# How deep a footing on a 5 foot wall enclosure?

**URL:** <https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274>\
**Category:** Factual Questions\
**Created:** [July 7, 2016, 12:54am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274 "2016-07-07T00:54:20Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Mangosteen](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)\
**Post date:** [July 7, 2016, 12:54am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/1 "2016-07-07T00:54:20Z")

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I’m building a dry stack 24’ by 32’ 5 1/2’ tall concrete block enclosure (four walls) with a small opening. Its a garden area. (The trade winds off the ocean are relentless.) I know that if it were a free standing wall, it would need a good footing to prevent it from falling either forward or backward, but the side walls in this enclosure will offer a lot of support.

Its in Hawaii so there are no frost worries. The soil is a nice sandy loam.

How deep should the footing go? How much re-bar do I need? Do the blocks need to be filled?

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**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\
**Post date:** [July 7, 2016, 2:52am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/2 "2016-07-07T02:52:15Z")

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[smile] … will you need a building permit?

8" x 16" perimeter footing should be enough … leave the top of the footing about an inch or so _above_ grade … it would make a nice mow strip … filling, like with concrete? That would be expensive, not sure you’ll need it for just a garden wall; fill it with soil and plant something across the top.

You might have far cheaper options … is your heart set on a concrete block wall?

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**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\
**Post date:** [July 7, 2016, 2:59am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/3 "2016-07-07T02:59:20Z")

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Rebar … not a bad idea, not god awful expensive … two runs of 1/2" is fine.

You’ll not be able to put a building on this, it’s just a wall right? Rebar here just keeps the footing all in one piece, things happen over the decades …

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**Author:** ![Mangosteen](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)\
**Post date:** [July 7, 2016, 4:03am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/4 "2016-07-07T04:03:48Z")

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> [@watchwolf49](#):
>
> [smile] … will you need a building permit?
> 
> 8" x 16" perimeter footing should be enough … leave the top of the footing about an inch or so _above_ grade … it would make a nice mow strip … filling, like with concrete? That would be expensive, not sure you’ll need it for just a garden wall; fill it with soil and plant something across the top.
> 
> You might have far cheaper options … is your heart set on a concrete block wall?

Here in Hawaii we can build structures up to 1000 square feet without a permit if it is on AG land (which mine is).

So you are saying 8 inches deep and 16 inches wide for the footing?

A concrete structure is what I am thinking about because anything that termites can eat will soon start to deteriorate. We get over 150 inches of rain a year so this also destroys structures pretty fast. Need something that will last under these pretty difficult conditions.

What cheaper options were you thinking of?

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**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\
**Post date:** [July 7, 2016, 7:13am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/5 "2016-07-07T07:13:39Z")

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I’d suggest a test run of whatever you decide on - that much rain on sandy-ish soil just might cause wash-out, creating gaps under the footer.  
Or maybe I’m confusing two issues.

But yes, tie the footer together with rebar and tie the blocks to the footer. How much steel you need on the vertical? Don’t ask me - but I would fill the holes that have rebar coming up through them.

And, with that rain: Waterproof cap over the blocks - get as pretty as you wish, but make sure the blocks to do not fill with water.

Now, get off my lawn while I mis-remember some more stuff about building things.

😉

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**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\
**Post date:** [July 7, 2016, 7:23am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/6 "2016-07-07T07:23:15Z")

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> [@Mangosteen](#):
>
> I’m building a dry stack 24’ by 32’ 5 1/2’ tall concrete block enclosure (four walls) with a small opening. Its a garden area. (The trade winds off the ocean are relentless.) I know that if it were a free standing wall, it would need a good footing to prevent it from falling either forward or backward, but the side walls in this enclosure will offer a lot of support.
> 
> Its in Hawaii so there are no frost worries. The soil is a nice sandy loam.
> 
> How deep should the footing go? How much re-bar do I need? Do the blocks need to be filled?

At that length I think it needs piers to stop it falling over, even though it’s only 5’. It is going to have piers isn’t it?

And to stop the roof from pushing it over if it has a roof .

It always needs a good footing to stop it falling apart at the bottom – although with no roof or fill 8 x 16 seems excessive to me, maybe that’s standard where you are.

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**Author:** ![davida03801](https://avatars.discourse-cdn.com/v4/letter/d/b5e925/32.png) [@davida03801](https://boards.straightdope.com/u/davida03801)\
**Post date:** [July 7, 2016, 11:37am UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/7 "2016-07-07T11:37:22Z")

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You said Dry stack. Are you filling the cells with mortar then ?

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<div class="post-metadata">

**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\
**Post date:** [July 7, 2016, 1:37pm UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/8 "2016-07-07T13:37:05Z")

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Ask your local building inspector. Different areas have different “problems” (or no problems) with soil. In some areas, there can be constant settling. Movement of soil. Or other areas no movement. Could be water drainage problems which can cause soil to move/settle. [Permafrost problems in cold areas.]

Anyway the local building guys would know what the best design would be for your particular area.

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<div class="post-metadata">

**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\
**Post date:** [July 7, 2016, 1:39pm UTC](https://boards.straightdope.com/t/how-deep-a-footing-on-a-5-foot-wall-enclosure/759274/9 "2016-07-07T13:39:27Z")

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> [@Mangosteen](#):
>
> Here in Hawaii we can build structures up to 1000 square feet without a permit if it is on AG land (which mine is).

So, it depends completely on the cost of the permit … here they run a lousy couple hundred dollars and for a project this expensive, maybe not a bad idea have an engineer go over the drawings … you know, call it cheap insurance.

> [@Mangosteen](#):
>
> So you are saying 8 inches deep and 16 inches wide for the footing?

Indeed, seems a bit much but this footing is carrying a lot of weight … plus that’s hurricane country ain’t it?

> [@Mangosteen](#):
>
> A concrete structure is what I am thinking about because anything that termites can eat will soon start to deteriorate. We get over 150 inches of rain a year so this also destroys structures pretty fast. Need something that will last under these pretty difficult conditions.
> 
> What cheaper options were you thinking of?

I’m thinking a wood fence, you should be able to get 15 years out of a pressure treated post even with the rain. I only get 100" here and they work fine. Termites is something we don’t have much of though … perhaps replace the wood posts with galvanized steel posts. I don’t have a lot of experience mitigating termite damage _but_ my understanding is that as long no wood it touching the ground, the termites won’t get up into the wood parts of the fence.

Unfortunately, I’m sure you’ve looked around your neighborhood and see most everyone there have cement block walls instead of wood … and that’s a wisdom definitely better than what I can give you here over the internet. If you can afford it, then build it … it _will_ last a lifetime and more.

=+=+=+

My commiserations on that rainfall total, you must live on the “dry” side? It’s the violence associated with the plant growth that gets me, every time I turn around there’s a plant reaching out trying to kill me.