How to Clean Your Siding Before Painting

Properly cleaning your home’s siding before painting is a crucial step to ensure the new paint adheres and lasts. Following these detailed cleaning methods will allow the paint to bond tightly and provide a beautiful, long-lasting finish.

Why Cleaning Your Siding is Important Before Painting

Cleaning siding prior to painting serves several important purposes:

Removes dirt, mildew, grease – Over time, siding accumulates dirt, mildew, pollution, grease splatters, insect droppings and other contaminants. Thorough cleaning removes these so paint can adhere directly to the siding surface.
Improves paint adhesion – For paint to properly bond, it must be applied to a clean, sound surface. Cleaning eliminates peeling paint flakes, chalkiness, oxidation and other material that can cause poor adhesion.
Enhances paint durability – Paint applied over a dirty surface will peel, flake and fail prematurely. Proper cleaning allows for maximum durability from quality paint.
Prepares for primer/paint – Cleaning opens up the siding’s pores to accept primer and paint. Primer also adheres optimally to clean siding.
Improves appearance – Paint looks its best when applied to clean siding. Cleaning removes unsightly stains, chalky areas and residual dirt.
Adds value – A properly painted home with pristine siding has greater curb appeal and resale value. Cleaning siding helps achieve this ideal result.

How to Clean Different Types of Siding

Cleaning techniques vary slightly depending on the type of siding:

Vinyl Siding

Vinyl is prone to collecting dirt in its grooves. Follow these steps:

Rinse the siding with a garden hose on a low setting to avoid driving dirt farther into the grooves.
Mix a mild detergent like dish soap or vinyl siding cleaner with warm water in a bucket. Use a soft bristle brush to scrub the mixture over the surface and into the grooves. Avoid abrasive brushes.
Rinse thoroughly with the garden hose. Repeat if needed for heavily soiled areas.
Allow the siding to fully dry before priming or painting.

Wood Siding

Wood siding should be cleaned gently to avoid damaging the surface:

Rinse the wood siding with a garden hose on a low setting.
Fill a bucket with warm water and add a small amount of mild detergent. Use a soft bristle brush to gently scrub the detergent solution onto the wood.
Completely rinse off all soap residue with clean water. Allow wood to fully dry before priming and painting.
For mildew stains, scrub with a cleaning solution of 1 part bleach + 3 parts warm water. Rinse thoroughly. Allow wood to dry completely.

Fiber Cement Siding

Follow these steps for properly cleaning fiber cement siding:

Rinse the surface with a garden hose on a low setting.
For light dirt, mix 1/3 cup mild laundry detergent with 1 gallon of warm water. For heavier grime, use 1/3 cup heavy-duty laundry detergent.
Use a soft bristle scrub brush to apply the cleaning solution. Scrub gently to lift dirt. Avoid abrasive scrubbing.
Thoroughly rinse off all detergent residue with clean water. Fiber cement takes longer to dry fully. Allow extra time before painting.

Brick and Stone Siding

Brick and stone have porous surfaces requiring special care:

Spray siding with a garden hose on a low setting to lightly rinse.
Use a stiff bristle brush and mild detergent solution to scrub the masonry surface. Avoid abrasive cleaning.
Rinse thoroughly with clean water. Brick and stone take longer to dry out fully. Allow extra drying time before painting.
For mildew, algae or moss, use a pressure washer on a low setting then apply cleaning solution. Rinse and allow extra time to dry.

Metal and Aluminum Siding

Metal siding requires gentler cleaning methods:

Rinse the surface lightly with a garden hose on low pressure.
Fill a bucket with warm water and mix in a mild detergent. Use a soft cloth to gently wipe away dirt and grime. Avoid abrasive scrub brushes.
Completely rinse away all detergent residue with clean water. Allow metal siding extra time to fully dry before painting.
For stubborn grime, use a specially formulated metal cleaner before rinsing thoroughly.

Cleaning Solutions for Siding

When mixed with water, the following cleaners work well for cleaning siding:

Mild liquid dish detergent – Dish soap like Dawn effectively cuts through grease and grime. Use warm water and avoid abrasive scrubbing.
Trisodium phosphate (TSP) – Hardware stores sell TSP as a heavy-duty cleaner for siding and masonry. Rinse thoroughly after use.
Sodium metasilicate – This is a less-caustic masonry cleaner safe for painted wood, vinyl and other sidings. Rinse completely afterwards.
Oxalic acid – Available as wood cleaner, this removes stubborn tannin bleed and iron stains from wood siding. Rinse thoroughly.
Bleach – When mixed with water, bleach helps clean mildew and moss from siding. Avoid bleach on metals and rinse siding fully.
Mineral spirits – For deeply cleaned painting prep, mineral spirits remove grease and oils from siding. Use proper safety precautions.

Avoid harsh cleaners like ammonia, hydrofluoric acid, or alkaline compounds that can damage siding. Always test cleaners first in an inconspicuous area before full use.

How to Clean Siding Before Painting

Follow these key steps when cleaning siding in preparation for painting:

Inspect and Prepare the Surface

Inspect siding for cracks, deterioration, mold or damage needing repair.
Repair any gaps, holes or cracks that may allow water intrusion behind siding.
Fill depressions or holes with appropriate patching compound for the siding type. Allow time to cure fully.
Scrape off peeling paint down to a sound surface. Use proper lead safety if old paint is present.
Smooth rough paint edges by sanding to avoid a visible lap line with the new paint.
Remove any rust from metal siding using sandpaper or steel wool before applying primer.

Remove Surface Contaminants

Clean the siding using the methods above for the specific siding type.
Use the necessary cleaner to cut through and dissolve dirt, grease, mold and other contaminants.
Avoid damaging the siding surface by scrubbing too vigorously with stiff brushes or high pressure spraying.
Completely rinse off all cleaning solutions. Residual chemicals can interact poorly with paint.

Allow Siding to Dry

Ensure all portions of the siding have dried completely before painting.
Vinyl and metal siding typically dry quickly while wood, masonry and fiber cement take longer to dry out.
Check siding in shaded areas that are slow to dry. No dampness should be present before priming or painting.
Allow 1-2 days of dry weather for full drying. Accelerants like heat guns can speed drying if needed in humid climates.

Apply Primer and Paint

After drying, apply appropriate primer to any bare wood, metal or repaired areas of siding.
For vinyl or fiber cement, priming may not be needed if the surface is intact. Consult paint manufacturer guidelines.
Allow primer to dry fully before applying the topcoat of exterior paint per the manufacturer’s directions.
Two coats of quality exterior paint are recommended for optimal protection and appearance.

Tips for Effective Siding Cleaning

Follow these useful tips when cleaning siding:

Always start cleaning from the top and work down methodically. This avoids streaking from dirty rinsing water.
Apply cleaning solutions starting at the bottom edge of the house or lowest point of soffits/overhangs so drips don’t stain lower siding.
When using a pressure washer, start at low pressure and increase slowly as needed. Excess pressure can damage soft materials.
Follow the wood grain when cleaning and brushing wood siding. Scrubbing across the grain can damage the surface.
Rinse cleaning solutions off fully before moving on to the next section. Leftover chemicals can interact with paint or new batches of cleaner.
Wear protective eyewear, gloves, and clothing during cleaning. Chemical solutions and debris can be hazardous.
Dispose of dirty cleaning water properly, such as in a dirt area rather than the street where it can flow to storm drains.
Never mix cleaning solutions together, especially chlorine bleach and ammonia. This creates toxic fumes.

Frequently Asked Questions About Cleaning Siding Before Painting

How do you clean old, dirty siding before painting?

Rinse the siding thoroughly with water first. Mix an appropriate cleaner with warm water then scrub dirty areas, allowing the solution time to dissolve built-up grime before rinsing. Repeat as needed until clean.

What is the best way to remove mold and mildew from siding?

Mix together 1 part bleach and 3 parts warm water. Use a scrub brush to apply this solution to moldy siding. Allow 10 minutes contact time before rinsing clean. Repeat as needed. Wear gloves and eye protection.

Can I pressure wash vinyl siding before painting?

Yes, you can pressure wash vinyl siding at low pressure (1200 PSI or less) and at least 12 inches away using a wide spray nozzle. This avoids driving dirt into the siding. Rinse thoroughly afterwards.

How long does exterior siding need to dry before priming and painting?

Vinyl and metal siding typically only need 1 day of good weather to dry fully.
Wood, masonry and fiber cement need longer – 2 days minimum. Verify no moisture is present before painting.

What’s the best way to clean cedar shake siding before painting or staining?

Use a low-pressure garden hose rinse followed by gently scrubbing the wood grain with a soft bristle brush and mild detergent mixed with warm water. Rinse fully and allow 2-3 days to dry.

Conclusion

Preparing siding for painting by thoroughly cleaning the surface is time well invested. Following the proper cleaning methods for each siding type allows quality paints and primers to properly bond for long-lasting protection and beauty. Ensuring siding is completely dry before applying paint also prevents problems. With some diligence and effort, your freshly painted home will showcase clean, revitalized siding for years to come.