Expert: Bruce E. Johnson - 4/19/2009

Question
I have recently started the process of building a deck onto our ranch style house with slab foundation.  We have a 11' x 18' cement patio in which I have demolished.  I was going to build over the top of it but after reading articles regarding doing that I was persuaded because of drainage issues since we have no slope to our back yard.  After breaking up and removing the concrete I discovered that there is no stud running underneath the sliding glass doors so I would have not be able to install the ledger board as I originally thought.  In addition to this I only have 6" from the ground to the bottom of the door frame.  Can you give me some guidance on how to proceed.  I would appreciate the help.

Answer
Hi greg, no "stud" under your door frame?  I'm not sure what you are telling me here.  If your house is on a monolithic concrete slab then you have concrete under your door frame.  If this is the case then you can attach your ledger to the house with concrete anchors or Tapcons.  I'm unclear as to why you removed your concrete patio.  I have built tons of decks on top of old concrete patios but I guess it's too late to discuss that issue.   Anyhow, you need to use pressure treated wood for your patio construction.  If you only have six inches to play with then you may need to dig some trenches and pour some concrete grade beams to set your patio joists on or inset some pressure treated 4x4s.  I am enclosing a simple sketch..I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com