Deck maintenance and safety

A deck takes more weather than almost any other part of a house. Sun dries it out, rain soaks it, and it swells and shrinks with every change. The U.S. Forest Products Laboratory notes that this cycle causes checks, cracks and raised grain, and raises the risk of mildew, decay and insects. [1]

Good deck care has two parts. The surface needs regular cleaning and a fresh finish. The structure underneath, the parts that hold the deck to the house and the ground, needs a yearly safety check. This guide covers both. For what repairs cost, see deck and exterior stair repair.

Cleaning and finishing a wood deck

Know when it needs a new coat. The Southern Forest Products Association suggests a simple test: on a dry day, pour some water on the boards. If it beads up, the finish is still working. If it soaks in, it is time to seal or stain. [2] See the deck stain or paint deterioration finding.

Choose a penetrating finish. The Forest Products Laboratory recommends penetrating finishes for deck boards: water-repellent preservatives (clear or lightly tinted) and semitransparent stains. [1] Paint and solid-color stain form a film that traps moisture and wears through under foot traffic, so both groups advise against them on deck boards and stair treads. They are fine on railings. [1, 2]

Plan on refinishing every year or two. A clear water repellent lasts about a year on exposed surfaces but is the easiest finish to reapply. [1] The Southern Forest Products Association suggests reapplying water repellent about every two years, and semitransparent stains generally last longer. [1, 2] Decks in full sun wear faster than shaded ones.

Let new wood dry first. New pressure-treated lumber is often wet. The Southern Forest Products Association advises waiting until the wood is dry inside and out, and the right wait depends on how the lumber was treated and dried. [2] If the boards came with a factory-applied water repellent, the Forest Products Laboratory suggests letting them weather for 2 to 3 months before finishing. [1] The water test above tells you when it is ready.

Clean gently. Deck cleaners and brighteners remove dirt and mildew. Aggressive scrubbing or power washing can tear up wood fibers, especially on softer woods. Never mix bleach with products containing ammonia, which creates toxic gas. [1] Give a cleaned deck at least two warm, windy days to dry before you apply a finish. [1]

Wood or composite

	Wood (usually pressure-treated pine)	Composite or PVC
Finish	Needs a water repellent or stain every year or two [1, 2]	No stain or sealer for the surface
Cleaning	Deck cleaner, gentle scrubbing [1]	Soap and water and a soft brush [3]
Pressure washing	Can damage the wood fibers [1]	Depends on the product. Trex allows up to 3,100 psi with a fan tip on its newer lines but says not to pressure wash its early-generation boards. [3]
Mold and mildew	Mildewcide in water-repellent preservatives helps [1]	Grows on pollen and dirt left on the surface, so regular cleaning matters [3]
What still needs care	Boards, framing, railings	The framing underneath is usually still wood, so the safety checks below still apply

For composite, follow your brand's care guide. Trex, for example, says to use a plastic shovel, not a metal one, for snow, and to clean food and grease stains within seven days. [3]

The yearly safety check

The North American Deck and Railing Association (NADRA) calls yearly checks critical for keeping decks safe, and recommends having a professional look at your deck too. [4, 5] Walk the deck and look underneath it once a year, ideally in spring. Use a screwdriver to probe wood for soft spots.

1. Ledger board. The ledger is the board that attaches the deck to the house. It should be fastened with bolts or lag screws, not nails. The American Wood Council's deck guide allows only listed fasteners for this connection and does not allow attaching a ledger to brick or stone veneer. [6] NADRA notes that older decks often used nails only. [5] Look for rot, rust, gaps between the ledger and the house, and missing flashing. See ledger board not flashed and ledger board improperly installed.
2. Flashing. Metal or plastic flashing over the ledger should shed water away from the house and be firmly in place. [4]
3. Posts and footings. Posts should sit on concrete footings with metal brackets, not buried in the soil. Probe the bottom of each post for rot. See deck post rot.
4. Joists and hangers. Look under the deck for soft or split joists and for missing or rusted joist hangers, the metal brackets that hold joists in place.
5. Fasteners. Tighten loose screws and replace rusted ones, especially at the ledger. The deck should feel solid with no sag or sway. [4] Treated lumber needs corrosion-resistant fasteners, such as hot-dip galvanized or stainless steel. [6]
6. Railings. Push on every railing and post. They should not move. [4]
7. Baluster gaps. In North Carolina, the City of Raleigh's deck guide calls for guards on decks 30 inches or more above the ground, at least 36 inches high, with no more than 4 inches between pickets. [7] A 4-inch gap keeps a small child's head from slipping through. See baluster spacing too wide.
8. Stairs. Handrails and stringers (the angled boards that hold the steps) should be firm, and gaps in the stairs should be under 4 inches. [4] Handrails are generally set 34 to 38 inches above the stair nosings. [6, 7]
9. Lighting and trees. Make sure stair and walkway lights work, and look for dead branches hanging over the deck. [4]
10. Grills and fire pits. Keep heat sources on a non-combustible surface and away from anything that can burn, following the manufacturer's instructions. [4]

Rules differ by place

Deck rules come from the building code your state and city adopt, and they are not the same everywhere. North Carolina's code, for example, allows stair risers up to 8 1/4 inches, according to Raleigh's guide. [7] Other places use different numbers. If you are adding a deck, rebuilding one or replacing stairs or railings, check with your local building department about permits and the rules that apply. Many older decks were built before today's standards. That doesn't make them unsafe, but loose railings, wide baluster gaps and a nailed ledger are worth fixing.

When to call a professional

Stop using the deck and call a contractor if:

• The ledger is pulling away from the house, or is fastened with nails only.
• Posts, joists or the ledger are soft when you probe them.
• The deck sways or bounces when you walk on it.
• A railing moves when you push on it.

HomeCloud is a licensed general contractor that evaluates homes and prices and does the repairs. We can send you a priced estimate for deck repairs or safety upgrades. If your deck sits against siding, our guide to what kind of siding you have explains how to keep that wall dry too.

Sources

1. USDA Forest Products Laboratory, Finishes for Wood Decks (FinishLine, 2013)
2. Southern Forest Products Association, Finishing, Maintenance and Inspection
3. Trex, How to Clean a Trex Deck
4. North American Deck and Railing Association, 10-Point Consumer Checklist
5. North American Deck and Railing Association, Check Your Deck During Deck Safety Month
6. American Wood Council, Prescriptive Residential Wood Deck Construction Guide (DCA 6)
7. City of Raleigh, All Decked Out? Deck Guide