SOG Turndown for Tenant Slab 1

• Oct 30, 2017

• #2

DETstru

Structural

Nov 4, 2009

395

If the interior slab on grade will be placed by the tenant at a later date, just do the stem wall.
It leaves an empty space for them to route any plumbing or electrical along the exterior and avoid the need for dowels or a visible construction joint.

 

Upvote 0 Downvote

• Oct 30, 2017

• #3

XR250

Structural

Jan 30, 2013

5,992

When i design a turned down slab, I typically rely on the counterweight of a portion of the interior slab to resolve the eccentric loading. If you only have a strip, you would have not have a fat enough guy on the end of your teeter totter. It still can work - just gotta check the numbers.

 

Upvote 0 Downvote

• Oct 30, 2017

• Thread starter
• #4

T_Bat

Structural

Jan 9, 2017

213

Thanks for the insight. I'm leaning toward the turndown with a strip of slab about 3'-4' wide to help with eccentric loading XR250 points out. The architect is fine using this and we should still have plenty off room where the plumbing needs to go.

 

Upvote 0 Downvote

• Oct 30, 2017

1
• #5

JAE

Structural

Jun 27, 2000

15,593

Here's a photo of a turn-down slab method on a project from some time ago - steel framed commercial.

The owner had all sorts of problems with the joint between the first exterior slab strip and the subsequent tenant-provided interior slab.
Essentially the interior slab moved relative to the exterior slab (or visa-versa) and the joint opened up and created problems with floor tile, bumps in carpet, etc.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

Upvote 0 Downvote

• Oct 30, 2017

• #6

hokie66

Structural

Jul 19, 2006

23,208

JAE's point is well taken. If the tenant is to provide the slab on ground, leave it to him. Make the external structure independent.

 

Upvote 0 Downvote

• Oct 30, 2017

• #7

CANPRO

Structural

Nov 4, 2010

1,110

A little off topic, but I'm curious - is this a common arrangement, having the tenant responsible for the slab? Seems like a very bizzare setup, having everything included but the floor.

 

Upvote 0 Downvote

• Oct 31, 2017

• #8

jayrod12

Structural

Mar 8, 2011

6,277

It likely 50/50 around here for that arrangement in CRUs. It allows each tenant to run their required mechanical sub-slab while allowing the developer to "finish" the building.

 

Upvote 0 Downvote

• Oct 31, 2017

• #9

XR250

Structural

Jan 30, 2013

5,992

@JAE:

Was that due to slab curling?

 

Upvote 0 Downvote

• Oct 31, 2017

• #10

JAE

Structural

Jun 27, 2000

15,593

No - we believe it was mostly settlement in the exterior footing (within allowable ranges) but with any downward movement the piece of slab extending into the building a few feet acts like a wing and the entire gradebeam & "wing" section then rotates with the wing end coming up relative to the interior slab.

They also most likely didn't provide any dowels or other means of resisting vertical differential movements across the joint.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

Upvote 0 Downvote

• Oct 31, 2017

• Thread starter
• #11

T_Bat

Structural

Jan 9, 2017

213

CANPRO - I have not had much experience with this arrangement but for projects involving developers it seems relatively common for the reasons that jayrod12 mentions.

JAE - if properly keyed joints and dowels are used I wouldn't think that the result in your figure would be an issue. Although I feel a little less certain now ha!

 

Upvote 0 Downvote

• Oct 31, 2017

• #12

jayrod12

Structural

Mar 8, 2011

6,277

A stemwall removes the possibility of that sort of rotation outright. That would be the way I would go. It can't be much more expensive and then it is done "right".

 

Upvote 0 Downvote

• Oct 31, 2017

• #13

XR250

Structural

Jan 30, 2013

5,992

Around here, the developer usually pours the whole slab and they cut it up as needed. It is super efficient :>

 

Upvote 0 Downvote