# Forum Home Renovation Structural Renovation  how deep do i dig post holes for timber carport

## jeffdolling

how deep and what width do i dig to set 115mm posts for a timber carport. thanks

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## intertd6

Truthfully it should be designed by an engineer because of the cantilevered bracing aspect of the structure, the footing standard will only give you a footing size for loads imposed on it & resisting the uplift forces.
regards inter

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## Moondog55

While Inters is the correct answer the old rule of thumb is 1/3 of the post in the ground; so for a 3meter post above ground that's a hole 1500 deep

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## Godzilla73

> While Inters is the correct answer the old rule of thumb is 1/3 of the post in the ground; so for a 3meter post above ground that's a hole 1500 deep

  Err what???

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## shauck

> Err what???

  Yeah, I had to think about that one too but the equation is right if you look at it like this, 1/3 of 4500 (3000 + 1500= 4500) is 1500. He's saying 1/3 of total length.

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## ringtail

1500 is madness. Just excavate a 900 x 450 hole or whatever size hole the engineer wants and concrete in high wind type hot dipped stirups. Timber in the ground is a rubbish concept. Bracing can be done on the roof and between the posts with a screen.

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## goldie1

> While Inters is the correct answer the old rule of thumb is 1/3 of the post in the ground; so for a 3meter post above ground that's a hole 1500 deep

   Isn't the old rule of thumb 1/3 of whats above the ground is the hole depth i.e. 3 meter post above  
gound is 1meter in the ground ?

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## Moondog55

I thought that was for fences; for posts I always use 1/3 of total length; especially for posts that take a wind load such as sail shade posts

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## shauck

What Moondog says sounds familiar. I've read it somewhere but that would be unbraced posts. I've found this example which had all details of building a carport and included footings but for a braced carport (stirrups). Not saying it's definitive, just a reference.    
from this file  Plans required for carport pergola etc.pdf

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