estwing and all that does is bend the head over!
Tough stuff!