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Legality of timber frame construction

Started by plantman, July 21, 2017, 08:42:09 PM

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plantman

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 ?

Don P

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.

plantman

Thanks. So I would think that the architect or engineer drawing the plans might also inspect the wood in most instances ?

Don P

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

jfl

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

plantman

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 ?

Jim_Rogers

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.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Don P

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.

plantman

yes, thanks to all. I'll check with the local building dept.

CMI80

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

Roger Nair

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.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Don P

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.

MbfVA

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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Don P

 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.

MbfVA

 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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Ianab

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.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

SwampDonkey

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. ;)
"No amount of belief makes something a fact." James Randi

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Don P

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.

MbfVA

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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Don P

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.

MbfVA

What I'm getting at related to our situation in particular is this:
our wood is "free", if we don't count opportunity cost, so our plan would be to "oversize" sufficiently to avoid grading.

Our 175 acre forest is loaded with white and red Oak, in particular.

You've been threatening to come up here, Don?  We need to get together with the guy in Northern Virginia and build those bleachers for watching me getting crushed by a 5 ft tree falling on my SSL & its tree saw, or at least my jumping out & running really really fast.  We just transported the Liebherr track loader to the farm, so now I've got some serious pushing power with its 34,000 #.  The only problem is destroying the root ball, cutting down regeneration.

That 4x12 you mentioned must've been really bad.  What about it made you want to pull it out?

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Brad_bb

My experience:
When timberframing, your wood is going to be green.  You cannot Kiln Dry hardwood timbers 4 inches and thicker because you can dry the outer inch, but the inside of the timber will still be green.  I you purchase Doug fir, which is non native unless you are in the pacific northwest, they do kiln dry those, and they do better in a kiln than hardwood, but I think the center of your timbers are still going to retain moisture.

There's nothing wrong with using green timbers.  It has been done for thousands of years.  It takes big timbers dozens of years at least to dry to ambient conditions.  Most of the movement from drying occurs in the first 1.5 years though. 

Your timberframe should be engineered, not for the sake of the code/building department, but so that your timbers are sized appropriately, and the foundation is correctly engineered.  This is a must in my book.  You should not intentionally "overbuild"  because that can cause other problems and costs.  When the engineer goes to analyze your frame, he will use material properties for the wood you are using.  Sometimes, for simplicity, he'll use properties for the weakest wood you are using.  For example a frame where white oak, mixed oak, walnut, and beech are used, the engineer did his calculations using the properties of the beech. 

Grading timbers.  In my area, the timbers do not need to be grade stamped.  Grading is very important though for YOUR frame.  By grading I mean a visual grading by an experienced timberframer.  You can learn to do this too.  This is not a grading for "grade 1", "grade 2", etc, but rather grading your timber as to whether it is suitable for a particular area of the frame.  For example, posts can often tolerate more knots, wane, etc, while horizontal members like tie beams or rafters must be far better.  Recognizing the location of defects and where they would fall in a tie beam is very important.  A defect in the middle bottom of a tie beam is very bad.  A defect towards the ends may be just fine, or on the top.  Once you have timbers in hand, you need to look at them and decide where they go, how they will be oriented, and whether or not they will be acceptable.   You may have to cull a few timbers and order additional if they don't make the grade.

The inspector.  The ones I've dealt with are not all that experienced when it comes to timberframing.  They recognize that it is traditional and works, but defer to the engineer and the timberframe guys themselves as being far more  knowledgeable.  When they see the quality of the work being done, they are more assured that things are being done right or being overbuilt(more safety margin).  That may or may not actually be true, but that has been their perception.

Some counties are very strict, rule oriented, and cannot think or make decisions outside the box.  Sometimes you can just get the kind of inspector/code guy that is disagreeable, or overboard on relying on rules on paper.  Hopefully you'll get lucky and find a reasonable person that will work with you.  In their defense, they are covering their butts too.  They have to justify why they allow something that may not be in "the book" specifically.  The book is written around stick framing as that was and is what is predominant.  So sometimes we're trying to fit our round peg in their square hole.
Anything someone can design, I can sure figure out how to fix!
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SwampDonkey

I wonder if architectural and civil engineers are grading steel?  :-\

"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

MbfVA

Thank you for the detailed comments, Swampdonkey.  We are going to involve a timber framing expert at some level, and definitely will get our plans stamped by an engineer whether the building inspector requires it or not.   The timber frame company most likely to help us has engineers on staff so we're in good shape there. Based on what I know of their work, and on that of the others we're talking to, the building inspectors around here are completely comfortable with them. And I've spoken with the building inspector in this county already; he indicated that experts will prevail with him.  Nice guy, lives nearby.

Albemarle County and Charlottesville are right next-door, and if you can satisfy them you can satisfy anybody.

We have almost no softwoods on our property except for Seiter (Siri is stupid, go on what it sounds like), so we will likely be building with oak and related.   when I say we will oversize, I mean oversize enough for our structure to be qualified using "grade 2", and satisfy the engineer & building inspector.

One of our goals is to do some trading with the timber frame company, wood for work.  So far, we have two good healthy fish sniffing that bait.

I wonder how many building inspectors know wood species well enough to distinguish when looking at a great big timber.  I can smell oak & cedar, but I can't tell you which precise one it is.

I'm well settled on the green timber question, though my mind remains open to alternative views. In other posts I have marveled at how even experienced ArchiText don't know that green timbers work.  I don't guess Siri is a member of AAA , try again Siri, AIA.

Don, P, you had expressed some disagreement on the green timber framing question as well.  If you care to explain more, I'd love to read it.  Your posts are generally some of the best on this forum on any given day.  I am sure I am not alone in appreciating that.

I thought the comments about types of defects was really good. I'm still waiting on Don to tell us what was wrong with that 18 foot timber that he want to pull out. Pictures would help  smiley_nananana.
www.ordinary.com (really)

Don P

Do remember the title timberframer is one that someone applies to themself. It may or may not mean they have been trained to grade or know what they are looking at. My oopsed timber was installed by timberframers. Hopefully they are going to the upcoming grading school. The same can be said for an engineer, they may or may not be qualified to grade but they do carry insurance and are supposedly working within their area of expertise.

I'll try to get a pic tomorrow. It isn't horrible but it is not on grade, I spec'ed #1 or better. The job is ag exempt. The only timbers that have been checked were done so by me after I was concerned with some of the dimensions coming out of the timberframers' "from experience". They were not happy with the sizes I was coming up with. Happily a friend who is an engineer came by to see the job while we were having one of those discussions and I asked him to check me. He asked why I felt the need to cut it so fine, he would have gone up another size.

Steel is "graded" to various strength properties at the mill, analogous to commodity lumber. There are no backyard steel mills producing structural steel. The engineer comes in at fabrication design and implementation just as with wood.

The inspector does not know what he is looking at, he defers to the gradestamp. He does have the right to call for a reinspection. The overseeing agency would then send out their check grader. I've had bootleg stamped lumber show up on a jobsite as well as unstamped lumber, both from lumber suppliers trying to save a buck and slide stuff through. The unstamped was garbage and went back, the bootleg was of excellent quality and I took the risk that the inspector wouldn't look at the stamps or if he did wouldn't know. I did tell the driver to let the folks upstairs know that wouldn't happen again. I don't agree with the law but am subject to it.

Green lumber and timbers. Green wood shrinks. No you cannot predict how it will react as it dries nor can you account for all of it. The only advantages of using green wood in construction are for the benefit of the builder or supplier not for the benefit of the building. That is a decision that needs to be weighed when working either way. I've done a fair amount of both.

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