Residential Slab Foundation 1

[TRAK.Structural]

I'm reviewing some drawings by others (see below) and wondering if this type of detail for a slab foundation is common for residential construction. More often I've seen a monolithic turndown at perimeter walls, i.e. no construction joint/separation between the thickened edge foundation and the interior slab. Which way do you see this detail most often? Are there pros/cons between this approach and the monolithic approach?

 

[SE2607]

e

Famous last word...


For sure. But a good and complete set includes coordinated elevations. If an architect is rushing me, sure. I'll strip all dimensions and elevations off of my set if they won't give me a reasonable amount of time to coordinate and confirm we match. But if I have a good set to design from and the architect cares about the final product, I'll show structurally significant dimensions and elevations on my drawings (especially foundations).

I don't disagree with the exception of ELEV = 0'-0" on the detail shown by the OP. What benefit does that provide?

 

[phamENG]

In the location where this is cut, is it at first floor elevation, or is it at a slab depression? Perhaps a lower sublevel? I often have garages that are 7" to 16" below first floor, so knowing by looking at the detail where I am vertically can be helpful in reading the detail and understanding it in context with other details.

 

[TRAK.Structural]

I guess I'll chime in since this whole discussion started with the detail I posted.

I think "typ" is useful and I do use it often.
For floor elevations, I have some generic language about referring to arch/civil/grading for actual elevations and that the FFE from those sources is equal to 0 on my drawings. Having negative elevations relative to the 0 datum has never been an issue in my experience.
I've also typically mostly seen the slab just poured over the top course of CMU, just wanted to see what the experience of others has been.

 

[canwesteng]

e

I don't disagree with the exception of ELEV = 0'-0" on the detail shown by the OP. What benefit does that provide?

How do you intent to coordinate between sheets without an elevation? Maybe on residential drawings you have so few sheets it doesn't matter, but it's terrible practice to not put an elevation somewhere.

 

[SE2607]

How do you intent to coordinate between sheets without an elevation? Maybe on residential drawings you have so few sheets it doesn't matter, but it's terrible practice to not put an elevation somewhere.

I don't think "coordination between sheets" is best done by details. Foundation details are going to be called out on foundation plans and framing details are going to be called out on framing plans. I sometimes get a question from a contractor asking me where a particular detail applies. That tells me the contractor is reading the drawings backwards. He/she should be reading the plans and then going to the details, not vise versa. If there are changes in the framing or foundation plans, those changes in elevations should be shown by a detail indicating the difference in elevations.
On architectural projects, elevations and most dimensions are dictated by the architectural design. For structural engineering, architecture is the container. If the architectural dimensions cannot be maintained due to a structural requirement (e.g., a wall needs to be 8 inches thick instead of 6 inches thick), that should be reported to the entity responsible for the architectural design, revise the architectural drawings and then continue the structural design.
I maintain that, with few exceptions, putting elevations on structural drawings where the elements are drived by another discipline (e.g., architecture), is a mistake and is inviting conflict.
I have personal, and painful, experience in this matter. It is not hypothetical to me.