Deck Season is Coming: Repair, Stain, or Replace?

April in Missouri means one thing for your deck: inspection time.

Your deck just survived five months of freeze-thaw cycles, ice, snow load, and cold rain. Before you drag the patio furniture out and fire up the grill, you need to take an honest look at what you’re standing on.

I work on decks all spring and summer across St. Louis County, St. Charles County, and into the Metro East. The question I hear most is: “Can this deck be saved, or does it need to go?” The answer isn’t always obvious, but there’s a systematic way to figure it out.

Let me walk you through the inspection, the decision framework, and the real costs involved.

The Deck Inspection: 30 Minutes That Matter

Grab a screwdriver, a flashlight, and a notepad. You’re looking for three categories of problems: surface issues, structural issues, and connection issues.

Surface Assessment

Walk every board. Not a casual stroll — a deliberate walk where you’re paying attention to what you feel and see underfoot.

What you’re looking for:

• Splintering and cracking. Surface checks (small cracks along the grain) are normal on older wood and mostly cosmetic. Deep splits that go through the board’s full thickness are structural concerns.
• Warping and cupping. Boards that have twisted, bowed, or cupped (edges higher than the center) create uneven walking surfaces and hold water, which accelerates rot.
• Soft spots. Push the tip of your screwdriver into suspect areas. Solid wood resists. Rotted wood lets the screwdriver sink in with little effort. Check the ends of boards where they meet joists — that’s where moisture lingers longest.
• Color and finish. If your deck was stained or sealed, pour a small amount of water on the surface. If the water beads, the finish is still working. If it soaks in immediately, the finish has failed and the wood is unprotected.

The screwdriver test is your most important diagnostic tool. Do it on every board that looks suspect, especially at the joist lines where boards are fastened. Wood rot is often invisible on the surface — the top of the board looks fine, but the underside where it contacts the joist is soft and crumbling.

Structural Assessment

Now get underneath the deck if possible, or at minimum look at the accessible structural components.

Joists. These are the horizontal framing members that the deck boards sit on. Check for:

• Rot or soft spots, especially at the ends where joists sit in hangers or on the beam
• Cracks or splits, particularly at fastener locations
• Insect damage — termites and carpenter ants target damp wood

The International Residential Code requires deck joists to be a minimum of 2x6 lumber for most spans, with maximum spacing of 16 inches on center for standard decking materials. If your joists are undersized, over-spanned, or damaged, that’s a structural failure waiting to happen.

Beams and posts. Check where posts meet the ground. Wood posts set directly in soil or concrete are the most vulnerable to rot. The American Wood Protection Association standards require ground-contact-rated preservative treatment for wood in contact with soil, but even treated wood degrades over time.

Push firmly on each post. If there’s any wobble or give, investigate further. A post that’s rotted at the base can fail suddenly under load — and “load” includes your family and friends at a barbecue.

The ledger board. This is the single most critical structural component on an attached deck. It’s the board that connects the deck to the house, typically bolted through the rim joist of the home’s floor system.

The North American Deck and Railing Association and the International Residential Code both emphasize ledger connection as the primary point of failure in deck collapses. Water infiltration behind the ledger causes rot in both the ledger and the house’s rim joist, weakening the connection until the deck separates from the house.

Pull back any flashing at the top of the ledger and look for:

• Staining, soft wood, or visible rot
• Gaps between the ledger and the house wall
• Missing or inadequate flashing (there should be metal flashing directing water away from the connection)
• Corroded or undersized fasteners

If the ledger is compromised, this is not a repair-and-stain situation. This is a safety issue that needs immediate professional attention.

Connection Assessment

Fasteners. Look at the nails or screws holding your deck boards down. Are they:

• Popping up above the surface? (trip hazard and water entry point)
• Corroding? (standard steel fasteners will rust in treated lumber — you need stainless or coated fasteners)
• Pulling out? (sign of wood deterioration at the fastener point)

Railing posts. Grab each railing post and push it sideways. The International Residential Code requires deck railings to resist a 200-pound lateral load at the top. A post that moves noticeably under hand pressure doesn’t meet that standard.

Check how the posts are attached. Posts bolted through the rim joist or fascia with through-bolts are the strongest connection. Posts notched into the deck boards or attached with only screws or nails are weaker and more prone to failure. If your deck is above 30 inches off the ground, railing integrity is a safety-critical issue.

Stair stringers. If your deck has stairs, check the stringers (the sawtooth-shaped boards that support the treads). Stair stringers take concentrated loads and are frequently exposed to ground moisture at the bottom. Rot at the base of stair stringers is extremely common and makes the stairs dangerous.

Decision Time: Repair, Stain, or Replace?

Based on your inspection, you’ll fall into one of three categories.

Stain or Seal (Cosmetic Refresh)

When it makes sense:

• Structural components are solid
• No significant rot or soft spots
• Boards are sound but weathered or graying
• The existing finish has faded or worn away
• Fasteners are tight and intact

What’s involved: Power-wash the deck to remove surface grime, mildew, and old finish. Let it dry for at least 48 hours — this is important; applying stain to damp wood traps moisture and causes peeling. Apply a penetrating stain or sealant.

Stain vs. seal: Stain adds color and provides UV protection along with moisture resistance. Clear sealers provide moisture protection but let UV radiation continue to break down wood fibers. In Missouri’s sun exposure, I recommend stain over clear sealer for better long-term protection. The Forest Products Laboratory (USDA Forest Service) confirms that pigmented finishes significantly outperform clear finishes in durability and UV protection.

Cost: DIY staining runs about $1 to $3 per square foot for materials. Hiring it out typically costs $3 to $6 per square foot in the St. Louis market, including power washing and prep.

A typical 300-square-foot deck: $300 to $900 DIY, $900 to $1,800 professional.

Repair and Refinish (Targeted Fixes)

When it makes sense:

• Some boards are damaged but the framing is sound
• A few joists need sistering (reinforcement) but the overall structure is solid
• Railing posts need tightening or replacement
• Fasteners need upgrading
• The ledger connection is intact and dry

What’s involved: Replace damaged boards and sections of railing. Sister compromised joists by bolting new lumber alongside the existing joist. Replace corroded fasteners with stainless or coated alternatives. Restain or reseal after repairs.

Cost: Varies widely depending on scope. Board replacement runs $3 to $8 per linear foot for materials plus labor. Joist sistering is typically $100 to $300 per joist. Post replacement runs $50 to $150 per post.

A typical repair job on a 300-square-foot deck with six boards replaced, two joists sistered, and a full restain might run $1,500 to $3,500.

Replace (Full Rebuild)

When it makes sense:

• Multiple joists are rotted or compromised
• The ledger board is damaged or the connection to the house is failing
• Posts are rotted at the base
• More than 40% of the deck boards need replacement
• The deck was built without proper code compliance (no ledger flashing, undersized joists, improper connections)
• The deck is old enough that repair costs approach replacement costs

What’s involved: Full demolition and rebuild. This is permit territory — most municipalities in St. Louis County and St. Charles County require a building permit for new deck construction. The permit process includes plan review and inspections to verify compliance with the International Residential Code.

Material choices:

Pressure-treated lumber remains the most affordable option. Modern treated lumber (using micronized copper azole or MCA treatment) is effective against decay and insects. The American Wood Protection Association sets retention standards for treated lumber used in different applications. Budget roughly $15 to $25 per square foot for materials on a treated lumber deck.

Composite decking (brands like Trex, TimberTech, Fiberon) costs more upfront — $25 to $45 per square foot for materials — but requires no staining, resists rot and insects, and carries 25-year or longer warranties. The framing underneath is still pressure-treated lumber, so structural maintenance remains important.

Hardwood decking (ipe, cumaru, garapa) is the premium tier — $30 to $60+ per square foot for materials. These tropical hardwoods are naturally resistant to decay and insects and have exceptional longevity, but they’re heavy, hard to work, and expensive.

Cost for a full replacement: A 300-square-foot pressure-treated deck, professionally built with proper permits and inspections, typically runs $6,000 to $12,000 in the St. Louis market. Composite decking pushes that to $10,000 to $18,000. These numbers include labor, materials, permits, and basic railing.

Wood vs. Composite: The Real Talk

I get this question every time someone is deciding on replacement material, so let me lay it out.

Pressure-treated wood is cheaper, takes paint and stain well, and feels more traditional underfoot. But it requires maintenance every two to three years (cleaning, staining, or sealing), and it will eventually rot despite the treatment. In Missouri’s climate, expect a well-maintained treated lumber deck to last 15 to 25 years.

Composite costs more upfront but virtually eliminates surface maintenance. You wash it occasionally. That’s about it. Modern composites also resist fading, staining, and mold better than earlier generations. The tradeoff: composites get hotter underfoot in direct sun (relevant in Missouri summers), they can’t be refinished if scratched deeply, and some people don’t like the synthetic feel.

My honest take: if you’re planning to stay in the home long-term and you don’t want to restain every few years, composite pays for itself over time. If you’re selling within five years or you prefer the look and feel of real wood, treated lumber is the practical choice.

Permits and Code: Don’t Skip This

If you’re replacing a deck or building new, check with your local building department. In St. Louis County, unincorporated areas are governed by the county building department. Incorporated municipalities have their own permitting offices.

St. Charles County municipalities — O’Fallon, Wentzville, St. Peters, and others — all require permits for new deck construction. The permit process ensures your deck meets current code for structural capacity, railing height, stair dimensions, and ledger connection.

Building without a permit is a gamble. If you sell the house, the unpermitted deck will come up during the buyer’s inspection. At best, it complicates the sale. At worst, you’re required to bring it up to code or remove it.

The Timing

In Missouri, deck season runs from late April through October. The best time to schedule deck work is April or May — before the summer rush and while temperatures are ideal for stain application. Most exterior stains require application temperatures between 50 and 90 degrees and no rain for 24 to 48 hours after application.

If your deck needs work, now is the time to make the call. By June, most contractors in the St. Louis area are booked out several weeks for deck projects.

What To Do Next

Go inspect your deck this weekend. Use the checklist above. Be honest about what you find. And if you’re not sure whether what you’re seeing is cosmetic or structural, take some photos and send them our way. We’ll take a look and give you a straight answer.

We handle everything from board replacements and railing repairs to full refinishing. If it’s time for a rebuild, we can help you navigate the options and get it done right.

Your deck is where you spend your Missouri summers. Make sure it’s safe, solid, and worth spending time on.