I agree as well. I would not think twice about drilling and attaching a no-loan pergola to the surface of an existing slab. However, for whatever reason I don't think that's code. But would it be enough - probably. Might depend on the quality of the original slab job, are we all the way to the very edge, how heavy will the load be, how well was the subgrade prepared/compacted, has there been any erosion under it.

The CA building code provides methods that, in my non-engineering opinion, are overbuilt by a factor of 2 (at a minimum). Most of the production home slabs we pour today can, in may places, bear the load of the house without any grade beneath them - cantilevered if you will. They are that overbuilt. But in an earthquake - who knows...

I think what I suggested is, at the same time, current code, and probably overbuilt for a pergola.

Hopefully someone with more expertise can jump in here. Good luck!

What sort of ground are you on? I'm assuming no frost depth to worry of. What about renting a portable post hole digger and boring? Drop a few inches of sand and pea gravel in, Sonic tube placed in and above grade, concrete pour.

Assuming your patio is just a slab poured on the ground, I agree, this is the best solution. Do you know for sure there is no footing under the patio?

Judging from the OP's location, those houses are more likely built in the 80s -90s. Exterior concrete slabs are just sitting over dirt without footing.

I like the earlier comment about the span between rafters. This, and the type of roofing will determine the types of beams and footings. I personally would dig and pour concrete footings with rebar. Steel footings that accept wood posts bolted into them, above grade. I made a patio/ pole barn thing last year and did it this way. My center posts are 4x6 and I made a center glue lam beam from two 4x4 posts.

Yep, Simpson's CB66.

I'm building one too.....one day......

http://farm5.static.flickr.com/4064/...241fe79d6e.jpg

Exactly. That's what I used. But I welded 1/4" rebar to them to give more strength to the concrete. I used a lot more concrete than I would have thought I needed at the outset. The footings allow some adjustment of the wood before you bolt them down.

I used groundhogs when I built my new deck. https://www.youtube.com/watch?v=6tIdEp4LywM Simple and less mess than drilling and pouring piles.