Does code require identifying wood grades of existing structures?

[jacky89]

I received comments from the Daly City Building's Division in California and one of the comments is "Provide documentations and evidence to verify the lumber grades and species for the original construction (IBC/CBC 2303.1.1). All I am doing is installing a 4x4 skylight that requires cutting one truss member in a small 60yrs old residential house. Every other engineer and plan checkers in other jurisdictions I asked said they've never been asked or asked to provide documentations on the lumber grades of an existing house. Is it even legal for them to request this? I would like to hear your feedback. Thanks.

 

[EngineeringEric]

They can ask for anything. And cutting one truss member makes the truss no long valid to transfer loads unless it is analyzed... and a 4' skylight may require cutting two consecutive trusses unless the skylight is more like 3'10"x3'10"

 

[jayrod12]

I've been asked to provide verification of lumber grades when we have needed to assume a specific grade (i.e. D.Fir SS instead of D.Fir No. 2). However that was only twice it has happened and both were commercial projects in 100 year old warehouses.

 

[steellion]

How would one go about identifying the wood species? Call the local lumber yard and ask which wood is most prevalent? Or just be extra-conservative in the design. You can estimate the grade of wood by looking at it.

 

[jayrod12]

In my cases we had a company come out and take samples and test the lumber to ensure it met or exceeded the design values we were using. They had a professor (specializing in wood) from the university consult when they needed an expert opinion.

 

[steellion]

Jayrod, that's probably overkill for the project the OP is describing, but it is good to know that option is available for larger projects.

 

[jayrod12]

Definitely overkill. Expensive too. Like I said it was only to prove we had stronger lumber than the city was willing to accept without testing. And it was a huge commercial remodelling and the reinforcement costs would've tanked the whole project.

In the OPs case we just assume a low enough grade that the City doesn't question it. If you have some reasonable assumptions I've found them to be reasonably accomodating.

 

[woodman88]

Per the 2010 CBC


"3401.4 Building materials. Building materials shall comply with the requirements of this section.

3401.4.1 Existing materials. Materials already in use in a building in compliance with requirements or approvals in effect at the time of their erection or installation shall be permitted to remain in use unless determined by the building code official to be dangerous to life, health or safety. Where such conditions are determined to be dangerous to life, health or safety, they shall be mitigated or made safe.
3401.4.2 New and replacement materials. Except as otherwise required or permitted by this code, materials permitted by the applicable code for new construction shall be used. Like materials shall be permitted for repairs and alterations, provided no hazard to life, health or property is created. Hazardous materials shall not be used where the code for new construction would not permit their use in buildings of similar occupancy, purpose and location.
3401.4.3 Replacement, retention and extension of original materials. [HCD1] Local ordinances or regulations shall permit the replacement, retention and extension of original materials, and the use of original methods of construction, for any building or accessory structure, provided such building or structure complied with the building code provisions in effect at the time of original construction and the building or accessory structure does not become or continue to be a substandard building. For additional information, see Health and Safety Code Sections 17912, 17920.3, 17922(d), 17922.3, 17958.8 and 17958.9."

and

"3401A.4 Building materials. Building materials shall comply with the requirements of this section.

3401A.4.1 Existing materials. Materials already in use in a building in compliance with requirements or approvals in effect at the time of their erection or installation shall be permitted to remain in use unless determined by the building code official to be dangerous to life, health or safety. Where such conditions are determined to be dangerous to life, health or safety, they shall be mitigated or made safe.

3401A.4.2 New and replacement materials. Except as otherwise required or permitted by this code, materials permitted by the applicable code for new construction shall be used. Like materials shall be permitted for repairs and alterations, provided no hazard to life, health or property is created. Hazardous materials shall not be used where the code for new construction would not permit their use in buildings of similar occupancy, purpose and location."

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[BAretired]

If one or two trusses are to be cut, two things must be checked:

1. The cut trusses are properly supported at panel points at each end of the opening.

2. The adjacent trusses are adequately reinforced to sustain the additional load from headers supporting the cut trusses.

Knowing the grade of the existing lumber does not help very much in assessing the capability of the existing trusses to carry additional load. Their capacity is more likely to be governed by the connections than by the grade of truss members.

BA

 

[JStephen]

On a humor site, I had seen a cover shot of this book, with the caption, "Yup, it's wood!", perhaps this would be an application for it:

http://www.amazon.com/Identifying-W...d=1406056001&sr=8-1&keywords=identifying+wood

 

[msquared48]

Well, I would assume a local likely species and grade for the time and area and use 2 grades less than that.

I have had to do that here for more than one municipality to get it to pass for older structures without sampling and lab testing.

I would certainly analyze the connections using the lower stress grade values to be conservative without formal testing.

Mike McCann, PE, SE (WA)

 

[jacky89]

I assumed Douglas Fir Larch No. 2, which is conservative, and analyzed in Risa 3D. I am also doubling up the affected chords. But even without doubling up, it is still within code limits with one truss cut. The design is very conservative as I explained in my submitted calcs. The plan check comment (among many other ridiculously difficult comments) is:
"Provide documentations and evidence to verify the lumber grades and species for the original construction (CBC 2303.1.1).

How much does it cost to have someone grade and certify the wood? Where can I find this service?

 

[jdgengineer]

Have you tried calling the plan reviewer directly and discussing the comment? I've found most plan reviewers to be pretty accommodating to you on the phone if you have a reasonable request.

 

[Ron]

Jacky89...you gave the age of the structure as 60 years. That would put construction in the mid 1950's. If the trusses were pre-fabricated and have metal truss plates, then it is likely that there are grade stamps on the truss members. Most pre-fabricated trusses are going to have No.2 or better top and bottom chords and can have No. 3 diagonals, usually of pine or fir.

The West Coast Lumber Inspection Bureau has been grading lumber along the west coast since the 1920's, so it is likely that your lumber is grade stamped.

Here's a link to their website:

WCLIB

The building department has every right to ask for this information, particularly since you are modifying a structural component. You will not likely be able to get any good documentation of the lumber properties unless you can find a grade stamp and photograph it. This is all assuming you have no original plans.

 

[jacky89]

The truss were not prefabricated and uses plywood gusset plates.

It's hard to imagine the building department would ask this every time someone makes any change to a small single family house. My analysis assuming conservative DFL No.2 results in a lot of remaining capacity. Most old structures here use lumber equal to No. 1 or better.

If they require evidence and documentation for grade of lumber for all existing residence in this city, then no one will be able to do any kind of structural work regardless of how minor it is. The residents are also generally low-income in this city.

 

[hokie66]

But it is California, after all.

 

[Ron]

Grading lumber for your purposes is not that difficult. You can get a copy of the grading rules for your area and do it based on the rules. Call the grading bureau that does the grading for your area and talk to them. I gave in my previous post a place to start.

Yes, this takes time but you'll learn something.

 

[jacky89]

I know several experts at grading lumber. But the issue is they are not a lumber grading agency and would not comply with this code section.

2303.1.1.1 Certificate of inspection. In lieu of a grade
mark on the material, a certificate of inspection as to
species and grade issued by a lumber grading or inspection
agency meeting the requirements of this section is
permitted to be accepted for precut, remanufactured or
rough-sawn lumber and for sizes larger than 3 inches
(76 mm) nominal thickness.

 

[jacky89]

I checked with the structural plan checker and he said it must be graded by a certified lumber grading agency. I asked him has anyone been able to install a 4x4 skylight in the city and he said no. He said no one will be able to prove to him the unknowns in an existing truss system. He also said the lumber grading agency will most likely not come to my house to grade the lumber.

Now I really see why the house prices in Daly City are not going up like the cities around it. It is near impossible, if not impossible, to get any kind of structural permits. Even very simple work that would be over-the-counter permits at neighboring cities will have to take months to get in this city.

 

[BAretired]

Would it be possible (I didn't say practical) to insert a new truss or beam each side of the skylight such that you are not relying on the existing trusses?

BA