Can You Pressure Wash Composite Decking Without Ruining It?

Composite decking has become an increasingly popular alternative to traditional wooden decks over the last couple of decades. Made from a mixture of wood fibers, plastics, and other polymeric materials, composite decks offer benefits like durability, resistance to rotting, splintering, cracking, and warping. With a wood-like appearance but less maintenance than natural wood, it's no wonder many homeowners opt for composite decking to create beautiful and low-maintenance backyard escapes.

But like any deck, composite or otherwise, periodic cleaning is essential to keep it looking fresh and new. Power washing, also known as pressure washing, is a common cleaning method used to remove stubborn dirt, grime, stains, and even mold or mildew that can accumulate on decking over time. However, many composite deck owners have concerns about pressure washing, worrying that the high-powered spray could damage the deck surface.

What Is Composite Decking Made Of?

To understand the cleaning needs and concerns with composite decks, it helps to first understand what these decks are made of. The primary ingredients in today's composite decking are:

• Wood flour or wood fibers - usually recycled waste wood materials
• Plastic or PVC - typically polyethylene or polypropylene
• Bamboo fibers - a renewable alternative to wood fibers
• Recycled rubber, plastic, and other polymers
• Minerals like limestone
• Pigments for color

These materials are mixed together under heat and pressure to create durable composite boards that resist moisture, swelling, warping, and rotting. Advanced technologies and polymer science give composite decks their strength, longevity, and low-maintenance nature.

Composites are harder and denser than traditional wood. While this is great for durability, it also means that pressure washing needs to be done carefully to avoid scouring or cutting into the surface.

How Does Pressure Washing Work?

Pressure washers use an electric motor or gas engine to power a water pump that pressurizes the water flow. This high-pressure water is then ejected from a nozzle on the spray wand. Pressure levels are measured in PSI (pounds per square inch).

Typical residential power washers have PSI ratings of:

• 1500-2000 PSI - Considered light-duty or medium pressure
• 2000-3000 PSI - Heavy-duty for tougher cleaning tasks
• 3000+ PSI - Commercial-grade pressure washers

In addition to PSI, pressure washers can be adjusted via different spray nozzles. The nozzle opening determines the shape and pressure concentration of the water jet. Fan spray nozzles are wide (about 40deg) and distribute pressure across a larger area. Narrower 0deg nozzles concentrate the pressure in a focused stream.

Can You Pressure Wash Composite Decks?

The short answer is yes - you can safely pressure wash composite decks IF you use the proper precautions and techniques. While composite materials are durable, the wrong pressure, angle, or nozzle can still damage the deck.

Here are a few tips to pressure wash composite decks safely:

• Use lower pressures - 800-1000 PSI is ideal for composite decks.
• Choose a wide fan spray nozzle - at least 40deg.
• Keep the nozzle 6-12 inches away from the deck surface.
• Avoid concentrated, narrow-angle nozzles.
• Work in manageable sections to avoid over-spraying one area.
• Rinse away cleaning agents thoroughly.

Always test a small, inconspicuous area of your deck first before doing the whole thing. Check for any damage to the surface composition after testing. Then adjust your technique accordingly - pressure, nozzle distance, and angle as needed.

Potential Damage from Power Washing

Using too much pressure is one of the biggest risks when power washing composite decks. The impacts can include:

• Surface etching - Results in a rough texture and can wear down the protective coating.
• Pitting and cavities - Damage to the composite material itself.
• Line streaking - Occurs when the nozzle is held too close or moved too slowly.
• Removal of color pigments - High pressure can blast away colored coatings.

Excessive power washing can shorten the life span of your composite deck. The rougher surface is also more prone to trapping dirt, stains, and showing wear after damage occurs.

Other Cleaning Options for Composite Decks

While pressure washing is effective when done properly, it may not be right for all cleaning needs or desired results. Here are some alternative cleaning methods to consider for composite decks:

• Mild soap and water - Great for routine cleaning and removing light dirt.
• White vinegar - Helps eliminate mold, mildew, and organic stains.
• Baking soda - Acts as a gentle abrasive to scour away grime.
• Oxygen bleach - Removes stains without harsh chemicals.
• Scrub brush - Dislodges dirt from textured grooves.

These methods require a bit more elbow grease but are less likely to harm the deck. They allow you to target problem areas safely. However, heavy-duty grime and mildew growth will still require pressure washing in many cases.

When to Pressure Wash Your Composite Deck

Here are signs it's time to break out the power washer for a deep clean of your composite deck:

• Visible mold or mildew growth
• Difficult stains that other cleaners cannot remove
• Ground-in dirt trapped deeply in the grooves
• Noticeable color fading
• Routine soap-and-water cleaning no longer works

Ideally, a thorough pressure washing is recommended every 1-3 years for composite decks. For high-traffic areas like stairs or around pools, annual power washing may be needed.

How to Avoid Damaging Your Composite Deck When Pressure Washing

Here are some top tips to keep your composite deck looking beautiful after pressure washing:

• Carefully read the manufacturer's recommendations.
• Remove furniture, grills, decor and any removable parts.
• Sweep away debris like leaves before starting.
• Test PSI and nozzle setting on a small area first.
• Use maximum 1500 PSI for composite decks.
• Choose a 40deg wide spray nozzle.
• Keep nozzle 6-14 inches from the deck surface.
• Work slowly, avoiding lingering in one spot.
• Wet deck first, then apply cleaner before power washing.
• Rinse away all chemicals thoroughly after cleaning.
• Allow deck to dry fully before replacing items or using.

Taking these precautions allows you to benefit from the deep cleaning power of pressure washing safely. It helps remove built-up grime from your composite deck without causing damage.

When to Call a Professional

While DIY pressure washing can save money, there are some instances when it's wise to hire a professional deck cleaning service instead. This includes situations like:

• Severely soiled or stained decks requiring major restoration.
• Multi-level decks or difficult to reach areas.
• If you lack the proper power washer.
• For newer decks still under warranty - hire a pro to avoid voiding it.
• If you're uncomfortable pressure washing composites yourself.
• For periodic deep cleaning maintenance every few years.

Professionals have commercial-grade equipment, specialized skills and experience to tackle tough cleaning jobs while protecting your deck investment. They can also apply protective treatments during cleaning to help repel future stains.

When maintained properly, composite decks provide years of enjoyment with their warm, natural-wood look. While composite materials are low-maintenance, they still require periodic deep cleaning to look their best. Pressure washing is an effective cleaning method when done with care and the proper technique.

The keys are using moderate pressure, keeping the nozzle at the optimal angle and distance, and checking for any surface damage after testing a small area. With the right precautions, you can safely pressure wash composite decks to remove years of dirt, stains, mold and mildew.

For heavily soiled decks or challenging cleaning jobs, hiring a professional service may be the best option. But for routine maintenance cleaning, DIY pressure washing lets you restore and protect your composite deck while saving money. Follow these tips and enjoy your fresh, revitalized composite deck for seasons to come.