Christopher,

Point taken, A good TF engineer is worth his weight in golld 10X over, there is however, a disappointing trend taking place in engineering. "CYA" engineering has become the norm rather than the exception. It is due to lawsuits and I understand it is not going away. Today's engineers seldom place any materials in testing these days and do most structural analysis based on tables and computer modeling. These tables are in essence only "rule of thumb" for a given GROUP of species. Seldom is follow up testing done to verify complete working unit. Real world application:

Scenario 1

1. Logger cuts tree without knowing end use.
2. Mill cuts into lumber not knowing end use.
3. Lumber grader grades timber not knowing end use of timber and based on grade tables. Grade tables are based on average safe working loads.
4. Engineer specifies joints and timbers based on average safe working loads per his tables and adds a little CYA factor.
5. Hourly laborer lays out and cuts each timber which is grade stamped based on shop drawings which reflect a enginners stamp.
6. Frame is erected by commercial timberframing company and then they leave.
7.Holes are bored through it by Electricians, plumbers, HVAC techs, security system installer, Cable TV installer, etc. who have no knowledge of timber framing structural elements.
8. Local Building inspector looks at Stamped plans and graded timbers and calls all good as he has little knowledge of timber frames and CO is issued.

Scenario 2

1. A frame is designed with sound historically proven joinery.
2. Local trees are selected for specific purposes by timber framer, based on his cut into logs of appropriate length and labeled for sawyer.
3. Local sawyer cuts logs to specified dimensions. Any questionable timbers are culled and set aside for scantlings.
4. Timbers are layed out and cut by timber framer with knots, crown, twist, shake, check and grain runout taken into consideration for each timber.
5. Frame is erected by neighborhood help without engineer or building inspector involvement.
6. All sub trades work under supervision of timber framer.
7. Timber framer hands keys to the new owner upon completion.

Evaluate:

Which one of these structures would you want to live in?
Which one is most likely standing 200 years form now?
Which one is most environmentally responsible? Which one is most likely to be involved in costly litigation?
Which one costs the least?

Too bad that housing is a function of legality these days rather than craftsmanship isn't it.

I have seen too many high dollar engineering screwups. My faith in engineers is not as great as it is in real world testing and a working knowledge of the materials at hand.

"Leave it to an engineer" is often the kiss of death rather than assurance of positive outcome.

Thought I'd throw these in for comment and fuel. In place 10 years (admittedly not 200..) but look as good as the day. Wisconsin, 35 lb snow, 6" pitch, mixed unseasoned oak, 22' span, KD NRO spline, 1 1/4" pegs. Getting the curve out of one piece, repeating the same radius throughout the series of trusses, was highly impractical without this approach. Comments? C'mon I can take it..

crabtree, I don't have as much experience as you but I recognize a good argument when I read one.

After answering Scenario 2 with all questions except for the litigation one. I wondered, where can you find this sort of deal. In any area or state is this acceptable (to the powers that be)? And if not how do you coup d'etat?

Hi Crabtree,

It might appear to some that you are implying that the two scenarios described above are mutually exclusive i.e. elements of one are not generally found to be present in the other and this is not a reasonable argument.

Regarding litigation being pursued against an "engineered" frame - who is that would be called upon to provide expert advice against the original defficient frame design - a designer, an engineer, a building inspector or a carpenter ?

I understand your frustration but please be assured that there are engineers in this world that do know their arris from their elbow.

Regards

Ken Hume P.Eng.

Two ways to do that...

One: owner pulls ALL the permits and pays 'cash' for everything (no construction loan). House can be lived in and inherited but not sold without a ton of waivers from the buyer.

Two: add one more step, call in an engineer after the fact for an "as built". Might have to go through several engineers (or park a tractor on the roof) to get that done.

Dovetail,

I like it! looks like it exhibits the majority of the "rules" I submitted. Was this an engineered design? Did you mill your own timbers? Can you give us any more details on the joinery selection?

Mo,
Please don't credit me with a lot of experience as I am certainly a novice. The situation I created was a hypothetical of two extremes. I don't neccessarily condone either. Just something to make people think about the laws of averages.

Ken,
I would propose litigation will brought by the owner or a future owner against all involved in the construction from designers and engineers down to local inspector. He will need no expert other than a few pictures of the frame coming apart and estimates for repair or worst case scenario the death certificate of a family member killed in its collapse.

As an engineer, how much of your work is based on computer generated models and tables? What measures do you take to insure that the aforementioned tragedies don't occur in your designs? Please do not take any of this as a personal indictment. As I said a good engineer is worth his weight in gold.

As a professional have you seen builders trending towards a loss of craftsmanship and a turn towards profit margins?

To all:

How is it that codes will permit people to live in mobile homes stacked on concrete blocks and built out of 2X3's with extremely flammable panelling while a guy trying to build with massive timbers in a time proven method has to get in line at the local engineering firm or provide proof it won't fall apart.

Hi Crabtree,

How long have you got ?

It might be more appropriate for TFEC members to provide some answers to your questions as this type of issue falls within their balliewick.

There are significant and well recorded historical precedents as to what types of timber frame design will survive over the longer term.

Timber frame buildings do not usually fail catastrophically but instead tend to slowly yield to the ravages of time.

Fire will affect a timber framed building more slowly than an equivalent size balloon (stud) frame building since it will take longer for the primary components to fail as the fire gradually wastes their section. Design for fire resistance has more to do with providing sufficient escape time for occupants than trying to preserve the structure itself.

Computer modeling is probably the greatest step forward yet made in building structure design. This facility is particularly useful where custom or esoteric designs are being pursued since it helps identify potential problem areas within a frame but also don't forget that it also identifies those components that are not highly stressed and could therefore be made from lower grade materials thus with good design engineering it might be possible to produce a more cost effective design that could be sold more affordably or alternatively provide a higher profit margin to a builder without the need to unduly compromise safety.

Most people do not want to pay for design or engineering and some believe that they are quite capable of handling all technical issues by themselves and up to a point this can be true i.e. when a frame is being built to a building pattern that has passed the test of time then the scope for encountering major problems are probably greatly reduced. It is where the uncertainty or consequence of failure becomes higher that engineering input should be sought.

The issue of legislation must also be considered in that some states / provencies / countries reserve certain building design matters to engineers and it would appear foolhardy to ignore those requirements.

Applying good old fashioned common sense combined with experience is a pre requisite to undertaking any safe building programme but raises the issue of how a person is able to aquire experience and get to know his own limitations without harming himself or others arround him who might have had no say in the decision making process.

Building timber frames is a complex process and I have seen more than my fair share of building solutions with which I have not been particularly happy. Its a terrible feeling when a person is smiling ear to ear proudly displaying their work and inside you are thinking "OMG". How do you tell them ? Should you tell them ? Will they thank you ? Will they hate you ?

The longer term solution lies with bodies like the TFG and CF where free exchange of thoughts, ideas, concerns, and solutions will help to spread knowledge and understanding of timber framing issues and practices in so doing will hopefully improve the general levels of personal safety and building performance.

These are complex issues and cannot really be done justice on a short post on a bulletin board.

Regards

Ken Hume P.Eng
http://www.kfhume.freeserve.co.uk

I've got one of those situations in front of me on another BBS. Nothing to fatal but it could lead to premature failure of a shed/small barn frame. So far I've kept mum, the knee braces look good (in photos) and there is a lot of solid sheathing that will help keep the frame rigid.

The situation is compounded by the fact that it's a wood working project contest entry and the only other TF entered in the contest is my own. To make matters more interesting, the person in question has listed their occupation as Engineer, while I'm listed as a Medical Technologist/Landscape Designer/Wannabe Timber Framer.

As an engineer, what would your reaction be to a "complete neophyte" pointing out flaws in something you designed and built (from tree to finished product)?