Typical small building foundation in Maryland

[HankTexas]

I am a structural engineer in Texas. Normally a foundation for a small building (15' x 50') would be a monolithic slab with a thickness of 6 inches and grade beams around the perimeter that are 12" wide by 18-24" deep. I have a project in Maryland where the frost line is shown as 29". If someone from the Maryland area is reading this could you tell me if a monolithic slab is typical for this type of construction or is the slab poured over a pre-poured foundation or some other type of construction?

 

[MacGruber22]

I live/practice in Maryland, and turn-down slabs are typical if bearing/shear walls (and possibly posts) loads are light and the soil is decent. If you need perimeter piers, you could locally widen the turn-down. I have done that many times. Of course, you could interrupt the turn-down with traditional spot footings - I do that too. The only problem you may have is along your 15' long (presumably) shear walls. If there are no/minimal wall openings, you may be able to get away with a widened turn-down. but, if you have a situation with a number of wall piers you may want to switch to a more conventional wall footing configuration.

15'x50' is a weird aspect ratio. Is this agricultural or a wash bay? I'd round that 29" to 30".

"It is imperative Cunth doesn't get his hands on those codes."

 

[HankTexas]

Thanks so much for the response. This is a small building used to house equipment for a large satellite antenna which is our primary business. The building is as I said about 15' x 60' supported on 4 wooden timbers equally spaced across the long dimension. The building is 'sheltered' with a shed type building enclosed on three sides which will be approximately 18' x 60'. I have designed many small foundations but mostly in the southern states, not many in northern states where I understand the frost line can be a problem due to freezing water trapped under the foundation. The project is too small to employ the recommendations of a geotech engineer so I'm trying to mitigate the chances of a large error due to inexperience in the local area.

The 29" was not the beam depth but the frost line shown in the specifications. My plan was to use a 6" slab with 12" x 36" beams turned down at the perimeter and 12" x 24" beams under the 4 timbers mentioned above. I also plan to specify a couple of contraction joints by cutting the slab about 1" deep along the short dimension and cutting every other rebar.

Any comments you have would be appreciated.