# Concrete Footings in Black Clay Soils



## serbcccc3 (Mar 30, 2017)

I am building a 14ft driveway gate and 2ft brick columns on either side of the gate.  In thinking about the concrete footings I had a couple of questions.

1. For footings in expansive black clay soil, what is recommended depth for driveway gate posts (8ft tall 5in square steel posts) in this type of soil?  The clay absorbs water like no other, but when it dries, it is hard as a rock and cracks.  The gate company had a standard recommendation of at least 18" square hole, at least 3' in depth.  I thought maybe 2' square footing at 3ft, but I didnt know if it was overkill.
2. For the footings for about 6' tall brick columns 2' square, I was thinking around a 3' square footing, but wasnt sure on the depth of that footing.

The gate will weigh in the neighborhood of 330lbs, single swing off just one post.

Both of these footings would be connected in one pour (see picture)






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## nealtw (Mar 30, 2017)

Welcome to the site.  We would hope the pros would know what they are doing.  The depth of the footing wants to be below the frost level and large enough to spread the load into the soil.
Making it bigger won't hurt but usually when they get bigger they also get thicker.


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## serbcccc3 (Mar 30, 2017)

nealtw said:


> Welcome to the site.  We would hope the pros would know what they are doing.  The depth of the footing wants to be below the frost level and large enough to spread the load into the soil.
> Making it bigger won't hurt but usually when they get bigger they also get thicker.



Thanks for the response - im not a pro though just a DIY'er.  This would be my first project dealing with concrete footings for something like this at the house.  I live in the Houston area, so we have pretty much no issues with frost here, our frost depths are 6" and we rarely have cold long enough for it to be of concern.

I think my main concern is the post holding the gate and the lateral force it puts on the post in determining what type of footing to have.


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## slownsteady (Mar 30, 2017)

Your location plays into the plan. Frost won't be an issue i guess. Clay is usually a tough soil, so I would think the lateral forces on the gate won't be a big issue, either. But the pro estimate you got will give you a good sense of the minimum requirements for your area.
Thinking outside the box for a second, rather than a bigger footing, you could try some kind of "wing"  - lateral support at or below ground level. Or even tie the post to the column for extra support.


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## nealtw (Mar 30, 2017)

serbcccc3 said:


> Thanks for the response - im not a pro though just a DIY'er.  This would be my first project dealing with concrete footings for something like this at the house.  I live in the Houston area, so we have pretty much no issues with frost here, our frost depths are 6" and we rarely have cold long enough for it to be of concern.
> 
> I think my main concern is the post holding the gate and the lateral force it puts on the post in determining what type of footing to have.



Engineers look at weights, leverage, and resistance to wind and such. So with out hiring one of those you can only go with experience and hopefully the gate company knows what they are talking about.


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## Snoonyb (Mar 30, 2017)

Is the gate operator assisted and is there a wheel support?

Is the primary gate post concrete filled and did they include a rebar schedule with their approximation?


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