Anchoring an open carport?

[MushCreek]

I'm planning to build an open-sided carport for parking. I plan to build it out of heavy timbers, and a tin roof to match the house. What I'm wondering about is how much trouble to go to anchoring it to the ground. Just about everyone around here (upstate SC) has a cheap metal carport. Some are on concrete slabs; some aren't. What I don't know is how they're anchored from blowing away. My parking space won't have a slab, so I need footings of some kind.

I'm from FL, where code requires as much up-lift resistance as they do downward force. Where I am now, high winds are rare, but not non-existent. I figure an open carport is a pretty good sail if the wind kicks up, and the idea is to protect the car, not damage it. I'm just wondering how big/deep to make the footings. They make forms called Bigfoot, that are bigger at the bottom so that the footing itself won't pull out of the ground. It would be a lot of digging, though, and our clay-based soil is tough digging. Thoughts?

 

[matt_i]

I would use an 18-24" cube of concrete on each leg. Dunno if you could get the mix truck to hit you with only ~1 yard but that seems about right in total.

Another way to look at it would be to think a yard of concrete is around 4000 lbs, you gained roughly 1000# of uplift compensation on each leg.

 

[MushCreek]

That's the way I anchored my raised deck. I have a concrete mixer. The carport would have 8 posts.

 

[rsanter]

Look up Earth Anchors

 

[Old Man Roger]

If I remember correctly, code in south Florida is 24x24. We get lots of hurricanes..lol

 

[Stuart in MN]

I'd pour concrete footings, then fasten the wood posts to the footings with something like a Simpson Strong-Tie post base.

They would hold the posts down, as well as keep the wood above grade so it won't rot out.

I'm no structural engineer but for a car port I don't think you would need the load bearing capacity of the Bigfoot forms - just a cylindrical hole in the ground that goes down below the frost line should be adequate.

 

[MushCreek]

I used similar post bases on my deck, but they actually had a part that was embedded in the concrete as well. No frost depth here; code is 12" minimum depth for footings.

 

[6768rogues]

Almost everywhere is at least in a 90 MPH wind zone according to building codes. Anchor it down. Would you want to be downwind with your carport coming at you doing 90 MPH?

 

[lakeroadster]

One option is to follow the lead of the pole barn folks.

Auger holes 36" deep and place a 17" dia. x 4" thick concrete puck in the bottom of the hole.

Then use pressure treated columns for the supports.

Use galvanized nails to attach short pressure treated 2x6's to two sides of the column at the bottom. These 2x6's provide the protection against uplift.

You can see the 2x6's in the photo below.

 

[TheKidinBuff5789]

Just about everyone around here (upstate SC) has a cheap metal carport. Some are on concrete slabs; some aren't. What I don't know is how they're anchored from blowing away. My parking space won't have a slab, so I need footings of some kind.

They use these... I have a fully enclosed metal building that I had them put up and they used these. I believe they are 4 feet long, sledged hammered into the ground. Just like the picture shows.

 

[MushCreek]

The metal carports I've seen around here have that metal bottom rail like the first picture. They probably anchor them just s you've shown.

I think I'll just pour footings as deep as I can dig them. Maybe even make them a bit bigger at the bottom. Once the back-filled clay sets up, they won't go anywhere.

 

[shedfullatools]

I did a carport attached to my building, only has two posts and has the building for shear but has to withstand high winds on a weekly basis here. I dug two holes around 30 inches deep and close to two feet across and poured 3-4'' of cement in the bottoms. Once that hardened up for a couple days I placed the posts and poured 12'' of concrete around them, quite a few bags of cement to a post but worth it in my opinion. I also drilled holes and put Rebar through the bottoms of the posts before pouring the concrete around them to make damn sure they cant pull out of the cement

 

[Ji m]

I anchored my tarp carports two different ways

one I laid pressure treated 2x12's down on the flat sides first,
screwed the legs to the 2x12's,
and ran 3/4" plywood between the boards so the weight of the cars damn near made it hurricane proof.

^a little ghetto, but sooner or later everyone of these thats not properly fastened ends up in the neighbors yard.

In my new house I poured footings for the 4 corner posts,
sunk L bolts in the concrete before it set up and hopefully it's not going anywhere this time either.

 

[jubilee]

Here’s the way I anchor sheds, carport, or what have you. I dig a 2’ hole with post hole diggers. I take a 30” piece of 3/4” or 1” all thread ( depending on structure) and weld scrap iron, old bolts, or whatever on about 20” of it. Drop it in hole and cement it with quickrete. I drill holes in my sill to go over all thread. Nut and large washer or plate on bottom of sill ( with lots of anti-seize) nut large washer or plate on top of sill. You can easily level structure initially and level at anytime in future if needed.

 

[Charlie51]

Here's a roof that used to be over a mobile home. Some of the plywood across the upper front was removed to pull the mobile home out. Last winter it leaned against the house, so it was pulled straight and some diagonal bracing put in at the top. This winter with the snow melting off of it unevenly, it fell over the other way. The posts were nailed into metal bases fastened to a concrete pad. Picture taken a couple of days ago.