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Author Topic: Legality of timber frame construction  (Read 2032 times)

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Offline plantman

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Legality of timber frame construction
« on: July 21, 2017, 08:42:09 pm »
Please excuse my ignorance but I'd like to hear from people who build timber frame construction for a living. My question is this, I've heard that in most locals wood used for structural purposes must be dried and graded. So does that mean no one can cut on their own mills and build with the green wood ?

Offline Don P

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Re: Legality of timber frame construction
« Reply #1 on: July 21, 2017, 09:00:27 pm »
Must be graded, the only mention in the codes of drying is with regards to fire retardant treated lumber.
Most northeastern states and a few others have some form of native lumber law which allows the sawyer to self grade. The building official always rules though.

Heavy timber falls outside of typical prescriptive construction covered in the IRC (International Residential Code) and falls under the clause that says that anything not covered by the structural provisions of that code shall be built according to accepted engineering practice. The building official would correctly ask for an engineer's stamp on the design.

So you may need to have the plans reviewed by an engineer then cut the timbers and have them graded. Application of those rules varies wildly.

Offline plantman

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Re: Legality of timber frame construction
« Reply #2 on: July 21, 2017, 09:59:06 pm »
Thanks. So I would think that the architect or engineer drawing the plans might also inspect the wood in most instances ?

Offline Don P

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Re: Legality of timber frame construction
« Reply #3 on: July 21, 2017, 11:01:58 pm »
One would think. Correctly you would contact whichever grading agency serves your region and bring in one of their graders.

RDP's, (registered design professionals, architects and engineers) are not trained or under oversight to grade lumber. My BO, building official, does allow an engineer to grade. This does preserve a path of liability insurance where if I grade I can assure you my insurance would not cover it. (I've been to grading school and have showed an engineer how to grade :D. He has retired and I'm hoping our new young engineer can get free and go to the upcoming TFGuild's grading class). I've talked with the engineering department at one of our universities about teaching grading and letting us bring their students out to learn and grade. That is something they are not at all interested in promoting. They feel that grading is a specialized activity requiring special training, skills and experience. I understand that but also know that the moment we begin to break down a tree or stick of wood and use it, we are grading and engineering. Recognize it and cross train everybody. ... if I were king for a day  :D

Offline jfl

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Re: Legality of timber frame construction
« Reply #4 on: July 22, 2017, 08:32:22 am »
Since i have access to my own woodlot and sawmill, I overdesign and take only the best pieces. Right now I'm building a chicken coop of 8 feet by 10 feet with mostly 8x8...

If you get the problem of grading your own wood, it is countebalanced by the fact that the wood is cheap...

jf

Offline plantman

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Re: Legality of timber frame construction
« Reply #5 on: July 22, 2017, 01:34:39 pm »
So it sounds like calling in a person who has credentials and is covered by insurance to grade wood is going to be extremely expensive and that probably isn't going to happen unless you are Bill Gates or Warren Buffet building a ski lodge. And that everyone else building timber frame construction might have a engineer design the structure but no one is grading the wood and somehow the building inspectors let this slide ?

Offline Jim_Rogers

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Re: Legality of timber frame construction
« Reply #6 on: July 22, 2017, 04:18:03 pm »
In my area, the traveling inspector can come to my sawmill yard and inspect and grade the timbers that I have cut for a timber frame, from local woods.
The grading agency for New England will not issue a grade stamp to a portable mill, because they need to know where the stamp is on any day that they want to "drop in" for a surprise inspection.
The inspector looks at all four sides of the timber and both ends and then stamps the timber. He also provides a document saying that he inspected the timbers and all passed. This document goes to the building inspector showing that the local wood is good enough for the frame.
In other areas of the country there are other agency, and companies that do "on site" inspections (for a fee) of timbers for timber framing.
You just have to find them and make an appointment for an inspection and get it done.
In my area the fee is not that much.
Usually, less than $300 (it is one day's pay for the inspector).
That covers his travel time to and from your site and his paperwork, and the inspection.

I hope that you understand that it can be done and then you'll comply with building inspection departments rules.

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Offline Don P

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Re: Legality of timber frame construction
« Reply #7 on: July 22, 2017, 05:11:25 pm »
First find out what the inspector requires, as I said enforcement varies widely. Although it is not a bad idea either way, another set of experienced eyes is never a bad thing. None of us were born endowed with clothes, knowledge or job prospects.

It will have a cost. For me it starts at $350 plus windshield time. Look at the cost of your wood vs purchasing timbers. IF the inspector requires grading then factor bringing in a grader or if allowed, an engineer. I've bought graded timber yet own a sawmill, do the math and see what works best.

When I talked to the agency grader, where I am if I'm not in a hurry he can drop in while on his rounds. I would need to be available on short notice but this would help defray the travel cost considerably.

I think Jim is in NeLma territory, I would use TP here, south of me would be in SPIB or TP's territory.

One thing to remember is a bad piece of wood in a stick frame is not that big of a deal, the structure has lots of redundancy. As you move to fewer and larger members that redundancy fades.

Offline plantman

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Re: Legality of timber frame construction
« Reply #8 on: July 22, 2017, 07:04:50 pm »
yes, thanks to all. I'll check with the local building dept.

Offline CMI80

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Re: Legality of timber frame construction
« Reply #9 on: July 22, 2017, 07:28:33 pm »
Jim and DonP,
Do your graders take into account the moisture content of the timbers ?  I'm in the early stage of a timber frame cabin. I have my timbers cut and stickered. I talked to a local grader about getting them graded and he told me that if the moisture was over 16% he would not pass them because the strength of green timber is much less then air dry/kiln dried. Which I agree with, but if you want to cut the joinery in green wood, how do you do that before the timbers are graded ? All that work and then there's the chance they won't pass !
Plus the length of time to air dry 8x8 and larger timbers and the chance of them moving before you can get them locked together in the frame is much greater.

Thanks for all the help you provide us new timber framers !

Steve

Offline Roger Nair

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Re: Legality of timber frame construction
« Reply #10 on: July 22, 2017, 08:21:32 pm »
The design values in the NDS, that is the National Design Specification, are for green timber, therefore the engineered frame will qualify as a green timber frame and as the wood dries the frame becomes stronger.  Commercially available lumber 2 by whatever stock has been dried so that is a different tier in the marketplace.  Your grader should know this or works in a different field in a segmented market.
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Offline Don P

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Re: Legality of timber frame construction
« Reply #11 on: July 22, 2017, 10:07:02 pm »
I had the NDS on the desk here, this is the part Roger is referring to, page 50 of the supplement, footnotes to table 4D (which is the table of design values for timbers 5x5 and larger)
1. Lumber Dimensions: Tabulated design values are applicable to lumber that will be used under dry conditions such as in most covered structures. For 5" and thicker lumber, the GREEN (Caps are theirs in the manual) dressed sizes shall be permitted to be used (see table 1A) because design values have been adjusted to compensate for any loss in size by shrinkage which may occur.
You can download the "Supplement to the NDS, Design Values for Wood Construction" at awc.org
Graders are generally not familiar with it though. There's that lack of cross training problem, graders should have a bit of engineer in them.

His bible is the National Grade Rule.
Have your grader review paragraph 44 in the NGR manual;
http://nlga.org/wp-content/uploads/2016/02/Sect.-1-General-Provisions-Paras-1-48-pgs-7-21.pdf

If the grader is having trouble with this ask for him to contact the tech folks at his agency, it sounds like he is out of his depth with heavy timber and might need to talk with his superiors to become more comfortable. This is sort of understandable, heavy timber is not the bread and butter of most graders, dimensional lumber is... which is also allowable green but not typical. So, he's being a mullethead but it is understandable and the best way to help him to the light if he resists you is up through his channels where he will trust the input.

For the complete grading manual;
http://nlga.org/en/publications-for-download/
(US and Canada both use the same manual, I got my hard copy while training outside of Atlanta at TP) The interpretations section at the end has good drawings that help flesh out the written parts.

Edit;
I went back through Doc PS-20 last nite, (you can find it at the ALSC site and at NIST). It is the enabling document that originally set up lumber grading and is the mandate that grading operates under. There again it addresses green lumber in much the same language as what is posted above.

Offline MbfVA

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Re: Legality of timber frame construction
« Reply #12 on: July 23, 2017, 07:08:06 pm »
There is definitely a lot of misunderstanding about the use of green timber. I can tell you that from the people I have talked to including architects, with 180 different opinions on that.   I suppose that means it should not be surprising that  lumber graders are  also susceptible to confusion.

My understanding is that in Virginia where we live, and Don P also, a professional engineer (PE) can overrule the building inspector  on most if not all issues.   Don?

I know how that guys going to process his chickens, he's just gonna walk them under the 8x8s and drop them on them.   As the resident CPA here, I would urge him to consider opportunity cost.
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Offline Don P

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Re: Legality of timber frame construction
« Reply #13 on: July 23, 2017, 09:59:54 pm »
 I'm helping point out the right to use green materials, I haven't said I agree with it  :D.
The barn project I'm making timbers for now, the trees are often standing just a day or two before going in but that is not my preference.

The building official does trump the engineer, he rarely exercises that unless there is a glaring error. Anyone can appeal the building official's interpretation of the code to the technical review board, this is even more rare. It is certainly the inspectors grace I am operating under when he allows the engineer to grade.

We processed 50 yardbirds under a popup 10x10 tent a couple of weekends ago. Both the structure and small scale on farm chicken processing are considered ag exempt. Still takes a lot of
pluck  ;D.

Offline MbfVA

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Re: Legality of timber frame construction
« Reply #14 on: August 05, 2017, 01:19:20 am »
 I was told by a licensed professional engineer in Richmond years ago just the opposite, that the professional engineer can overrule a building inspector. That could've changed, or the guy could've been wrong, but that's what I was told. I'm a CPA, but I can't overrule the IRS unfortunately.

Isn't it also true that if the plans call for grade 2 for structural timbers and an engineer stamps them, that takes care of the problem?  Please add precision if I'm oversimplifying.
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Offline Ianab

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Re: Legality of timber frame construction
« Reply #15 on: August 05, 2017, 02:21:38 am »
The Building Inspector ultimately has the final say, but it would be unusual for them to go against an Engineer's report.

It's usually the reverse, where they come across something that's not "standard", and so tell you to go and get an Engineer to check it out and sign off on it. Once you have the Engineers approval, it would be bizarre for them to go against that. Engineer said it wont fall down. Building Inspector's job is then to make sure you follow the approved plan correctly. 

If the Building Inspector doesn't approve something, he has to justify the reason.
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Offline SwampDonkey

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Re: Legality of timber frame construction
« Reply #16 on: August 05, 2017, 04:55:13 am »
Here, you can get a grade stamp when you have completed the grading course of the Maritime Lumber Bureau (local grading authority). But the mill can not be used portable and it along with the stamp has to be at said address for inspection at any time. There was an article in a past issue of Atlantic Forestry Review of a gentleman in southern New Brunswick who got his stamp for grading his own lumber.

We had engineered plans for a potato packing and storage facility a few years ago. We cut all the logs for it and hauled the wood to a local saw mill. There was no stamps on the cut pieces. All we had to do back then was have the engineer approve the lumber. There was no lumber grader involved. I asked father in later years about the lumber and how it was graded. In typical fashion he responded, "It was all # 1". :D

I just demolished the old farm house and the demolition boss said it was one rugged well built house. No graders back then 150 years ago. ;)

Pre-commercial thinning pays off. :)

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Offline Don P

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Re: Legality of timber frame construction
« Reply #17 on: August 05, 2017, 08:25:12 am »
I've been through a grading course with one of our grading agencies and since I have a stationary mill they would issue me a stamp if I pay their fee. That is too expensive for my little operation but is certainly an option for some stationary operations, you would need to figure out the cost/benefit.

It is always worthwhile to learn how to grade, this is not something we were born knowing and it helps if everyone knows what they are looking at. At the end of the day yesterday I was looking over some installed 4x12x18' joists I had sawn. I'm going to need to remake one and have them take down and replace it. I missed a defect I really can't let go and the carpenters didn't look or know how to look at the timbers with grading in mind. This doesn't excuse my miss... but how much better if everyone knows and is looking. This isn't to say we should be overly picky or waste time staring at our navels, simply working with the power of knowledge. It is the difference between simply seeing a dimension and assessing the wood as it passes through your hands. Mastery vs being a laborer. That is part of my issue with how we try to regulate these things. We have dumbed down that end use carpenter, turning him into a parts assembler. By not training and expecting him to look at the wood we receive a lower level of performance. We have not necessarily taken the better path.

 The building official is the authority having jurisdiction, Ianab explained that all correctly. As I mentioned earlier I can appeal his decision to the TRB. I can also go through the civil legal process, this isn't as nice but is sometimes more effective. The TRB is biased towards the strict interpretation of the building code, civil is likely to look more to the entire spectrum of law. I'll give an example. Building officials in VA would like to inspect all buildings, understandable. The ag exemption which is state law says that legitimate ag use buildings are exempt. The ag exemption affidavit in most building departments in the state excludes equine from the ag exemption. They attempt to view them as pets... to which I say do you want to inspect dog houses  :D. The TRB tends to support the building departments' view. State law specifically, in multiple case, views equine, even recreational, as ag and legitimately exempt. I started down the civil path and we now exempt equine barns as per state law.

Not that I'm saying the inspectors eyes on your building are a bad thing at all. It simply allowed ungraded lumber in the horse barn. We could have slain that dragon the other way and allowed me to grade.

Offline MbfVA

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Re: Legality of timber frame construction
« Reply #18 on: August 05, 2017, 08:49:21 am »
Maybe the man who told me that a professional engineer could overrule the building inspector had in mind what you all are saying, that usually it was the building inspector insisting on the engineer's report, and he wasn't likely to overrule a  professional opinion he asked for.

In my 4 years as a local elected government official, I sometimes found that there were practices born of experience that were not necessarily in the rulebook.  Sometimes, maybe often, that was because we and other legislators--local, state, and sometimes federal--had not done their jobs.

No one addressed my proposition about number two lumber?  Of course, all this discussion is moot if the local inspector doesn't enforce the rule.
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Offline Don P

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Re: Legality of timber frame construction
« Reply #19 on: August 05, 2017, 09:05:45 am »
If the plans call for a species and grade and the building official is comfortable with the engineer's ability to assess that, then yes, problem solved.

Calling out #2 actually means nothing without attaching it to a species as well. You need to know species and grade in order to look up the design values the engineer used in design. For instance # 2 Dougfir has a different set of "strength" properties than #2 white pine.