signage footing requirements?

[hans@dha-architects.]

I can't find anything in the code regarding this, but we've got a monument sign going in for a building, about 9' long x 3' high x 12" wide, with a 3' section of it at 6' high x 24" wide, all made of brick, is it necessary to sit this on a 42" deep footing? my engineer seems to think so, but that just seems overkill - I'd think sitting it on a 3' x 11' x 8" thick slab, set about 6" below grade on 6" of gravel would be sufficient, no? IRC allows structures of 400 sf or less without frost protection, so not why this wouldn't fall under that exception (although the project falls under IBC)

 

[jar546]

Wind load has a big effect on this along with frost depth. The IRC has nothing to do with this project. It has to be engineered. There is nothing prescriptive about it and the "I think" part does not count.

 

[Mark K]

You won't find proscriptive provisions in the IBC or IRC for signs.

You will find provisions in the IBC that allows you to find the forces which will allow you to determine the size and depth of the foundation. Typically only engineers know how to perform the calculations. In such situations the engineer will consider what he perceives to be the best/cheapest solution

You can ask your engineer to explore another configuration but who pays for the additional time the engineer will have to spend. In my experience the initial solution of the engineer is not far from the optimum

Have you considered the consequences of frost heave with the smaller foundation?

 

[Sifu]

Appx. H, in the unlikely event it was adopted. I use it for guidance in the absence of adoption, and it directs the sign to be designed to resist wind load.

 

[steveray]

Frost protection you can get out of.....Not structural.....

(Amd) 1809.5 Frost protection. Except where otherwise protected from frost, foundations and other
permanent supports of buildings and structures shall be protected from frost by one or more of the following
methods:
1. Extending a minimum of 42 inches (1067 mm) below finished grade;
2. Constructing in accordance with ASCE 32; or
3. Erecting on solid rock.
Exception: Free-standing buildings or structures meeting all of the following conditions shall not be
required to be protected:
1. Assigned to Risk Category I, in accordance with Section 1604.5;
2. Area of 600 square feet (56 m2) or less for light frame construction or 400 square feet (37 m2) or
less for other than light-frame construction; and
3. Eave height of 10 feet (3048 mm) or less.
Shallow foundations shall not bear or be installed on frozen soil.

 

[e hilton]

my engineer seems to think so, but that just seems overkill -

The engineer will provide stamped drawings for his design … can you do that for yours?

 

[fatboy]

We require engineering.

As Jeff said, not in the prescriptive IBC.

 

[classicT]

See https://codes.iccsafe.org/content/I...oils-and-foundations#IBC2021P1_Ch18_Sec1807.3

 

[fatboy]

Looks like engineering to me.