A question on types of timber roofs

[Emerger]

Hi Everyone. I have seen three basic types of timber frame roof and would like to know if there is any particular name for each of them. I'm going to try to upload some pictures from a timber frame site. Bear with me.

One type has bents or trusses with purlins inside of them, flush with the top. Another has bents or trusses with purlins running the full length but set on top. The third one is simply common trusses supported by a ridge beam.

Do these have names or style names?



 

 

 

[kantuckid]

I've done the lower picture but used 2x6 T&G decking on more trusses, or 4x6 or 3x6 rafters, no purlins. 

Cold climate factor can say you need more roof insulation and drive the choices too as does type of ceiling desired inside, appearance wise. 

[Brad_bb]

Some of the timberframe books might give name, but I'd call the first and third purlin systems and the second common rafters.  The first type can also have common rafters on top of the purlin system.  In that case you don't need as tall a rafters.  on one side of my shop I have purlin system with 4x6 rafters laid on flat (4 inch side if vertical).

One tip, in the second picture you have common rafters with tails overhanging.  If you want the look of tails overhanging, attach the tails separately.  It's really difficult to seal rafters tails sticking through the wall especially as they initially shrink and seasonal expansion and contraction.  It's better to not break the envelope of the building so you can seal the building and add the tails after for looks.

[Don P]

First one I'd call principle rafter common purlin with dropped in purlins on a queenpost-ish bent. With the rafter feet unrestrained the queenposts are taking vertical load in compression and delivering that to the ties rather than being tension elements here.

Second is common rafters on a ridgebeam. The ridge support post is putting a healthy point load midspan on the tie.

Third I'd call principle rafter continuous purlin with kingpost-ish bents. The purlins on top do less damage to the principle rafters. The tie is not really well positioned to restrain the rafter thrust

It's not that big of a deal to run grooves for drop in blocking for those tails. It would be a good idea to run the design through an engineer versed in TF.