House Painter Houston • Exterior Mold & Mildew Treatment
Exterior Mold & Mildew Painting
Houston’s humidity feeds exterior mildew year-round. Painting over mildew without killing it first makes it grow back faster. We treat, wash, and coat with mildew-resistant product — in that order.
Executive Summary: Exterior Mold & Mildew Painting
Exterior mold and mildew painting covers the biocide treatment, cleaning, and repainting of Houston exterior surfaces with visible mildew or algae growth. In Houston’s humid climate, mildew is not a painting problem — it is a moisture management and prep problem that determines whether the new coating stays clean.
Standard mildew treatment system: apply diluted bleach or biocide solution to all affected surfaces → dwell time → pressure rinse → full dry → mildew-resistant primer → 2 coats of mildew-resistant 100% acrylic exterior paint. Most projects complete in 2–4 days. Estimated cost: $2,000–$10,000.
Painting over mildew without treatment accelerates regrowth. The mildew organism on the surface feeds on the new paint as a substrate and grows back faster than it grew on the old paint. Biocide treatment before painting is non-negotiable in Houston.
The Fast Facts on Exterior Mold & Mildew Painting
What does mold and mildew exterior painting cost?
The short answer is an estimated $2,000 to $10,000 depending on home size, mildew extent, and surface type. Limited mildew on one shaded wall at the lower end; heavy whole-home mildew on a large property with multiple surface types at the upper end. Your written quote is confirmed after an on-site assessment.
How do you treat mildew before painting?
The short answer is a biocide wash solution — typically diluted sodium hypochlorite with a surfactant or a commercial biocide product — applied to all affected surfaces before pressure rinsing. Biocide is applied first, allowed to dwell for 10 to 20 minutes to kill the organism, then pressure rinsed and allowed to dry. Pressure washing alone moves mildew without killing it.
What paint prevents mildew from coming back?
The short answer is a mildew-resistant 100% acrylic exterior paint — most quality exterior products include a mildewcide additive. Sherwin-Williams Duration Exterior and Benjamin Moore Aura Exterior both include mildewcide. In Houston, correct ventilation and moisture management matter as much as the coating — a mildew-resistant paint cannot compensate for a constantly wet surface.
Typical Houston Exterior Mold & Mildew Painting Projects
Three recent projects across Greater Houston.
North-Facing Mildew Repaint — Katy (77494)
February 2026 · 2,800 sq ft home, north-facing walls 80% mildew coverage. Biocide wash, pressure clean, full dry time. Mildew-resistant primer + 2-coat Duration Exterior. Clean at 12-month check.
Stucco Mildew Treatment — Pearland (77584)
October 2025 · 2,200 sq ft stucco, rear-facing elevation. Wet area from adjacent drainage. Biocide treatment, masonry primer, 2-coat elastomeric with mildewcide. Drainage grade corrected by owner before painting.
Fence and Porch Mildew Cleanup — Meyerland (77096)
December 2025 · 120 linear ft wood fence + porch ceiling. Heavy mildew from adjacent tree canopy shade. Biocide wash + penetrating stain on fence, mildew-resistant paint on porch ceiling. Both surfaces clean 8 months post-application.
All prices are estimates. Final scope confirmed in your written quote before work begins.
Houston Mildew on Exterior Paint Is a Prep Problem
Mildew growing back through new paint within 6 months
Mildew was painted over without biocide treatment. The organism was still alive on the surface — new paint became its food source. Mildew grows back faster on new paint than old. Biocide treatment before pressure washing kills the organism. This must happen before any paint is applied.
Black streaks on fascia and trim from overhead shade
Tree canopy and overhangs trap moisture and create ideal mildew conditions on fascia and porch ceilings. These areas need biocide treatment, mildew-resistant primer, and a mildew-resistant topcoat with mildewcide. Increasing air circulation under the overhang reduces regrowth rate.
Mildew at the base of walls and on lower siding courses
Ground-level mildew typically indicates grade or drainage issues. Paint over a continuously wet surface will not stay clean regardless of the product. We identify moisture sources during the estimate walk and note them — the source of moisture should be addressed before or alongside the painting work.
Schedule a Walkthrough
We assess mildew extent and identify any underlying moisture sources before writing a number.
Our Process: Done Right the First Time
- 1On-Site Estimate & Surface AssessmentWe walk the full exterior, assess surface condition, identify cracked caulk, soft wood, mildew, and failing paint. You get a written, line-item estimate before we start — prep scope included, not added later.
- 2Full Prep: Wash, Scrape, Caulk & PrimePressure wash to remove chalk, dirt, and loose paint. Scrape all failing paint to bare surface. Caulk every joint, seam, and window surround. Spot-prime bare areas and repairs. Landscaping and hardscaping protected throughout.
- 32-Coat Finish & Final WalkthroughTwo coats of surface-matched exterior coating applied in appropriate weather conditions. We do not paint in direct Houston midday sun or when rain is forecast within 24 hours. Final walkthrough before we leave — no drips on concrete, no paint on windows.
What to Expect: Your Project Timeline
| Stage | When | What Happens |
|---|---|---|
| Estimate & booking | Within 24–48 hours | On-site surface assessment, written quote, color and product selection |
| Pressure wash | Day 1 | Full house wash; mildew treatment where needed; 24–48 hr dry time before paint |
| Scrape, caulk & prime | Day 2 | Scrape failing paint; caulk joints; spot-prime repairs and bare surfaces |
| First coat | Day 2–3 | First exterior finish coat in suitable conditions; not applied in direct midday sun |
| Second coat & walkthrough | Day 3–5 | Second coat; final inspection; concrete and landscaping clean before departure |
These are estimates. Wet weather or heavy prep can extend the timeline.
The Right Time to Schedule Exterior Mold & Mildew Painting
You see black or green growth on the north-facing walls or shaded surfaces.
Visible mildew is active organism growth. Treatment now is faster and cheaper than treatment after it has spread to adjacent surfaces.
A previous repaint developed mildew within one year.
Mildew under the previous paint was painted over without treatment. The only correct fix is biocide treatment, confirmed-clean surface, and mildew-resistant coating system.
Adjacent tree removal increased sun exposure on previously shaded walls.
Walls that were shaded and mildew-prone now have more UV exposure. This is an opportunity to repaint with a mildew-resistant product while the surface is newly accessible.
Best Time to Book
Late fall and winter are the best times to treat and repaint mildew-affected surfaces in Houston — lower humidity slows regrowth during the repaint window.
The Henry Contractor Difference
Weather-smart scheduling
We do not paint in direct Houston midday sun, when rain is forecast within 24 hours, or when humidity exceeds coating manufacturer specs. Paint applied in the wrong conditions fails early — we schedule around the Gulf Coast weather, not around the calendar.
Full prep, no shortcuts
Pressure wash, scrape, caulk, and prime are standard on every exterior job. Skipped prep is the reason most exterior paint jobs fail in 3–4 years instead of 7–10. We do not skip steps to hit a low bid.
No hidden fees
Your written estimate includes the prep scope. If additional rot, caulk failure, or surface damage is found during prep, we document it and get your approval before expanding. Nothing changes without your sign-off.
Transparent Pricing for Exterior Mold & Mildew Painting
| What Drives the Cost | Standard vs. Premium | Hidden Costs to Watch For |
|---|---|---|
| Square footage and number of stories; a single-story 1,800 sq ft home is a different scope than a two-story 3,500 sq ft home with multiple roof lines | Standard: 100% acrylic exterior latex, 2 coats. Premium: Sherwin-Williams Duration or Emerald Exterior for better UV resistance and longer repaint cycle | Wood rot found during prep — boards need replacement before painting; quoted and approved before crew starts |
| Surface condition; paint in good condition needing refresh vs. failing paint requiring full scrape and reprime | Standard: pressure wash, caulk, spot-prime, 2 coats. Premium: full scrape to bare surface, bonding primer, elastomeric or high-build topcoat | Lead paint testing for pre-1978 homes before any sanding or scraping begins |
| Access difficulty; single-story ground-level work vs. multi-story with ladder or scaffold requirements | Standard: one field color + trim color. Premium: multi-color scheme with accent body, trim, shutters, and door coordinated per designer or HOA spec | Failed caulk on all window and door surrounds adds material and labor time to prep |
Mold and mildew treatment + repaint: $2,000–$10,000 depending on extent. Written quote fixed before work starts.
Get an Exact Number
We assess mildew severity, extent, and moisture source before writing a number.
Exterior Mold & Mildew Painting vs. DIY vs. Cheap Labor
| Feature | Henry Contractor | DIY | Cheap Labor |
|---|---|---|---|
| Prep Work | Pressure wash, scrape, caulk, prime — every job, every surface | Wash and prime if motivated; scrape often skipped on hard-to-reach areas | Minimal prep to hit a low bid; failing paint painted over |
| Weather Scheduling | Scheduled around Houston heat, humidity, and rain forecast; no midday direct sun application | Painted on available days; weather conditions not assessed | Painted whenever crew is available; weather failures common |
| Product Selection | Surface-matched exterior coating; 100% acrylic or elastomeric by substrate | Mid-range acrylic; not always substrate-specific | Cheapest available exterior flat; wrong product for surface type common |
| Caulking | All joints, seams, and window surrounds caulked before paint | Caulked on request; gaps and failed caulk common after first rain | Not included; water intrusion through failed joints |
| Pricing Transparency | Written prep-inclusive quote; no mid-job add-ons | Estimate grows with prep scope clarification | Low headline; prep, caulk, and second coat add-ons mid-job |
Who We Partner With
Houston Homeowners
North-facing and shaded walls in Houston are the most mildew-prone exterior surfaces in the state. We treat and repaint with the correct system.
Property Managers
Rental and HOA properties with recurring mildew complaints need a correct-treatment repaint, not a surface repaint that accelerates the regrowth cycle.
Sellers After an Inspection Finding
Exterior mildew is one of the most common inspection findings in Houston. Correct treatment and repaint before listing removes it.
Proudly Serving Greater Houston
We proudly provide professional painting services to homeowners and businesses throughout the Greater Houston area, including: The Woodlands, Katy, Sugar Land, Pearland, Cypress, Memorial, and surrounding neighborhoods.
See our pressure washing service for periodic mildew maintenance, or return to the exterior painting hub.
Frequently Asked Questions
The short answer is an estimated $2,000 to $10,000 depending on home size, mildew extent, and surface type. Localized mildew on one shaded elevation at the lower end; heavy whole-home mildew on a large property with multiple surface types at the upper end.
The short answer is a biocide wash solution applied to all affected surfaces before pressure rinsing. Biocide is applied first, allowed to dwell for 10 to 20 minutes to kill the organism, then pressure rinsed and fully dried. Pressure washing alone moves mildew without killing it — biocide treatment before rinsing is the correct sequence.
The short answer is a mildew-resistant 100% acrylic exterior paint with a mildewcide additive. Most quality exterior paints include mildewcide — Sherwin-Williams Duration Exterior and Benjamin Moore Aura Exterior both do. In Houston’s humid climate, a mildew-resistant coating slows regrowth but cannot compensate for a constantly wet surface or active drainage problem.
The most common causes are painting over live mildew without biocide treatment, persistent moisture from drainage or irrigation issues, or inadequate air circulation under an overhang. The organism survives beneath the paint and grows back through topcoat. Biocide treatment before painting kills the organism at the surface — it does not address underlying moisture sources.
Yes — biocide wash and pressure rinse without painting is a periodic maintenance option for surfaces not ready for full repaint. We offer pressure washing and biocide treatment as a standalone service. Surfaces with failing or faded paint benefit from treatment followed by full repaint to extend the clean period.
Ready to upgrade your property?
Fill out the free estimate form at the top of the page to get started, or call us directly to schedule your on-site walkthrough.