Roof Overframing Section

[kmart30]

Attached is a basic section of what is going on. They are adding a small addition and they want the new roof lines to match up with existing hence the reason for the giant sail of a rafter getting over framed. Its close to an 8/12 pitch going over existing trusses(truss is just for illustration and not the actual configuration of the truss). Also, they want to remove the old existing exterior bearing wall shown as the gray dashed line. I just wanted to throw this out there and get a different pair of eyes on this and maybe some feedback; any major concerns we should be looking for here?

 

[ajh1]

Is there going to be a support beam to replace the existing wall that is to be removed? If not, then the entire assembly (old truss plus new beam) needs to be built out into a complete truss or some other means of support between the outer supports. Just scabbing on the new beam above the existing truss will not make it stable.

 

[kmart30]

Yes of course. A new beam will replace the existing wall and the trusses will be fastened to the beam with hangers as required. Should we orient the mid-span strut for the new rafter support normal to the rafters as shown or more like the pony wall above? There will more than likely be a splice at this point because of the +30'length of this rafter and I am just thinking it will end up more like the pony wall above when they build it.

 

[dik]

Can you use a parallel chord truss and clear span it? Trusses are highly competitive and there is likely little 'wiggle' room. Members may have some, but, truss plates are pretty near 'exact'.

Dik

 

[kmart30]

I thought about that but the contractor wants to stay away from trusses on this one which is understandable with this situation. I guess its easier for his framers to conventionally frame it and make the small adjustments in the field. All the truss yards are backed up right now and prices are going through the roof. I was also thinking about placing a tie from the bottom of the pony wall to the rafter to help with the uplift and reduce the load on this strut, we are in 130mph with exposure D....

 

[dik]

In these environs, you can get trusses for likely less than you can buy 'sticks'.

Dik

 

[dianium500]

@dik
I think it depends on where you live. If this is Florida, I would agree, that trusses are cheaper. Up north, I have heard otherwise. Also, trusses have gone up in price by like 30% in the last few months. For something like this I would frame.

@kmart30
How are you planning on getting the shear to transfer to the new wall? That would be my biggest concern in a 130 mph exp cat D wind zone. You'll need some cross bracing and other lateral support to do so.

 

[kmart30]

Yes that was one of the main topics that was brought up with getting the shear into the new wall. We were thinking some cross bracing at the purlin/stut location and over the beam to transfer shear into the upper diaphragm connected to the new wall. Any better suggestions?