Why wood roof trusses?

The purpose of a truss is to transfer the loads placed on it to the vertical wall members where the load is then transferred to the frame.

A roof truss has two types of loads which are applied to it. 1)live load and 2)dead load.
Dead load is the weight of the roof materials, Air conditioners, vents, etc. Once constructed, these loads will not change throughout the life of the RV.

A live load is the additional weight or stresses which are applied to the roof, such as snow, human weight, and most importantly stresses applied during transportation.

Your roof is designed to flex. If it didn't, failure would be imminent. When the roof flexes, the top part of the truss is under a compression force and the bottom under tension. In other words the top of the truss is trying to get shorter from the weight it supports and the bottom is trying to get longer. Because of these forces, a properly designed wood truss is more forgiving than a metal one...especially aluminum. Aluminum tends to fatigue and stress crack where wood will not.

Thus ends "Structural Engineering" 101.

My Salem Hemisphere has wood trusses and I am very glad it does...just sayin.

Whoops, just noticed I need to update my signature.

I guess some folks don't know we still have lots of RV's and mobilehomes made in the '60s and '70s and '80s with all side and roof wood framing still being used with no rot issues.


Wood vs aluminum per NUWA makers of of HH II units says this about wood vs aluminum.

Why doesn't NuWa use an all aluminum structure like popular Indiana manufacturers?

** NuWa made the decision to begin the use of aluminum structure based on marketing and the fact that many people were concluding that an "aluminum caged" product was superior in construction technology, weight and strength. Our 40+ years of experience as a leader in 5th wheel design suggests that may be "flawed" information. We have proven that wood construction need be no heavier or less strong than aluminum construction, that is built properly. We now build both materials, and are comfortable doing either, however our opinion is still that wood construction provides a superior product, and today we use both in the construction of our trailers. The strength of the NuWa trailer is actually created by the superior and light weight Blue Dow foam lamination concept.

NuWa uses an aluminum substructure in the sidewalls and ends of the coach only. No aluminum in the floors or attics, where metal promotes conduction of cold and moisture resulting in condensation.

90% of the walls are Blue Dow Structural Foam, rather than wood or aluminum. This creates a superior insulation and the only product with a guaranteed sidewall R Factor. (Water absorption in standard white foam reduces R Factor over time, and the use of Blue Dow Structural Foam eliminates this problem.)

NuWa's aluminum substructure sidewall is actually a "hybrid" wall, as we core fill the aluminum with wood in those areas where additional strength is required, because aluminum will not hold a screw. Not so with the lower priced brands. With NuWa's combined use of wood and aluminum substructure, you get a superior product because of NuWa's unique Blue Dow foam vacu-bond process, which makes the sidewalls virtually resistant to water penetration. **

goducks10 wrote:

My understanding was that Noah made the Arc out of wood only because he couldn't weld. :)

The replica in Kentucky is made of wood as well, although I don't think they used "gopher wood"

proxim2020 wrote:

creeper wrote:

But, my house is not bouncing down the road twisting all the time. There is a reason wooden boats are no so popular anymore and large ships are made out of metal.

Wood has lost favor mostly for economic reasons. Companies can pump out finished fiberglass and metal boats in very few labor hours. It can take a month for an equivalent wooden boat and with a good chunk of the cost is in tons of labor. For example, you can buy a plastic canoe for around $600. A wood strip version would cost well over $1,600. The larger the boat, the worse the economics.

Wood boats are still quite popular especially with the self builders. I'm in the early stages of building a new canoe out of wood. There's tons of sailboats, yachts, and fishing boats, etc trolling around out there that were built 30+ years ago. Wood has been the choice around the world for thousands of years. Materials are cheap and easy to get, it's stronger than steel, resilient, and easy to modify. Coat it with epoxy and you got a boat that can easily last 20+ years. Maintenance is pretty much a wash between materials. All boats require a lot oyf maintenance and the material just dictates the method.

I know off topic but would love to have a old restored Chris Craft wood runabout. Back to topic wood does have some advantages in RV'S along with the negatives. They have already been covered so I won't repeat them.

Wood is the wrong material to be used anywhere in a RV. I am convinced they all leak or trap moisture. At a minimum marine grade should be used in floors. The industry got the public hooked on pretty with low pricing. We see one thread after another on soft floors,mold etc. It's all metal top to bottom for me.

creeper wrote:

But, my house is not bouncing down the road twisting all the time. There is a reason wooden boats are no so popular anymore and large ships are made out of metal.

Wood has lost favor mostly for economic reasons. Companies can pump out finished fiberglass and metal boats in very few labor hours. It can take a month for an equivalent wooden boat and with a good chunk of the cost is in tons of labor. For example, you can buy a plastic canoe for around $600. A wood strip version would cost well over $1,600. The larger the boat, the worse the economics.

Wood boats are still quite popular especially with the self builders. I'm in the early stages of building a new canoe out of wood. There's tons of sailboats, yachts, and fishing boats, etc trolling around out there that were built 30+ years ago. Wood has been the choice around the world for thousands of years. Materials are cheap and easy to get, it's stronger than steel, resilient, and easy to modify. Coat it with epoxy and you got a boat that can easily last 20+ years. Maintenance is pretty much a wash between materials. All boats require a lot of maintenance and the material just dictates the method.

creeper wrote:

deltabravo wrote:

Shadow Catcher wrote:
They do not care about quality!

Using roof trusses made of wood has NOTHING to due with quality, or lack thereof.

Houses use wood roof trusses, but no one complains about them being of subpar quality.

But, my house is not bouncing down the road twisting all the time. There is a reason wooden boats are no so popular anymore and large ships are made out of metal.

My understanding was that Noah made the Arc out of wood only because he couldn't weld. :)

totaldla wrote:
I don't think we're talking about parking in the surf.

A lot of folks camp on beaches but that's not the reason I tried to correct your post. The point is there are compromises and trade-offs with materials used. Nothing is as absolute as "100 times better".

deltabravo wrote:

Shadow Catcher wrote:
They do not care about quality!

Using roof trusses made of wood has NOTHING to due with quality, or lack thereof.

Houses use wood roof trusses, but no one complains about them being of subpar quality.

But, my house is not bouncing down the road twisting all the time. There is a reason wooden boats are no so popular anymore and large ships are made out of metal.

Wood is cheaper, it's that simple.