Why deck structure deserves attention
Decks are exposed to weather year-round, and their structural parts, many hidden under the boards, can deteriorate long before the surface looks bad. Deck failures, when they happen, can injure people. An inspection of an older deck is worth doing every year, and before hosting a large gathering.
Warning signs
- The deck moves or sways when people walk on it.
- The deck pulls away from the house, or there's a gap between the deck and the wall.
- Soft or spongy spots in boards, joists or posts. Probe wood with a screwdriver; it shouldn't sink in easily.
- Rusted, corroded or missing connectors, bolts and nails.
- Cracked or leaning posts, or posts sitting on bare soil or a crumbling footing.
- Loose or wobbly railings, or railings with openings large enough for a child to slip through.
- Stairs that flex, have loose treads, or lack a handrail.
The ledger connection
When a deck attaches to a house, it's held by a ledger board fastened to the house's rim joist. The ledger connection is critical. It should be fastened with through-bolts or structural screws, not just nails, and flashed so water can't get behind it and rot the ledger and the house framing. Missing or failed flashing at the ledger is a common cause of hidden rot. If your deck has no visible flashing at the ledger, or you see stains on the wall below it, have it inspected.
Footings and posts
Footings carry the deck's weight to the ground. They should be sized for the load and, in cold climates, set below the frost line so frost can't heave them. Posts should be connected to footings with metal post bases that keep the wood off the concrete, and to beams with proper connectors or notches. Posts buried directly in soil or concrete tend to rot at ground level.
Joists and beams
Joists and beams should be sized and spaced for the span and the load. Look for sagging, cracks, rot and missing joist hangers. Joist tape on the tops of joists slows moisture damage under the boards.
Railings and stairs
Railings must resist a person falling against them. Posts must be fastened securely, not just nailed. Openings should be small enough to keep children from slipping through. Stairs need consistent riser heights, solid stringers and handrails where required.
Repair or rebuild?
Replacing boards, adding connectors, rebuilding stairs or replacing railings are common repairs. If the ledger, footings and much of the framing are deteriorated, rebuilding the deck may be safer and more cost-effective than piecemeal repairs. A contractor should explain the condition of each part.
Questions to ask
- How is the ledger attached, and is it flashed?
- Are the footings adequate and below the frost line?
- Are connectors and fasteners corroded?
- Do the railings and stairs meet current safety standards?
- Is it worth repairing, or should the deck be rebuilt?
- Will repairs need a permit?
Deck inspections when buying a home
A general home inspection may note a deck's condition, but it may not look closely at the ledger, footings and connectors. If the house has an older or high deck, consider a dedicated deck inspection before closing.
Temporary safety measures
If you find a serious problem, such as a rotted ledger, a cracked post or a loose railing, keep people off the deck or the affected area until it's repaired.