Pressure Washing Houston • Mold & Mildew Removal
Mold & Mildew Removal Service
Houston mildew is a year-round problem — the humidity never fully drops. Pressure washing without biocide treatment moves mildew around the surface and it regrows within months. We kill it first, then wash it off.
Executive Summary: Mold & Mildew Removal Service
Mold and mildew removal service covers the biocide treatment and pressure washing of exterior surfaces affected by mold, mildew, algae, or moss in Houston. The method matters: pressure washing without biocide treatment moves the organism, it does not kill it. Regrowth on a recently disturbed surface is often faster than on the original surface.
Standard mildew removal: organism identified → correct biocide or fungicide applied → 15–30 minute dwell → pressure wash at substrate-appropriate PSI → rinse. Estimated cost: $100–$2,000 depending on area and surface type.
Houston’s Gulf Coast humidity makes mildew removal a recurring maintenance item rather than a one-time fix. Annual treatment keeps buildup manageable. Surfaces in permanent shade under tree canopy may need semi-annual treatment.
The Fast Facts on Mold & Mildew Removal Service
What does mold and mildew removal cost?
The short answer is an estimated $100 to $2,000 depending on affected area, surface type, and organism severity. A single mildewed wall at the lower end; whole-home exterior mildew treatment at the upper end.
How do you prevent mildew from coming back after washing?
The short answer is biocide treatment during every wash. Biocide kills the organism so regrowth is significantly slower than after a pressure-only wash. In Houston, annual treatment keeps exterior mildew from becoming a structural or aesthetic problem.
What is the difference between mold, mildew, and algae on exterior surfaces?
The short answer is the organism type, but the practical treatment is similar for all three. Black streaks on siding are often Gloeocapsa magma algae. Green growth on north-facing surfaces is usually algae or moss. Black or gray patches on painted surfaces are typically mildew. All three respond to biocide treatment before pressure washing.
Recent Houston Mold & Mildew Removal Service Jobs
Three recent pressure washing jobs across Greater Houston.
Whole-Home Mildew Treatment — Pearland (77584)
March 2026 · 2,200 sq ft single-story, all four elevations. Heavy mildew on north and east faces, moderate on south and west. Biocide applied to all surfaces, 20-minute dwell, soft wash on siding sections, medium wash on concrete foundation. Clean at 30-day check.
North-Facing Fence Mildew Removal — Katy (77494)
November 2025 · 140 linear ft cedar fence. Black mildew throughout north face. Biocide dwell, medium pressure wash on cedar. Owner reported no visible regrowth at 8-month follow-up.
Pool Deck Algae Treatment — Memorial (77079)
January 2026 · 520 sq ft concrete pool surround. Green algae on all pool-edge sections from constant moisture. Algaecide treatment, medium pressure. Deck slip-safe and clean. Quarterly treatment recommended.
All prices are estimates. Final scope confirmed in writing before work begins.
Mildew That Comes Back Within 3 Months Was Not Treated — Just Washed
Green or black growth returning 2–3 months after washing
Pressure-only washing displaces surface mildew without killing the organism. The biologically active root layer remains in the surface pores and regrows. Biocide applied before washing kills the organism and significantly slows the regrowth cycle.
Mildew on surfaces where painting will not stick
Paint or stain applied over mildew-contaminated surfaces does not bond — it adheres to the mildew layer and peels with it. The surface must be treated and washed clean before any coating is applied.
Mildew staining through a recent exterior repaint
If mildew returns through a fresh coat of paint within one season, either the paint did not include mildewcide or the surface was not treated before painting. We assess and treat the source when combining mildew removal with pre-paint washing.
Schedule a Walkthrough
We identify organism type and surface material before selecting treatment chemistry.
Our Process: Clean the Right Way
- 1Organism Identification & Chemical SelectionWe identify the type of growth — algae, mildew, or moss — before selecting the correct biocide or fungicide. Algae on concrete requires different chemistry than mold on wood siding. The correct chemistry kills the organism; the wrong chemistry just lightens its color temporarily.
- 2Biocide Application & DwellBiocide or algaecide solution applied at the correct dilution to the affected surface and allowed to dwell for 15 to 30 minutes. During dwell time, the chemistry penetrates to the root of the organism. This is the step that determines whether the organism is killed or just washed off.
- 3Pressure Wash & RinseSurface washed at the appropriate PSI for the substrate — soft wash on siding, medium pressure on concrete, fan-nozzle on wood. Thorough rinse removes all biocide residue and treated organic material. Plants are rinsed after to clear any biocide overspray.
What to Expect: Your Service Timeline
| Stage | When | What Happens |
|---|---|---|
| Arrival & setup | On-site | Equipment staged; plants pre-soaked; outlets protected |
| Chemical pre-treat | 15–30 min | Detergent or biocide applied and allowed to dwell on surface |
| Pressure wash | 1–3 hours | Surface washed at correct PSI; problem areas addressed with surface cleaner |
| Rinse & inspect | 30 min | Thorough rinse; surface inspected for remaining staining |
| Site clean & departure | 15 min | Equipment removed; waste water cleared; property returned clean |
Most mold and mildew removal jobs: 2 to 4 hours. Whole-home treatment of all four elevations may extend to 5 hours.
The Right Time to Schedule Mold & Mildew Removal Service
You see black or green growth on the north or shaded walls.
Exterior mildew is easiest to treat before it becomes heavy. Light growth responds faster to biocide treatment and requires less dwell time.
You are painting in the next 4–6 weeks.
Paint applied over mildew-contaminated surfaces peels. Mildew treatment and washing must happen before any exterior coating is applied — and the surface must be fully dry before paint.
HOA or rental inspection noted mildew on exterior.
Exterior mildew is a common HOA maintenance finding. Biocide treatment and washing addresses the condition quickly.
The Henry Contractor Difference
Right pressure for the surface
Power washing concrete at 3,000 PSI is correct. The same pressure on painted siding strips paint. On shingles, it shreds granules. We match PSI to surface type — and switch to soft wash (under 500 PSI with chemical dwell) for surfaces that require it.
Biocide before the rinse
Pressure washing mildew without biocide treatment moves the organism around the surface without killing it. It regrows faster on a freshly disturbed surface. We apply biocide solution first, allow dwell time, then rinse — every time mildew is present.
No damage to landscaping or electrical
Pre-soak all plantings before washing, cover all exterior outlets, and direct waste water away from storm drains and plant beds. We protect adjacent surfaces as part of standard prep — not an afterthought.
Transparent Pricing for Mold & Mildew Removal Service
| What Drives the Cost | Standard vs. Premium Service | What to Know Before Booking |
|---|---|---|
| Square footage and surface type; a standard driveway is different scope from a large property with multiple surface types | Standard: one detergent type, single pass. Premium: biocide pre-treat + detergent + high-pressure rinse for heavily contaminated surfaces | Active mold or algae requires biocide dwell time — adds to the service window |
| Staining severity; light surface grime vs. embedded oil, rust, or heavy mildew growth | Standard: standard pressure, single rinse. Premium: hot water or rotary surface cleaner on heavy concrete staining | Height or restricted access adds staging time and equipment |
| Chemical requirements; standard wash vs. biocide, degreaser, or oxidizing cleaner | Standard: water only or mild detergent. Premium: targeted chemical for stain type | Environmental compliance for commercial sites: waste water containment may be required |
Mold and mildew removal: $100–$2,000 depending on area. Written quote fixed before work starts.
Get an Exact Number
We assess surface type, staining level, and area before writing a number.
Mold & Mildew Removal Service vs. Garden Hose vs. Rental Equipment
| Feature | Henry Contractor | Garden Hose | Rental Equipment |
|---|---|---|---|
| Pressure & Technique | Matched to surface type; soft wash where required; correct PSI by material | Garden hose pressure inadequate for embedded stains or mildew | Fixed PSI regardless of surface; etching or surface damage common |
| Chemical Treatment | Biocide or detergent applied to dwell before rinse; stain type matched to chemical | No chemical treatment; water only; mildew regrows quickly | Generic soap; not matched to stain type |
| Surface Safety | Surface-specific technique; no high pressure on shingles, painted siding, or wood grain | Nozzle distance inconsistent; etching or wood splintering common | No surface assessment; damage to softer surfaces common |
| Waste Water Management | Plant beds pre-soaked; outlets covered; waste water directed from drains | Runoff unmanaged | No containment; chemical runoff into storm drains or plant beds |
| Pricing Transparency | Written quote per surface; fixed before work starts | Material and time costs unpredictable | Low per-surface rate; add-ons for chemicals and setup common |
Who We Partner With
Houston Homeowners
Year-round mildew is a fact of Gulf Coast living. Annual treatment prevents buildup from becoming structural and keeps the exterior looking maintained.
Property Managers
Rental and HOA properties with mildew on exterior surfaces generate tenant and board complaints. Scheduled annual treatment is a low-cost maintenance line item.
Pre-Sale Sellers
Mildew on exterior siding is visible in listing photos and noted by buyers. A single treatment visit before listing removes the concern.
Proudly Serving Greater Houston
We proudly provide professional pressure washing services to homeowners, businesses, and property managers throughout the Greater Houston area, including: The Woodlands, Katy, Sugar Land, Pearland, Cypress, Memorial, and surrounding communities.
See our house exterior washing service or return to the pressure washing hub.
Frequently Asked Questions
The short answer is an estimated $100 to $2,000 depending on affected area, surface type, and severity. A single mildewed surface at the lower end; whole-home exterior mildew treatment at the upper end.
The short answer is no — pressure washing alone moves the organism across the surface without killing it. Biocide solution applied before washing kills the organism at the root level. The pressure wash then removes the dead material.
The short answer is annual biocide treatment. Houston’s humidity means mildew will return over time — biocide treatment kills the organism so regrowth is significantly slower. Annual washing prevents heavy buildup from developing.
Mold typically appears as dark, irregular patches and penetrates deeper into porous materials. Mildew is a surface-level powdery or flat growth. For exterior pressure washing purposes, both respond to biocide treatment applied before washing.
The solutions we use are managed away from plant beds, and all surrounding vegetation is pre-soaked with water before biocide application and rinsed after. Standard exterior biocide dilutions used in pressure washing are not concentrated enough to cause lasting damage when properly managed.
Ready to get your surfaces clean?
Fill out the free estimate form at the top of the page to get started, or call us directly to schedule your on-site assessment.