Metal carport-anchor options

[California]

1) I'll vouch for freak winds in the Sacramento Valley. Long ago (1972) when I was a journeyman Carpenter one of my first jobs was a hay barn repair 100 miles south of where Flusher is. Something like a tornado had picked up this huge hay barn and set it down crooked. Infrequent, but not impossible. I can see how the insurance companies would want high local building standards.

2) for a smaller tarp-carport 20x20 I tried HF's corkscrew dog anchors. Fail! At about 2 ft long I thought they had a good grip. Until rain turned the soil into 2 ft of muck. Then several came loose and I could wiggle others out by hand. I don't recommended them for anything.

Added: (I just remembered) -
Before the ground was saturated, two of the HF corkscrews snapped off at ground level!

I had screwed them into the ground on a slant to make the pull sideways. Above the corkscrew, the shaft is crimped so the dog leash ring won't slide all the way up the shaft. Both broke at the crimp. One from weather, the other when I was screwing it in further with a lever. After I welded them back together they never broke again. I suspect terrible metallurgy.

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[flusher]

Now you've got the mass to hold it down I presume you know that all your connections from concrete to ridge need to be up to the same task. EG Hold downs at studs, hurricane ties at top plates to rafters, straps across rafters at the peak, shear panel siding or cross bracing, etc.

A 85mph wind load requirement certainly seems high, but "rules are rules" and they just seem to make them more ridiculous daily. For curiosity I'd call the local weather station and inquire when was the last time the wind got even near that velocity in your area.

The vendors who are supplying bids have to certify that their structure will handle the 85 mph wind loads. Which means that they have to supply the engineering calculations for their designs so I can get the building permit.

Here in Tehama County you need a building permit and certified engineering for a carport but not for agricultural sheds used to park tractors, implements or to store hay. If I wanted to use that 720 sf carport structure as a tractor storage shed, I'd have to supply a plot plan showing that the location of the shed satisfies the setback requirements from roads and existing buildings in order to get a building permit for what's called an "ag exempt" building. Engineering certification is not required for an ag exempt building. That ag exempt permit is quite a bit cheaper than a normal building permit for a house, shop, or carport. Locating that large carport at the end of my gravel driveway makes it hard to argue that I'm only going to park my tractors there and not use it to cover my car and truck.

 

[flusher]

1) I'll vouch for freak winds in the Sacramento Valley. Long ago (1972) when I was a journeyman Carpenter one of my first jobs was a hay barn repair 100 miles south of where Flusher is. Something like a tornado had picked up this huge hay barn and set it down crooked. Infrequent, but not impossible. I can see how the insurance companies would want high local building standards.

2) for a smaller tarp-carport 20x20 I tried HF's corkscrew dog anchors. Fail! At about 2 ft long I thought they had a good grip. Until rain turned the soil into 2 ft of muck. Then several came loose and I could wiggle others out by hand. I don't recommended them for anything.

We had 65 mph winds here 2 years ago. Blew down trees which took out some power lines. Took 3 days for PG&E to restore power to my area.

Those corkscrew anchors are pretty dinky. The carport vendors offer those helical mobile home anchors as an option for installation on gravel or soil.

Just as a test, I bought one of those 3" dia x 30" long helical soil anchors (aka ground anchor, earth anchor) from TSC

Harvest 30 in L Earth Anchor with 3 in Dia Auger - 3610008 | Tractor Supply Company

I managed to screw it into the ground vertically about 24" deep. It appears to have some level of holding strength, but the shaft sort of flops around which makes me think it's not that great an anchor. I suppose you could pack some dry post concrete mix around the shaft to stabilize it. I'll chain that anchor to the 3pt hitch on my Mahindra 5525 which has 3525 lb lift capacity and see if I can pull that anchor out of the ground.

 

[Brad_Blazer]

You imply that you need a PE to design your footings. If the carport vendors can supply an engineered design for "free" that is great. At the very least they should provide the reaction loads for wind and snow. If you hire an engineer yourself you can provide input on whether you prefer piers, anchors, or continuous footings but he will have to do the calculations.

To dig footings yourself with minimal disurbance you can rent a trencher. Deep piers and footings should get credit for gripping a certain amount of soil so the amount of concrete does not have to equal the wind lift reaction load. Your local engineer should be able provide a design to save you money in that regard.

In this part of NC carports are not considered permanent so they do not need a permit. IIRC according to my vendor my carports are supposed to withstand 75mph wind. My 8' tall carport got tweaked in a heavy wind but the rebar pins driven into the soil held. I winched it straight and added some corner bracing to fix it. The crappy 8x10 tin storage shed next to it blew away in that storm because the floor had rotted where it was screwed down. The trampoline blew away that day too.

 

[whistlepig]

When we had the 84MPH gusts (this went on for a couple of hours) we had a prefab 15' x 36' free standing three sided run in shed for our horses. For sure I thought for sure this thing was going to get rolled over. The 15' end faced the wind. It didn't get hurt. Our house faced the wind. It took the worst damage. If you going to set something up with the wind in mind put the short side towards the wind. The neighbors on both sides of me lost the roofs on their pole barns. Both their pole barns faced the wind. My two pole barns have the end facing the wind. My pole barns didn't get hurt. One more thing. If you have a choice between the sheet metal being nailed on or screwed on for sure go with the screws.