Discovering mold or rot on your deck can be alarming—but acting quickly can save you thousands in deck repair costs or even prevent a full replacement. Texas’ humid climate makes decks especially vulnerable, so knowing how to assess and fix damage is crucial.
This guide covers:
✅ How to tell mold vs. rot (with pictures)
✅ DIY fixes for minor damage
✅ When you need professional moldy deck repair in Texas
✅ Cost comparisons: repair vs. replacement
✅ Prevention tips for Texas climates
Appearance: Black, green, or white fuzzy patches
Feels: Slimy or powdery
Location: Top of boards, railings
Fix Cost: $200–$800 (clean + seal)
Appearance: Brown crumbling wood, dark streaks
Feels: Soft/spongy (screwdriver penetrates easily)
Location: Joists, posts, ledger board
Fix Cost: $500–$5,000 (depending on extent)
Pro Tip: Push a screwdriver into suspicious areas—if it sinks ¼” or more, you likely have rot.
<10% affected? → Spot treatment
10–30% affected? → Board replacement
>30% affected? → Call a deck repair pro
Supplies Needed:
Deck cleaner (oxygen bleach recommended)
Stiff brush or pressure washer (≤1500 PSI)
Mold inhibitor spray
Process:
Wet deck to prevent spores spreading
Apply cleaner, scrub with grain
Rinse thoroughly
Apply mold inhibitor
Let dry 48+ hours before sealing
Warning: Never use chlorine bleach—it damages wood fibers.
For Small Areas (<6″):
Cut out rot with chisel
Apply wood hardener
Fill with epoxy putty
Sand smooth
For Large Areas:
Replace entire boards/joists
Use ground-contact rated pressure-treated wood
Apply waterproofing membrane to cuts
Seek pro help if:
✔ Ledger board is rotting (where deck attaches to house)
✔ >3 structural joists are damaged
✔ Footings or posts are compromised
✔ You’re unsure about safety
Texas-Specific Risk: Hidden termite damage often accompanies rot in humid areas.
| Solution | Cost per Sq.Ft. | When to Choose |
|---|---|---|
| Mold cleaning | $0.50–$1.50 | Surface mold only |
| Board replacement | $8–$20 | <30% damage |
| Joist/beam repair | $25–$60 | Localized rot |
| Full deck replacement | $15–$35 | >40% damage |
Annual Cleaning
Use oxygen bleach solution
Clear debris between boards
Proper Sealing
Reapply oil-based sealant every 2–3 years
Focus on end grains (most absorbent)
Improve Drainage
Ensure ¼” slope per foot away from house
Install gutter extensions if roof drips on deck
Small mold/rot spots can become structural hazards in just 6–12 months in Texas humidity.
DIY if:
Damage is superficial
You’re comfortable with carpentry
Call deck repair pros if:
Structural elements are involved
You see widespread damage
