Roof Strength Question

[SteveH]

I'm proceeding with the construction of a 5 foot wide Teardrop and while planning ahead with the design in my head, I'm wondering if 2 X 2" pine (ripped 2 X 4) will strong enough for the roof "rafters"?

I'm planning on a ceiling skin of either thin plywood or masonite and the same for the outer skin, covered with aluminum (If I can afford it).

What are your opinions?

Thanks

[Joseph]

I'm wondering if 2 X 2" pine (ripped 2 X 4) will strong enough for the roof "rafters"?

Strong enough for what? I used 1x2s mounted flat so my roof is 1" thick. It's plenty strong as long as I don't get up there and dance... \:D/

Joseph

[Woody]

Maybe you should consider hardwood of some sort like oak, it is alittle more stable and won't sag over time like pine might

[steve wolverton]

SteveH - Are you thinking of installing an AC unit on the roof? I'm also using 1x2's and 1/8" hardboard for my roof.

[BrianB]

I doubt pine rafters will sag if you have an inner skin of some sort.

I am planning on using 2x2s for the roof so that I could have an extra half inch of insulation on the top. Done right, it should be plenty strong.

[SteveH]

OK, let's see if I can answer the questions correctly....no, no dancing on the roof. My dancing days are over, much less dancing on roofs!

Yes, I've considered hardwood, but it's the cost thing. The next cheapest wood available here is poplar, and only in 1X widths, and since the tear is 5 foot wide, there will be joints in the covering that must be on a rafter, so doubling the 1X poplar is too expensive.

No air conditioner on the roof, but since it is 5', I'm concerned about strength. If it were 4', it would be a lot easier because there would be fewer joints to deal with and stronger by virtue of the smaller dimention.

I'm in no way sorry about going 5' wide, but it does complicate things and runs the cost of materials up by about 50%. As an example, my floor required the purchase of 3 sheets of 3/4" ply because it is 9' long. Granted I have some left over, but most all of the other materials will be birch because of asthetics. I might be able to use some as work top or tables for the gallery area if I cover it with Formica.

Anyway, just hate the thought of putting so much time and money into this and have it come out too weak.

[Joseph]

Anyway, just hate the thought of putting so much time and money into this and have it come out too weak.

Again - too weak for what? Between the rafters and the inner and outer skins you are not going to have a problem, especially with 2x2s. My Scotty has 2x1 rafters laid flat like my teardrop and it's 76" wide.

Joseph

[tdthinker]

I am using 2x2 oak for all of it. We have a pallet that is like stacked 4 feet high with 8-12 foot lengths. bye

[Woody]

If you use pine get the premium stuff with out knots

[ALAN GEDDES]

My first two tears I spent big money for good clear 1 x 2's. Watched the way the grain ran and so on. On the Freebie Challenge project I ripped 2 x 4's into 1 1/2 x 1 1/2 ribs, again watching grain and also not using pieces with major knots. Ended up with a severe bow in two adjoining ribs after installing interior paneling. Pulled it down and when I installed outer roofing it all popped into place fine. If you think about the curve and two pieces of panelling it just has to straighten it out and I had my 140 lb bod on top of it when I was filling and sanding with no sag at all.

[darkroomsource]

I purchased clear oak 1 by 1 1/2" and 1 by 1 1/4" (they didn't have enough already ripped 1 1/2" stock, these ribs measured 7/8 by either 1 1/8 or 1 3/. I spaced them 24 inches apart on end, so they extend 1 1/8 to 1 3/4" into the cabin. I put 1/4" plywood on top, glued the plywood to the ribs, and glued the ribs to the side.

When I put the skylight in, I sat on the roof, I weigh 250 pounds.

Strong enough?

[josephhanson]

I used 2 X 4 boards cut to 1" by 1 5/8 on my 6' wide trailer. when I attached the vent in the roof, I was sitting un top of the trailer(I didn't dance) the roof didn't sag. It should hold up just fine with raindrops up there. I used 1/4" luan inside, 1" extruded foam center, 1/4" luan outside, and a filon shell.

[SteveH]

So.....what I am understanding here is, no matter what I use for "rafters", the general concesus is, it will work.

Thanks everyone for your inputs.

[asianflava]

The bend (tear profile) will also help with the strength. With an inner and outer skin bent to the profile, sagging should not be a problem.

[Joseph]

So.....what I am understanding here is, no matter what I use for "rafters", the general concesus is, it will work.

I'd avoid Silly Putty, but other than that, yeah.

Joseph