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UBC code in IBC?

mtlogcabin

mtlogcabin

SAWHORSE
Joined
Oct 17, 2009
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Location
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1997 UBC 2320.12.8 Blocking

Roof trusses shall be supported laterally at points of bearing by solid blocking to prevent rotation and lateral displacement.

One of those things we have been enforcing for decades. I am now being challenged on the requirement and can not find similar language in the 2012 IBC.

Am I missing it or perhaps it is in some referenced standard somewhere. FYI: We are in a seismic zone "D"
 
It's in IRC

R802.8 Lateral support. Roof framing members and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation. For roof rafters with ceiling joists attached per Table R602.3(1), the depth-thickness ratio for the total assembly shall be determined using the combined thickness of the rafter plus the attached ceiling joist.

Exception: Roof trusses shall be braced in accordance with Section R802.10.3.

So should be in Ibc
 
2009 IBC 2308.10.6 requires blocking of rafters and ceiling joists, 2308.10 wood trusses takes you back to 2303.4 which puts the design professional into the truss design drawings and then 2304.1.2 deals with the restraint.

This is the stuff that a smart (or maybe unsmart) builder would challenge someone on just so they could watch our head explode
 
cda said:
No the 2308 edition of the Intergalactic Building Code
Click to expand...
That's funny

I'm still waiting on the International Doghouse Code. I'm sure it will be required for MCP down the road.

BSSTG
 
# >

**BSSTG**,

Soooooo, ...is obtaining the MCP worth it now for you ? :o

Just curious sir !..........Thanks !

< #
 
IRC 802.8 is for framed roofs

IRC 802.10.3 states trusses shall be braced to prevent rotation. However it does not state how or mention solid blocking at the raised heels

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 accepted industry practice such as the SBCA Building Component Safety Information (BCSI) Guide to Good Practice for Handling, Installing & Bracing of Metal Plate Connected Wood Trusses.

I do not have a copy of the BCSI Guide so I do not know if it is in there.

I am being challenged on an IBC 2012 building so the IRC is not going to help

I have been looking in IBC 2308 thinking it should be there but have not found anything yet.
 
2012IBC

Rafters: 2308.10.6 Blocking? and 2308.8.5

Trusses: 2303.4.4 Anchorage is the responsibility of the design professional
 
A co-worker just reminded me IBC 2308 is not applicable because our ground snow exceeds 50 psf

2308.2 Limitations.

Buildings are permitted to be constructed in accordance with the provisions of conventional light-frame construction, subject to the following limitations, and to further limitations of Sections 2308.11 and 2308.12.

1. Buildings shall be limited to a maximum of three stories above grade plane. For the purposes of this section, for buildings assigned to Seismic Design Category D or E, cripple stud walls shall be considered to be a story.

Exception: Solid blocked cripple walls not exceeding 14 inches (356 mm) in height need not be considered a story.

2. Maximum floor-to-floor height shall not exceed 11 feet, 7 inches (3531 mm). Bearing wall height shall not exceed a stud height of 10 feet (3048 mm).

3. Loads as determined in Chapter 16 shall not exceed the following:

3.1. Average dead loads shall not exceed 15 psf (718 N/m2) for combined roof and ceiling, exterior walls, floors and partitions.

Exceptions:

1. Subject to the limitations of Sections 2308.11.2 and 2308.12.2, stone or masonry veneer up to the lesser of 5 inches (127 mm) thick or 50 psf (2395 N/m2) and installed in accordance with Chapter 14 is permitted to a height of 30 feet (9144 mm) above a noncombustible foundation, with an additional 8 feet (2438 mm) permitted for gable ends.

2. Concrete or masonry fireplaces, heaters and chimneys shall be permitted in accordance with the provisions of this code.

3.2. Live loads shall not exceed 40 psf (1916 N/m2) for floors.

3.3. Ground snow loads shall not exceed 50 psf (2395 N/m2).

4. Vasd as determined in accordance with Section 1609.3.1 shall not exceed 100 miles per hour (mph) (44 m/s) (3-second gust).

Exception: Vasd as determined in accordance with Section 1609.3.1 shall not exceed 110 mph (48.4 m/s) (3-second gust) for buildings in Exposure Category B that are not located in a hurricane-prone region.

5. Roof trusses and rafters shall not span more than 40 feet (12 192 mm) between points of vertical support.

6. The use of the provisions for conventional light-frame construction in this section shall not be permitted for Risk Category IV buildings assigned to Seismic Design Category B, C, D, E or F.

7. Conventional light-frame construction is limited in irregular structures assigned to Seismic Design Category D or E, as specified in Section 2308.12.6.
 
if you are under IBC do you have a structural design professional that should have been responsible for the truss design or at least a review? Also how tall are the energy heels? I too have been surprised by review of truss drawings how little permanent bracing there is. I have a copy of the SBCA Document and there really is no help for you there. It is a free download try:

support.sbcindustry.com/docs/06_BCSI_booklet_FINAL.pdf
 
Energy heels are 16 inches. I have thrown it back to the contractor to have the truss manufacturer make the call if blocking at the raised heels are needed or not.

This is just one of those old code requirements we all knew all buildings had to do in our seismic zone.

One more plan review comment we will have to add on the review
 
I did find something under 2308 Braced Wall Panels but I can't use that section because of my ground snow

2308.3.2.2 Top plate connection.

Where joists and/or rafters are used, braced wall line top plates shall be fastened over the full length of the braced wall line to joists, rafters, rimboards or blocking above in accordance with Table 2304.9.1, Items 11, 12, 15 or 19, as applicable, based on the orientation of the joists or rafters to the braced wall line. Blocking at joists with walls above shall be equal to the depth of the joist at the braced wall line. Blocking at rafters need not be full depth but shall extend to within 2 inches (51 mm) from the roof sheathing above. Blocking shall be a minimum of 2 inches (51 mm) nominal thickness and shall be fastened to the braced wall line top plate as specified in Table 2304.9.1, Item 11. Notching or drilling of holes in blocking in accordance with the requirements of Section 2308.8.2 or Section 2308.10.4.2 shall be permitted.

At exterior gable end walls braced wall panel sheathing in the top story shall be extended and fastened to roof framing where the spacing between parallel exterior braced wall lines is greater than 50 feet (15 240 mm).

Where roof trusses are used and are installed perpendicular to an exterior braced wall line, lateral forces shall be transferred from the roof diaphragm to the braced wall over the full length of the braced wall line by blocking of the ends of the trusses or by other approved methods providing equivalent lateral force transfer. Blocking shall be minimum 2 inches (51 mm) nominal thickness and shall extend to within 2 inches (51 mm) from the roof sheathing above and shall be fastened to the braced wall line top plate as specified in Table 2304.9.1, Item 11. Notching or drilling of holes in blocking in accordance with the requirements of Section 2308.8.2 or Section 2308.10.4.2 shall be permitted.
 
Could this be an example for why in some states we require Structural engineers vs C.E.'s to design and stamp the drawings?

Remember, code is only a minimum. As AHJ's we have the right and authority (subject to your individual political environments) to require more than the minimum (please do so where deemed appropriate).

Very good discussion, thank you all.
 
ADAguy said:
Remember, code is only a minimum. As AHJ's we have the right and authority (subject to your individual political environments) to require more than the minimum (please do so where deemed appropriate).
Click to expand...
What? Spoken like a true Nazi.
 
Down here on the Tx coast we require all truss plans and install directions be done by PE too. In Tx. coastal counties we deal with the high wind aspect of it and it's driven by Tx Dept. of Insurance. Makes life easier on the inspector for sure.

Earilier today I went back and read up on the IRC and IBC on the subject. I had thought that the PE was required in all cases to stamp the truss designs. I see now I was mistaken. Even on the earlier editions of the codes they have that caveat "where required by the statutes of the jurisdiction" or some such similar verbage.

I even had it added into our ordinances that last 2 places I worked to require windstorm engineering on all plans for all types of construction excluding dog houses. That ordinance change has removed a lot of discussion on the subject. Don't have to dig up code references that way.

BSSTG
 
We always require engineered trusses. The blocking of the raised heels has never been a requirement on their drawings probably because they assumed it was still in the codes like I did and we where requiring it. We only have 4 truss manufactures that supply our area so I will be able to get a handle on it. I just need to know where to send them for the requirement(s) if there are any.
 
mtlogcabin,

Is this a cantilever design where the top cord is higher? If so it should fall on the engineer to catch/design the connection. You might see a framed 2x box used to prevent the roll??
 
this is a subject I think needs a code change. For us who live in cold climates where more insulation is desired and don't want it pinched out at the exterior wall the trusses are designed with an energy heel. Basically a wall like extension constructed in the truss. These heels will likely get taller with greater insulation thickness specifications. So you have several choices, block between the bearing points of the truss or extend exterior shear sheathing up along this. I too am in an area that both wind and snow take me out of the "Conventional light frame" guides in chapter 23. I believe that the truss suppliers should resolve this by details. If one looks at the BSCI booklet there is a good graphic of the transfer of loads from roof deck down into the walls.

There is a real run around here. With wood you get 3 choices of design and for me the conventional one falls away leaving the other 2 that are guides to structural engineers designing with wood. They are not easily read. And finally they don't adequately address the bracing (they throw it back to the trusses and anyone involved in specifying or designing them). The BSCI does discuss installation bracing and permanent bracing but no examples cover the raised heel load transfer or if it acts as a point of failure if not fully braced.

Under the residential code there is a height when more than just exterior sheathing will do and there needs to be blocking and bracing between trusses figures R602.10.
 
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