Do I Need to Sand Between Resin Layers?

When repairing a resin boat, building up the repair in several layers of resin or fibreglass is a common method for achieving both strength and a smooth finish. But do you really need to sand between each layer? Here’s what you need to know for a professional result.

Why Sanding Between Resin Layers Makes a Difference

Sanding each cured resin layer before applying the next serves two main purposes: it increases mechanical adhesion, so your repair remains strong, and it helps create a flawless finish. Un-sanded, glossy surfaces can prevent the new layer from bonding as well as it should. By lightly sanding, you create a slightly roughened surface that subsequent layers grip to more effectively.

How to Prepare for the Next Layer

Once your resin layer has fully cured, start by lightly sanding the surface using a fine to medium grit sandpaper. Focus on evening out any high spots and creating a uniform dullness across the repair area. After sanding, thoroughly remove all dust using a clean cloth or vacuum—dust left behind can prevent proper adhesion and may create imperfections.

If you’re using a high-strength repair kit like the Resin Fibreglass Repair Kit, follow the included instructions for ideal curing and sanding times between steps.

When Skipping This Step Becomes a Problem

If you pour new resin over a smooth, unsanded surface—especially after the previous layer has cured—it can lead to delamination or a weak repair. This step is even more crucial for repairs on high-stress or wet areas, such as those found on boats. Taking the extra time to sand between layers can help guarantee long-term durability and a better-looking finish.

Related guides

How To Repair Resin Boat

Following best practices like sanding between resin layers ensures a durable, professional repair for your resin boat. For more comprehensive guidance, visit our main page on how to repair resin boats.