Author Topic: A case for prescriptive post frame construction  (Read 732 times)

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Offline Don_P

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A case for prescriptive post frame construction
« on: March 21, 2018, 01:29:10 PM »
I was up early this morning watching the snow, figuring out what to do today, having a cup of coffee and reading the latest copy of Rural Builder that had come a few days ago. There was a particularly timely article about moving to make residential post frame buildings prescriptive construction. I wrote the editor and asked for permission to repost it. Sharon wrote back asking to use my note as a letter to the editor next month. She also sent a pdf copy of the article and posted it on their website with her blessing to spread it around. I agree wholeheartedly.

http://www.constructionmagnet.com/news/locked-residential-make-case-prescriptive-post-frame-building-code

Offline MountainDon

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Re: A case for prescriptive post frame construction
« Reply #1 on: March 21, 2018, 02:49:15 PM »
 [cool]   I'll read that D/L tonight

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline akwoodchuck

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Re: A case for prescriptive post frame construction
« Reply #2 on: March 22, 2018, 07:52:12 AM »
That'll be a longshot to say the least......post/pole frame has always always been about a cost/convenience/performance tradeoff.....prescriptively bringing post foundation performance up to conventional foundation levels would erase the cost differential, so not sure why anyone would want to do it.....

Offline NathanS

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Re: A case for prescriptive post frame construction
« Reply #3 on: March 22, 2018, 08:35:56 AM »
I was wondering the same... how exactly does this work as a residence... would a 30-40 year life span be acceptable? Can posts sunk in the ground last longer? I have never seen an old pole building around here. After 30 years they all seem to start tipping over.

What is the life span on a mobile home... 30-40 years? Might make sense when you think of it that way.

Toward the end of the article they mention the advantage of stilts on flood plains, steep banks, or for snow (?), but in those cases the inspector would likely require an engineer anyhow?

For a storage building, workshop, garage, parking bay, cord wood storage.. I can see provisions in there for those. Like the article said, people get around it with ag exemptions all the time, and the code could make those buildings safer and last longer.

Offline Don_P

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Re: A case for prescriptive post frame construction
« Reply #4 on: March 22, 2018, 05:03:18 PM »
I think that what we have seen over and over here shows that there is a need for a better way. Many people do not want to spend the money to build a conventional perimeter foundation. We've also seen that they will not hire an engineer. Without some form of guidance they try to do it on their own. What we've seen most often is a concrete pier with a wooden post pinned to the top that extends up and is again pinned to a girder, then a rigid box is built on top of these pinned connections. I'm using the word pinned in the engineering definition of the word, free to rotate. The brackets being used clearly state this. The bracing of these elements is almost always inadequate.

A post frame is rigid at these points, the post extends unbroken from the top plate down to the pier, or, to the footing. In other words the prescriptive methods do not require that the post extend into the soil, they require a rigidly braced and connected frame. There are other approvable methods besides the conventional pole barn. The post may have a moment resisting connection to a prescriptive pier at grade, it may have a moment connected concrete or steel lower end that extends into the ground, or, as envisioned above the treated post may extend into the soil to the footing. We do allow prescriptive treated basements and crawlspace foundations, the PWF. Look to permacolumn or strongway systems for those alternative post bases I'm describing, and there are other ways as well.

The path we've been on isn't working very well and there is an obvious need for more alternative yet safe foundations. If we remove the engineer requirement from typical, simple structures and replace that with engineering based guidance in how to do this safely and prescriptively those who wish to avoid building a conventional foundation have another way to build without having to make it up as they go along. An engineer that monitored this site for awhile wrote to me saying he could see in many of these build threads when the light would come on for many owner builders, too late and too invested in their path to change directions.

I'm not as sure the current path works, that a person should either use a conventional foundation, or hire an engineer to design an alternative, or step outside of law and try to figure it out themselves. I'm advocating for door number 3, and 4, and 5, broaden the prescriptive methods. Is it a longshot... well in 20007 we got the log home standard through, a prescriptive way to build log homes. That is a much smaller and diverse market segment. As long as I use methods that we know through long experience work, I can design and build without requiring an engineer's stamp. I can be pretty sure I've built a safe and compliant house. Broadening prescriptive codes do not infringe on us. I can still step outside of those prescriptive methods by having an engineer design those parts that are not prescriptive.

Offline akwoodchuck

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Re: A case for prescriptive post frame construction
« Reply #5 on: March 23, 2018, 07:54:21 AM »
See, this is my problem with the question, fundamentally: as builders, we should be educating people, not encouraging them in their delusions. A proper post frame foundation is not cheaper. When you factor in proper bearing, bracing, drainage, insulation, frost heave/rot protection, etc. they can get to be more expensive/ time consuming than a conventional foundation. Most post /pier foundations are a ticking time bomb of heartache and wallet ache. The public perception that these systems are a significant cost savings is the biggest problem in DIY building in my opinion....my mantra is, "every building needs good shoes, and a good hat...the rest is gravy..."

Offline NathanS

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Re: A case for prescriptive post frame construction
« Reply #6 on: March 24, 2018, 11:06:01 AM »
Thanks for the explanation Don. It will be interesting to see if prescriptive solutions will make their way into the code.

My non-pro take on it was what akwoodchuck is saying. By the time you do everything right, I don't understand how it will end up saving money for a residence.

150 years ago they were sending stones down canals that would then be hauled by horses to hand dug foundations... If there were an alternative you'd think they would have found one.

Outbuildings.. now that may be a different story, especially with 48" frost depth.

Probably one of the most difficult parts of the build was spending all that money on a foundation you can't see yet. Piers offer the illusion of 'easing into' the expense.

Offline Don_P

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Re: A case for prescriptive post frame construction
« Reply #7 on: March 24, 2018, 04:19:01 PM »
Do you both see the assumption that your argument is based on? "It will cost as much or more to meet the prescription". You do not know this, nor does that matter. Open up the possibility. Then, if cost is the motivational factor (also an assumption, we do not know this) let people determine for themselves which way is cheaper to meet the objective. Motivation does not matter here, there can be many more than we can foresee... remote site, terrain, site impact, etc. This is a structural code, I'm not interested in what motivates personal choice as long as the product I build is safe. I've built quite a few log homes. Personally, I think they are money, maintenance, and energy hogs, but if that is what trips your trigger I'll meet or exceed the prescriptions, I build them well. It is impossible to justify a timberframe home on a cost basis, it is not my place to tell people how to spend their money on their dream. I build a safe shelter while accommodating that dream. I do what the engineer says and the product is safe in the end. They have worked towards prescription in fits and starts, I hope they make it happen one day. Some of the timberframe portions of the project I'm working on now would fall under the post frame prescriptions.

As for the unsuitability of post frame for residential construction structurally, that horse has already left the barn. Prohibiting residential post frame altogether probably isn't going to happen.  It is allowed and many have been built under the engineering provisions of the code. In other words it is already a proven and approved method structurally. This is simply moving it from engineered to prescriptive. What I am agreeing with is recognizing that it is already common and proven, we can publish the successful methods and avoid engineering on every one. In saying that, I also think it is part of our job to educate, yes, make those arguments, The code is about minimums, I'd like to see us get up to that level of performance. You are hoping to convince to a level above that, that's fine
« Last Edit: March 24, 2018, 04:51:20 PM by Don_P »

Offline Beavers

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Re: A case for prescriptive post frame construction
« Reply #8 on: March 26, 2018, 04:40:31 AM »
A proper post frame foundation is not cheaper. When you factor in proper bearing, bracing, drainage, insulation, frost heave/rot protection, etc. they can get to be more expensive/ time consuming than a conventional foundation.

I've learned this with my cabin build.   d*
Of course I built in an area where it's easy to get a concrete truck to.  A lot of the builds I see on here are pretty remote and I can see where a post frame is the only option.

Offline MountainDon

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Re: A case for prescriptive post frame construction
« Reply #9 on: March 26, 2018, 05:15:04 AM »
I would love to see post frame as a prescriptive option. There are only three choices for a transit mixer in our area and all three of them will only go as far as the place on the road where the National Forest starts. Unfortunately, there are 3 miles of FS road before our property is reached. Too far to wheelbarrow the concrete.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Adam Roby

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Re: A case for prescriptive post frame construction
« Reply #10 on: March 26, 2018, 04:31:29 PM »
Still hoping that one day the creators of LEGO decide to get into the construction business. 

Lightweight, lasts forever, anyone can put lego together, naturally waterproof...  probably all a cost thing.

Offline azgreg

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Re: A case for prescriptive post frame construction
« Reply #11 on: March 26, 2018, 05:01:48 PM »
Still hoping that one day the creators of LEGO decide to get into the construction business. 

Lightweight, lasts forever, anyone can put lego together, naturally waterproof...  probably all a cost thing.




 

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