Post Hole Foundations
Post Hole Foundations
(OP)
Hi all,
I'm wondering if any one has information on post hole footings, i.e. how they work (cantilever action?) and how to design them (reinforcement, overturning moment).
Any help is appreciated.
Thanks.
I'm wondering if any one has information on post hole footings, i.e. how they work (cantilever action?) and how to design them (reinforcement, overturning moment).
Any help is appreciated.
Thanks.






RE: Post Hole Foundations
Your start point is likely going to be the IBC post foundation formulas, if you're looking at small scale items that aren't significantly deflection sensitive.
RE: Post Hole Foundations
Mike McCann, PE, SE (WA)
RE: Post Hole Foundations
RE: Post Hole Foundations
1) cantilever action can be relied on for posts up to 900mm in height (limitation given in the timber framing code AS1684.2)
2) for heights above 900mm cross bracing sets are required to provide racking resistance
3) footing depth is determined by considering two factors. First is how much lateral/uplift capacity is required to resist wind loads. Second is how deep the footing needs to be to resist predicted ground movement in reactive sites prone to shrinking/swelling soils.
For lateral resistance, I usually just design as normal piers by estimating the un-drained shear strength of the soil based on the classification given in the soil report(20-30kpa usually - but I would prefer a geotech to make a recommendation rather than having to estimate values for each job). I have not seen the IBC reference before, thanks TLSH.
Jake
RE: Post Hole Foundations
Even the local building codes here (NW GA, US) get pretty restrictive on "post holes" for outdoor decks. You need to define your problem (your application and your country and state/province) much, much better.