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

 

[msquared48]

When you are talking trusses, I do not see how this will be an extra $600.00 when the trusses have to be designed aqnd stamped by a Structural engineer anyway...

Are these new or existng trusses, or, new or existing stick framing, that the article was referring to?

Mike McCann
MMC Engineering

 

[TrussRay]

This is a retro fit application. The truss, joist, rafter, beams etc. have to be reverse engineered. We do stamp the engineering & cover letter, same as a tenant improvement.

Regards,
Ray

 

[msquared48]

Got it...

Mike McCann
MMC Engineering

 

[hokie66]

It does sound like overkill to me to require engineering evaluation of houses for installation of solar panels. They don't weigh much, unless you are putting storage tanks on the roof.

Our populist government in Australia is giving $8000 rebates for installation of solar panels. As far as I know, no individual structural assessment of the roof is required.

 

[TrussRay]

That's true they don’t weight much PSF. The problem is that the installers are having to be more and more competitive and pushing the capacity of the railing system w/ as few roof penetrations as possible. In some cases the clearspan is 6' wide and 5' deep with connections (depending on the installers application) having a single leg supporting 2 arrays (doubling my trib area).

It's not just gravity that causes issues, its wind. The added dead + wind tend to fail in combined stress on the top or bottom chords (tension / compression + bending). The other wind issues are where these systems are on a flat roof and on a tilted mounting system sloping +/-30 degrees. I’ve now got a sail to worry about with positive and negative pressure (rotation) on the same member. Longer truss spans (esp. scissors / vaults) tend to fail in gravity loads. Most solar applications perform fine on the structure, 5% or so need recommendations.

Most importantly, who is liable at this point? There is no engineering, the city say it's ok, there is no solar warrantee & the only way a homeowners insurance policy will pick this up is with engineering. I would have to imagine that people purchasing solar panels and placing them on their property would be asking this question.

 

[RVSWA]

For existing conditions just have them remove 4 of the 5 layers of old roofing material to reduce the weight so you can claim you've improved the structures performance.

 

[TrussRay]

That’s assuming asphalt shingles exist & multiple layers have been applied. I have seen some remove the tile and lay shingles for those locations where the solar is being located. This proves to be a much better application however, the questions remains. Who is responsible?

If framing were done the same perhaps I could take comfort in that a case study could be made. Every home is usually framed by a different contractor with many crews who purchased lumber & trusses from one of many suppliers.

 

[frv]

Here's a thought- nobody is going to be walking on top of these things. Do they weigh more than 12 psf? If not, they essentially would replace the roof live load, wouldn't they?

Of course, your load duration factor is more severe for dead than roof live, but at least that's a reasonable way of looking at it, in my opinion.

BTW- I'm not familiar with the IRC. Are the roof live load requirements the same as in the IBC? (That's where I got the 12 psf- this is "worst case" in the sense that I'm assuming the members were originally designed for the lowest value allowed in the IBC)

 

[TrussRay]

This is the strongest argument that has been brought up and could be valid as long as it’s construction live load. It still doesn’t mean that the members below would perform successfully. Once you move into elevations where snow is figured, the snow live load couldn’t be substituted for dead load.

Once these structures are modified, do they get brought up to existing building codes (the modified supporting members)? UBC vs 2006 IRC / IBC poses new wind issues that can cause components to fail by that change alone. How would one go about checking an existing member, following the original building code and NDS values?

How many of us have seen this condition (see photo). A typical framer might just pass this on because it is often their doing. In a framers world this can be considered normal practice. They need working access to fit an FAU and make it happen. What are the chances that a solar installer would even know to be looking for this? After all, their concern is above not below.

As far as the 2006 IRC vs the IBC, yeah there are some differences. With the IRC typically the live load use is 20 PSF for slopes less than 18.43 degrees and 16 PSF if they are equal to or greater.

By the way, thank you for everybody’s input so far. I've been challenged with these very issues and only want to do what is correct. Solar is a wonderful product and there are many advantages offered for it on both state and federal levels right now. I disagree with those that on one hand claim that solar is for the preservation of human health, and on the other hand claim that having to review it structurally is a deal breaker. It’s not that 95% of these projects work fine, it’s the potential for one of the 5% to go terrible wrong.

 

[SteelPE]

I saw a news report yesterday where a family was being charged $100,000 (I think) to convert their house to alternative energy (solar and geothermal). After government rebates (state and federal) they were paying $53,000. I can’t believe $1000 would be a deal breaker.

 

[hokie66]

And I can't believe anyone would pay that much to convert to any system when the one they have works fine.

 

[jheidt2543]

"It isn't easy being green"
-Kermit the Frog

 

[civilperson]

For the price of the engineering analysis, build a steel support system back down to the ground and share the lateral loads with the structure. I do not trust stick built homes to be engineered, just built by rote and with empirical rules from carpenters and codes.

 

[TrussRay]

Let's be clear about this, the materials & labor to apply such a system alone would cost more than the $600.00 we charge for a (typical) residential review. The design and profit should be double of your cost. Every house is unique and under different conditions. Take for instance, a 2 story single family house in Ohio verse California. Each varies in shape, building code and loading conditions with respect to the elements they are exposed to.

As far as engineering is concerned for houses, this is exactly the point. Whether your home is manufactured with dimensional lumber / rafters / beams OR trusses / wall panels, the idea of knowing what happens when we apply something new is important. This is not only because of it being responsible, but because it’s an opportunity to validate the actual existing conditions.

Field Issues:
• Poor quality or incorrect material is used.
• Handling of material causing damage to members prior to installation.
• Components installed backwards & or upside down. I've worked on repairs for a house (just outside of Las Vegas, NV) where a contractor installed floor trusses upside down, backwards & cut the "extra length" off. (there was no extra length – trusses were used @ incorrect locations)
• No bracing installed (temporary or permanent).
• Removal of sections of top chord, bottom chord or webs. I’m working on a house now where the homeowner cut top chords & webs from multiple trusses to lay (2) layers of plywood for larger storage & walking area in their attic.

Let me pose another question:
Shouldn’t a building & safety department require empirical data before it takes makes such a decision of not requiring an engineering review for solar installation? It seems that the burden of proof should be in the form of data, not some swagger words from a lobbyist.

 

[kslee1000]

My personal opinion:

I think City has no business to make the call, as it is not a explicit public safety issue. Rather, it sould be settled between the house owner, and his/her insurance company. Why we want the government tell what we can do or not? Unless you believe the society we are in has more dummies than people have common sense.

 

[JedClampett]

IMHO, these kind of issues have a way of resolving themselves. The installer whines about having to involve an engineer, which reduces his bottom line. The City backs down on the requirement. Eventually there's a problem or a series of problems. The insurance companies do their due diligence and blame the solar installer. He realizes that it's cheaper to get the engineering done up front rather than have a fight on his hands. He'd rather pay an engineer (where he can recover his money) than a lawyer.

 

[kslee1000]

Jed:

Yes. Isn't that all this society about - free choice at your own risk, which is to be balanced by who pays the bill when things fail (the insurance), and those to representing all involved in court (layers). Let the system works its own way out without politics. Too messy already.

 

[TrussRay]

kslee1000:

With that being said, I should be allowed to build my own home, with my own money, no permits, no engineering that I could sell to someone else later on down the road?

How would it make you feel knowing that your 2 year old daughter could be sleeping in a room, under a roof that is supporting 35psf and is composed of DF 2x10 @ 24" O.C. with a clear span of 24'-0"? It looks good, does that make it valid? There is a reason society has developed CBC, IRC, SBC & IBC and they are not relying on common sense to save cents.

 

[kslee1000]

New construction is part of public concerns. Once you bought it, what ever you want to do is your own business, unless major changes that may jeopardize the stability of the house, thus endanger your neighbors, and innocent passing-bys.

Many things has potential to kill use - a gas range, a boiler, bath tub...Do you want everything to be reviewed by a professional engineer? Oh, the baby cradle kills too (more often than roof).