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California jumps ahead, allows tall wood buildings

CodeWarrior

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In an apparently unprecedented move, California has adopted the tall wood building provisions of the 2021 IBC before the code has been released. Article here:


Seems surreal considering California’s tough WUI requirements restricting use of exterior combustibles and of course, the recent wild fires that were out of control this year. Also, are these buildings more vulnerable to terrorist attacks?
 

cda

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Where are they going to get the wood???

You are not allowed to cut a tree in Ca
 

tmurray

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Canada has 18 storey cross laminated timber in the 2020 code. It has been done in British Columbia for years now. It's important to understand that there are a fair number of tall buildings already in service med of timber. While there is more of a risk to fire during construction, there is no additional risk once the fire separations are in place. This is evident when looking at insured losses of these buildings compared to traditional steel and concrete structures.

For cladding systems, I'm not sure what you are saying. You can still use non-combustible cladding on these structures.
 

mtlogcabin

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Where are they going to get the wood???

You are not allowed to cut a tree in Ca
Last year there where only 6 manufactures in the US (1 in our county) and I think 2 or 3 in Canada. So unless they are going to ship the trees to Oregon I doubt the validity of this statement in the article.

Number 2, it will increase the pace and scale of our wildland fire prevention and forest management goals of treating 500 thousand acres per year by thinning the forest of smaller diameter trees that can be used in the production of cross laminated timber and other mass timber assemblies.

 

rktect 1

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Have you ever seen a picture where there are like 3 or more townhomes and the middle one caught fire leaving the other two standing because they were protected.

Now imagine the middle floor burning out and what the aftermath looks like
 

tmurray

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Have you ever seen a picture where there are like 3 or more townhomes and the middle one caught fire leaving the other two standing because they were protected.

Now imagine the middle floor burning out and what the aftermath looks like
The difference is the CLT product in comparison to light timber. Mass timber products create a char (like an intumescent product) which insulates the wood and increases fire performance. Depending on the size of the member, they can perform better than steel in a fire situation. Light wood framing does not perform the same as it lacks the cross-sectional area to create the char, while also maintaining structural support.
 

cda

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Have you ever seen a picture where there are like 3 or more townhomes and the middle one caught fire leaving the other two standing because they were protected.

Now imagine the middle floor burning out and what the aftermath looks like


You did not add to the cake mix, a fire sprinkler system
 

Robert

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The difference is the CLT product in comparison to light timber. Mass timber products create a char (like an intumescent product) which insulates the wood and increases fire performance. Depending on the size of the member, they can perform better than steel in a fire situation. Light wood framing does not perform the same as it lacks the cross-sectional area to create the char, while also maintaining structural support.
Would these be classified as Heavy Timber in the code? It sounds like it. One upshot is wood produces less carbon than steel plants.
 

Mark K

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I would like to see a link to the specific action the Building Standards Commission took. Which state agency adopted the the code change? In California for most code provisions the Building Standard Commission does not adopt the provision but rather approves the adoption by another agency which may have jurisdiction over fire issues.

Was this a change to the fire requirements but not to the structural provisions. There is a question of what is the R factor to be used for seismic design. It is not all about static strength. This may only apply to residential occupancies since no state agency has the authority to modify the model code with respect to structural provisions for residential, office, and commercial occupancies.

The point is that the devil is in the details especially in California.
 

Yikes

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My company designs a lot of residential buildings that are subject to prevailing wage rates. Once you go over 4 stories, commercial prevailing rates apply. OVer 60', OSHA requires a construction elevator (with a full time prevailing wage elevator operator). Over 75' we're in the highrise provisions.
Most of the developers in this market find that the financial sweet spot is to design to 4 stories of wood frame.
 

mtlogcabin

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Would these be classified as Heavy Timber in the code?
Yes the codes place this material in the Type IV construction type

1018 IBC
602.4 Type IV.
Type IV construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of solid wood, laminated wood, heavy timber (HT) or structural composite lumber (SCL) without concealed spaces. The minimum dimensions for permitted materials including solid timber, glued-laminated timber, structural composite lumber (SCL), and cross-laminated timber and details of Type IV construction shall comply with the provisions of this section and Section 2304.11. Exterior walls complying with Section 602.4.1 or 602.4.2 shall be permitted. Interior walls and partitions not less than 1-hour fire-resistance rating or heavy timber complying with Section 2304.11.2.2 shall be permitted.
 

mark handler

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Yes the codes place this material in the Type IV construction type

1018 IBC
602.4 Type IV.
Type IV construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of solid wood, laminated wood, heavy timber (HT) or structural composite lumber (SCL) without concealed spaces. The minimum dimensions for permitted materials including solid timber, glued-laminated timber, structural composite lumber (SCL), and cross-laminated timber and details of Type IV construction shall comply with the provisions of this section and Section 2304.11. Exterior walls complying with Section 602.4.1 or 602.4.2 shall be permitted. Interior walls and partitions not less than 1-hour fire-resistance rating or heavy timber complying with Section 2304.11.2.2 shall be permitted.
YOU ARE SPECULATING BASED ON CURRENT CODE.
They are altering the code and may change all this stuff, time for me to retire again......
 

mtlogcabin

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YOU ARE SPECULATING BASED ON CURRENT CODE.
Just how am I doing that by copying the code language as published

spec•u•late spĕk′yə-lāt″
►​

  • To assume to be true without conclusive evidence.

  • To engage in a course of reasoning often based on inconclusive evidence; conjecture or theorize.
 

mark handler

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Just how am I doing that by copying the code language as published

spec•u•late spĕk′yə-lāt″​

►​

  • To assume to be true without conclusive evidence.

  • To engage in a course of reasoning often based on inconclusive evidence; conjecture or theorize.
Yes the codes place this material in the Type IV construction type
 

steveray

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How did I not realize before that Type IV requires the exterior wall to be non-combustible?.....Now I really don't understand how it is a "lesser" construction type than III....
 

Yikes

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The linked article also links to another article which says there will now be 3 new classifications for Type IV:
  • Type IV-A – Wood buildings up to 18 stories tall
  • Type IV-B – Wood buildings up to 12 stories tall
  • Type IV-C – Wood buildings up to 9 stories tall
FYI, i forwarded the article to one of our engineers, and he commented:
"After 5 stories the lower levels will not work with just wood, you’ll need either moment frames or concrete/masonry shear walls with the seismic loads we have" in Southern California.
 
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