California Surveyors Forums

Hello.

I've been asked to revise an el. cert that we did back in 2008 and put the same data on the current form per request of the insurance company. One of the questions on the current form is whether the openings were engineered or not. This was not on the previous form. We had indicated the openings with the number of them and the square footage of such. I am unsure whether those openings were engineered or not then. What should be indicated on the new form here? Thanks.

"unknown" after I talked to the owner. Most owners don't know cause they weren't around at the time of construction, and even if they were, would they think to ask?

From looking at photos, they look like just regular old mesh vents. I'm not sure if those would be classified in 2008 as "flood openings" or not.

mesh vents qualify fine for non engineered vents providing the bottoms of the vent are within 1 foot of the adjacent grade. Each 1 square inch of actual opening (subtract the mesh) will provide enough opening for 1 square foot of building enclosure.

Engineered vents on the otherhand are specialty vents which have engineering documentation on their ability to pass flood waters. Oftentimes these are used only in special circumstances, such as when one wants a vent which is sealed closed until the flood waters occur. Or, when due to space limitations don't allow room for vents and 1 square inch per each square foot is insufficient, that a superior hydraulic capacity vent is desired which has engineering analysis performed to show each 1 square inch of opening will provide a better hydraulic characteristics than required for the regulation minimum of 1 square foot of building enclosure. Some common, commercially available flood vents go by trademark names such as SmartVent, etc.

Hope this helps, if not, take a look at FEMA Technical Bulletin # 1, 2008, found here:

http://www.fema.gov/media-library-data/ ... _1__1_.pdf

There is some good flood opening info here:
http://www.smartvent.com/professionals/ ... /surveyors

In addition, only the flood venting that is below the BFE can be counted.

Another consideration for the installation of flood venting in an existing T-foundation stem wall, would require a structural engineer to evaluate if the foundation still meant the requirements for earthquake, etc...

LA Stevens wrote:In addition, only the flood venting that is below the BFE can be counted.

Can you point me to the reference?

Anthony,

If a portion (or all) of a flood vent is above the BFE, how can that portion provide equalization of hydrostatic pressures?

Cap'n Aueb V. Us.

Thanks for all your responses. I looked at the Smart Vent literature and I think the vents that are on the unit I did are classified as "flood openings" and are definitely not engineered.

Mike,
You should have attended the CLSA Conference as Sarah Owens from FEMA Dist. 9 (Oakland) made a presentation.

Larry, nowhere in the instructions, or her presentation made the reference to only the openings below the BFE can be counted.

Taken from the FEMA Bulletin No. 467 which is still valid "The bottom of each opening can be no more than 1 foot above the adjacent grade."

I have attached the FEMA Bulletin No. 467 for your reference

Keith,

How in the world would that portion of the flood vent which is above the BFE, provide hydrostatic equalization during a 100-year or lower flood event? The whole NFIP and building requirements are based on 100-year event being the maximum and the venting is also to be designed for that same event status. If you want to count vent openings above the 100-year BFE, then you are designing for statistically less frequent event. Designing for a less frequent and increasingly more dramatic event, would require re-evaluation of base assumptions and conclusions. Such as whether 1 square inch of opening per square foot of floor plan will provide adequate rate of equalization for a flood event which may have a more rapid rate of rise.

So long story short, no, absolutely no, and heck no, vent portions above the BFE cannot be counted. They provide absolutely no purpose in a 100-year or lessor event.

Lets agree to ignore hydrostatic pressure, and other engineering principles.

I'm talking about a governmental form with instructions on how to count the vents, "count those within 1 foot of NG."

The instructions do not say "ignore those above BFE." If I'm wrong, tell me where in the instructions that is or link to a hand out.

Anthony Maffia wrote:Lets agree to ignore hydrostatic pressure, and other engineering principles.

I'm talking about a governmental form with instructions on how to count the vents, "count those within 1 foot of NG."

The instructions do not say "ignore those above BFE." If I'm wrong, tell me where in the instructions that is or link to a hand out.

Besides common sense, here's your citation. From pg. 17 of Technical Bulletin 1-93 on Openings in Foundation Walls for Buildings Located in Special Flood Hazard Areas (FIA-TB-1) http://www.fema.gov/media-library-data/ ... _1__1_.pdf

"Only those portions of openings that are below the BFE can be counted towards the required net open area."

Guidance also found on page 13 of Tech Bulletin 1-08 in addition to page 17 dedkad referenced.

Anthony and Keith, note that I referenced this same bulletin in this thread on 3/18 in hopes the curious and un-enlightened would actually read it. It is disappointing that you took no initiave to actually read a very informative guidance manual which gave very clear answers to the subject matter.

Well then William,
I must say in all the years of multiple training sessions by FEMA, they have never pointed this out correctly, so thank you for clarifying this.
As all good surveyors should realize, we need to continue learning and this only supports our efforts. Kind of disappointing that a FEMA employee(s) would speak incorrectly as to what really is needed, and to do it at the CLSA Conference is not good.

Now additional time will be needed to calculate each opening, time to revise estimates, lol.

Good morning Keith,

Please correct me if I'm wrong, but I don't remember that the presentor spoke incorrectly. Just like the instructions on the elev cert, guidance that the bottom of vent must be within 1' of grade is not speaking incorrectly as to the limitation on the location of top of vent.
I'm pretty sure the presentor never said that the top of vent could be higher than the BFE. I'm quite sure if she had that I would have stood up and made issue of that. Not addressing a situation is not equivelant to being incorrect.

Jeff

"..........ONLY THOSE PORTIONS of openings that are BELOW the BFE can be counted towards the required net open area. Stacked vent devices may be installed or large-dimension openings may be provided (Figure 13). In both cases, if the BFE does not reach the top of the opening, ONLY THE PORTION that is BELOW the BFE will count as contributing to the required net open area......"

IMO, this should be submitted to a regional FEMA office for clarification with regards to the preparation of Elevation Certificates by surveyors.

The handout is largely geared towards design professionals, and is older than the current form and its instructions.

Perhaps asking the question will send a signal that the instructions for the form should be revised before the next update comes out this year. The current form expires in a few months.

Anthony said it, but I had already done it. After realizing there are two valid definitions to calculate the vent space I sent an e-mail to the District 9 Office in Oakland asking for clarification since it was not mentioned at the conference per Technical Bulletin 1 (TB1). Only Fema form 467 was discussed. TB1 has caused a lot of confusion in the surveying community, and some pushed back when TB1 was discussed at other presentations.

This is where there is confusion, because both documents are correct. Others have previously inquired, so headquarters was asked to clarify the correct method for calculating vent space. They had a long discussion with their different departments and are supposedly coming up with a policy to clarify that. Until a policy comes out, surveyors are supposed to collect the dimensions of the vents within a foot of grade and that FPAs are supposed to figure out how much is below BFE. (per 467)

It was suggested if you take the additional time to be specific and calculate the vent space below the BFE per TB1, that you clarify that in your comments.

So yes I have learned something, but not really, have you?
Looks like FEMA has even more conflicting issues at hand other than FIRMs with grossly incorrectly plotted zones.