Truss to stick built transistion...

[Darren Emery]

Wondering if others get any kind of detail from either the truss company, or a dp, on the transistion from truss roof to stickbuilt? It fairly common around here, on the more complicated roof system, for the truss company to not build a complete roof package; some small areas have to be stick built for infill.

I don't worry about this much when its a small area, and a short span, but occasionally, we'll get an entire roof slope stick built, and scabbed onto the trusses. I've never seen details from the truss company as to how these areas should be tied together, or how if the loads that land on the other trusses have been considered in the calculations.

 

[pwood]

most truss companies (alpine for one) have engineered drawings that detail all these situations. sometimes i require the dp to include these drawings or their own as part of the submittal package.

 

[Mark K]

The truss loads should reflect these additional loads. Typically this will mean a special truss design for the transition truss while other times they may decide to tie together several of the regular truss.

Similar issues can occur if stick built framming is placed over the sheathing on the truss.

If there is a design professional on the project he needs to coordinate the interface between the two systems. If there is no design professional the truss manufacturer needs to make sure the loads are properly accounted for.

It is likely that the truss manufacturer will not have anything to do with how the other members are attached to the trusses. If there is no design professional involved you take your chances.

 

[Uncle Bob]

Darren,

I've never seen or had to deal with this senario;

"occasionally, we'll get an entire roof slope stick built, and scabbed onto the trusses. I've never seen details from the truss company as to how these areas should be tied together, or how if the loads that land on the other trusses have been considered in the calculations."

It brings several questions to mind;

1. How is any load from the stick built, going to effect the truss system?

2. I can see where the additional load might negate the Truss Manufacturer's responsibility for the truss system. Have you ever requested information from the Truss Manufacturer about the effect of additional (stick built) loads on the truss system?

3. Wouldn't any additional stick built loads on the truss system have to be approved by the Truss Manufacturer; to protect the integrity of the structure?

I would think that plans sent to the Truss Manufacturer would include details of this additional stick built section; and the Truss Manufacturer would include the requirements for carrying the additional load.

Uncle Bob

 

[Mule]

When we have this type of scenario the truss plans indictate how the framing is to be constructed.

 

[peach]

Are you talking about like hip or valley framing (which are always field installed)?

 

[Mark K]

This is one of those situations where the use of the IRC is probably not appropriate. The IRC makes a number of assumptions about the building. When the building is not compable with those assumptions then you need somebody to look at it as a system. The truss manufacturer is not set up to play that role and does not want to take responsibility for the complete building.

 

[RickAstoria]

This seems like a possible TPI1-2007 (or whatever is the current edition) situation. I'm going on a limb that the trusses of light metal plate connected trusses.

The responsibility of the truss to building interface is that of the RDP/Building Designer. It is your (RDP/BD) responsibility to determine the means and methods of interfacing the truss with the building the building system. This is why there is coordination and providing of information and working with the truss designer/truss engineer (TD/TE). Unless, the RDP/BD is also the truss designer / truss engineer. Note, there is distinction of terms used. Truss Designer / Truss Engineer (one is non-licensed and the other is a licensed engineer). Also there is a VERY particular separation of terms between TD/TE from the Truss Manufacturer . The TD/TE & TM maybe one in the same OR separate entities altogether. There is a noted distinction of terms used.

When one is serving multiple hats then they assume responsibility for each defined role in the standard.

 

[Rio]

If the transition's loading the truss it should be taken into account by the truss engineer. If it's just transitioning from trusses to conventional and there are no substantial load issues then it's not an issue.

 

[88twin]

regardless if it's an infill or overbuild situation the details should ALWAYS be in the truss calcs, WITH connection details.

the only time i don't concern myself is when it's a shed roof patio cover with rafters attached to trusses at ext. load bearing walls.

and even then im looking for total loads and transfer to footing.

one mistake i've found quite often is that framers will delete the "sleeper" under rafter heel in an overbuild situation

(false dormer "dog house").

 

[SCBO1]

While designing trusses there are areas that are too small to design a truss, like some valley area's, often it will be noted on a truss layout to stick frame. In some cases the truss designer has bearing issues that prevent a truss from being used in a certain area of the roof design.

Pc1

 

[MarkRandall]

As the design professional, I make sure the set of construction documents shows loads from stick framing being applied to a truss. The truss shop drawings are then reviewed to make sure the load was calculated in the design. It's not real common, but not uncommon either to have a mixed framed system. I can't remember offhand seeing details of the connections on the truss shop drawings.

 

[Mark K]

If the stick built framing is relatively small I would require that the loads be reflected in the truss designs and move on.

If the stick built framing was significant I would request that the problem be resolved by a registered design professional. This typically would mean an engineer because many architects do not have an adequate grasp of the issues. If the project was permitted using the IRC I would argue that this is one of those areas that the IRC does not adequately address.

Do not expect that the truss manufacturer will step in to sort out the problem. The truss manufacturers are scared that if they go beyond their trusses that they will be considered the engineer of record for the whole building. Thus you will not see truss designs that show the joist hangers and other details of attaching other framing to the trusses.

The truss designer as opposed to a licensed truss engineer is typically a technician lacking the sophistication to sort out the problem. They typically just know how to run a computer program. I contend that when the manufacture has the truss designs performed by a truss designer and there is no licensed engineer to review and stamp the design that there is a violation of state licensing laws.

 

[akabob]

Here's what we do. Actually, I've never seen details for a stick framed infill, or "California fill" area as we used to call it come from a truss manufacturer. Sometimes these fill areas are done with trusses and then details/calcs would be provided.

In most cases the additional load added by the infill framing (a little more on the dead load) would be so minimal as to not be a concern. We just make sure that it's framed and attached appropriately.

In some cases an additional or uneven lateral load from wind might be an issue and in those cases, the truss manufacturer's engineer would have to address it. Otherwise, questionable/additional loads would have to be addressed by the project engineer or architect of record.

 

[RickAstoria]

If the transition's loading the truss it should be taken into account by the truss engineer. If it's just transitioning from trusses to conventional and there are no substantial load issues then it's not an issue.

Yes, but the RDP/BD shall have informed the TD/TE this to be taken into account. This is coordination. Otherwise, the RDP/BD shall apply a means of transition that does not attribute load to the truss that would exceed the factor of safety parameter.

 

[RickAstoria]

While designing trusses there are areas that are too small to design a truss, like some valley area's, often it will be noted on a truss layout to stick frame. In some cases the truss designer has bearing issues that prevent a truss from being used in a certain area of the roof design. Pc1

A simple truss is a triangular frame. A simple 3 piece triangle is a truss. Even a conventional roof with collar tie or ceiling joist of upper-most floor ties in at the same area (on top of the wall top plate) as the rafters technically forms a simple truss. This would be a rudimentary truss. As for valley areas..... that can be a bit of a fun topic. Some basic engineering calc or space frame designing technique is in order perhaps.

There is a lot of choices to make in this but the ultimate responsibility is the RDP/BD for the coordination of the overall design.

 

[RickAstoria]

If the stick built framing is relatively small I would require that the loads be reflected in the truss designs and move on.If the stick built framing was significant I would request that the problem be resolved by a registered design professional. This typically would mean an engineer because many architects do not have an adequate grasp of the issues. If the project was permitted using the IRC I would argue that this is one of those areas that the IRC does not adequately address.

Do not expect that the truss manufacturer will step in to sort out the problem. The truss manufacturers are scared that if they go beyond their trusses that they will be considered the engineer of record for the whole building. Thus you will not see truss designs that show the joist hangers and other details of attaching other framing to the trusses.

The truss designer as opposed to a licensed truss engineer is typically a technician lacking the sophistication to sort out the problem. They typically just know how to run a computer program. I contend that when the manufacture has the truss designs performed by a truss designer and there is no licensed engineer to review and stamp the design that there is a violation of state licensing laws.

True but some states allow exemptions that will exempt truss "engineering" if the designing of a truss is for an exempt building. So, if the person has adequate ability to design the truss then so be it. In my work, I hire a TE or I am the TD as well as the BD. This is because of the exemption laws. If I hire someone else, they'll be licensed. If I am not going to hire someone else then I assume the role as a peripheral extension (an appurtenance) to the designing and specification of the an exempt building within the laws of Oregon. Other states, well, it would be decided in light of the laws of those states. If the person designing the truss is not licensed then they can't use the term "engineer". Of course, the designer of the trusses shall comply with state laws and licensing requirements (unless otherwise exempted) if they design trusses for use in those states. In Oregon, a TD may design trusses for use in SFRs and exempt buildings but may not do so for a non-exempt building. Because the buck stops at me because I am the overall designer of building and have ultimately the responsibility to the overall design of the building, I choose to either have a TE (licensed engineer in the jurisdiction where the project is located) or I do the design of the truss elements (at obviously higher liability risk) where exempted. Of course, these trusses would be designed specifically for the building I design.

 

[JayHawkInspector]

Hey Darren I see you from Manhattan, Ks and in Kansas any contractor can sit at home on his home computer and draw a set of house plans and get it approved, it’s the state law (K.S.A. 74-7031) my best advice to you is get yourself a WFCM (Wood Frame Construction Manual) which would give you the prescriptive method for framing such situations. The IRC refers to the WFCM for instances like you have also the BCSI (Building Component Safety Information) will help you out for trusses and how they are connected to framing and braced. Here in Kansas there are no such things as RDP/Building Designer for residential construction.