Carport post and footing repair...

[WES999]

Well come to find out, the genius who built the carport set the 4 x 6 posts (non PT) on top of the dirt, no footing, no attachment at the top of the post. Posts are starting to rot on the bottom and carport has settled some. ( big surprise)

Here is my plan to repair, looking for comments, suggestions or anything I am forgetting.

Carport post and footing repair:

1. Jack up carport to level, add temporary supports.

2. Dig hole to frost line, (Mass. is 48”) flair out bottom of hole to make footing

3. Add some gravel and compact.

4. Use a 10” cardboard tube form with a trash bag on the bottom like this

http://www.finehomebuilding.com/how-to/video/build-a-deck-footings-piers.aspx


5. Pour concrete, insert anchor bolts http://www.homedepot.com/p/Grip-Rit...anized-Anchor-Bolt-1-Pack-128GAB50E/203399746

6. Attach 4x6 post base http://www.homedepot.com/p/Simpson-...ble-Post-Base-ABA46Z/100375175?keyword=aba46z

7. Use a 4X half base to attach top of post . http://www.homedepot.com/p/Simpson-Strong-Tie-Z-MAX-Galvanized-18-Gauge-4x-Half-Base-BC40Z/100375216

8. Use new PT 4x6 posts.

Is 10" dia adequate for a footing? I could not find much info on carport footings, but I did find a lot of info in deck footings, some were 12" or more. Do I need any rebar in the footings? Some recommended adding some. Am I missing anything?

Thanks

 

[semipro]

Sounds like you're on the right track. Fine Homebuilding is a great technical resource. A few thoughts:
The diameter of the footing is dependent upon applied load and the load bearing capacity of the soil. I'd suggest you consult a local building inspector to determine what's commonly done in your area.
The footer at 10" diam. and 48" deep will be relatively heavy which is a good thing. Concrete weighs about 150 lb per cubic ft.
I'm unclear on how you intend to attach the posts to the carport beams but a proper tie in using metal hardware (e.g. hurricane clips) or other means is required to prevent uplift in high winds. (I'm assuming you're planning on replacing the whole post here).
As shown in the video you linked to I'd bring the concrete above grade a bit to keep the hardware dry and to have your line trimmer beating on concrete not post.
Don't underestimate how corrosive the ACQ treated lumber can be. Use hot dipped galvanized or SS fasteners. I believe Simpson requires you use their fasteners or equivalent ones to meet performance specs. Don't assume you can use screws instead of the approved nails and meet specs.
Digging 48" can be tough. Contracting someone to install augered anchors is an option. I don't know the cost but its generally less disruptive than what you're planning with the digging.
Its unclear how your carport is built. If racking is a possibility you may want to install some diagonal braces between posts and beams to prevent it.
Edit: A little re-bar installed vertically may help by tying your j-bolt together with the whole depth of the footing to provide better uplift protection. It may be overkill but its easily done. If done I'd try to link the j-bolt to the re-bar by putting a small bend in the top of the rebar and interlocking the j-bolt with it. Seems like overkill though for an attached carport.

 

[Highbeam]

I never understood those concrete tubes. Maybe it is a frost heave thing that we dont have in my climate. Here, we just fill the hole with cocrete and maybe use a hoop of the sonotube for the form above grade. 10" column is fine but the flared bottom should be much bigger. Concrete is cheap, go extra big if you are guessing.

 

[peakbagger]

http://www.hotandcold.tv/professor hill.html Check out Dicks Hills paper on frost heaves in Maine which may change your concept on building a footing. If the fourth link down.

Thanks for Tom in Maine for hosting this file

 

[flyingcow]

The professor knows what he is talking about. Nice link