Fiberglass Fabrics

What Oz Fiberglass Cloth to Use: A Comprehensive Guide

Mark Cafero

21 February 2026

Quick Answer: Use 4 oz cloth for small repairs and detail work, 6 oz cloth for general-purpose boat repairs and floors, and 10 oz cloth for structural applications like transoms and hull reinforcement. Heavier cloth = more strength but harder to conform to curves.

Choosing the right fiberglass cloth for your boat repair or build can be tricky. With various weights available, each serving a different purpose, it's essential to understand the differences and applications. This guide will break down the commonly used fiberglass cloth weights and when to use each.

Understanding Fiberglass Cloth Weights

Fiberglass cloth is measured in ounces per square yard (oz/yd²). Common weights include:

4 oz – Lightweight, flexible, great for surface finishes
6 oz – All-purpose weight, ideal for most boat repairs
10 oz – Heavy-duty, for structural reinforcement

4 oz Fiberglass Cloth

Best for: Small repairs, tight curves, cosmetic finishes

4 oz cloth is thin and highly conformable. It's perfect when you need the fiberglass to follow complex shapes without bunching. Use it for:

Final surface layers
Small crack repairs
Covering tight radius curves
Cosmetic touch-ups

6 oz Fiberglass Cloth

Best for: General boat repair, floor overlays, deck work

6 oz is the workhorse weight for most marine applications. It offers a good balance of strength, workability, and resin absorption. Use it for:

Boat floor repairs
Deck overlays
Hull patches
General fiberglass layups

Shop 6 oz Fiberglass Cloth →

10 oz Fiberglass Cloth

Best for: Structural repairs, transoms, hull reinforcement

10 oz cloth is thick and strong, providing maximum reinforcement. It's harder to conform to tight curves but excels in flat or gently curved structural applications. Use it for:

Transom rebuilds
Stringer reinforcement
Hull structural repairs
High-stress areas

Shop 10 oz Fiberglass Cloth →

Weight Comparison Table

Weight	Thickness	Conformability	Strength	Best Application
4 oz	Thin	Excellent	Light	Detail work, finishing
6 oz	Medium	Good	Medium	General repairs
10 oz	Thick	Limited	High	Structural work

Tips for Choosing the Right Weight

Consider the curve: Tighter curves need lighter cloth
Think about layers: Multiple layers of light cloth can be easier to work with than one heavy layer
Match to your project: Structural repairs need 10 oz; cosmetic repairs can use 4 oz
Use the right resin: Fiberglass cloth works best with epoxy resin