Ledgers may also pull away from the building due to lateral loads. Current building codes now require the deck ledgers to have additional lateral connections to the floor framing inside the building. (Figure 1) This specification can complicate repair or replacement scopes as it may require the removal of interior ceiling finishes to implement the proper connection.

Decay When exterior wood decks are subjected to elevated moisture conditions, as typically occurs with normal environmental exposure, decay can ensue. When the wood is not allowed to dry after short-term water exposure, this decay can be significantly accelerated. This is often a major concern with decks that have a soffit below. If any water is allowed to breach the deck surface, it can collect on top of the soffit material and result in extended water exposure to the framing elements. This condition can be especially concerning, as the soffit material may conceal the extent of the damage until there is little to no remaining structure. (Photo 3)

Figure 1: Ledger connection to interior floor framing (2009 IRC)

Deck ledgers are also often improperly integrated into the weatherproof building envelope. When ledgers are either incorrectly flashed or not flashed at all, premature decay may occur at the ledger, leading to deterioration of framing and the compromise of the fastener connections.

Guardrails Guardrail connections to the deck structure are vital to overall deck safety, but are often inadequately constructed. For several years, building codes have required that guardrails “be able to resist a single concentrated load of 200 pounds, applied in any direction at any point along the top, and have attachment devices and supporting structure to transfer this loading to appropriate structural elements.” Due to the leverage arm, applying this load laterally to the top of a 42-inch-high guardrail results in an almost 2,000 pounds of force acting two inches below a 2-by-8 deck framing system where guardrail connections are commonly located. The often-used lag screw or bolt attachment of the guardrail posts to the side of the deck rim joist is not capable of resisting this load. Guardrail posts should be bolted through the deck rim joist and attached to tension hold-down connectors that are fastened to the deck floor framing.

When repairing or replacing guardrails, one should also be cognizant of the opening limitations that a four-inch diameter sphere shall not pass, as many guardrails were installed prior to this code requirement.

Photo 3: Rotting and crushing of a 10-year-old deck rim joist

Hidden wood-decay damage can often be found below concrete topping slabs when present. Concrete can crack, and even when it does not, it is a permeable material. After water travels through a concrete topping slab, it can become trapped on the surface of the wood deck sheathing below. These types of deck systems commonly are not constructed with a proper drainage plane below the concrete topping slab, and often fall victim to premature deterioration due to decay.

What to Do Many industry trade associations and connector manufacturers offer consumer checklists that can be helpful in identifying deck safety issues. Investigation of the deck by a qualified engineer can provide a reliable and comprehensive deck safety condition assessment. If a problem is identified, an engineer can properly assess the condition and provide advice regarding required repairs to the existing deck, or the need for a complete deck replacement.

So as the springtime grilling season hits full stride, as tempting as it may be to run out onto the deck to check on the bacon wrapped jalapenos, you may just want to take a look underneath the deck first. Happy (and safe) grilling!

www.wscai.org

25