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What’s the best type of foundation system for small additions?

workdog2 | Posted in Energy Efficiency and Durability on

What’s the best type of foundation system for small additions (20′ x 28′) & (18′ x 16′)?

Just a straight trench or formed “T” ? Better slab or crawl space ? How to finish & insulate inside of crawl space flooring & block ?

Guess I’m looking for the best solutions for a foundation for small additions here in Michigan as stated above.

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  1. GBA Editor
    Martin Holladay | | #1

    In your climate zone, most contractors would choose between a concrete slab and a crawl space foundation. The site, the existing grade, and the drainage may affect the decision about how to proceed.

    To build a crawl space wall, I would excavate to below the frost depth and pour concrete footings. Then I would pour concrete stem walls. (Concrete block walls have more problems than poured concrete walls.) I would insulate the crawl space walls on the interior. For more information on crawl spaces, see Building an Unvented Crawl Space.

  2. kevin_in_denver | | #2

    Here is a very inexpensive and non-invasive foundation system that is slowly gaining popularity. What is holding it back is typically conservative builders and structural engineers.

    If your jurisdiction requires a soil report, then you may be able to find a geotechnical engineer who can work with the engineers at Pin Foundations and get the plans stamped.

    The floor insulation and vapor control details are important:

    In most cases, this system means:
    1. No excavation contractor
    2. No concrete contractor

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