Footing Question

[Son_of_Izzy]

We are in the process of replacing our rear deck and want to address some water drainage issues as part of the project. In the past, large amounts of water have flowed by our deck during heavy rainstorms. To address this we plan to do the following:
Improve the grading out from our rear foundation wall.
Install a curb at the perimeter of the deck to divert water away from the deck and building foundation.
Grade the ground outside of the curb so water flows towards a storm drain in the common area adjacent to our new deck.

Another function of the curb will be to support Simpson CBSQ66 post bases wet set in the curb that will support the outer deck beam. One of the requirements for the Simpson CBSQ66 post bases is that they have a minimum of 3” side cover in concrete. Since the post base is 6” wide, I have to add 3” inches of side cover to each side which gives me a 12” minimum for the curb width. According to what I have read about concrete footings on this site the footing has to be 2x the curb width or 24” and the depth is the same as the curb width which is 12”.

Based on the above I end up with a 30’ long footing that measure 12” deep by 24” wide.

I have the following questions:
Must the footing be 12” deep or would 8” be sufficient for this application?
Is drainage rock required under the footing?

DECK DRAWING SIDE VIEW

http://www.fototime.com/BFACEC312F17912/orig.jpg


DECK DRAWING TOP VIEW

http://www.fototime.com/211B599811F7E82/orig.jpg


VIEW OF PARTIALLY COMPLETED FOOTING TRENCH

http://www.fototime.com/A45ACF481346A5F/orig.jpg

[Rich]

Quite honestly I would build the curb and footing as the same thing.. create a 12" x 18" stemwall. Most likely the discussions you've read about footings on the site are in relation to a home built on top of it.
Drain rock isn't absolutely necessary in this instance, but may help with any water that gets inside your drainage curb.

[Son_of_Izzy]

Thank you for taking the time to read my post and reply.

Is this what you are suggesting?

http://www.fototime.com/77FB33EF85DDD45/orig.jpg

[Rich]

Yep. Good graphic drawings too (a picture is worth a thousand words).

[Son_of_Izzy]

Rich,

Thank you for your suggestion. I did not realize the footing could be eliminated. This will reduce the amount the concrete needed for the curb by 46%. We just need to dig down another 8” if we are not going to use drain rock under the curb. Maybe we should dig the last 8” only 12” wide and use the side of the trench to form the lower part of the curb. NOTE: We do plan to provide drain rock and pipe on the inside slope of the curb.

Howard


http://www.fototime.com/8418519FEDCD73C/standard.jpg