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Size of ridge beam, columns, and rafters? (remote location)

remotebuilder777's picture

Am building a roof on a two-story home in a remote mountain area Central America. There are no local lumber yards with information or tables, and we have no access to structural engineers, thus my hope for advice here on the forum. (rough sketch attached). 

The home is square: 32.5 feet x 32.5 feet, and two-story. First floor is concrete block construction, 2nd floor is wood with 3"x6" joists supporting the floor and walls and roof.

Roof would be a simple gable design with let's say a 4:12 pitch but I am open to other pitch depending on what works best.

My (4) second floor exterior walls will be standard framing with 2"x4"s, 8' high and 16" OC. At this point on the 2nd floor, there will only be the four exterior walls, and one wall running down the center (down the ridge line of the roof).

I know I could go with trusses, and may do so, but would prefer rafters in order to have an open ceiling: 

Basically looking for advice on:

1. How many columns to adequately support ridge beam(s)? What size of columns to support the ridge beam(s)? 

2. What approx size ridge beam(s)? Or better with two smaller ridge beams bolted together? What sizes? Please note we have no LVL or special lumber here - ridge beams have to be standard lumber. Can ridge beam be in sections? Or does it have to span all the way across? I ask because we have no lumber available that long here. 

3. Should the rafter sit on top of the beam, or attach to the sides like a ridge board? Lower pitch roof better to sit on top?

Note:* The only roof loads would be 1/4" or 1/2" plywood base, then aluminum laminate sheets (4"x8" sheets). There is no other load except rain as it does not snow here. We do have high winds at times though and so I would install strong ties all around.

Note" * We do not have LVL ridge beams or anything like that here in Honduras. We have standard 6x6, 4x6, 3x6, 2x8, or 2x10 lumber. Things here are very basic and so we have to work with what we have available.

Personally, I was thinking (six) 6" x 6" columns spaced apart down the center (about 6' 1/2" feet apart, then ridge beam of (2) 3" x 6" lumber bolted together, then the rafters sitting on top of that, obviously with birds mouth above and at exterior walls.

Rafters would be around 19' long and thus another reason I am seeking advice here as I do not want to have an issue with sagging rafters or push out on the two exterior walls.

Please see attached (Very rough) sketch for kind of an idea. It's really just a square with support down the middle and rafters sitting on opposite sides of the structure. 

Thanks very much for any advice.

Joe

Joe, (post #216590, reply #1 of 2)

With support under your ridge all you need is a single 2x10. Break your splice on the rafters, I would use some collar ties on the rafters also. For metal you need to use either 5/8 ply or 1/2" with 1x4 stripping . The screws wiil back out if there is not enough meat to screw into.

Pretty site!

You will get more answers at Breaktime3.

KK

Size of ridge beam, columns, and rafters? (remote location) (post #216590, reply #2 of 2)

Hi KK, thanks for the info. Just one thing you shared I don't quite understand. What metal are you referring to? Metal gusset plate?

Thanks for the link to the other site; I will check it out.