Deck post to footing connection

[MikeC]

I'll make this quick. Sonotubes filled with concrete, terminating above grade. Deck was built with posts resting on top of concrete and no connectors. Is there a listed bracket available that can achieve the requirements of section R507.4.1 of the 2018 IRC without the need for disassembly of the deck?

 

[e hilton]

Simpson RPBZ retrofit post base.

 

[MikeC]

Simpson RPBZ retrofit post base.

Thanks. I figured simpson made something, but I wasn't sure where to start looking.

 

[Glenn]

FYI: There is no know "load" being resisted laterally. It's been argued, believe me... "someone leaning against it" "it should support against a riding lawn mower hitting it". "In my region in winter we see a lot of snowmobiles hitting deck posts".

Ultimately, cars hit buildings everyday and we don't require buildings to resist that impact. For a decade of deck code discussion, "resist lateral displacement" is what could be agreed on.

You can use a load rated manufactured post base, but truth be told, we have no target of load we are trying to resist. I would accept anything that keeps the post on the footing under "normal" lateral loading. PS. There is no uplift resistance required of decks in the standard wind zones.

Just make sure it can't get kicked off the footing.

 

[jar546]

There is no uplift resistance required of decks in the standard wind zones

Not everyone is in a standard wind zone and we are seeing more straight line wind events in areas that are "standard." Why would someone not design a deck to prevent uplift?

 

[Glenn]

Not everyone is in a standard wind zone and we are seeing more straight line wind events in areas that are "standard." Why would someone not design a deck to prevent uplift?

what would they design it to? Decks work way differently than roofs when it comes to wind pressure. They are more similar to walls, in that it takes direct pressure. At this time, nothing in the IRC design tables have included uplift as a force to resist against. Notice the post to footing detail on the far left in the 507 figure. No uplift connection other than friction. the min 12 inch embedment is only for lateral. I am not aware of anyone studying the effects of wind uplift on deck structures. There was some research a decade ago in regard to lateral movement from wind, and it was found to be less than what the occupants could generate (lateral live load). Even that research hasn't been significant enough to get a mainstream discussion about lateral live loads.

A roof experiences uplift differently than a deck. The attic below has different air pressure than above the roof. This difference in air pressure from lateral moving wind lowers the air pressure and creates an uplift on the roof. Sort of like the negative pressure on the leward side of a wall. Decks don't experience this same phenomenon.

So I'm not saying they shouldn't be studied or able to resist, I'm just saying they aren't being studied and most of them are already resisting. In my experience, which is limited to my experience, I have never been presented with a deck that pulled UP from the ground in failure (other than hurricanes). I have been shown decks that racked laterally (deformed) due to lateral wind loads, no diaphram design, and a hidden fastening system holding the decking only with friction. This was a wind load failure, but not "uplift". (mountains of Colorado, high wind)

I look forward to reading more comments from other people's experiences. Thanks!