The real enemy is not water
It rains little in Baja California, and yet roofs get ruined. The reason is thermal: the daily cycle of heating and cooling expands and contracts the slab every day of the year. That constant movement opens fissures, and water enters through them during the few rains that do occur.
The practical consequence is that here the right waterproofing is not just a water barrier: it is also a reflective layer that lowers surface temperature. Reducing thermal movement extends the life of the system and, along the way, reduces the heat entering the house.
When to waterproof
Before the rainy season and with the slab completely dry. Applying over a damp or ponded surface wastes the product: it does not bond and it seals moisture inside, where it later pushes the coating up into blisters.
Preventive maintenance is cheaper than repair. A system inspected and renewed on time costs a fraction of repairing a slab that has already leaked, with the damage that implies to ceilings, services and interior finishes.
Preparation decides the outcome
Thorough cleaning. Removal of all loose or debonded material from the previous system. Crack repair. And reinforcement of the critical points: coves, downpipes, parapets and penetrations.
Most leaks do not start in the middle of the slab: they start at the junctions. Waterproofing that is impeccable on the field and careless at the cove leaks just as if it had never been applied. If the previous system is debonded or cracked, it must be removed before applying the new one.
Acrylic or asphalt
Elastomeric acrylics are the usual choice on exposed concrete roofs. Impac 5000 and Impac 7000 are formulated from acrylic resins and ceramic thermal particles with high solar reflectance, with 5 and 7 year service lives respectively; the 7000 is also 100 % ecological and carries a guaranteed minimum life.
Impac Sokül 7 goes a step further on the thermal side: it effectively reduces heat because it contains insulating microcells, added to the reflective effect of its white colour, with a 7 year warranty. For jobs calling for an asphalt base there is the Fibred Asphalt Emulsion: water-based, asbestos-free, creamy and thixotropic, reinforced with synthetic fibres, cold-applied, fast-drying and non-flammable.
How to decide in practice
Start from the substrate and the previous system. Clean concrete slab exposed to sun: reflective elastomeric acrylic. Surface with a sound existing asphalt system: continuing in the same family is usually right. Priority on lowering interior temperature: the acrylic with insulating microcells.
What never works is applying one system over another without verifying compatibility and condition. And what always works is checking the stated service life: the difference between 5 and 7 years is not a label detail, it is the maintenance interval you will live with.
