Marine Pour Foam – Mix Ratios, Expansion Volumes, and Density Guide

Marine pour foam, also called expanding foam, is a two-part closed-cell polyurethane foam used for flotation, insulation, and cavity filling. At Fiberglass Florida, we stock only 2 lb and 4 lb density pour foams, covering most marine and structural needs. Below you’ll find answers to the most common questions about mix ratios, expansion volumes, and applications.

What Are the Mix Ratios for Marine Pour Foam and How Does Expanding Foam Work?

Marine pour foam comes in two liquid components — Part A and Part B. When mixed, they react to form a rigid closed-cell foam that traps air, making it lightweight, buoyant, and water-resistant.

Mix Ratios

• Ratio: 1:1 by volume (equal parts Part A and Part B).
• Use calibrated containers for accurate measuring.
• Mix quickly (20–30 seconds) and pour immediately.

How Expanding Foam Works

• Two liquids combine to create millions of tiny closed cells filled with gas.
• Closed-cell structure resists water absorption.
• Provides excellent flotation and thermal insulation.

How Much Does 2-Pound Pour Foam Expand and What Volume Will It Fill?

Two-pound density pour foam is the most common choice for marine flotation and general cavity filling. It offers excellent buoyancy while keeping weight low.

Expansion Volume

• Mixing 1 gallon Part A with 1 gallon Part B yields about 9 cubic feet of expanded foam.
• Lightweight yet durable for most marine and insulation uses.

How Much Does 4-Pound Pour Foam Expand and What Volume Will It Fill?

Four-pound density pour foam is stronger and more impact-resistant than 2 lb foam, making it ideal for structural applications and high-traffic areas.

Expansion Volume

• Mixing 1 gallon Part A with 1 gallon Part B yields about 4.5 cubic feet of expanded foam.
• Greater density means more strength but less expansion.

Shop 2 lb and 4 lb Marine Pour Foam at Fiberglass Florida.