When to use a Thickened Slab, when to use a Strip Footing

[Revv]

Hey Guys,

SO I was wondering, do you have a rule of thumb for when to use a strip footing or a thickened slab? I'm not sure I fully understand the issues associated with both. It should be noted alot of my work is done in Arizona, where there is very little frost depth requirement, and alot of my work is done in North Dakota, where there is obviously deep frost depth requirements. Obviously we can't use thickened slabs for the exterior of the North Dakota Buildings due to frost depth..but what other considerations are there? Loads?Etc?

Thank you in advance!

 

[XR250]

I usually ask the contractor for their preference. If the load is high, you need to deal with the eccentric loading of the thickened slab.

 

[le99]

The thickened slab is a stradegic design tool mainly used in the SOG or mat foundation. The strip footing is, by namesake, a long narrow footing to carry mainly the gravity line load by itself. So, when to use which is mainly depending on the type of construction and the type of floor.

 

[hokie66]

Thickened or ribbed slabs, in my experience, are normally restricted to single story dwellings. The type of footing systems for housing tends to be regional, and depends to a large extent on the soil conditions encountered.

 

[Aesur]

I haven't encountered any particular rules of thumb for this thus far, it seems that if I prefer one the contractor/architect prefers the other. Normally I consider things such as how tall the building is, what is the loading on the footing, etc. As XR250 said a thickened slab has eccentricity issues, especially when dealing with higher loading. You can try to use the slab to "restrain" the turndown from rotating, but you need to look at it on a case by case basis. If doing a post tension slab on grade, you most likely will be looking at thickened slab edges versus strip footings.

 

[MotorCity]

Strip footings to support exterior walls (below frost line), thickened slabs to support interior walls.

If width of thickened slab exceeds 3x width of supported wall or line load, use strip footing.

 

[dik]

Just a caution, thickened slabs may restrict the SOG movement and may cause unwanted cracking of the slab. You might not want to introduce a 'restraint'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik