Properly preparing your deck before staining is a crucial step that should not be skipped. Power washing is recommended prior to staining because it removes built-up dirt, mildew, mold, and other debris from the wood’s surface. When these contaminants are not fully removed prior to staining, they can cause problems with how the new stain adheres and lasts on the deck.
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Why power washing is recommended
Power washing utilizes high-pressure water to thoroughly clean the deck by blasting away stubborn surface debris and opening up the wood grain. This allows the new stain to properly penetrate into the wood for maximum adhesion and protection. Without power washing first, the new stain will just coat over the existing dirt, mold, mildew and other contaminants.
Over time, this can lead to premature peeling, cracking, or uneven wear of the stain. Power washing cleans the surface down to the bare wood so the stain bonds directly to the deck boards rather than the layers of debris.
Removes built-up contaminants
Regular foot traffic, outdoor weathering, and seasonal growth of mold and mildew leads to buildup on the deck surface over the years. This buildup accumulates in the wood pores and acts as a barrier preventing proper penetration of the new stain.
Power washing’s high-pressure water flow provides the scrubbing action needed to thoroughly clean and prepare the deck by removing these barrier layers from the surface and pores.
Opens up the wood grain
The high-pressure wash also opens up the wood grain by clearing away tiny dirt particles lodged inside. This allows the new stain to soak deeper into the now clean, opened up grain for superior adhesion.
Without power washing, the wood’s pores remain partially clogged and closed off to the new stain. This results in poor penetration and bonding of the stain to the surface only.
Consequences of skipping power washing
Neglecting thorough power washing before staining a deck can lead to a number of consequences that shorten the finished look and lifespan of the newly stained surface:
Poor stain adhesion
Existing dirt, debris, mold and mildew left on the deck acts as a barrier that blocks absorption and adhesion as the new stain is applied. Rather than soaking into the bare wood, the stain just coats right over the contaminants.
Over time, the new stain can start peeling away in patches as its weak bond to the contaminants gives way. This leaves unsightly stained flakes or peels and exposes the raw, unprotected wood underneath.
Spotty, uneven appearance
Without proper cleaning, the deck is likely to end up with uneven absorption of stain. Areas still coated in dirt, mildew or other buildup will resist the stain, resulting in a blotchy appearance.
The cleaner areas will readily soak up more stain and darker, while the contaminated areas resist proper staining. This gives the finished deck a spotty, uneven look.
Premature fading
Existing debris not removed by power washing essentially creates a barrier between the new stain and bare wood. This can lead to premature fading as the contaminants degrade or wear away over time.
Rather than being properly absorbed deep into the wood grain, the stain sits on top of debris that then wears away, taking the pigment with it. The stained surface of the deck fades unevenly, resulting in dull, patchy areas.
Growth of mold, mildew and algae
Failing to properly clean away existing mold, mildew and other organic growth before restaining provides a food source for future regrowth. Any spores or roots not removed by power washing have a better chance of feeding on the fresh stain and restarting their spread.
Without power washing, the new pigmented stain also tends to adhere poorly and flake off as regrowth occurs. This leaves tidemarks or stained patches on the deck as protection breaks down.
Shorter lifespan of stained surface
All of the consequences above lead to a much shorter effective lifespan for the stained deck surface. Poor adhesion, uneven appearance, premature fading, and recurrent growth problems mean the freshly stained deck will start to fail within just 1-2 years.
Proper power washing provides the necessary prep work to help quality deck stain last 3-4 times longer. The stain bonds tightly to bare wood and provides lasting beauty and protection when the surface is power washed first.
How to properly power wash a deck
Power washing takes some care to get the cleaning power needed without damaging the wood. Follow these tips for properly power washing a deck before restaining:
Clear off loose debris
First, remove any furniture, planters or other items from the deck. Sweep off loose debris so the power washer can focus on removing adhered contaminants from the wood grain.
Test an inconspicuous area
Check the power washer on an inconspicuous section of deck to determine proper distance and pressure. Holding the wand too close or using excessive pressure can damage the wood.
Adjust nozzle distance and angle
Maintain at least 6-8 inches between the nozzle and deck surface. Avoid holding the wand at a direct 90-degree angle, as angling it slightly helps prevent damage.
Apply cleaning agents
For especially dirty or mildewed areas, first apply a cleaning solution or wood brightener before power washing. Let it soak in for 5-10 minutes before rinsing.
Rinse thoroughly
Make sure to thoroughly rinse and extract any cleaning agents after use, preventing interference with the new stain.
Allow to dry
Let the deck dry completely before applying stain, typically 24-48 hours. The wood should have less than 18% moisture content.
Conclusion
Skipping proper power washing before staining or restaining a deck can lead to a variety of problems like poor adhesion, uneven staining, premature wear, and recurring mold growth. Thoroughly cleaning the wood surface using a power washer removes debris buildup so the new stain can properly adhere and last.
Allowing time to power wash, test pressures, completely rinse, and let dry ensures the freshly stained deck has maximum protection and lasting beauty.