Building Homes or Extensions/floor cracks


I recently bought a slab home, built in 1997, in Phoenix.  The house is on expansive soil, but a structural engineer said the inside of it looked okay.  However, I later found the cement slab floor, under the carpet has large horizontal cracks (they do not protrude) - by large I mean 1/2" or more.  I only looked at a small portion under the carpet.  Others in the area told me they found them too and just covered them over with carpet. (The engineer did not see these cracks under the carpet since I hadn't pulled it up then)  The carpet place said they usually fill in the cracks although I'm not sure how.  Do you think I need to have the whole floor recemented or don't the cracks matter?  Thanks

Hi Dave, concrete cracks.  That is the nature of the beast.  Most house slabs crack because there is generally no expansion joints  or control joints to encourage the cracking to take place where you want them.  A half inch wide crack though seems a little extreme especially if there is some elevation difference from side to side.   However, unless there are some issues with the opening and closing of doors and windows I would tend to agree with the engineer.  The cracks can be patched prior to carpet going down.  I would use a pliable crack filler instead of just a cement product because these cracks will close up and reopen during the course of time and a filler that will expand and contract with the slab will give you better service over the years.  I hope this information helps please feel free to write again regarding this or other matters, sincerely, Bruce Johnson,

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Bruce E. Johnson


I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.


Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

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