Expert: Dan Griffin - 3/29/2010

Question
Our house was built in 1976 and has a two car garage. The house is built above one parking bay of the garage but above the other is an exterior deck with a concrete floor about 18'x 24'. The surface was finished in flagstones with mortared joints which have deteriorated quite a lot. The walls of the garage are concrete block & in the center between the parking bays are six metal support columns. The slab ceiling has a 2'section that pitches down toward an I beam where the deck above ends and the house begins. We have been collecting buckets of rainwater in this area & in one corner. Recently a new leak has started in one of the concrete seams. We first suspected the water was getting in through the crevices where the walls of the house meet the deck surface but after investigating further we found flashing where the surfuces meet. Could the deck be porous enough to create the overall leaks? Also, we had a new gutter system installed & we are concerned that that might not be removing water properly. We don't know who to call for advise. Should we contact a mason, a roofer or a structural engineer? Since we plan to re-surface the deck, we were going to remove the old flagstone to see if a crack would be revealed. What steps would you take first? Thanks.  Sam

Answer
Sam, sorry it's taken so long to answer.   It sounds to me as if the stone covered patio portion is allowing water intrusion.  Yes, concrete is NOT waterproof.  It can be treated several different ways to help the condition.  If the problem is new and the guttering work is new, it sounds as if they may be related.

As to professional help, contact a waterproofing contractor.  A good builder or a top notch concrete man could be capable.  The concern would be that if you don't solve the problem, you will ultimately rust out the beam and columns.  I suspect you will have to remove the flagstones along the house wall to get to the problem.

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