Do I Need to Prepare Surfaces Before Waterproofing?

Why preparation affects adhesion and durability

Waterproof coatings work by forming a continuous film or penetrating layer over the surface. If the substrate is not prepared, contaminants can sit between the coating and the material, weakening the bond. In cold or wet climates, any trapped moisture under a coating can freeze and expand, making the problem worse.

Common preparation steps include:

• Removing dust, dirt, grease and old flaking coatings
• Drying the area fully before application
• Lightly abrading or sanding smooth, non-porous surfaces
• Checking the manufacturer’s guidance for primers or special primers

Practical preparation by surface type

The right preparation depends on the material you are treating. For concrete and masonry, the surface should be sound, clean and dry, with any laitance or loose material removed. For products like Resinstone, absorbent concrete benefits from a clean, dry profile so the resin can penetrate properly. For wood restoration with a product such as EpoxyWood, the surface should be perfectly dry and sanded before application.

Always read the product data sheet, as some coatings are suitable for multiple surfaces only when the substrate has been correctly prepared, including prepared steel or tile surfaces.

When this matters: snow, ice and freeze-thaw cycles

Surface preparation becomes even more important on outdoor areas that are regularly exposed to snow and ice. Water expands when it freezes, and any water trapped beneath a poorly bonded waterproof layer can cause cracking or delamination over repeated freeze-thaw cycles. A properly prepared surface gives the coating a stronger mechanical grip, reducing the chance of water getting underneath.

For driveways, paths and other weather-exposed areas, preparation is the first step in building a waterproofing system that will cope with seasonal movement, de-icing salts and standing meltwater.