[Stonehenge]

In a previous thread some of us talked about the footing required to build a short pier or column of retaining wall block. The general consensus was that a small, 4" slab poured several inches to a foot below grade was sufficient.

I'm trying to dovetail that with my knowledge (however slight that is) of when you need to pour a footing that goes below the frost line.

So in general, what size or scope or type of work do you need to go from a small, thin slab to a frost free footing that extends up to 4' below grade?

[Paul]

When ever the structure that is sitting on it is not flexable or is attached to something that is not flexable.

[Tim]

For walls to be 8' high or better, we have poured spreader footings. These are below the frost line, and are 16" to 20" wide, and 12" deep. Some stickler codes require them to be formed, as opposed to using earthen restriction. Code here also calls for a frost footings to be 42" deep by12" wide when ever a building is larger than 24' by 30' in dimensions. Same thing in the case that Paul stated as well. Otherwise we have dummy footings with 2 runs of continuous #4 rebar suspended in the center that are 12"x 12" below finish grades. The pier post footings here are now getting way out of hand. Rebar baskets, 12"- 36" diameters, and also 42" deep! The days of the hand operated post hole digger are about gone here. Tim

[Stonehenge]

Wow - that seems like a lot. Even the literature from Unilock doesn't spec footings like that for piers made from their materials.

So for the project pictured below, what kind of footing would you recommend (if mine isn't enough, I'm pretty sure I won't be redoing it).

[Stonehenge]

That wall is about 16" in height, total length of about 20'.

[Tim]

If I would have used a concrete footing on this project at all, I would probably have did a 4" deep - bell shaped footing with the wider end at the bottom being 12" wide. I would have to consider the existing base, and determine if it would be prone to settling(newer home, black dirt instead of virgin clay or loam) if I were to just use 12" of compacted inch down rock instead of concrete. Whatever you did on it, I still love the way its looks completed. I could see a similar wall going up at your new location kind of snaking it's way along that elevation change running from 10pm to 4pm in the lower left hand area of the new house picture you posted in the other forum. Tim

[Tim]

Another quick note, The pier pads that are to be used in supporting an enclosed deck, either three season or four season, also have to have an architect do their original drawings, and sign off on the footing sizes and locations before the City of Davenport will approve the job! Tim

[Stonehenge]

Thanks Tim -

The footing you recommend is about what my mason said as well. Though I'm not familiar with a 'bell shaped' footing. Can you explain?

And I like that wall we built so much that I want to do something like that at the new place. Maybe something bigger and more involved. Having the mortared joints and the ability to adjust heights with the mud really makes the wall look nice.

[Tim]

S.H.,
It is just a footing that is wider at the bottom than at the top. It looks like a bell, so that is what they call it. It is less prone to settle side to side because of the wider base. The bottom should be flat, virgin, or compacted before pouring the concrete. Tim

[Stonehenge]

Thanks.