By Michael J. Sladki, P.E., ECS Mid-Atlantic
In the Summer of 2020, two residential decks collapsed in Virginia Beach, resulting in multiple injuries.
In response, the City of Virginia Beach passed a zoning ordinance requiring owners of short-term rental properties to have their decks inspected by a licensed structural engineer every three years.
Structural forensics are the tools used to determine the cause of structural failures and prevent them in the future. Visual observations by a structural engineer are one of most effective methods used in structural forensics. After performing over 100 deck inspections across the coast this checklist of common issues has emerged:
1) Connectors
Ledger boards are required to be attached to the structure with bolts or lag screws. Typically, these ledgers are also constructed with a lip board to be used as a bearing point for joists. In many cases, these ledgers and lip boards are only attached with nails. Given the highly corrosive salt environment, the nails found are often corroded, almost to the point of complete section loss.
2) Lateral connections
Current code requires positive lateral attachment of the deck to the structure. Often, this connection is found missing, which allows the joists to slip off the ledger lip support, either due to shrinkage, natural curling/warping of the joist and lateral movement. This is one of the most common ways that a deck will fail.
3) Beam bearing
Beams should be secured to piles with through-bolts and should be supported in a bearing condition. In many cases, beams are found simply bolted to the side of the pile with no bearing support. In the highly corrosive environment, bolts with the appearance of only minor corrosion on the head are found to be completely disintegrated in the middle
4) Beam splices
Beam splices should occur at locations of support and all piles of the beam should be securely fastened to one another. In many cases, piles observed are only nailed together (see above about nails in the corrosive environment). In other cases, beam splices occur at mid-span of the beam, which is structurally unsafe.
5) Handrails
In many cases railing posts consist of a notched 4x4 with a single bolt into the band board.
While this connection may seem secure during initial construction, it quickly loosens and becomes a safety hazard.
6) Bay Windows
Bay windows are typically constructed by cantilevering the floor joists over the lower-level wall.
When designed with the intent of a future deck being installed, the joists will be sized properly to account for this future load. However, if not designed properly, the deck may overload the structure and create a critical issue with the building structure itself. Given that original drawings and design for the home are often not available, a much more detailed investigation is required.
Should you notice any of these issues, contact ECS to assist with these critically important safety inspections.
Michael Sladki is vice president, principal & engineer at ECS Mid-Atlantic, LLC.