Steel rafters will typically be manufactured / welded using the specifications in your house plans. The size and pitch of your roof will be needed to determine the design and the materials required. Most people use trusses instead of rafters but rafters are a cheaper option for smaller, simple home designs and gives the option of using a vaulted ceiling. I assume that you will need to present your plans to your municipaility to obtain a building permit so the rafter specs would normally be part of that package?

I plan to use rafters in my next construction and will probably be using 38mm or 50mm x 3.5mm angle bars with 10mm or 12mm rebar (deformed bar) for crossmembers. Again, the actual material size and dimensions will have to be calculated based on unsupported span lengths.

 

steveB....
sorry, i should of been more clear. the stuff i'm looking for is a lightly plated channel and comes in 2x4, 2x6, 2x8'' etc. dimensions, might be an 1/8'' thick. it's common in panamá and i think i've seen it used here but i must be shopping in the wrong places. i'm not building a house but i'd like to use it on a water tower project i'm helping out on.

thanks...
norm : ))~

 

I think they may call it a "furring" here. Here is a picture of a "j channel furring" that I googled.

 

I don't want to rain on your parade, but just contacted an international welding school here and he said that is not available here.
You can get standard steel c channel in those sizes at Matiao, rejoice and YY

 

They call it purlins here

 

My mistake; I guess the furrings were used in the ceiling. We used 2" x 4" x 1.2mm x 6.0 mtr C-Purlins, welded horizontally across the trusses, to support and screw the steel roofing. I bought mine at Worldwide Steel Group in Cebu for P426.64 along with alll the other steel / iron for my house (saved quite a bit over Dgte prices), but that was 2 years ago.

 

There are 2 different kinds of purlins with a substantial difference in price.
One kind is black (rusted) and the other one is galvanised, more expensive and less maintenance but very bad for the one who weld it (poisonous fumes)

 

Perlins are available at Matiao and Rejoince (and other hardware stores) in various sizes and styles, from "hat type" to C perlins, L perlins, and some I can't pronounce. Most are galvanized.

Trusses here are generally made of angle bar. The truss is the framework, and the perlins mount atop the truss for attaching the roofing material.

Larry