Short Answer
Depending on the material, pressure and technique, improper pressure washing can damage siding, seals and finishes.
Detailed Explanation
Pressure washing can be appropriate for some siding materials when done correctly, but improper pressure washing can cause significant damage. High pressure can force water behind siding (causing moisture intrusion), crack vinyl siding, damage the surface of fiber-cement siding, strip paint from painted surfaces, damage sealants around windows and doors, and force water into wall cavities. The appropriate pressure, nozzle, distance, and technique vary by material. For most siding, low-pressure washing with appropriate cleaning solutions is safer and more effective than high-pressure washing. If pressure washing is used, it should be done by someone who understands the material and the proper technique — or better yet, use a soft-wash method that relies on cleaning solutions rather than pressure.
Why It Matters
Improper pressure washing can cause water intrusion and material damage that leads to costly repairs. Understanding the risks helps homeowners choose safe cleaning methods.