Unsupported Residential Foundation Design Methodology 3

[bigmig]

So how do so many engineers design a basement retaining wall with a footing at the base that is barely wider than the wall, and claim "the loads balance out"?

The footing below a 9 foot retaining wall is 20 inches wide, 12 inches thick. It has no overturning resistance and is clearly designed to act as a pin-pin model.

A few questions (asking for a friend):

1. how does a 1/2" diameter anchor bolt at 4 to 6 (!!) ft in a 2x plate on center support a top of wall reaction of nearly 450 plf. The bolt has 1/4 to 3/8 of gap because they drill it with a 1 inch bit so they can slide the sill plate over the bolts easier. Do not say friction.
2. when you have a walkout basement, and one of your walls clearly does not 'balance' against an opposite opposing side of the house, then what? Do not say "we pick it up in internal framing" or "the J bolts pick up everything".
3. if you pour your slab perimeter with a 1/2 inch expansion gap (ACI says don't pour them tight) how exactly does that slab at the base form a reaction against your wall? It is air. Does air transfer load?
4. how do you transfer 450 plf into a floor in a condition where the floor joists are parallel to the wall. I have seen the plans. There is no blocking between joists.

I see really smart people doing this (I see your plans come across my desk once in a great while), and am just wondering, what am I missing? Were you born before the age of physics, or perhaps in a world where gravity and fluid pressure do not actually exist? Are your contractors magically buying sill plates with the anchor bolts literally 'grown' with the tree the board was cut from? If so, please teach me your magical ways.

 

[jerseyshore]

Contractors do this in every single walk out basement in my area. It's for cost but also aesthetic so you don't have a big tall ugly concrete wall with no siding as the grade slopes down.

Besides the front wall load, these side walls are now cantilevered retaining walls that aren't designed as such. I have this fight with them too often.

This is really rare around here. Can't remember the last time I saw a house framed that way.

Lot of flood zone houses only have CMU up to flood height, then wood studs above, but nearly every walk out has CMU all around.

 

[GaStruct]

This is really rare around here. Can't remember the last time I saw a house framed that way.

Lot of flood zone houses only have CMU up to flood height, then wood studs above, but nearly every walk out has CMU all around.

Really? Good market for a SE then. I literally almost never see full height walls on three sides of a walk out.

How do they make it look good if not using brick/stone veneer?

 

[jerseyshore]

Really? Good market for a SE then. I literally almost never see full height walls on three sides of a walk out.

How do they make it look good if not using brick/stone veneer?

Usually just parging if they don't have stone. Bi-levels are very common in NJ where houses are on hills.