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  #16  
Old 2/24/07, 10:53 AM
David P. Valley's Avatar
David P. Valley David P. Valley is offline
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Default Re: Joist blocking

Quote:
Originally Posted by homebild
The IRC R 502.7 does NOT require lateral support above girders overwhich floor joists intersect except in Seismic Zones D1 and D2.

The fact they are lapped and nailed to each other is enough to satisfy the lateral restraint at the ends requirement.

The joists in the original photo require no solid blocking between them unless the house is in an active earthquake zone or other local codes require it.
Thank you. That backs up my original posts.
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  #17  
Old 2/24/07, 9:54 PM
Robert J. OConnor's Avatar
Robert J. OConnor Robert J. OConnor is offline
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Default Re: Joist blocking

Quote:
Originally Posted by homebild
The IRC R 502.7 does NOT require lateral support above girders overwhich floor joists intersect except in Seismic Zones D1 and D2
Sounds like just someones misinterpretation, as that is NOT how the code requirements read, or the intent of that code section. This is a quote of the 2003 IRC ...
Quote:
502.7 Lateral restraint at supports.
Joists shall be supported laterally at the ends by full-depth solid blocking not less than 2 inches (51 mm) nominal in thickness; or by attachment to a header, band, or rim joist, or to an adjoining stud; or shall be otherwise provided with lateral support to prevent rotation.

Exception: In Seismic Design Categories D1 and D2, lateral restraint shall also be provided at each intermediate support.
The converse of the Exception is not true if lapped joist are face nailed together. Just face nailing the joists together does not provide torsional rotation restraint, which is the intent of that IRC section. Imagine a single 2x10 spanning across a 30' wide house with just support over a center bearing wall (yea, I know they don't come that way, but just imagine it) ... it would twist like a wet noodle near the middle ...

Blocking or solid bracing is indeed required at joist laps over bearing walls or beams (there are some other options ... but face nailing laps is not one of them). That is also why IRC R502.7.1 requires solid blocking, diagonal bridging, or bottom brace boards (no other options) at 8' centers for deeper members. Read the IRC commentary book to confirm those for yourself.

If your still not sure, read Sections 2.3.1 and 3.3.1 of the AFPA "Wood Frame Construction Manual" and commentary (referenced in IRC Chapter 43) which is a little more technical, but should make the lateral restraint requirement crystal clear.

JMO & 2-nickels ...



Robert O'Connor, PE
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  #18  
Old 2/26/07, 1:30 AM
homebild homebild is offline
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Default Re: Joist blocking

Quote:
Originally Posted by roconnor
Sounds like just someones misinterpretation, as that is NOT how the code requirements read, or the intent of that code section. This is a quote of the 2003 IRC ...

The converse of the Exception is not true if lapped joist are face nailed together. Just face nailing the joists together does not provide torsional rotation restraint, which is the intent of that IRC section. Imagine a single 2x10 spanning across a 30' wide house with just support over a center bearing wall (yea, I know they don't come that way, but just imagine it) ... it would twist like a wet noodle near the middle ...

Blocking or solid bracing is indeed required at joist laps over bearing walls or beams (there are some other options ... but face nailing laps is not one of them). That is also why IRC R502.7.1 requires solid blocking, diagonal bridging, or bottom brace boards (no other options) at 8' centers for deeper members. Read the IRC commentary book to confirm those for yourself.

If your still not sure, read Sections 2.3.1 and 3.3.1 of the AFPA "Wood Frame Construction Manual" and commentary (referenced in IRC Chapter 43) which is a little more technical, but should make the lateral restraint requirement crystal clear.

JMO & 2-nickels ...
Sorry to disagree.

But the AFPA Wood Frame Construction Manual does NOT support your claims although it does 'recommend' blocking between joist over girders.

The main problem is that the AFPA Wood Frame Construction Manual is NOT 'Code'. It is simply recognized by the ICC Codes as an approved alternative to the 'Code' where the plans submitter agrees to build to its standards. Otherwise, it is NOT "Code" and retains absolutely no authority AS "Code". And as an 'engineer' you should know better.

You should also be aware of R102.4 of the IRC Code which states:

Quote:
"Where differences occur between provisions of the code and the referenced codes and standards, the provisions of the code shall apply."
In short: The written Code takes precedent over the referenced standards in Chapter 43 at all times and not vice versa.


Because of this, your claim that "blocking or solid bracing is indeed required at joist laps over bearing walls or beams" is simply baseless.

Under the 'prescriptive' code this just does not apply.....except in D1 and D2 seismic zones.

I have had this discussion many times with ICC instructors and each time have been informed that the intent of the Code has NEVER been to require blocking between lapped joists when they terminate over girders EXCEPT in seismic zones D1 and D2.

I have also called the ICC directly on this question (as a member) and have had their enegineers advise me of the same.

Code Commentaries published by the ICC likewise do not support your position.

That said, it is up to the local authority having jurisdiction, the local code enforcement official to ultimately interpret the Code as he sees fit.

Not you.
Not I.
Not anyone else.

Whether or not blocking is deemed 'required' by Code over girders where joists lap is left up to the Code Official and no one else BY LAW wherever the ICC codes have been adopted.

So I must continue reject your faulty interpretations for what they remain.

Respectfully submitted,

homebild

Last edited by homebild; 2/26/07 at 1:54 AM..
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  #19  
Old 2/26/07, 5:56 AM
David P. Valley's Avatar
David P. Valley David P. Valley is offline
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Default Re: Joist blocking

So....In the long run, it all depends on what jurisdiction you are inspecting in.

Massachusetts code states...

2305.14.2 Bridging: In all floor, attic and roof framing, except as hereafter noted, there shall not be less than one line of bridging for each eight feet (or 2450 mm) of span. The bridging shall consist of not less than one-inch by three-inch lumber, double nailed at each end, or of equivalent metal bracing of equal rigidity.

A line of bridging shall also be required at supports where adequate lateral support is not otherwise provided. Midspan bridging is not required for floor, attic or roof framing in occupancies in Use Groups R-2 and R-3, except where the joist depth exceeds 12 inches nominal or where the minimum uniformly distributed live load exceeds 40 psf (195 kg/m2).
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  #20  
Old 2/26/07, 1:15 PM
Robert J. OConnor's Avatar
Robert J. OConnor Robert J. OConnor is offline
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Default Re: Joist blocking

Homebuilt ... I didn't state that the WFCM is a code requirement, but it is a good reference from the IRC (including Chapter 43 & R301.1.1) that I have used myself as a chief building official to interpret the IRC based state code here in NY, and does not give as much latitude.

I guess we will just have to agree to disagree on what constitutes lateral support for joist ends under the IRC ... as just face nailing does not provide a continuous member (there are still ends) or provide the intended lateral stability ("lateral support" per IRC 502.7). I do agree the "legal" requirement is up to the AHJ ... but wearing that hat I wouldn't buy face nailing is "lateral support" for a minute.

Now, if the joist bottoms are adequately toe-nailed to a wood beam/wall (often omitted or done wrong ... and forget about a steel beam without a top plate) as well as the usual sub-floor joist nailing, in addition to the face nailing of laps ... then we could talk about possible "alternates" for lateral stability/support an AHJ might be able to accept.

JMO & 2-nickels ...



Robert O'Connor, PE
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LIU CW Post Adjunct Professor
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I am absolutely amazed sometimes by how much thought goes into doing things wrong ...

Last edited by roconnor; 2/26/07 at 6:17 PM..
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  #21  
Old 2/26/07, 1:55 PM
Jeffrey Wortham Jeffrey Wortham is offline
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Default Re: Joist blocking

I have to admit. I feel better now.

If so many of my esteemed colleagues, , are arguing over this, I don't feel like a moron for not knowing it when I looked at it.



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  #22  
Old 2/26/07, 2:08 PM
Robert J. OConnor's Avatar
Robert J. OConnor Robert J. OConnor is offline
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Default Re: Joist blocking

Quote:
Originally Posted by dvalley
So....In the long run, it all depends on what jurisdiction you are inspecting in.
For the "legal" requirement, absolutely. The old joke ... "the code is not whats written in the book ... the code is what the building official says is written in the book" ... actually has some truth to it.

For a Home Inspector a lack of blocking at joist laps over beams and walls is a "defect" (Reference Pg. 129 of "The Complete Book of Home Inspection" by Becker, Principles of Home Inspection" by C.D., et al).

If an AHJ later comes along and interprets that blocking is not a "legal" requirement for certian situations ... who cares. HI's do not enforce or interpret codes.

And an HI is not just looking for joist lap blocking over beams/walls. It is also considered good practice to have bridging (joist blocking or cross bracing) about every 8 feet max. The intermediate bridging/blocking is usually the sticky one for HI's (helpful to stiffen up floors, but controversial on if that should be flagged for 2x12 and smaller joists as it's not required by model codes) ... with blocking at joist laps the no brainier to look for doing a home inspection.

JMO & 2-nickels ...



Robert O'Connor, PE
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I am absolutely amazed sometimes by how much thought goes into doing things wrong ...

Last edited by roconnor; 2/26/07 at 6:11 PM..
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  #23  
Old 2/26/07, 2:20 PM
David E. Helm's Avatar
David E. Helm David E. Helm is offline
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Default Re: Joist blocking

I do not quote code, but in my locale, admittedly in a seismic zone, the local authority requires solid blocking at all bearing points. In my personal opinion, I would call the lack of blocking a defect (and have many times). Incidently, there is a recycled timber company not far from here. I recently saw, at their yard, 36' long 2X14's being loaded onto a truck for delivery.



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  #24  
Old 2/27/07, 8:12 AM
homebild homebild is offline
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Default Re: Joist blocking

Unfortunately, trying to retrofit 'codes' by home inspectors after-the-fact is really the heart of the problem here...

If an existing structure one is inspecting has been built to Code standards that do not require blocking between joists where they overlap a girder, then the installation is a legal installation and requires no correction...no 'calling out'. Period. The installation has been done correctly. Period.

The only time a home inspector may have some grounds by which to cite a suspected 'problem' such as the one we are discussing, is if he is inspecting a new building that is currently being constructed.

It is not uncommon for code inspectors to sometimes 'miss' standard inspection items and the home inspector has a better case of pointing out what he suspects is a 'defect' because the process is ongoing and the Code under which the structure is being built known.

Even then, however, it is ultimately the authority having jurisdiction, the code official, who gets to make the final call...and the Code Official has the authority to waive strict Code requirements when he deems fit.

Trying to point out supposed code 'defects' by home inspectors becomes a very slippery and extremely grey process in most instances, and a far less sound practice than that performed by Code Inspectors at the time of their inspection.

Appealing to 'Codes', then, becomes very difficult for home inspectors no matter what type of structure is being inspected, and without knowing the code in effect at time of construction or extenuating circumstances noted by the Code Official at the time, or even what portions of the Code that may have been stricken or amended for local adoption, quite impossible.

In my jurisdiction, if a home inspector tried to point out the non-blocked joists over a girder in the above photos, I would tell him he was wrong. I would testify to the same if ask for my opinion as a professional witness.

Blocking between joists a good practice where they terminate over a girder in a non seismic zone? YES

A requirement under Code? Absolutely not.

Last edited by homebild; 2/27/07 at 8:17 AM..
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  #25  
Old 2/27/07, 11:47 AM
Robert J. OConnor's Avatar
Robert J. OConnor Robert J. OConnor is offline
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Default Re: Joist blocking

Homebuild ... you have to understand that Home Inspectors are not doing a code compliance or code based inspection. It is an installation and performance based inspection, that really isn't about the legal construction requirements. Many HI's do use current model model codes like the IRC as a guide for installation related issues, and possibly certain local restrictions if they are aware of that. But apparent "defects" should NOT be flagged as a "violation". Only the local AHJ can make that determination.

One example is an older home with 2-wire circuits and all 2-prong non-GFCI receptacles. It may have met the local codes in effect at the time time of construction, and be completely legal (not known). That is for others to decide. But the receptacles should get flagged as a defect with a recommendation to upgrade the devices without a doubt.

Then take the example here of no joist lap blocking on say a home under construction where an HI is doing phased inspections. It is beyond a home inspection to know exactly what the local codes are, and sometimes more importantly how the local AHJ interprets those requirements. But the lack of blocking should get flagged, and let others make the call if thats not a legal requirement.

I have even recommended things on new construction that I knew were not a legal requirement of the local building codes. Locally it is considered good practice to add bridging in the middle for larger floor joists like 2x10's or 2x12's that are at the upper span limits (in addition to the rim joist attachment and lap blocking, locally interpreted as being required by code). So a lack of that bridging may get flagged, and it is then up to the client to decide if he wants to pay the framer to add the mid-span bridging that the AHJ doesn't require (as it's not an IRC provision or usually a "legal" local code requirement).

JMO & 2-nickels ...



Robert O'Connor, PE
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I am absolutely amazed sometimes by how much thought goes into doing things wrong ...

Last edited by roconnor; 3/2/07 at 12:35 PM..
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  #26  
Old 3/1/07, 3:54 PM
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William J. Decker William J. Decker is offline
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Default Re: Joist blocking

See Below:

Quote:
Originally Posted by homebild
Unfortunately, trying to retrofit 'codes' by home inspectors after-the-fact is really the heart of the problem here...

Not really. The miscommunication comes from arguing the point from two entirely different points of view: Builders (who are only held to local code standards) and home inspectors (who are, as far as liability is concerned, heald to a higher standard of practice, especially when there is a significant risk of personal injury or property damage).

If an existing structure one is inspecting has been built to Code standards that do not require blocking between joists where they overlap a girder, then the installation is a legal installation and requires no correction...no 'calling out'. Period. The installation has been done correctly. Period.

The above statement assumes that:
  • The house was completely inspected by the AHJ and the AHJ inspector actually did their job. This is, sadly, not always the case.
  • That the AHJ can, if there is a problem later, be held financially responsible for their mistakes (in the case that they missed it) or for their deviation from national standards (if the 'local code' is inferior to national standards).
  • There are many 'local codes' that are much 'looser' than national standards. Remember, local AHJ codes are usually more a political compromise than an actual technical specification.
  • A good home inspection (say, for a 4,000 SF SFH) will take about 2 1/2 to 4 hours. Are you trying to tell me that a local aHJ inspector takes that kind of time on a house?
The only time a home inspector may have some grounds by which to cite a suspected 'problem' such as the one we are discussing, is if he is inspecting a new building that is currently being constructed.

Wrong. Home inspectors are not local AHJ inspectors and have a higher duty to the client (and can be sued accordingly). Home inspectors cannot 'enforce' their recommendations, only recommend. Two different things. Two different standards. In fact, in license states, we are required by law to call out things that would, to a code inspector, grandfather out.

It is not uncommon for code inspectors to sometimes 'miss' standard inspection items and the home inspector has a better case of pointing out what he suspects is a 'defect' because the process is ongoing and the Code under which the structure is being built known.

We don't do 'mere local code'.

Even then, however, it is ultimately the authority having jurisdiction, the code official, who gets to make the final call...and the Code Official has the authority to waive strict Code requirements when he deems fit.

Especially when his palm is greased. (No offense, I live in the Chicago area )

Trying to point out supposed code 'defects' by home inspectors becomes a very slippery and extremely grey process in most instances, and a far less sound practice than that performed by Code Inspectors at the time of their inspection.

Again, in licenses states (where home inspectors require state licneces and contractors (usually) and local AHJ inspectors (almost always) don't), the standards required by law for home inspectors is higher. We work for the client, not the government.

Appealing to 'Codes', then, becomes very difficult for home inspectors no matter what type of structure is being inspected, and without knowing the code in effect at time of construction or extenuating circumstances noted by the Code Official at the time, or even what portions of the Code that may have been stricken or amended for local adoption, quite impossible.

Again, your assumption is that local code is the highest, and best standard. Not a valid assumption.

In my jurisdiction, if a home inspector tried to point out the non-blocked joists over a girder in the above photos, I would tell him he was wrong. I would testify to the same if ask for my opinion as a professional witness.

I have been an 'expert witness' many times. Once, I called out the lack of GFCI protection in a house built in the 70s. An electrician was called and he said it was OK 'per code'. Later, someone git an electrical injury from the lack of the GFCIs. I was sued. I won (because I called it out). The judge pointed out that the electrician's liability was limited to code. He also pointed out that mine wasn't. Different type of inspection, different level of service required, different liability threshold.

Blocking between joists a good practice where they terminate over a girder in a non seismic zone? YES

A requirement under Code? Absolutely not.
Why would a good contractor want to 'just get by', just do the bear minimum required by local law? Why not do the best practice?



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  #27  
Old 3/1/07, 7:17 PM
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Marcel R. Cyr, CMI Marcel R. Cyr, CMI is offline
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Default Re: Joist blocking

Quote:
Originally Posted by wdecker
See Below:



Why would a good contractor want to 'just get by', just do the bear minimum required by local law? Why not do the best practice?
Money!!!!

Nice Will.

Marcel



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