Construction Industry/second floor deck

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Expert: - 3/29/2011


Question

sun deck
I am renovating a 2nd floor sun deck. The deck was originially a wood deck 3/4" 1X8 topped with sheet metal, 1 1/2" of tar and gravel . The deck measures 22 feet wide where it attaches to the house and extends out away from the house 16 feet. The deck is built on 2X10's on 16 inch centers. I would like to replace the wood deck (which is above a living space) with a two inch concrete deck. Will the 2x10's on 16 inch centers surport the concrete deck dead load? The walls of the structure are 4X4's on 8 inch centers. If I double up the 2x10's with glued and screwed 1/2" plywood in between the the 2x10's will the laminated 2x10's surport the concrete dead load? What do you suggest? Thanks Roy.

Answer
Hello Roy,

Your description is very good.  The "tar and gravel" is probably a 1" layer of rigid insulation and then tar and gravel applied on top.  I don't quite understand the 4x4's on 8 inch centers.  Do you mean 18" centers?

However, removal of the old roofing and deck is a good place to start.  Your idea of creating a laminated beam is a bit of overkill.  If you added another joist (the layout would then be 8" o.c.) that would be very adequate for the load.  

More important would be the beam or bearing wall that is carrying the joists.  

Prepare your deck with 3/4" T&G plywood glued and nailed 8" o.c. at seams.  Next install a layer of 30# roofing paper - asphaltic building paper.  Most likely the joists are already pitched to allow rainwater runoff.  If you want to keep that effect, create an edge form to receive the concrete.  Next install an 8" sheet metal (aluminum) flashing to the wood deck and up 8" on the adjacent walls.

You will probably have to pump the concrete.  Order a "fly ash" mixture of "light weight" concrete.  Your joists will support this added weight.  

Concrete is a porous material and the concrete should not be left exposed.  If you will have furniture and walk on the deck, I suggest you install a hard surface such as ceramic tile.  

You could check with your local building department and ask the Plan Reviewer what, if any, codes apply and are you in compliance.  This type of work should be considered remedial maintenance and should not increase your property taxes.

I hope this has been helpful.

Roger
Ask The Contractor  

Roger Zona

Expertise

I am experienced in all types of construction: residential, industrial and commercial; single family, multi-family, mid-rise and high rise buildings (16 story office building) as well as remodeling, additions and tenant improvements. I can field most any question that relates to general construction. I have consulted with infrastructure (utility) contractors also and have a good general knowledge of underground utility construction for subdivisions and commercial projects.

Experience

After college, I began my career in the construction industry. I chose to become an apprentice Architect and 4 yrs later I opened my own architectural design firm. Six years later I moved to Florida to buy & develop land and build. I became a State of Florida Certified General Contractor and operated my business for 45 years. I built all types of residential and commercial buildings including warehouses, shopping centers, high rise apartments and office buildings and developed sites for other contractors. I retired and became a consultant to the construction industry. I maintain my license and continuing education requirements, operate a small construction company and write a weekly newspaper column for the Palm Beach Post (a Cox publication) with the byline "Ask The Contractor". I am the "technical editor" for a publisher of books that relate to home maintenance.

Organizations
Previously - NAHA Currently - FLCA (Florida Licensed Contractors Assoc.)

Publications
Palm Beach Post newspaper - weekly Q & A column Happy Herald monthly real estate publication - monthly column

Education/Credentials
Michigan State University University of Detroit BS in Engineering

Past/Present Clients
I built a home in Palm Beach for a member of the Pulitzer Family. I was responsible for the completion of a twin hi-rise condominium project for G.E. Credit. I was a partner in the successful development of a P.U.D. (Planned Urban Development) subdivision. I represented the largest home builder from France (Bati Service, S.A.) in the development of a subdivision and the design and construction of the homes.

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