0.75 oz vs 1.5 oz Fiberglass Mat: Which Weight Should You Use?

Choosing between 0.75 oz and 1.5 oz chopped strand mat comes down to one question: do you need flexibility or strength? This guide breaks down the differences so you can pick the right weight for your project.

Quick Answer

Use 0.75 oz mat for flexibility, curves, and keeping weight down.

Use 1.5 oz mat for structural strength, flat surfaces, and most boat building.

Comparison

When to Use 0.75oz Chopped Strand Mat

The lighter 0.75 oz mat excels when:

• Tight curves and contours - Conforms easily without bridging
• Weight-sensitive builds - Kayaks, race boats, aerospace
• Cosmetic repairs - Minor dings and scratches
• Gradual layup - More control over thickness
• Hard-to-reach areas - Easier to handle

Shop 0.75oz Chopped Strand Mat

When to Use 1.5oz Chopped Strand Mat

The heavier 1.5 oz mat is the industry standard:

• Boat building and molds - Most common in marine
• Structural repairs - Transoms, stringers, floors
• Flat surfaces - Less conformability needed
• Faster buildup - Fewer layers required
• Auto and industrial - Panels, enclosures, tanks

Shop 1.5oz Chopped Strand Mat

How Many Layers?

Pro tip: Combine both - 0.75oz on curves, 1.5oz on flat areas.

Resin Compatibility

Both work with:

• Polyester resin - Most common, economical
• Vinyl ester - Better water resistance

Not for epoxy - CSM has styrene-soluble binder. Use fiberglass cloth or biaxial for epoxy.

Technical Data Sheets

• 0.75oz CSM Data Sheet (PDF)
• 1.5oz CSM Data Sheet (PDF)

Bottom Line

Start with 1.5oz for most projects - it is the industry standard. Choose 0.75oz for tight curves or weight-critical builds. Best approach: keep both on hand.

Shop 0.75oz | Shop 1.5oz | All Chopped Strand Mat