Resources and Deck Safety
Understanding Your Deck's Structure
Having a basic understanding of how a deck is built can be very beneficial when evaluating the safety of an existing deck, as well as when you're choosing a contractor to build your new deck.
The two most important features of a structurally safe deck are the footings and the framing. Knowing what to look for when evaluating your existing deck will help you to determine whether or not your deck is safe. Being familiar with these features will also help you compare what different contractors may offer. Below, we have outlined correct and incorrect deck building practices that will help you evaluate your current deck and familiarize yourself with the best building practices.
Footings
All local jurisdictions in our area require concrete piers (cylindrical concrete columns) that extend below the frostline. In most cases, these piers will be 12 or more inches in diameter and 42 inches deep into the ground. When a deck is being built, a building inspector will come out to the site and verify that all footing holes are the correct size and depth.
The other footing option is called the helical pile. Helical piles are essentially giant steel screws that are driven a minimum of 7 feet into the ground. These are not as common as concrete piers, but are structurally equivalent. We will use these types of footings in some areas that have highly expansive soil or high water retention.
Common footing problems with new and existing decks:
Concrete piers are undersized. Either they do not extend below the 42 inch frostline, or they are smaller than 12 inches in diameter.
Lack of any footings at all. We have come across some decks that have no footings at all, simply posts that are sitting on top of the ground or dug into the ground. If your deck doesn't appear to have any footings, it can be a serious safety hazard.
Framing
Many local jurisdictions will require an inspection of the deck framing prior to any floorboards or railing being installed. A deck's framing mainly consists of: posts, beams, floor joists, and the ledger board. Click the button below to view some framing diagrams of a basic deck.
Common framing problems with new and existing decks:
1) Incorrect ledger board connection. The ledger board is one of the most critical structural components of any deck. This board carries much of the deck weight and must be properly connected to your home. Ledgers must be attached to the framing of your home with special fasteners (lag screws, LedgerLok screws, through bolts). Many existing decks that we see are fastened over siding and not directly into the home's frame, which is common on older builds. A majority of these are also fastened using only basic screws or nails that are not designed to carry a load. If your deck's ledger isn't fastened with a code-compliant fastener, please consult a professional contractor or a building inspector as this is a severe safety hazard, especially on highly elevated decks.
2) Incorrect post-to-beam connection. The other most critical structural component of a deck is the beam. The beam, like the ledger, is what carries the weight of a deck. Improper beam connections to structural posts are a severe safety hazard. The diagram below illustrates the most common incorrect connection, as well as code-compliant connections.
The incorrect connection is extremely dangerous because it relies on nails, screws, or bolts to carry the entire load of the deck. The code-compliant connection relies on the deck's load to be transferred directly to the beam, which is further transferred directly to the posts below it. If your post-to-beam connection is not one of the approved connections above, please contact a professional or building inspector as this can be a major safety hazard, especially on highly elevated decks.
3) Unapproved fasteners in joist hangers and metal hardware. All nails or screws that fasten load-bearing metal hardware, such as joist hangers, must be code or manufacturer approved. We have seen many decks where basic screws or siding nails have been used to make these connections, and these fasteners do not have the shear strength to handle deck loads. If you are unsure of whether or not your deck's fasteners are approved, consider consulting a professional contractor or a building inspector.
4) Improper stair stringer connections. All stair stringers must be connected to the deck using metal hardware. If you do not see any metal hardware connecting the stairs to your deck, there is a risk that staircases can detach from the main deck. Please consult a professional contractor or building inspector to evaluate your stair stringer connections.
Congratulations! If you have stuck around long enough and made it to the end of this page, you will hopefully now have a better understanding of basic deck construction and the potential hazards present in your existing deck. Please feel free to email us or give us a call with any questions you may have.
