Building Codes

• City or state building codes determine the way decks are structured and built. Not following the codes can get a homeowner into trouble with the authorities, and provide a situation where punitive fines are leveled and the deck being torn down. Before any work is done make sure the plans are approved by the proper authority.
  
  

Pressure Treated Wood

• Standard building codes provide that any wood in direct contact with concrete be pressure treated wood. Concrete acts as a wick and draws moisture up from the soil. This keeps the bottom of the wood against the concrete patio constantly damp. Non-treated wood soon become an open invitation to mold, decay and insect damage. Pressure treated wood, however, resists those problems and will last for many years.
  
  

Vapor Barrier

• Another way to help prevent problems is to lay a vapor barrier across the concrete before attaching the floor joists. The vapor barrier can be cut into strips and laid directly under where the joists will attach, or the whole patio can be covered to prevent any moisture from seeping upwards. If you are laying insulation between the joists then a whole patio covering will work best.
  
  

Slanted Floor

• Concrete patios are designed to have a slight slant away from the house to prevent water from puddling on them. If you lay the floor joists directly onto the concrete the floor will also take on the same slant. This is acceptable since you don't want the deck floor to puddle water either. However, the slant is subtle enough that some people miss it, but when they add rails around the deck, or even a roof, they wonder why nothing will square up at the corners. Adjust any further construction to work around the slanted floor for proper square railings and corners.