Exterior Decks

By Stephen McDermott

Exterior wood framed decks are a common accessory for residential homes.  Who doesn’t enjoy coffee and the newspaper or just lounging outside on their deck on a gorgeous morning?  They offer increased living space for a homeowner and also help increase property values. 

The construction of the structural components of the main frame of the deck (joists, beams, and columns) are important, however, it is not uncommon to hear a news report of the collapse of an occupied deck.  Currently, there are no provisions in the Massachusetts State Building Code to enforce periodic review of these decks.  The responsibility lies solely with the Owner to be diligent about maintenance of their deck. 

Wood framed decks are exposed to the environment year round and should be constructed with treated lumber to resist decay, especially in places like New England where they are subjected to a full range of temperatures and exposure conditions.  From my experience with various wood framed decks, maintenance is usually limited to the replacement of deck boards and rarely focuses on the actual deck framing, anchorage to the house, or footing support.  Unless, of course, a noticeable problem arises such as lateral or vertical settlement, the feel of a bouncy floor, or visible “pull-out” or separation of a main element attachment to the house.  The decks are also susceptible to the corrosion of fasteners (nails, screws, lag bolts) and metal support angles due to their exposure to the weather.

Over time it is not unusual for columns, beams, and joists to be replaced due to wood decay.  Some wood column repairs attempt to splice new lumber to an existing wood column, which, in some cases, results in a reduction of lateral stiffness of the column at the splice location.  The quality of installed lumber and strength of the actual construction are important.  I have observed that the wood frame of an eighty year old multi-story deck is still structurally sound while the framing of a deck is severely deteriorated after only five years.

In my opinion, an exterior deck should be inspected by an engineer every five years. The inspection should include a review of the wood framing (joists/columns), footing settlement, anchorage of the deck to supports (exterior wall and columns), railings, stairs, and deck boards.