Can you take the existing post mounts, and move them up the post?
Meaning...unscrew any screws holding the metal post mount to the post.
Slide said post mount 2 feet up the post, and have helper hold it.
Install oversized anchors of any brand or style that you want, since now you have lots of access to the concrete.
Slide post mounts down and anchor.

I'd rather have one big bolt than two smaller ones cracking together.

Really the only need is to prevent lift-off in a raging storm.
The pergola is mostly air space and a lot of wood weight, so not much is needed there.

SatMan, is your recommendation Red Head concrete anchoring system screws and Sika anchoring adhesive. I'm particularly curious as I'm planning on doing a glazed pergola of about 20 square meters at my place. And we once had 125mph mph winds, so I guess it will happen again. :(

I just logged on and see there are many great ideas. like someone said earlier, Mark bolt hole, unbolt the existing bracket, move up the pole and drill away. We normally use the typical Simpson or Hilti two part epoxy for stuff like this. Its get mixed when coming out of the tube by itself. Shove in bolt, slide bracket back down, come back tomorrow with a ratchet, tighten nuts and be done in 10 min. Sleeve anchor (Again, Hilti or Redhead is all we use) would be another way of dealing with it.

I have never used those post anchors so I wonder about the shear strength on it if wind is a big concern?

A threaded rod can be used instead of the Red head pictured. Screw the nut onto the bolt and tighten everything down.

Is it ok to have the posts on the existing pad, as opposed to cutting out and pouring a deeper footing?

Thanks Look. Where I don't need absolute strength I've used 12 or 14 gauge 100mm screws to hold timber to concrete successfully such as in fence building type situations. With the big winds and lift type situations with my glazed pergola I'm wondering about those Red Head threaded screws/bolts or wedge type bolts instead.

More then enough for a simple pergola unless its heavy with a real roof, big timber and so on, then a pad should be considered.

The Redhead bolts and epoxy should be enough but I am not a huge fan of the expansion bolts in your situation. Anymore then that, consult an engineer. Around here, we have to hire an engineer to witness the epoxy application that's spec on the plan and he has to sign off on it at the site. Chaching', another 350 bucks

Yep, I was about to suggest this.

If you use Red heads or the expanding anchors I would use the concrete epoxy as well. The bolts have a tendnacy to strip out the threads and the expansion bolt has a tendancy to slip so I would use epoxy on those as well if you go that route.

I would stay away from tap cons, they have a tendancy to snap.

I’ve had many people try to install anchor bolts and they have not blown and brushed out the dust. You’ll get minimum adhesion with the dust, so unless you really trust the installer, I can see an adult ( or engineer) there to supervise

The Red Heads I used are galvanized. Tap cons are not.

Living on the coast, corrosion is a consideration. Probably is for other areas too.

I also gave my brackets a coating of galv. spray......

http://forums.pelicanparts.com/uploa...1629987008.JPG

http://forums.pelicanparts.com/uploa...1629987008.JPG

http://forums.pelicanparts.com/uploa...1629987008.JPG

http://forums.pelicanparts.com/uploa...1629987008.JPG

I used google images and typed in" retrofit post anchor." Lots of choices but I like the 2-sided angle ones the best. Yeah a plinth style base should hide everything. Just make sure to raise the trim off the concrete about 3/16ths" and paint/seal inside, outside and edges.

Sliding a piece of aluminum under the post where it meets the concrete helps.

Well, there's a lot of factors to take in account.. Pad depth determines how deep you can go with fasteners (not just supporting the pergola weight). General construction of the pergola will determine the shear seen at the mounting points due to the wind load.. determining the size of the fasteners. Really, really should be engineered..

20 square is a lot of area,,, I've not used the red head fasteners myself in anything I've done at home or work,,

Simpler solution.

Remove half the hardware holding the roof on.

If it gets too windy it goes bye bye, pergola stays put.

You are welcome.

I'd probably just pay my home owner's insurance premium each year :D

....and hope ;)

A few considerations
 

The pictured post base, with 4 bolt holes has a bottom. You are ging to have to lift the post high enough to slide the base on the bottom of the post.

AND, you will need to put the bases on all the posts prior to drilling and bolting. To do this you could take a jack and a 4x4 post to raise the frame enough to get a base on then move to the next post. This could rack the framing enough to cause problems structurally.

Ideally, you want to get the bottom of the post up, off the concrete, even 1/4 inch to keep water from wicking up into the post, causing rot - doesn't matter if it is redwood or pressure treated - mother nature always wins.

I like the "L" bracket idea, two per post. After install, notch out the base trim, prime and paint it to protect the wood. Install it about 1/8 off of the concrete and bed the bottom of the trim in silicone or a good grade of waterproof/flexible caulk, to slow the water down from rotting the wood.

I've used lead shields, wedge anchors, self tapping concrete screws and epoxy. Not knowing the depth or quality of the concrete, i'd go with the Simpson Structural epoxy. The lumber yard will likely rent you the double barrell "gun" to do the work.

Next, take a good look at the post to roof framing connection. Simpson makes some decorative black connectors that might work for you and your "design consultant" :-)

good luck,
chris

I've used the Simpson "Mission Outdoor" plates and ties. Bought from these guys, highly recommended.

https://www.dhcsupplies.com/outdoor-accents.html?pi=2