Is it necessary to pour a footing if your post sits on solid rock?

[mike758]

I’m building a pole barn and hit solid sandstone on 5 holes, and had to dig down 3 feet (minimum post depth) with a jackhammer. The plans call for the posts to sit on precast concrete footing which I have, but I don’t feel like digging deeper then I have to and the holes also taper so they might not fit. The bottom of the holes are still solid sandstone.

Also, the plans call for the posts to be backfilled with soil, but I was wondering if I should fill those entire holes with concrete since the holes are in solid rock and probably won’t drain.

 

[LX-Markham]

These are all questions for the engineer who's stamp bears on the permit drawings.
Submit a Request For Information.

 

[tarmy]

Do you have any wind loads, shear or earthquakes? Is there any code dealing with heaving or lifting from freeze and thaw?

Hire an engineer...

 

[Pluribus]

Vertical load on the post is only one of the forces a building needs to handle. Post depth is how a pole barn typically deals with shear/racking forces.

Ditto on the engineer.

 

[John in OH]

Go with a request for information from the engineer. But at the very least, you need to chip the rock as necessary to create a flat surface for 100% the post's end to sit upon. You don't want a square-cut post sitting on a sloped rock nor do you want an angle-cut post sitting on an angled rock.

 

[mtwaterguy]

Post depth is how a pole barn typically deals with shear/racking forces.

Also helped when commercial girts are used.

 

[LX-Markham]

But at the very least, you need to chip the rock as necessary to create a flat surface for 100% the post's end to sit upon.

easier to use high strength grout to level out an uneven and/or rough surface.

 

[TommyK]

I would pin it to the rock and back fill with concrete.

 

[dutchgray]

I would have no problem with putting the post on the stone if the hole is the correct depth, if plans call for dirt fill it cant be that critical.
If the hole doesn't drain as it is filling it with concrete won't help, the post will still sit wet in the concrete. Not that it will rot down there, they rot out over a few inches around ground level where the post is neither dry or wet and where the air can get to it.

 

[mcbane]

Maybe hire a tractor with auger. Sandstone is super easy to drill.


Sent from my iPhone using Tapatalk

 

[In2toys]

Hire a guy with a skid steer & auger& carbide teeth. Not all tractors have down pressure

 

[RVDan]

If you’re allowed to use just a precast, you’re definitely going to be allowed to use solid rock.

But it’s up to the inspector isn’t it?

 

[mike758]

Good news, inspector came and said it’s ok. My biggest concern was failing inspection but it was pretty simple.