To effectively wash your house siding, start by rinsing with a garden hose, then apply a gentle cleaning solution like dish soap and water, scrub with a soft-bristled brush, and finally, rinse thoroughly. 

Here's a more detailed guide:

1. Preparation:

Gather your tools:
You'll need a garden hose, a soft-bristled brush (a long-handled brush is ideal), a bucket, and a cleaning solution. 

Choose your cleaning method:

• For routine cleaning: Use a solution of warm water and mild dish soap. 

• For tougher stains or mold/mildew: Consider adding a small amount of bleach to your cleaning solution (follow the instructions on the bleach bottle) or use a cleaner specifically designed for siding. 

Protect plants and walkways:
Cover plants and walkways with plastic sheeting or tarps to prevent overspray and damage. 

2. Cleaning:

Rinse the siding:
Start by thoroughly rinsing the siding with a garden hose to remove loose dirt and debris. 

Apply the cleaning solution:
Apply the cleaning solution to the siding using a spray bottle or by dipping your brush into the solution. 

Scrub the siding:
Use a soft-bristled brush to scrub the siding, working from the bottom up. 

Rinse thoroughly:
After scrubbing, rinse the siding thoroughly with clean water to remove all traces of the cleaning solution. 

3. Power Washing:

If using a pressure washer:
Ensure it's set to a low pressure setting and use a wide-angle nozzle to prevent damage. 

Test a small area first:
Before cleaning the entire siding, test the pressure washer on a small, inconspicuous area to ensure it doesn't damage the siding. 

Clean from the bottom up:
When using a pressure washer, clean the siding from the bottom up to prevent water from running down and re-soiling the cleaned areas. 

4. Drying:

Allow the siding to dry completely: After cleaning, allow the siding to dry completely before moving on to any other tasks. 

Tips for Specific Siding Materials:

Vinyl Siding:
Use a gentle cleaning solution and avoid using harsh chemicals or abrasive cleaners, which can damage the finish. 

Wood Siding:
Use a gentle cleaning solution and avoid using a pressure washer, which can damage the wood. 

Metal Siding:
Use a gentle cleaning solution and avoid using a pressure washer, which can damage the paint finish. 

Fiber Cement Siding:
Use a gentle cleaning solution and avoid using a pressure washer, which can damage the siding. 

Important Notes:

Avoid cleaning in direct sunlight: Cleaning in direct sunlight can cause the cleaning solution to dry too quickly, making it harder to rinse off. 

Clean regularly: Regular cleaning can help prevent the buildup of dirt, mold, and mildew. 

Be patient: Cleaning siding can take some time, so be patient and take your time to ensure a thorough job.  

This is an example of pressure washing vinyl siding. Pictures are curtsey of wikiHow.