This is not a competition. It’s only an exhibition.
Anyone see anything wrong?
maybe, I have seen engineered house plans that did not show any of what you are looking for in certain areas but did in other areas of the same house.
No bracing, but bracing is different with every set of trusses and this engineer may not have required them.
IRC R802.10.3 Bracing. “Trusses shall be braced to prevent rotation and provide lateral stability in accordance with the requirements specified in the construction documents for the building and on the individual truss design drawings. In the absence of specific bracing requirements,** trusses shall be braced** in accordance with TPI/HIB.”
I say it’s required by “today’s commonly accepted construction standards” unless an engineer says it isn’t necessary.
Thanks for the explanation Joe, cause I did not see anything wrong with those pictures.
Can you define TPI/MPC?
Design requirements and engineering of lateral requirements is usually left up to the engineer of record. We can not call out a deficiency based on what said in the IRC. It can not be applied to all situations we may encounter.
Consideration of permanent and temporary bracing of (MPC) wood trusses is critical for safety during erection and for reliable performance of a roof structure in service.
Temporary bracing is used to position and stabilize trusses until permanent bracing or other building components can be installed.
Permanent bracing is required to stabilize specific members of each truss throughout the life of the roof structure, when so required by design.
Based on truss design assumptions, various chords and webs require lateral support. The chords that require sheathing or the members that require lateral support at a specified interval are indicated on the truss design drawing.
Unfortunately, these design drawings are seldom available to the Inspector at the time of the Home Inspections.
Bracing, whether it is temporary or permanent, is required to help prevent the trusses from deflecting laterally and potentially causing the trusses to topple over or collapse.
The standard of practice is to leave the temporary lateral bracing that is used during the erection. Must of the time that is adequate unless the truss drawings have the lateral bracing tags afixed to the truss chords that indicate permanent bracing locations. When none of those tags are visible, during an inspection, chances are none were required.
Permanent truss bracing can include several different components, but are typically designed using one of the following options:
(CLBs) at required brace locations in conjunction with diagonals;
or properly nailed sheathing, either oriented strand board (OSB) or plywood. If carefully designed, some elements of temporary bracing can serve dual roles and become permanent bracing also.
It is also a known standard of practice for truss erection on some limited sized homes, that no lateral bracing is required for lateral stability. Once the sheathing is installed, at times, a complete diaphragm and is enough to provide the lateral stability of the design.
For all our readers, here are some links that might come in useful.
http://www.mcvicker.com/twd/gwdi05/page011.htm
Also, once the roof sheathing is nailed off, there’s no way those trusses are going to rotate without help from a hurricane or tornado, especially if ridge blocks are installed and nailed to. The bottom chords are tied off at the walls… how would the trusses fail due to lack of bracing?
Even in this area, the design rating on houses varies from 80 to 90 mph.
With roof truss lateral bracing you have to report it as either something to investigate or an upgrade, you can’t say its flat out wrong unless you have the plans that show it.
Kenton, do the nails through the sheathing always hit the truss? What happens if a piece or two of the sheathing is blown away in a storm?
I plan to keep to my practice of recommending lateral bracing unless an engineer states it isn’t necessary. Most new construction has horizontal or diagonal bracing. I conclude it’s a construction defect, that the ones that that don’t.
Today’s inspection made me happy.
Joe
Making any kind of statement on truss bracing is outside the SOP and would put you in a position to either prove it, if your an engineer, or be prepared to pay for the engineer the owner hired if it was designed correctly. You can get by on stick built roofs making comments on over spanning of rafters and joists if you use the code tables correctly, but bracing is a totally different matter.
The individual trusses in the picture would not require permanent bracing on the longest diagonal web member because they are in tension. However you have to also look at the entire roof/truss system as a whole when considering wind or seismic loading. Outside of reporting a broken or cut truss member or a damaged or missing connection plate I would state the stability and load capacity of the engineered trusses are outside the scope of the inspection. Even as an engineer after I checked the design I would have to disclaim any damage caused by forces that are outside the acceptable standards for your location.
How is commenting about a home’s perceived framing deficiency outside the SOP?
SC’s SOP:
- VISIBLE FRAMING:
A) Report if not visible.
B) Inspect and report the observed condition of the visible materials and structural components.
C) Describe and report defects and/or deficiencies.
Please explain the meaning of this building requirement. Does it say anywhere trusses do not need to be braced?
"IRC R802.10.3 Bracing. “Trusses shall be braced to prevent rotation and provide lateral stability in accordance with the requirements specified in the construction documents for the building and on the individual truss design drawings. In the absence of specific bracing requirements,** trusses shall be braced** in accordance with TPI/HIB.”
"Section 2.2.2 (d) and (e) of ANSI/TPI 1-1995 specifically addresses permanent truss bracing:
2.2.2 As this Standard does not cover the design for the complete
structural system of a building, the Building Designer shall provide for the
following in the design and detailing of the building:
(a) Truss deflections
(b) Truss movement due to moisture and temperature change
© Truss supports and anchorage accommodating horizontal, vertical or
other reactions or displacements
(d) Permanent truss bracing to resist wind, seismic and any other lateral forces acting perpendicular to the plane of the truss
(e) **Permanent lateral bracing as specified by the Truss Designer, to
prevent buckling of the individual truss members due to design loads."
**Source: http://www.woodscience.vt.edu/researchpapers/bracing.pdf
Randy, please explain page 41 to me. That part that says: "Always Diagonally Brace the Permanent Continuous Lateral Restraint"
Joe
Your quoting IRC code and TPI construction requirements. Are you doing code inspections or home inspections? I don’t know of any home inspection SOP that indicates a home inspector is to act as a code inspector. Just so we are on the same page my previous comments were limited to truss bracing. The fact you don’t see any does not mean they are required. I can say with confidence the truss manufacturer followed the design & bracing requirements and I am sure they were sent with the trusses. The only people that need them were the contractor and the local building code official. The TPI guide tells the designer they should check for the listed forces and design accordingly if the roof configuration does not warrant a permanent brace you don’t have to use one. As a home inspector you are not required to verify the need for bracing for engineered trusses. Making a statement that would indicate a defect in the truss system when you do not know for a fact if it complies with the original design will make you liable for any cost incurred if you are proven wrong. You are not reporting a visual defect you are making a design assumption. Hey I am not trying to pick a fight I am just trying to reduce your liability.
Randy, I’m not an engineer. And I appreciate your input.
Here’s what I struggle with: 95% of the time the bracing is present, the IRC seems to say bracing is required, my research these past few hours seems to say bracing is required. But you say it isn’t? That’s what I don’t understand.
Code is the basis for a lot of the calls we make. It’s a resource to back up logic. I’m not quoting code in my inspections. But when I have a question about something, I certainly use it to see what industry experts across the country have implemented as standard practice. All home inspectors do it; from citing cutting and notching of joists, to calling out a defect in water heater TPR piping. This issue is no different.
How can you be so sure if you haven’t seen the drawings yourself, and don’t know the wind speeds and seismic conditions for my area?
Do you think any other engineer might disagree with your conclusion?
(Just trying to learn, that’s all.)
Joe
Maybe this will help. The following IRC code basically says any engineered design element supersedes the general code requirements.
Engineered trusses fall under this exception. The only thing that supersedes the engineer’s design is the Offical Building Code inspector. They are given the final authority by law, if the city adopts the IRC, to accept or reject the engineer’s design. So if something has been designed and sealed by an engineer you have to use caution when quoting from the IRC.
R30l.l.3 Engineered design. When a building of otherwise
conventional construction contains structural elements
exceeding the limits of Section R301 or otherwise not conforming
to this code, these elements shall be designed in accordance
with accepted engineering practice. The extent of such
design need only demonstrate compliance of nonconventional
elements with other applicable provisions and shall be compatible
with the performance of the conventional framed system.
Engineered design in accordance with the International Building
Code is permitted for all buildings and structures, and parts
thereof, included in the scope of this code.
Joe
I missed your second set of questions. The reason I am confident the truss company followed the design guidelines is the engineering liability factor. Engineers are held to a higher standard of liability in the courts and while home inspectors think about liability engineering firms are consumed with it, goes with the territory. So to cover their butt I would almost bet the truss company made someone sign off when they received the truss drawings. Every engineered truss system is unique, even if the truss is the same dimension as the last house you looked at the loads are different. Different seismic requirements, different wind speeds, different building orientation or height and so on. So the IRC recognizes these differences by allowing specific engineering designs in lieu of what the IRC says if the designer can prove they meet or exceed the minimum requirements. So when you look at an engineered truss system or an engineered retaining wall don’t assume there is a problem if they don’t exactly conform to the IRC code.
Joe,
I would be very careful about calling out truss bracing unless you have a copy of the actual construction documents. The truss design dictates the need for bracing and factors in size of the truss plate and the grade of lumber used
Permanent Bracing For The Web Member Plane:
Permanent Bracing is typically installed in the Web Member Plane of a truss to collect and transfer forces caused by the restraint of members subject to buckling and/or transfer lateral loads from wind and seismic forces applied to the truss system. The same bracing can often be used to support both functions. The bracing is referred to as Permanent Stability Bracing and is the responsibility of the Building Designer
If bracing is missing on trusses, it’s not my call.
Did this truss system have tags (labeling) on them?