Rat Wall load capacities

[Blue XJ]

I'm looking to put a large shed in my backyard and the township requires an 18" deep ratwall to be poured under the foundation. My subdivision is trying to get me to brick the exterior of the shed. I can't find anyone at the township office or in the local code that I have been able to find online about how much weight can a ratwall of that size support.

Just generally speaking, is an 18" deep footing enough to support brick ~4 feet high of around the perimeter of a shed?

Located in SE Michigan.

 

[Bondo]

is an 18" deep footing enough to support brick ~

Ayuh,....... Ya need a couple more dimensions to figure it's strength,....

 

[matt_i]

I think where I live for a garage one can put up brick with a ledge on an existing pour without a pad footing.

If you have any doubts just pour the wall 2" thicker for more bearing.

I'd study the frost protected shallow foundation. The HUD has a .pdf file that is a cookbook for design anywhere in the continental US for unheated buildings. Simply putting insulation wings in the soil outside of the foundation would help you protect all of this work from frost heave.

 

[Firebrick43]

Weight capacity is not a function of depth. It’s purely a function of footer width. And footer width is a function of the underlying soils weigh bearing capacity. As far as 18” deep that is strictly to keep rodents from burrowing. You need either a frost wall and a footer(drops below the local frost depth, probably 42-48” in your area) or a the frost protected reinforced monolithic slab mentioned by Matt. It will require full XPS foam under it with wings and is really not recommended for non continuously heated buildings.

 

[nadogail]

Please forgive my ignorance, but what is a "rat wall"?

What kind of rats would require an 18" deep wall?

 

[Firebrick43]

Rat wall is just a solid wall to keep critters from borrowing under the slab.

The rodentia that require an 18” rat wall, whistle pigs, aka ground hogs.

 

[nadogail]

Thanks for adding to my education.

 

[SteveCh]

Thanks for adding to my education.

Don't worry, you are not alone: I've built all over and for decades and I've never, ever heard the term "rat wall."

 

[LX-Markham]

First time I’ve heard the term also.

The capacity of a poured concrete foundation wall is going to be governed by the soil capacity, not the wall.

 

[Kaizen]

Does the hoa know about the rats? Lol. Pretty brick and rat slabs.
Seriously. Does it have to be real brick?


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[imjustdave]

So you need a rat wall for rats.. .that to me isn't a foundation. its just for rats. heavy gauge metal could deal with that.
Define large Shed, to me shed = wood structure on some 4x6 skids that is temporary building and you can move it around fairly easily. 200 sq foot ish max size.

To me it sounds like your building a little bit more than a shed. If you need a permit I assume they have standards you will have to meet for a foundation and or slab on grade then build from there.

 

[Blue XJ]

The large shed that I am allowed can be up to 400 sq ft. However, if I stay below 100 feet, I do not need to pull permits or have it inspected. The neighborhood requires it to be on cement though, and match the style of my house, which is mostly brick. I have looked into the faux brick veneer, and have gotten mixed answers from the HOA on it, however, I would be willing to say it would pass as brick in this case.

I guess my main question was really, if I need to add 3 or 4' of brick, what type of cement needs to be under it to support the weight?

 

[Firebrick43]

The large shed that I am allowed can be up to 400 sq ft. However, if I stay below 100 feet, I do not need to pull permits or have it inspected. The neighborhood requires it to be on cement though, and match the style of my house, which is mostly brick. I have looked into the faux brick veneer, and have gotten mixed answers from the HOA on it, however, I would be willing to say it would pass as brick in this case.

I guess my main question was really, if I need to add 3 or 4' of brick, what type of cement needs to be under it to support the weight?

Portland cement mixed with gravel. AKA concrete.

But as stated before, the footer size and depth depends on you soil conditions and frost depth which is local information. We can not tell you that. A local engineer can. Although I would imagine that an 18” wide footer with 4 bars of rebar 48” deep would meet those if you have average or better souls with no muck. A 6” wall of either block or poured concrete would be on this with a brick ledge.

If you choose a frost protected shallow slab it is easier to figure out but you really should heat it.