Are keys pretty common for basement wall footings? 2

[reverbz]

Hey Guys,

I'm noticing I'm having alot of sliding on a basement wall design. Are footing keys pretty typical for these?

Thank you!

 

[KootK]

I've never seen a key on a basement wall in real life. I only every hear about it here from time to time. Usually folks are claiming interior side SOG / suspended slab restraint.

 

[skeletron]

Are we talkin' shear keys (concrete below the pad to essentially extend the stem further down) or keyways (2x4 flat across the pad-to-stem joint)?

I've never seen shear keys used in practice or typical residential design. My understanding is that they are expensive and challenging to build, despite every textbook example acting like it's a viable solution.

I've seen about 50-50 split of keyways being detailed on drawings but usually a 90-10 split that they don't appear in the field. I guess it depends on how the contractor wants to pour and the effectiveness of the dowels.

 

[jhnblgr]

Poor backfill material, no drainage, excavator too close to wall, backfilling before slab is installed. Going to need more information.

 

[ANE91]

I walk around my neighborhood and casually observe the ongoing residential construction — shear keys galore.

 

[XR250]

Never seen one here in real life. Or have I seen the expansion joint material compressing so the SOG actually provides restraint on concrete or CMU basements.

 

[Eng16080]

In my geographic region (Northeast) it's rare to see them. I think I've used them maybe once or twice, but on high capacity retaining walls not a basement wall. I assume the horizontal (sliding) reaction is being resisted by a combination of the SOG, friction at the footing interface, and footing dowels. I've never observed a failure related to the bottom of the wall pushing in.

 

[TRAK.Structural]

I've done them for larger commercial retaining walls but not in basements. I would think this would be very uncommon in any kind of residential application.

 

[BAretired]

I recall seeing a basement wall pushing in after backfilling and before casting the basement slab. Specifications should require basement slabs to be placed and cured before backfilling, but contractors sometimes take a chance, and backfill early.

Keys between footing and soil are not common. Concrete keys between wall and footing are common.

 

[milkshakelake]

Agreed with @Eng16080 . It's a non-issue when all those factors are at play.

 

[gte447f]

In my experience, for basement wall footings, shear keys are not a thing. For retaining walls, they are fine, and I have designed and specified them for retaining walls.