Washing Cedar Clapboards

By Robert Robillard on Home Maintenance

Washing Cedar Clapboards

How To Wash House Siding

The two reasons to wash the exterior of your house are the siding is dirty and looks crappy or you are preparing for the application of paint.   Washing of cedar clapboards prior to painting is not only part of the prep process but a best practice.

Paint Failure:

According to painting contractor, Mark O’Lalor, “there are many examples that illustrate the importance of great preparation. The most common is paint failure that is caused when a painting contractor fails to simply lightly sand and wash a surface prior to painting.”

The old adage “proper preparations prevents piss poor performance,” applies here.   When paint is applied to dusty, dirty siding it will adhere in the short-term, but will fail well before it’s intended lifetime.  To achieve a durable and long-lasting paint job, the first step is preparation, and the second step is using a quality paint.

There are two types of contaminants that cover house siding;

  • Natural dirt
  • Man made dirt

Natural Dirt

Natural dirt takes the form of many things and occurs naturally in the environment.  Contaminants such as;

  • Bird droppings
  • Insects and spiders
  • Mold
  • Mildew
  • Lichen
  • Spores
  • Tree sap
  • Moss
  • Dirt splatter
  • Pollen

Man Made Dirt:

  • Pollution from auto exhaust
  • Chimney soot
  • BBQ smoke
  • Acid rain

Washing Cedar Clapboards

Prepare A Cleaning Solution:

What is the best pressure washing detergent for washing homes from natural or man made dirt?  The best detergent is the one that works.

We have found that a custom mixture of bleach, TSP [Trisodium Phosphate] and dish-washing soap works well.  The dish-wash soap creates a surfactant to lower the surface tension between the liquids and solid surface.    This allows the cleaning solution to “stick” on vertical surfaces and and a cleaner to dissolve dirt, mold and mildew.  

This solution works well with both types of dirt found on house siding.

Protect Vegetation:

Prior to cleaning siding or washing cedar clapboards take a few minutes to wet down any vegetation , directly under the area to be cleaned.  Then cover the plants with plastic or a tarp.  [Do not leave on too long if working in direct sunlight]

Steps For Washing Cedar Clapboards:

The steps we use for cleaning are simple, they are:

  1. Wet siding and apply cleaning solution
  2. Scrub siding – Best practice.
  3. Rinse siding

Washing Cedar Clapboards

1.  Wetting Siding and Applying Soap:

There are many ways to apply the cleaning solution from using a nylon brush and bucket, to a pressure pump sprayer to a pressure washer.   We prefer using a pressure washer to wet, mix and propel the cleaning solution to the siding.

Apply cleaning solution and let it soak for about five minutes.

The pressure washer we use siphons 1-gallon of solution to 7-gallons of water sprayed onto the house.  We try to keep the spray nozzle 3 to 4 feet from the siding surface to prevent etching or damage.

NOTE – Inexperienced pressure washers can do a lot of damage to the house siding and home.  When pressure washers are used on high pressure,  wood and other surfaces can be damaged.  Etching of the siding or worse injection of water into the building envelope can also occur.    are must be taken not to spray under siding, into vents of other penetrations of areas where water will penetrate.

Washing Cedar Clapboards

2.  Scrubbing The Siding:

The best method for removing dirt from wood siding is to use a nylon brush and pole and scrub it off.  Hand washing is still the best practice when preparing a house for paint or cleaning the siding.   A little elbow grease goes a long way in the cleaning process.  Scrub in a back and forth manor ensuring full scrubbing coverage.

Washing Cedar Clapboards

3.  Rinse Siding:

Using the least aggressive nozzle on the pressure washer, or a hose rinse all of the detergent off the house in a “Top-Down” method.  Top down ensures that you avoid streaking of detergent and is the best method of rinsing off cleaning materials from the siding.   Rinse the siding well becasue soap allowed to dry on the siding can lead to oxidation (hazing) of the siding.

Remove plastic from the vegetation and give plants a fresh water rinse.  Let the siding dry 48-hours before priming, painting or until any bare wood is 100% dry.

Washing Cedar Siding Video:


If you enjoyed this post, make sure you subscribe to my RSS feed!

About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

All posts by Robert »

Not what you're looking for?

Search for more articles here. Enter keywords like roof leak, bookcase, deck, etc to find your topic.

© Copyright 2019 A Concord Carpenter · All Rights Reserved