Expert: Dan Griffin - 3/14/2010

Question
QUESTION: We are having a SUNROOM built from ground up off back of our house- will be aprox 390sf (15x26). What should we expect PSI to be at MININUM? We understand will be 4 inch "monolithical pour"- which means?

THANK YOU and yuor BRAIN! 80 year old lady in ABQ, NM

ANSWER: Bob, I would use 3000 or 3500 pound concrete.  I would expect that the finisher does not want air entrainment if he is going to hard trowel the surface.  Make sure that your contractor has plans to properly cure the concrete, especially if it is to be exposed.  Once the concrete is over a month old, you may consider having it sealed.  I would also make sure that there is a contraction joint at the mid point of the slab to help prevent random cracking.  This joint must be performed the same day the concrete is poured.

Hope this gave you the information you seek.



---------- FOLLOW-UP ----------

QUESTION: Thank you and they stated 3000psi and we will ask re the mid-joint (is this a deal breaker?) and I want to leave it rough and paint or stain in future- having them CURE it is a must, correct?

What do you feel a pre-fab TEMO sunroom should cost per square foot aprox? This price was aprox 40,000$ for 390 sf solid roof, 26x15 sliding door each side and 5x4 5ft windowsin front and 2 4x4 windows on each side, basic electrical,permits everything else needed inc the cement- sound fair?

Answer
Bob, concrete should never be more than 12: in any direction without a contraction or construction joing.  Concrete should never be made rectangular.  It tends to want to be squares.  In Fla you have the advantage of everything being sand so there is little or no ground movement or large temperature swings which tends to crack concrete.

Your pricing is up around $100/SF.  This sounds a bit stiff to me, and I think I would check pricing with at least one more contractor.  There may be reasons to go with the present bidder which include working in a gated community, HOA requirements.