Engg vs. Conventional Construction - residences in Florida

[elyengineering]

I'm interested to hear other engineers' experiences regarding use of conventional construction versus engineered designs for residences -- specifically in Florida.

My experience is as follows: have spent my career doing structural engineering in California (SF Bay area). Building departments here require engineering typically on custom homes, including modifications and additions.

Have recently been working in Florida and discovered that building officials in a particular county with 150 mph wind speeds do not require calculations to be submitted for residential designs. Including large, custom homes. If I'm correct, both the Florida Residential Building Code and IBC Residential both require engineering for lateral loads in areas where wind speeds are in excess of 110 mph.

 

[TFL]

I work in the northeast. it is my understanding that submittimng calculations is a west coast thing. no state in the east that i am aware actually requires the submittal of calculations. partly becasue no one is usually qualified to check them. tyically they just want a stamp on the plans to prove they were designed. which i personally think is more valuable. the plans are what they build from. it does not matter what the calcs say if the plans are wrong. i would rather see the time spent preparing better plans then calcs that are good enough to submitt.

many state have a peer review process were the owner hires a second engineer to peer review the plans for significant structures.

i would be curious what teh west coast people think of the value in submiting these calcs.

and yes at least BOCA, IBC and UBC codes have a line in it that says "shall submitt details and calculations" i don;t know about the sbc

 

[structuresguy]

I have been working in Florida for 6 years now. I have seen a recent trend of building departments requiring calculations be submitted. I was never asked before 1 year ago. Now in the last year, I have had several projects where this has been required. Mainly I deal in commercial world, but we also do condos and some custom homes. The last project it was requested was a single story tilt-up concrete 50x100ft classroom building with a concrete PSI joist and slab roof. I was very surprised they would ask for calcs on such a simple and robust building.

 

[archeng59]

why does a building official want calculations if the drawings are sealed and signed by a licensed professional engineer? Our office had to submit calculations along with sealed and signed drawings for a restaurant near Atlanta, Georgia. I've worked in Oklahoma for 10 years and never submitted calcs for any project here.

 

[henri2]

archeng59, I guess the calculations provide clear evidence that the structural drawings were based on actual structural analysis/design.

Look at it this way. This approach cuts out the individual who wants a quick buck and is prepared to kick back and just stamp drawings presented by a non-engineer and it also creates more work for those engineers who truly design.

I have not done any structural design in ages but out here in So. CA, calculation submittals (when I designed) were required for the majority of bldgs except for most typical Group R-3, Type V residential dwellings. Structural plan checkers would go through the calcs thoroughly.

 

[elyengineering]

Here's my perspective --

For design of structures that are not in seismic or high wind areas, I concur -- there's no reason to submit calculations, provided that a building is within the limits of conventional construction.

However, for design of structures within high seismic, or high wind areas (we're talking about a jurisdiction within 150 mph wind zone), the design of an engineered structure -- i.e. based on code level lateral forces, will be a wholly different animal from same building built by conventional construction methods. The lateral-load-resisting system will be entirely different, significantly beefier, by the engineered method.

As far as roles go, of course it's the responsibility of the designer to design according to the code. If my interpretation is correct, conventional construction does not apply even to residences in 150 mph wind zones. Does responsibiity apply only to designers? Only the building department has the ability to ENFORCE the code.

Bottom line - by my interpretation, wood framed residences, per the Florida Building Code (or by IBC measure) are required to be engineered where wind speeds are in excess of 110 mph.

One reference in particular is table R602.10.1, "Wall Bracing" of the 2003 IRC covers areas only up to 110 mph.

 

[TFL]

I hope this is not hijacking the original thread....

I completely agree that calculations are required by code for most buildings. I just don't know if i see the value in it. If the person who receives the calculations is qualified to review the calculations; then they should be qualified to do their own calculation if they think something does not work. If they are not qualified to review them, why am I taking the time to make them?

If with my experience, expertise and professional judgment i am completely comfortable designing a structure with no calculations and am willing to stamp it, why should anyone argue with me.... unless is does not work. If it does not work, sue me, discipline me what ever.

 

[archeng59]

most of the building officials and plan reviewers that I know are not structural engineers. some of the people in Oklahoma may have a background in construction or architecture. what about those in the western states? I've worked with the state fire marshal in Oklahoma to perform plan reviews. As an experienced structural engineer, I was able to look at the drawings to determine if they appeared to be properly engineered without needing to review calculations.

 

[azcats]

Many of the plan reviewers in the Phoenix area are registrants and understand structures and the code. Their reviews are incredibly detailed at times...sometimes to the point of being annoying.

Honestly, it seems really weird to hear of you guys submitting plans w/o calculations. Unless it's just an architect asking for a beam size, we always send calcs along with the drawings.

 

[EddyC]

Are we talking about doing the calcs and submitting them or doing the calcs and not submitting them?

 

[UcfSE]

We don't typically send calculations unless they are specifically reqested and are part of the contract. Usually this is for south Florida commercial projects and specialty engineering projects.

 

[elyengineering]

I find it weird.

It appears to me that not only are the calcs not being submitted/reviewed, but that they're not being done. The common practice seems to be conventional in Monroe County, Florida, where it should be engineered designs.

I would expect to see SOME level of review by the building official. Enough to determine that a design is engineered where necessary.

 

[archeng59]

in my opinion, if an engineer puts his seal and signature on the structural drawings, the engineer is guaranteeing that the building meets code and is safe. If the engineer is willing to accept the liability for preparing a design without doing calculations, that's up to the engineer. not good practice, in my opinion, but that's me. I perform calculations for every project I work on. None of my projects are generic enough not to do calcs. pardon the double negative.

 

[TFL]

eddy c,

I am talking about doing what ever calcs you feel needed to design with competance, putting them in a file and leaving them there until needed.

do i need to write down that 2X10s at 16" o.c. can span 10' in a house to make it ok?

I just think having to take the time to "pretty up" my calcs and send them in eliminates some of my efficieny by having to over document things for little perceived benefit. that being said certain things obviouly require calcs to be done regardless of the submittal required.

 

[elyengineering]

TFL -- I don't think you need to include 2x10's @ 16" oc in your calcs. I think that'd be quite optional.

However, for lateral-load-resisting system, I'd expect to show: What are the wind forces acting on the building?

What are the shear forces in the diaphragms?

What is the shear load in a given line of shear walls?

What is the uplift on roof framing members? What are the overturning forces in the shear walls?

The basics of an engineered lateral-load-resisting system, where an engineered system is required.

 

[henri2]

The IAS accreditation program for building departments and ISO (Insurance Services Office) Building Code Effectiveness Grading Schedule program may influence the position jurisdictions take in the future regarding submital of calculations..and also duties expected of plan check engineers.

Check these links:

http://www.iasonline.org/PDF/AC/ac251.pdf

Sec 5.0 with particular emphasis on Sec 5.4

http://www.isomitigation.com/bcegs/0000/bcegs0003.html

scroll down to Sec 1 and check sub-heading Review of bldg plans

http://www.iccsafe.org/news/nr/2005/0131IAS.html

for memorandum of understanding between IAS and ISO

 

[elyengineering]

Very helpful. Didn't know such a thing existed -- thanks.

I've also contacted the Florida Structural Engineer's Association to chat with them about code enforcement.

 

[JStephen]

I would be very interested in the responses if a structure failed, and the plan checker was then sued for negligence. With authority comes responsibility. We have some customers that require calcs, but will not review them or comment on them for exactly that reason.

 

[elyengineering]

Hi all and thanks for your input -- all was helpful.

FYI -- I've done some homework. According to the Florida Buildig Code,

a) conventional construction not allowed in zones > 100pmh basic wind speed (Sec. 2308.2)

b) minimum plan review criteria includes submittal of engineering calculations/wind requirements, where calcs are required, per above. (Sec. 106.3.5)

c) "The building official shall examine or cause to be examined the accomanying construction documents and shall ascertain by such examinations whether the construction indicated and described is in accordance with the requirements of this code and other pertinent laws and ordinances." (Sec.106.3)

It's all there in the code. I've written a letter to the building official in the subject city/county with all the above info. Will see how this goes...