Treating Cracks Before Waterproofing a Facade: Fissures vs Structural Cracks
Small fissures take a preparing primer; cracks above 0.3 mm are opened in a V, filled with product and sand and reinforced with polyester mesh.
Before waterproofing a facade with Coral Proteção Sol & Chuva Pintura Impermeabilizante (waterproofing paint), the treatment depends on the type of opening in the wall. A shallow fissure and a structural crack are handled differently, and skipping the heavier treatment on a moving crack lets water back in.
Fissure: a shallow opening
A fissure is a small opening in the render, shallow and without continuity, up to 0.3 mm wide. The treatment is to clean and brush the surface, removing dust and loose parts with a damp cloth, and apply the preparing primer for walls before the finishing paint.
Structural crack: an opening above 0.3 mm
A crack above 0.3 mm is a continuous opening caused by structural movement, and it needs a reinforced repair before the waterproofing coats:
- Open the crack in a V shape, up to 5 mm deep.
- Apply the preparing primer for walls.
- Fill the crack with a mix of 1 part Coral Proteção Sol & Chuva Pintura Impermeabilizante to 2 to 3 parts sand.
- Apply one coat of the product over a strip of polyester mesh.
- Finish with at least 3 coats of the product.
The polyester mesh is what bridges a moving crack so the film is not torn as the wall expands and contracts.
The film that goes over the repair
The waterproofing paint forms a rubberised, flexible film that prevents and fights infiltration from outside in, as well as cracks, algae and mould on external walls. It is applied in 3 coats as a reference, with 10% dilution, drying 30 minutes to the touch, 4 hours between coats and 24 hours for final drying.
Prepare the rest of the surface too
A crack is rarely the only issue on a facade. Walls with mould or grease need cleaning before any coat, and weak render or loose paint needs the preparing primer. The general preparation is covered in preparing a wall with mould or grease before waterproofing. What the film resolves and what still requires fixing the cause is in acrylic waterproofing for exterior walls with moisture, and the full range of options in types of wall and facade waterproofing. The technical bulletins are published at coral.com.br, and the products are sold through the Coral store.