Expert: Ted Barnhill (Principal, Design45 LLC) - 5/6/2008

Question
Mr Barnhill:

I am writing to you in particular because I am a fellow Minnesotan.  The entryway to my 50's rambler consists of an L-shaped slab, 4 steps to a landing, then another 3 steps to an upper landing.  I would like to dress the entry up by installing composite decking and railings over the existing slab.  There is currently a 9 inch step up from the slab to the doorway, so i should have room for the decking structure.  Is this plan reasonable?  Can I overhang a foot to visually cover the concrete slab underneath?  what type of structure goes underneath the composite decking?  The building centers give me great advice about building a deck sitting on traditional posts but have nothing to say regarding this situation.

Answer
Hi Brian,

Your idea is doable, if unorthodox.  Use treated lumber for your substructure - this includes the landing joists as well as the stair stringers.  With 2x6 or 2x8 at 16" on center you'll have no problem overhanging a  foot.  Be sure to choose exterior-appropriate hardware (e.g. "Simpson Strong-tie") to securely attach your deck to the concrete structure.  The overhang will also provide plenty of clearance for your stair stringers to clear the concrete steps.

It may be tricky to completely hide the concrete (landscaping will help).  Keep in mind that wood and composite materials will have a shorter life expectancy than concrete or other hard surfaces.  Other ideas that you might consider are acid-staining your concrete, or adding a new decorative topping, such as stamped/colored concrete.  (Incidentally, I plan to install an epoxy-pebble topping, sometimes found in pools or commercial lobbies, to dress up my own entry.)  As you already have the concrete structure, the costs may be very similar - it is a matter of whether you prefer a more permanent/grounded look (i.e. decorative concrete) or prefer to match the house (wood/composite).  

Good luck with your project, and feel free to post follow-up questions.  -Ted