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pressue blocking

Let in braces are a lousy bracing system. Not only is it weak compared to plywood the notches weaken the studs. I have seen pictures of failures in the studs due to the notching.

Do not blame the rotting on the use of plywood. A lot of the problem was the result of our efforts to make buildings tighter in response to the need to conserve energy. The problem is that when we made buildings tighter we did not have a good scientific idea of how moisture flows through buildings.

It wasn’t until Lstiburek and his fellow researchers started applying science to the problem that we learned how to do it right. And what is right in California on the coast is not the right way in Montana on the Canadian border.

Knowing how to do it right is only the first step. The designers need to define what was needed and the trades need to learn how to do it per the plans. We need to break old habits. Doing it like you did it 40 years ago no longer cuts it.

Old timers can contribute a lot, but in order to do it effectively we need to embrace and understand the new technology. If we do not keep up with the new knowledge we will rightfully be seen as irrelevant and will be ignored. Get on the train or retire.

Sustainability is here to stay. Rather than fight it we need to demand that the requirements be backed up with some objective thinking. The objective should not be to go back to the old ways but rather to make sure that the new requirements are effective.
 
Mark:

There are better ways to brace walls than shear plywood without sealing the walls up, are a good example. In fact in one of Lstiburek's articles he shows himself as a young man driving shims under the lap siding of his parents home to release the water trapped and blistering the siding from nailing the siding right on plywood, he states briefly something about newer systems and showed a picture of a Hardy Frame¹, but then goes right on to say we have to brace homes so they won't fall down and use plywood, he then launched into his pitch for rain screens. At this point from the rotted buildings I've seen I'm ready to say that any time you shear a wall you must use a rain screen. Before the 1998 CBC I avoided the problem by getting the engineer to approve putting the shear plywood on the interior behind the sheetrock, I doubt they would approve that now, engineers are requiring so much steel and Simpson products now that I am going to all steel frames. Furthermore, whenever there is shear plywood the green raters are putting in the G sheets OSB, that stuff is a disaster, by not having shear plywood they can't substitute OSB. In this addition the engineer still placed plywood on the walls, then the green rater substituted OSB to "clean up the forest floor" in the G sheets.

Mark said:
Sustainability is here to stay.
I was giving a talk to a Stanford Alumni group about Green Fraud and the Green Codes, I was asked what could be changed that would get me to buy into green codes, after thinking a minute I said that sustainability should be re-defined as building buildings that last hundreds of years instead of building sick buildings that are going to rot out in a few years.

¹ http://www.hardyframe.com/braceframes.htm
 
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conarb posted, "Before the 1998 CBC I avoided the problem by getting the engineer to approve putting the shear plywood on the interior behind the sheetrock, I doubt they would approve that now"

It is a very common practice in coastal Louisiana where the greatest concern is hurricane force winds.
 
Hey Conarb, in the "old days".... did you use galvanized water pipe, transite (asbestos) ducts, asbestos interior plaster, lead paint, standard glass (not tempered) for showers and doors and parrafin wax on your 16d's?????

(Just messing with you, everyone did!!!!)
 
Beach:

Of course, we replaced the paraffin with soap powder in the late 60s, one day it rained in 1971 when the inspector was there on a 65 unit garden apartment complex, soap suds ran down the studs and legs of my carpenters. Nice inspector, he didn't say anything but gave me that "knowing look", damn good thing it wasn't Uncle Bob, I'd still be in jail.
 
Beach:

Another funny story, Cal Berkeley housed it's married students in Albany in a place called Codornices village, Codornices Village was old two story WWII army barracks, they were covered in stucco that was badly cracked from settling. The Cal architecture people remodeled them and covered them in asbestos, my first job out of college was as a foreman on the carpentry crews stripping the stucco with 1x4s for the asbestos guys to cover the buildings. It was only fitting that Stanford guy's first job out of school was encasing Cal students in asbestos, and Big Game is coming up.

 
(RANT)

Construction Arbitrator: So. What is the deal. It is okay to employ the construction technique of pressure-blocking just so long you don't acknowledge it?

You have a depth of experience and possess personal capabilities that are enviable, and could be instrumental in furthering the idea that prescriptive codes for pressure-blocking, at least in limited circumstances, is a viable idea. But you appear to be too entrenced to even admit employing this technique on a limited basis.

We allow pressure-blocking in our ahj in limited circumstances, as do others that have responded to this thread. Then, there are those that criticize every inspector for allowing any deviation from the letter of the law of the code, sometimes pretending they don't . . . often, the same folks calling for reform and revolt against the ICC and the system of things.

Where do you stand? Are you saying you do or do not believe pressure-blocking should be accepted or rejected in all applications?
 
Fronts occurr at interfaces between presure cells or air masses, and are not features of the global wind belts.
 
Here in Oregon we call it power blocking. I've got to tell you it's great! Using power blocking gives the carpenter numerous angles and directions to toe nail and face nail a joist to a ledger without any worry about pushing the joist off of layout. All without having to deal with the thickness of the hanger messing with the drywall. If you've ever installed joists in joist hangers that utilize those 8 or 10d toe nails you know they're a joke.Course the carpenter doing the nail up lacks the engineering/insurance policy to back up his skill so most AHJ won't accept the personal responsibility to approve a very elegant carpentry technique.I'll edit this post to show some power blocking I've used on the addition I'm building to my own home.Bill

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Does anyone know if a study has ever been done?
KZQuixote said:
Using power blocking gives the carpenter numerous angles and directions to toe nail and face nail a joist to a ledger without any worry about pushing the joist off of layout. Course the carpenter doing the nail up lacks the engineering/insurance policy to back up his skill so most AHJ won't accept the personal responsibility to approve a very elegant carpentry technique.
NDS 11.5.4.2 Toe-Nail Factor would be the thing to use here. "When toe nails are used, reference lateral design values,Z, shall be multiplied by the toe nail factor, Ctn = 0.83."

Fig 11A shows the toe nail for that value. The nail is at a 30 degree angle to the joist and is started from a point 1/3 of nail length back from the end of the joist.

At 19% during installation and ~12% in service there is no pressure or friction to add to that in service. Not saying it doesn't work, those would be the design values I would check against. Elegant carpentry to me is to put the joist on the beam.
 
KZ: Good illustration.

What is required is a study of the power-blocking, or pressure-blocking technique that would include numerous calculations including for toenailing, face-nailing, and allowable spans.

I The strongest connection is achieved by face nailing the joist to the pressure block, as well as toenailing the joist through the pressure-block into the beam.

Yes, the joist on beam is best where applicable. But, this application, like a joist hanger or notchiong for a ledger, is for the application where having the nailing surfaces of the joist and beam aligned is the desired result.

Based on this thread and a similar thread on the archived ICC bb, pressure-blocking is practiced throughout the United States, at least on a limited basis. I suspect it is more common than expressed.

For examples, pressure-blocking may can be established as a legal framing connection for ceiling joist spans up to 8', or floor joist spans up to 4', where uniform loading exists.
 
Not sure where the term Pressure Blocking might have come from. Any carpenter who has nailed more than a few blocks knows the problem with not leaving some negative tolerance in the block length. Additionally, what might be tight at today's moisture content is certain to be loose once the building has dried out.

Jobsaver said: "The strongest connection is achieved by face nailing the joist to the pressure block, as well as toenailing the joist through the pressure-block into the beam."

Hi Jobsaver, Do not forget the back nails that the carpenter drives through the last joist into the newest block. This way the joist is face nailed from both faces as well as toenailed into the beam or ledger.

Power Blocking has got to be many times stronger than notching the joists onto a 2X2 face nailed ledger. Unfortunately, it'll never get published and accepted.

The deep pockets of Simpson Strong Tie will see to that.

Bill
 
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KZQuixote said:
Oh! If it could only be! Don't bet on it! The deep pockets of Simpson Strong Tie will see to that.Power Blocking has got to be many times stronger than notching the joists onto a 2X2 face nailed ledger.
Definitely on the ledger being weaker.

I am not sure that the Simpson Strong Tie pockets are deeper than the nail manufacturer's pockets combined with the lumber producer's pockets, both of which stand to benefit from prescriptive pressure-blocking.

Pressure-blocking? Power-blocking? Gotta find a new name that works for the engineering crowd . . . maybe Lateral Dimensional Lumber Framing Anchors? Carpenters can still call 'em blocks!
 
Not a formal engineering basis, but it would be great to get one of the university labs to do some formal testing on various methods.

Its an opinion based on personal experience. Simple tests with simple tools building frames, and sometimes taking them apart. Ledgers work well too, but are prone to splitting using some species.

I am surprised that there is not more support for the idea of testing.
 
Jobsaver said:
but it would be great to get one of the university labs to do some formal testing on various methods.
You're not going to get it from a university, universities work on grant money, there is Simpson grant money, but there is no pressure blocking industry to fund such a study, pressure blocks consume only scraps of lumber so their is no incentive for the lumber industry to fund such a study. Here is some information on drug studies, the same applies to building product studies.

San Francisco Chronicle said:

Money talks -- and very loudly when a drug company is funding a clinical trial involving one of its products, according to a study released Monday.

UCSF researchers looked at nearly 200 head-to-head studies of widely prescribed cholesterol-lowering medications, or statins, and found that results were 20 times more likely to favor the drug made by the company that sponsored the trial. "We have to be really, really skeptical of these drug-company-sponsored studies," said Lisa Bero, the study's author and professor of clinical pharmacy and health policy studies at the university.

The research, reported in the online editions of PLoS Medicine, a San Francisco medical journal, focused on studies of six statins -- including Pfizer Inc.'s Lipitor, Merck & Co.'s Zocor and the generic drug Mevacor -- that had already been approved by the Food and Drug Administration. The trials typically involved comparing the effectiveness of a drug to one or two other statins. "If I'm a clinician or funder of health care, I really want to know within a class of drug which one works better," Bero said. "What our study shows is that depends on who funds the study."

UCSF researchers also found that a study's conclusions -- not the actual research results but the trial investigators' impressions -- are more than 35 times more likely to favor the test drug when that trial is sponsored by the drug's maker.

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/06/05/DRUGS.TMP#ixzz15E2IFp3D

 
Scraps of lumber . . . sounds like a good green idea to me.

How much energy is consumed producing one house's worth of unnecessary Simpson Products. What is the carbon footprint from burning the scraps of lumber? Obama will fund the study!

Kidding. But pressure-blocking consumes a lot of nails too. Nails cost money.
 
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