Black mold is eating through your fence posts right now. Not staining them. Eating them.
Last week in Cypress, a homeowner ignored “just a few spots” for six months. Those spots rotted through two fence posts. Cost him $400 to fix. The spots? He could’ve cleaned them himself for $18 in bleach.
Here’s the 60-second test that tells you if this is a $18 problem or a $2,000 problem.
The 60-Second Test (Do This First)
Mix 1 cup bleach with 10 cups water in a spray bottle. Spray a black spot. Wait 60 seconds.
Spot lightens to gray/brown? Surface mold. Clean it yourself. Total cost: $60 in materials.
Spot stays completely black? Deep mold. Needs professional treatment. Cost: $400-800 depending on damage.
That’s it. One minute tells you everything.
DIY Cleaning (For Surface Mold Only)
ONLY do this if your bleach test showed spots lightening. If spots stayed black, skip to “Call a Professional” section below.
What You Need ($60 total):
- Clorox Outdoor Bleach (2 gallons): $18
- Pump Sprayer: $30
- Gloves: $7
- Safety Glasses: $8
How to Clean:
- Wet the fence with garden hose first (reduces bleach absorption)
- Mix solution: 1 part bleach to 4 parts water in pump sprayer
- Put on gloves and glasses (bleach burns skin, spatters in eyes)
- Spray black spots until wood looks wet, not just damp
- Wait 15 minutes (keep wet by respraying if it dries)
- Scrub gently with soft brush, following wood grain
- Rinse thoroughly with garden hose
- Check in 2 weeks – if spots return, you have deep mold
Time needed: 2-3 hours for average fence
This only works on surface mold. One Spring homeowner tried DIY on spots that stayed black in the test. Spent $60 and a Saturday. Two weeks later, spots came back darker. Professional inspection showed deep rot. Cost: $1,800 in board replacement. His $60 “savings” cost him $1,800.
Why Your Fence Has Mold (And Your Neighbor’s Doesn’t)
Walk your fence line. See where black spots cluster? That’s not random.
North-facing sections get 70% less sunlight. Stay damp until 2 PM. Your neighbor’s south-facing fence dries by 10 AM. That’s why they don’t have mold.
Under trees means fence stays wet 4 hours longer than sunny sections. I see this on 90% of Woodlands fences – black spots under tree canopy, clean fence in sun.
Near AC units means constant condensation drips. Fences next to AC units get mold 3x faster. Posts can rot through in 18 months.
Poor drainage at fence base. Water pools where builders didn’t grade properly. Mold starts at ground level and climbs up.
Your fence isn’t worse quality than your neighbor’s. It just has moisture, shade, and no airflow. Perfect mold conditions.
What Happens If You Ignore Black Mold
I’m showing you this timeline because “waiting to see what happens” has predictable results.
First 90 Days:
- Damage: 5-10 spots, surface level
- Fix cost: $60 DIY or $300 professional
- Still fixable: Yes, easily
Mike from The Woodlands was here in March. “Just a few spots by the AC unit.”
This Summer (4-6 months later):
- Damage: 20-30 spots, wood feels soft
- Fix cost: $800-1,200 (treatment + some board replacement)
- Getting expensive: Yes
Mike called in July. “Spots spread everywhere. Boards are turning black.”
Next Spring (7-12 months):
- Damage: Entire sections black, posts soft at ground level
- Fix cost: $2,000-4,000 (partial fence replacement)
- Too late for cleaning: Yes
Mike replaced 40 feet of fence. Posts were compromised. One storm could’ve brought it down.
That’s the progression I see every week. The timeline is always the same. Only the homeowner’s name changes.
When DIY Won’t Work (Three Warning Signs)
1. Bleach Test Failed
Spots stayed black after 60 seconds? That’s deep mold. DIY surface cleaning will fail. You need commercial fungicide that penetrates 3/4 inch deep. Only professionals have access to this.
2. Thumbnail Test Failed
Press your thumbnail into wood next to a black spot. Goes in more than 1/8 inch? Wood structure is compromised. Cleaning won’t fix rotten wood. Board needs replacement.
3. Posts Are Affected
Black spots on fence posts, especially at ground level? That’s foundation damage. Posts hold up your entire fence. Once posts are compromised, whole sections can collapse.
A Katy fence I’d seen in April collapsed in August during a storm. Homeowner had ignored black spots on one post. Insurance called it “deferred maintenance” – wouldn’t cover it. Cost him $6,200 out of pocket.
If any of these three apply, call a professional. DIY won’t work.
Why Professional Treatment Lasts 2-3 Years
Home Depot mold cleaner: $15, penetrates 1/8 inch, lasts 3 months
Professional fungicide: $200 per gallon, penetrates 3/4 inch, lasts 2-3 years
Here’s why that matters: Black mold roots go 1/2 inch deep. Store products kill surface mold but leave roots alive. Mold regrows in 2-4 weeks. You spray again. And again. After 4-5 cycles, you call us. By then, what was $400 treatable mold is $2,000 in board replacement.
We don’t just kill mold. We apply inhibitors that prevent new mold from establishing. One treatment protects for years.
The warranty difference: Store products have no warranty. Professional treatment – if mold returns during warranty period, we retreat free.
One Woodlands homeowner tried DIY three times over six months. Spent $180 + six weekends. Mold kept returning. We treated it professionally for $850. Zero mold regrowth for 28 months and counting.
His DIY: $180 + six weekends = failure
Professional: $850 one time = 28+ months protection
What Professional Treatment Costs
Let me show you real numbers from jobs I did last month:
Small job (5-15 surface spots):
- Cost: $250-400
- Time: 2-3 hours
- What’s included: Fungicide treatment, preventive application, 1-year warranty
Medium job (20-40 spots, some deep):
- Cost: $700-1,000
- Time: 4-6 hours
- What’s included: Commercial fungicide, minor board replacement (3-5 boards), 2-year warranty
Large job (40+ spots or soft posts):
- Cost: $1,500-2,500
- Time: Full day
- What’s included: Complete treatment, board replacement, post reinforcement, 3-year warranty
Sarah’s story (Bellaire): Had 20 black spots in March. I quoted $600. She wanted to “wait and see.” Called back in September with 60+ spots and soft wood. Cost: $2,400.
Her March choice: Wait = save $600 now
Her September reality: Waited = cost $1,800 more
Your 48-Hour Action Plan
Today (Do Now):
- Do the 60-second bleach test on 3-5 different spots
- Take photos of all black spot areas
- Stop sprinklers from hitting fence
- Press thumbnail into wood near worst spots
- Check posts at ground level for black spots
Tomorrow:
If bleach test showed lightening:
- Buy DIY materials this weekend
- Clean yourself ($60)
- Recheck in 2 weeks
If bleach test showed spots staying black:
- Text us a photo: (832) 258-6164
- Get professional assessment
- Don’t waste time on DIY that won’t work
Why 48 hours?
Every Houston rainstorm feeds mold growth. I’ve seen spots double after one week of afternoon thunderstorms. The problem gets worse while you decide.
Text Us Your Black Spot Photos
Send two photos to (832) 258-6164:
- Close-up of worst black spot area
- Wide shot showing how many spots total
We’ll text back within 2 hours:
- ✓ If DIY bleach cleaning will work
- ✓ If you need professional treatment
- ✓ If replacement is necessary
- ✓ Exact cost for professional work
Most Cypress fences I see have 10-20 surface spots that respond to cleaning ($400-600). Caught early, it’s manageable. Wait through summer, it becomes replacement.
Or call: (832) 258-6164
We’ll be honest about whether DIY will work or if you need professional help. No pressure – just honest assessment of what your fence needs.
Common Questions
“Can I just paint over the mold?”
No. Paint traps moisture and accelerates rot. The mold keeps eating wood under the paint. Fences painted over mold can collapse within 6 months.
“Will spots spread to my house?”
No, fence mold won’t “jump” to your house. But check your deck posts and house siding at ground level – they might have similar moisture problems.
“Do I need to replace the whole fence?”
Usually no. Most jobs are cleaning or partial board replacement. Full replacement only if multiple posts are compromised.
“How fast do spots spread?”
In Houston summer: spots can double in size monthly. What starts as 10 spots in March becomes 40 spots by July if untreated.
Service Areas: Cypress TX • The Woodlands TX • Katy TX • Spring TX • Bellaire TX
Text Photos: (832) 258-6164
Mold Treatment • Board Replacement • 2-3 Year Protection Guarantee
