cone shaped roof on hexagon frame
Hey guys I was hoping someone with some experience on cone roofs might be able to help me. I found some interesting info on here about cutting the plywood but still have a few questions.
*how would you go about attaching the rafter to the top plate? It’s circular meets hexagon.
*which plywood flexes with the most curve? I want to use 2 layers of 3/8 cdx… but is 1/4 inch just as good?
*What to do about collar ties and preventing spreading?
The project is supposed to look like a mushroom. The hexagon diameter is 9′ long point to long point. The roof is 2×6, 10 pitch, 12’diameter at bottom of rafters, 24 rafters
Replies
'Shroom Roof
user-537945 wrote:*how would you go about attaching the rafter to the top plate? It's circular meets hexagon.
Right... tricky framing challenge. I did a plan layout in Adobe's Illustrator to get a grip on the dimensions you're faced with. Attached is a scaled PDF; the outer circle is your 12' dia rafter tail circle.
No idea what this scales to; that circle ends up 7.2" dia. on my letter-size page.
*which plywood flexes with the most curve? I want to use 2 layers of 3/8 cdx... but is 1/4 inch just as good?
What purpose does this structure have in store? Will people be inside / do you need to meet code restrictions?
My thinking would be use 3 layers of 1/4" if decent ply stock is available where you are. 3/8" might give you fits trying to get two layers to follow your curve near the top, particularly when you're trying to get joints to lay flat along seams. Even with 1/4" it'll be a challenge, depending on how fussy your client might be on how the final roof finish looks up close over time. This gonna be tab-shingled?
*What to do about collar ties and preventing spreading?
Again code may be where you need to reference your eventual solution for your location roof load specs.
9' plate span isn't all that much so you may be able to get away with three collars secured to the mid-points of each plate chord. If you need more you could add ties low down between opposing pairs of rafters positioned so they don't interfere with each other vertically.
The project is supposed to look like a mushroom. The hexagon diameter is 9' long point to long point. The roof is 2x6, 10 pitch, 12'diameter at bottom of rafters, 24 rafters
PDF elements are colored according to your closing descriptiopn above, centerline for rafters. I may try to do a section drawing if I have time today, just for grins. Not something I do for a living but something to practice my drawing skills with when it's too cold to work outside where I am....
'Shroom Roof
Edited to add PDF attachment.