Grade Beam (V-Zone) Question

[USFEngineer]

I have a question regarding the location of a reinforced concrete grade beam. Is there any Fema or Building Code that specifies that the top of the grade beams must be at natural grade level? The reason I am asking is that we have designed a stilt home in a V-Zone that the county is demanding that the top of the grade beams be a grade level. We currently have them at -12".

I have never run across this before as a problem. They state that Fema technical bulletin 5-93 requires that all grade beams are at grade level.

Thanks in advance.

 

[msquared48]

There is a section in the publication you are referring to, but I do not read the intent the same as that of the county here. Look at page 6 of the publication under "Grade Beams".

The general intent of the publication is to prevent constructing any obstructions to floodwater flow which would raise the level of the flood. That being said, as long as the top of the grade does not rise above the NATURAL grade of the site, it is OK, provided that the grade beam has been designed to resist the effects of erosion and scour, which will occur with a flood, exposing the grade beam.

The fact is that the lower the grade beam, the less susceptible it is to scour. You are correct and the county is wrong here. Print out the publication, and include the paragraph with an explanation in your letter to them. Their requirement will make the structure more susceptible to the effects of the flood.

Good luck.



Mike McCann
MMC Engineering

 

[USFEngineer]

Thanks for the reply.

That is exactly my explaination in an email response to the head building official. There response is that this is there intrepretation and that is what I must do. I also discussed the fact I would be running into a problem with the elavator shaft if I raised all of my grade beams.

They even told me that if I was going to run into problems with the elevator to redesign my entire foundation using a different method. Needless to say we had an interchange of words. Either way, I have an appointment to meet with them on this issue on Wednesday. Is there any other method of going about this? If not, I do not think they are going to budge.

Thanks

Andrew

 

[msquared48]

Have you called FEMA and talked to one of their engineers for their reaction?

I would refuse to do what they want for safety reasons, and state so in writing. I would get their reaction in writing so the owner can sue the jurisdiction when his building washes away during the next flood. Ask thm how much liability insurance they have. The Cotrps of Engineers does have jurisdiction in flood control areas too. Talk to them too.

Mike McCann
MMC Engineering