A waterproofing contractor should possess the following important qualifications to ensure they can provide high-quality service and complete the project successfully:

1. Extensive Experience
   Experience is a key criterion when selecting a waterproofing contractor. They should have many years of practical experience in the waterproofing industry, especially in similar types of projects. This experience helps them identify and handle various complex waterproofing issues more effectively.

2. Professional Techniques and Equipment
   A good waterproofing contractor should possess the latest waterproofing techniques and efficient construction equipment. They should be able to use the most suitable waterproofing methods and materials according to different building structures and environments.

3. High-Quality Materials
   The contractor should use certified, high-quality waterproofing materials. The quality of the materials directly affects the durability of the waterproofing, so it's essential to choose materials that are widely recognized and have a good reputation.

4. Strong Communication Skills
   The contractor should have good communication skills, capable of clearly explaining the construction process, material selection, and project progress to the client. Good communication helps avoid misunderstandings and ensures the project runs smoothly.

5. Customer Reputation and Reviews
   A contractor’s customer reviews and reputation reflect the quality of their services. You can assess the contractor’s reliability and professionalism by checking online reviews, customer recommendations, or directly contacting previous clients.

These combined qualifications will help you select a competent and professional waterproofing contractor, providing a solid guarantee for your construction project.