Here’s a description and illustrations we’ve created for footing types we frequently reference in our work for sunrooms, pergolas, carports, screen rooms, and similar patio structures.

 

An isolated footing is used to support a single post. Isolated footings are independent footings which are provided for each support. they can be round (cylindrical) or square (rectangular).

A ribbon footing is another term for a continuous strip footing.

A thickened edge footing has deeper (thicker) concrete at the edge(s). That concrete is used to support columns/posts for gravity and uplift forces.  there are also code minimum footing requirements for patio slabs in both the Florida and International Building Codes.  More can be found about footings in the IBC here https://www2.iccsafe.org/states/newjersey/nj_residential/pdfs/nj_res_chapter4.pdf

larger thickened edge footings are used for construction of slabs on grade with integrated foundations.

there are other types of foundations such as stemwall, structural foundations on piles, and others which can be found online and outside the scope of this description of patio footings. Its important though to consider integrating different footing types since they will have different settlement characteristics over time.

Posts can be surface mounted or embedded into the foundations to achieve different results. an embedded post typically takes more uplift forces and resists bending/listing which is useful for design of lateral and uplift forces.

Important to note that in some areas footings like this are required to be below the frostline to prevent heave.  Generally however, footings for patio type use are exempt.  check with your local code and building official for clarification of needs in your area before installing any foundations and always consult a licensed professional engineer.

Here are some illustrations to further describe the above

 

 

Jul 6, 2018   263    Engineering Principles, General    
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