Decks, Patios, Porches and Docks - Concrete Post Anchors

I've just got a permit (good idea?) for my shade pergola but they tell me I need to have 12"deep 24" sided concrete bases for the posts - I already have a good concrete slab (>3.5") where the posts will be, do I really need to cut through the slab, dig down, then refill it all with concrete? I was planning on using Simpson anchors. I live in SoCal, so I understand the earthquake potential, but this seems rather excessive....

Yes, the permit was a "good idea" -- as a matter of fact, it was a GREAT idea!

24" sqaure cubes that are only 12" deep?? Man, you got off easy. It's more than just earthquakes -- mostly it's wind loads.

(When I put in my little 10' X 12' sunroom, the cornerposts were set in 24" cubes that are 42" deep!!) ((The aluminum posts are embedded 36" deep into that cube!!))

I know -- it may seem like overkill (and a lot of 'big brother' stuff) now, but if you ever sell the house, and the realtor asks about permits for the pergola, just pull out the permit for it, and you are home free. EVERYBODY is happy!

OK, thanks, I feel better about the permit. Still not convinced about the 12" deep holes - this pergola is totally open, just a couple of 4x4 posts with a couple of 2x8s across a span of 16ft with a few 2x4 rafters 20-24" spacing covered on top with lattice for shade. No sides or things. Is wind load on this that high?:confused:

"Is wind load on this that high?" -- Yes.

The wind load that you were required to build this pergola to meet was determined by the history of wind speeds in your area in the past. (Around here, I have to meet 80 MPH wind loads -- and we get them every few years.)

OK, thanks. Any suggestions on how to cut a hole in the concrete slab so that I can go down 12"? And out of interest, how deep is the slab likely to be that the house sits on?
Thanks for the advice.

Your patio is a seperate slab -- it will be about 4" thick.

To cut the 2 holes needed, use those abrasive masonary saw blades in a SkilSaw (circular saw). They wear out rather quickly, so buy 6 or 8 of them. (You can return any that you don't use.)

Make shallow passes -- each about 1/4" deeper than the previous. Once you have reached the limit that the saw can cut with a fairly full blade, use a sledge hammer to break up the concrete inside your square. Go easy with the sledge hammer though. Since you haven't cut all the way through the concrete, it is possible to crack the surrounding concrete with blows that are too heavy.

This will leave you with a 24" square at the surface of the patio that you can finish nicely when the footings are poured.