Gambrel Roof Question - 36 foot span

[schmism]

a design we did from time to time at the last place i worked (engineering truss designs)

went something like the attached.

there are some postitives and negitives
+
1) you can build it out of cheep 2x4 only trusses
2) easy to transport to site because its in pieces
-
1) requires feild assembly
2) requires 4 trusses

while it still requires more overall trusses they are easyer to handle individually and cheeper to make than one HUGE 36' truss

but you still have to supply LVL or some other material to support the floor.

The attached sketch is built with 4 trusses. 2 blue ones that make up the over all shape, and 2 green ones that overlap the blue ones at the top to provide an attachment as well as provide moment connection.

the 4 trusses are layed out at the site and attached then hoisted into place and set like tradtional trusses.

 

[schmism]

a second style 2 part truss.

commonly called a K web (room) truss. (because of the big K formed at the intersection at the floor and kneewall)

-This allows the room load to be carried by a 2' or deeper section "flat truss" within the overall roof truss design.
-allows the blue truss to be built to full 12' height
- a simple cap truss is used on the top to finish it off.

there are various ways to frame the connection between the cap truss and base truss in the attached config, its best to discuss it with the truss designer for pros and cons of each attachment style

 

[wedge40]

Here is what a place genned up for me last year.
Originally the roof was little shorter, but I had then make it a few feet tall to get the symmetry I was looking for. I'm not sure they get to 36' open span, but if they can I'd be interested.

Wedge

 

[scgargoyle]

Here's what mine (28') will look like. This design requires a loft or other cross pieces to keep the trusses from spreading. They are tied to the loft structure with rafter ties. Top angle is 30 degrees from horizontal; sides are 30 from vertical. All the joints are tied together with 1/2" plywood gussets, nailed and glued. You build them right up on the completed loft deck, so all you have to do is stand them in place.