Foam Series: How to Layer Foam for Cushions & Mattresses

Learn the Basics: Foam Terms You Need to Know

Before you start layering, it’s essential to understand a couple of key foam terms:

• Density: How much material is packed into the foam (relates to foam longevity).
• IFD (Indentation Force Deflection): How firm or soft the foam feels.

Not sure what those terms mean? Check out our guide:

• “Foam Series: Choosing the Best Foam for Cushions — 5 Key Terms to Know”

We also recommend reading:

• “Foam Series: Comparing Types of Upholstery Foam” 

This blog explains the different CushionRite® foam options available at Sailrite and which ones are best for your project.

The Benefits of Layering Foam

Layering foam allows you to:

• Customize firmness and comfort.
• Add thickness without sacrificing support.
• Improve moisture resistance (especially important for boats and outdoor use).

To try layering combinations before committing, order our Foam Sample Box (#124215). It includes swatches of every CushionRite foam we carry and an easy-to-follow insert explaining their uses.

How to Layer Foam: General Guidelines

When layering, start with a firmer foam on the bottom (higher IFD) for support, then add a softer foam on top (lower IFD) for comfort. Think of the base foam as a box spring — it stabilizes the cushion even if the top layer compresses over time.

Pro Tip: Add a layer of Moisture Prevention Underliner (#121766) at the very bottom (not inside the cushion cover). This breathable mesh promotes airflow and prevents condensation, mold and mildew — especially important in marine settings.

Choosing the Right Foam: CushionRite Premium vs. Dry Fast

In all our layering combinations, we never mix CushionRite Premium (high-density polyurethane foam) with CushionRite Dry Fast (open-cell foam). Here’s why:

• Use Dry Fast if your cushion or mattress will be exposed to moisture — it dries quickly and resists mold.
• Use Premium if you want long-lasting comfort — ideal for indoor or dry environments, and for liveaboard boaters.

Layering Examples From the Sailrite Team

The Basic Boat Mattress Formula

If you’re looking for a thinner, budget-friendly boat mattress and don’t sleep on it regularly, this simple 3-layer formula is a great place to start:

• Top Layer: 2" CushionRite Premium (Soft or Medium) or CushionRite Dry Fast (Soft)
• Bottom Layer: CushionRite Premium or Dry Fast (Firm)
• Base (Outside Cover): Moisture Prevention Underliner

This combo works well when headroom is limited or the mattress isn’t used every night.

Matt Grant's Recommendations (Sailrite VP)

Matt favors comfort and durability when layering foam. Here are his top two mattress builds:

Option 1: For Maximum Comfort (Low Moisture)

• Top Layer: 2"+ CushionRite Premium (Extra Soft, Soft or Medium)
• Middle Layer: 1"-2" CushionRite Premium (Firm)
• Bottom Layer: 1/2" CushionRite Flotation
• Base: Moisture Prevention Underliner

Option 2: For Wet Sleeping Berths (High Airflow)

• Top Layer: 2"+ CushionRite Dry Fast (Soft)
• Middle Layer: 1"-2" CushionRite Dry Fast (Firm)
• Bottom Layer: 1/2" CushionRite Flotation Foam
• Base: Moisture Prevention Underliner

Eric Grant's Recommendations (Sailrite Project Guy)

Eric emphasizes long-term durability, especially for liveaboards. His advice:

• Use at least 3" of CushionRite Premium (Firm) in any mattress you plan to sleep on frequently.
• Avoid using Dry Fast as the top layer unless you're dealing with serious moisture issues — it’s less comfortable than Premium.

Option 1: For Everyday Use

• Top Layer: 2" CushionRite Premium (Soft)
• Bottom Layer: 2"-4" CushionRite Premium (Firm)
• Base: Moisture Prevention Underliner

Option 2: For Extra-Thick Mattresses (if Space Allows)

• Top Layer: 4" CushionRite Premium (Soft or Medium)
• Middle Layer: 4" CushionRite Premium (Firm)
• Optional Layer: 1/2" CushionRite Flotation Foam with drilled holes for airflow
• Base: Moisture Prevention Underliner

Upgrade Your Foam With a CushionRite® Foam Protector Cover

For a polished, professional finish, encase your mattress in CushionRite Foam Protector. This soft, quilted fabric:

• Feels like a store-bought mattress,
• Is 100% polyester, breathable and moisture-wicking,
• Comes in a wide 106" width — perfect for custom sizing,

Use it to sew a zippered box cover around your foam layers (excluding the Moisture Prevention Underliner, which stays outside the cover).

Shop CushionRite Foam Protector

Final Thoughts: Customize Your Comfort With Foam Layering

With CushionRite foam and a little experimentation, you can build a cushion or mattress that meets your exact needs. Whether you're working on a boat, RV or home project, layering gives you full control over firmness, thickness and performance.

Still have questions? Our team is here to help! Contact us via chat, phone, or email — or drop a comment below.

Shop All CushionRite Foam