This week I'm taking a more serious tone to discuss a very important topic (and not just share the joy I take in our work). The fact is, we’ve earned a reputation as one of Philadelphia’s top builders of backyard and roof decks because we understand the critical elements in a safe and secure deck. The most important factor to consider when building decks is safety (waterproofing runs a close second in roof decks; I’ll address this topic in a later post). And two important components of a safe deck are the ledger-to-house connection (whenever possible) and railings.
An improperly attached ledger can lead to a deck collapse, as tension and compression forces work to pull the ledger away from the house. The primary force pushing down on the ledger is gravity, known as the vertical load (the weight of building materials plus the weight of people, furniture, etc. on the deck). In addition, lateral loads (such as wind and swelling / shrinking of the deck framing) can exert horizontal force away from the house.
We take extreme care to follow the 2012 International Residential Code for fastener-placement of the ledger board to the house. The IRC spacing guide includes specifics for the number and type of attachment bolts, the bolt stagger pattern, and their exact placement on the ledger board.
Railing posts must always be fastened to the deck framing with two galvanized ½” carriage bolts each (not lag screws) that are secured with washers and nuts. Yet we always take the extra step of attaching the posts to the inside of the perimeter of the deck. Then we use wood blocking to anchor them to the framing, helping to resist forces pushing on top of the post and reinforcing the framing itself.
This approach to railing posts takes more time, more material and decreases the useable deck space by a little bit — but these nominal differences become insignificant when considering the safety of those enjoying our decks.
The photos below show a roof deck we recently built in the Fishtown neighborhood of Philadelphia.