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Construction Industry/Pony Wall on concrete slab

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Expert: - 11/30/2009


Question
Hey Roger,

I plan on building an attachment garage butted up against a current garage (28X24, 8ft walls) on my place. The new garage will be built out of a garage I took down from another site (4 full walls and trusses (22X24ft, 8ft walls)). I've prepared the space beside the current garage, removing the top soil, placing road crush, tamping.. etc to a level of 5 1/2 inches below the floor of the current garage (planned slab height). I plan to build slab on grade, but I want to build a concrete pony wall to lift the walls 2-4ft above the slab. Reason for this is firstly that the roof slopes don't match and I don't want the hassle of trying to match that up and secondly for simple height. The problem that I'm thinking about is since I won't have any footings, I imagine I'd pour the slab first - build the forms for the pony wall and pour the pony wall second? What has me stumped is how well would the wall bond to the slab in the sense of wind loads or even for a good seal(vertical rebar for the walls would be part of the slab pour)? I know for my basement, I poured the footings, then the walls, then the slab.. so I'm just unsure if this would be right?

Answer
Hi Frazer,
I'm sorry, but I can't agree with your planned project.  All walls should have a foundation.  Depending on your climate conditions, that could mean a depth below a frost line or a slab on grade with thickened edges.  Here in Florida we build slab on grade with the slab perimeter edge thickness of 12" and 16" deep (under the slab) and tapering back to the slab of 4" thick.  Then we lay in a 1" x 8" board on top of the form to create a recess in the slab to receive concrete blocks.  Of course, we don't have freezing but I do have to be aware of the water table and other considerations.
As for the "pony" wall (or sometimes a "stem" wall or "knee" wall) it may be bonded to the slab with a couple re-rods every 4'. Rather than pour a pony wall, it would be lighter weight but just as strong to lay concrete block.  The cost of forming the wall and pouring concrete would be more than block.

I hope this has been helpful.

Roger
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Roger Zona

Expertise

I am experienced in all types of construction: residential, industrial and commercial; single family, multi-family, mid-rise and high rise buildings (16 story office building) as well as remodeling, additions and tenant improvements. I can field most any question that relates to general construction. I have consulted with infrastructure (utility) contractors also and have a good general knowledge of underground utility construction for subdivisions and commercial projects.

Experience

After college, I began my career in the construction industry. I chose to become an apprentice Architect and 4 yrs later I opened my own architectural design firm. Six years later I moved to Florida to buy & develop land and build. I became a State of Florida Certified General Contractor and operated my business for 45 years. I built all types of residential and commercial buildings including warehouses, shopping centers, high rise apartments and office buildings and developed sites for other contractors. I retired and became a consultant to the construction industry. I maintain my license and continuing education requirements, operate a small construction company and write a weekly newspaper column for the Palm Beach Post (a Cox publication) with the byline "Ask The Contractor". I am the "technical editor" for a publisher of books that relate to home maintenance.

Organizations
Previously - NAHA Currently - FLCA (Florida Licensed Contractors Assoc.)

Publications
Palm Beach Post newspaper - weekly Q & A column Happy Herald monthly real estate publication - monthly column

Education/Credentials
Michigan State University University of Detroit BS in Engineering

Past/Present Clients
I built a home in Palm Beach for a member of the Pulitzer Family. I was responsible for the completion of a twin hi-rise condominium project for G.E. Credit. I was a partner in the successful development of a P.U.D. (Planned Urban Development) subdivision. I represented the largest home builder from France (Bati Service, S.A.) in the development of a subdivision and the design and construction of the homes.

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