Construction Industry/Concrete Slab on Grade

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Expert: - 6/19/2007


Question
I am having a new nome built in Florida and I noticed that the contractor placed the block on the slab only 24 hours after it was poured. Shouldn't they wait for the concrete to cure properly before putting such a load on it and where can I find that information in writing?

Answer
Neil,
You are correct.  Normally a three day cure time is minimum.  Slabs on grade are not as great a risk as suspended slabs because the weight is distributed over a larger area.  You can call your local building department, ask for a plan review clerk and ask that very question - "does the code cover the condition of loads imposed on concrete" - and if so, what is the limit.  If the clerk doesn't know the answer, ask to talk to the Building Official.  Chances are you will not have a problem.  It also depends on how compact is the grade beneath the slab.  As a further precaution, ask your builder to provide a letter of guarantee that specifically includes the concrete slab and what the remedy will be if cracks appear in the next 1, 2, 3, 4 or 5 years.  The builder will tell you that cracks in concrete are normal and that there is no way to prevent them.  He's wrong.  Cracks can be anticipated and a control joint provided.  Plus, concrete reaches its design strength in 21 days.  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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