Clean all dirt and debris from the inside of the planter wall and allow it to dry thoroughly.
Brush water-based bitumen paint over the inside surface of the planter, keeping the brush strokes aligned in one direction. Allow the paint to dry for 30 minutes
Apply a second coat of paint. Brush it on in a direction perpendicular to the first coat, forming a 90-degree angle to the first set of brush strokes.
Wait seven days after applying the second coat of paint before filling the planter with dirt or potting material.
Things You Will Need
- Water-based bitumen paint
- Test the planter's moisture level before applying the waterproofing material. Tape a clear plastic sheet over a section of the planter and turn it to face the sun directly for two hours. If moisture forms underneath the plastic, the planter is too damp to seal and needs to dry further.
- Water-based bitumen paint cleans up with water easily if it hasn't dried. Mineral spirits are ineffective at cleaning this paint up.