Structural Reviews 4

[TrussRay]

Please read this quote...

“Peoria now, for example, is requiring a structural analysis by an engineer on all homes that put solar on. That’s a deal killer. If you find an engineer who is cheap, you may get by with $600, more likely $1,000, for every system. In a sense, Peoria is saying they don’t want solar on their homes,” Neary said. “It’s generally a deal-breaker.”

I provide the structural engineering for many of these. When this quote came out in a local publication the cities reversed their positions. The issue I have with this is there are many valid reasons to provide engineering for these. Why is it, that money for a structural review is governing the safety of human life? As I recall, that's why we're all doing what we do.
I'm currently putting together a PowerPoint presentation to my local MAG committee. If anybody has any opinions, ideas, feedback whatever - I welcome it.

If you would like to see the rest of this article:

http://utsolar.org/index.php/news/article/renewable_energy_bills_piling_up/

Regards,
Ray

 

[kslee1000]

I will check everything before purchase. But in no way I want the Government to tell me to get a engineer simply it (the items listed above) has potential to kill me and my cared ones. However, the government has an obligation to provide the best info it can provide to keep people educated on certain risks. Then, choice is mine.

 

[TrussRay]

kslee1000:

It's not about how you feel, it's about the laws that have been made based on past experiences. I’m not concerned with how courageous you are as a risk taker, I’m concerned about being a professional and providing a service that should be mandated as necessary. Read the code yourself:
• IRC 2006 Section R502.11.3
• IBC 2006 Section 2303.4.1.7
• Truss members and components shall not be cut, notched, drilled, spliced or otherwise altered in any way without the approval of a registered design professional.
You have the choice to choose whoever you want to in selecting engineering services. Nobody is making claim that you have to choose anyone particular, just that you should have specific conditions reviewed.

 

[kslee1000]

The argument will never end. Basically, the least govenment rules on way of live the better, even in our choosen profession. It's time for me to butt out to leave room and space to others to draw their's lines. Good discussion though.

 

[JoshPlumSE]

TrussRay -

Here's what I would suggest. Find as many good examples (with pictures) of roof failures for residential construction as I can. They don't have to be specifically related to solar panels. But, they should be the types of failures that you are concerned about with the panels.

Any presentation you give should involve a liberal of this pictures and the cost to the homeowner and such of these damages.... After all, a picture is worth a thousand words.

If you can't find good examples of this sort of failure, then I don't think your presentation will be very convincing... except to the technical minded like us engi-nerds.

Josh

 

[JoshPlumSE]

On a related note, I remember some of the post-Northridge Contractor - Owner - Engineer conversations. They went something like this:

Contractor to Owner: Your engineer is screwing you by driving up the cost with these ridiculous moment frames around the garage opening. I've been doing this type of construction for 30 years. Trust me, this engineer doesn't know what he's doing....

Engineer to Owner: Well, it's certainly true that people have been doing it his way for 30 years. Then there were a bunch of failures and even some fatalities during the Northridge earthquake because of it. That's why we do it differently now.... I can show you the post-disaster investigation pictures if you like. I've got a buch of reports on the subject in my office, come by anytime to take a look.

Those sorts of pictures give us the ability to "prove" to the owner (or architect) that we're not just overly conservative academics who don't understand the real world of construction. Because we know that is how we'll be painted by contractors.... at least those who've never seen their structures go through a design level e-quake, or hurricane.

Josh

 

[NITTANYRAY]

One item I have found in many structures that use wood roof trusses to be lacking is the lateral bracing for the web members. If the contractor is not told to install it it usually doesn't get installed. Even a small additional dead load placed on the roof could cause problems.
It is hard to explain to a home owner how the "Building Inspector" didn't see this defect.

 

[bdruehl]

ive seen the no dead load anymore argument for analyzig solar panel roofs. check to see when the roof was built/installed, if there was a permit for construction, and review the member sizes (truss,stick, or ridge beam construction). i am very interested if anyone can speicfy the exact code (cbc) where it would directly address that argument could be considered a faulty argument. like other posts and discussions ive read, might as well force the owner to have the original truss manufacturer analyze the truss again, cuz many of the values are proprietary (nevermind the truss plate forces which is where i think the magic happens)...

a roof that was built to code in the last (30 years?) should be able to handle a typical solar panel roof load... after review by a professional for obvious shortcomings. i think this subject could easily turn into ..."must analyze the entire house because of increased dead load..." that would also technically be a valid statement as well...

 

[TrussRay]

dbruehl,
California adopted the 2007 CBC, which is based on the 2006 International Building Code (IBC) with ammendments, the specific reference to modifications is as follows:

IBC 2006 2303.4.1.7 – Alterations to trusses. Truss members and components shall not be notched, drilled, spliced or otherwise altered in any way without written concurrence and approval of a registered design professional. Alterations resulting in the addition of loads to any member (e.g., HVAC equipment, water heater) shall not be permitted without verification that the truss is capable of supporting such additional loading.

As far as other areas of review, if the building codes state it then one should follow it.

There is more supporting evidence in requiring a structural review than there is otherwise. To my knowledge, there is no testing or data that qualifies all homes built will provide the necessary support of 4PSF dead load. In almost every discussion about this topic the areas avoided are wind, seismic & snow. Just for the record, it is not ok to use live load for dead load. Live load is a short term loading scenario and in all the calculations performed take advantage of it.

In my research I’ve found that the state of Oregon is a big supporter of green technology and the state building code reflects very specific guidelines for when a review is necessary and when one is not. I believe that this state has it together.

I spoke to Ravi Mahajan (P.E., C.B.O. Structural Engineer) from Clackamas County Oregon and they have posted the following:

http://www.co.clackamas.or.us/docs/dtd/solar.pdf

Ravi also was a contributing member of the OBC.

 

[hokie66]

I think you misspoke about the meaning of live load. "Live load is a short term loading scenario" need not be true. Otherwise, your arguments all make sense, but I still think reevaluation of roof framing just for installation of a few solar panels is overkill. Maybe your solar panels are heavier than the ones I am familiar with.

 

[TrussRay]

What I mean is that 2005 NDS allows the C_D (duration of load) to bending, tension and compression checks by 1.25 (7 day) for live construction verse the 1.0 (10 years) for dead loads. So therefore the allowable bending, tension or compression is higher when evaluating a 7 day load (short term) verse a 10 year (long term).

 

[hokie66]

Fair enough for short term loading, but a live load limited to 7 days is a rare occurrence.

 

[frv]

TrussRay-

I don't have my NDS in front of me, but I'm certain DL only Cd is 0.9. Floor Live Load is 1.0.

hokie- the 7 days is cumulative. All Cd factors are based on cumulative time the member is exposed to load pulses exceeding some value.

 

[TrussRay]

Correct, table 2.3.2 defines it as a permanent load (.9) – thank you for the clearification.

 

[StructuralEd]

My brother installs the systems here and they average $50,000.
I'd say $600 - $1000 is insignificant based on that.

There is good reason that requirements like that are put in place. Contractors who either don't know better or are irresponsible do things to potentially make buildings unsafe.

We had that go around here when "ballasted" roofing systems became all the rage many years ago and many buildings were loaded up without regard for design loads..

 

[cvg]

a residential roof top solar water heating system doesn't even approach $50,000. Typically they cost somewhere in the $5,000 to $10,000 range for residential use. A $1,000 permit fee plus $1,000 engineering fee is a 20 - 40% surcharge and with perhaps $250/month savings on your utility bill would increase the payback time by up to 8 more years. Yea, I would say that would be a deal killer for me.

 

[TrussRay]

Cvl,

With the older roof top solar water heaters, there was a much larger dead load imposed in a small concentrated area. If these are the systems you’re using then you should be getting engineering. Typically, these units are only affecting one truss type and the cost on this form of service is more like $400 (from our company) unlike the solar arrays. If your company uses an engineer and you have a consistent volume your price could even be lower. Most likely your using a newer systems that lay flat over the plane of the roof surface and run a constant stream of water through the roof top and into a tank mounted somewhere on the ground. This type of system is much lighter & uniform which does not have to deal with uplift. But, I would say that you’re still penetrating into the roof with places you into a grey area that nobody addresses (which I’m sure is fine anyhow).

The point is that if you’re paying $1000 for this type of review then I would suggest shopping around.

 

[TrussRay]

I'm sorry cvg - I'm not sure how to edit these and I misspelled your member name.

 

[cvg]

I'm not paying for any review or installing any kind of solar panels, just commenting on the fact that for a project like this with a $1,000 review plus a $1,000 permit fee (as was described in your link) would indeed be a deal killer for a $5,000 project with a payback time in the range of 20 - 30 years or greater. that may exceed the lifetime of a typical mortgage and is certainly not an incentive for anybody to retrofit solar heating on their house. The review plus permit fees will certainly be a disincentive to the average homeowner, especially in the Phoenix area which has been hit by the economic downturn perhaps as hard or harder than any other location in the nation (although Detroit is probably now giving it a run for its money). However, I agree that depending on what is mounted on the roof, a structural review is probably a good thing and perhaps could be shown to increase safety.

 

[FSS]

I love how some folks complain about having to get an engineer involved with residential construction. Last time I checked, when storms are brewing not too many people pack up and run to their engineered office buildings.

 

[racookpe1978]

Notice the original complaint came from the "enviro-lobbyist/propagandist/writer" as they regretted that a safety analysis check was a deal breaker for more people to not get the green-friendly/uneconomic-without-subsidy solar mods.