Outdoor Cushion Foam Guide:

Understanding Foam Density, Firmness,

Cushion Fillings & Choosing the Best Replacement Cushions

If you've ever shopped for replacement outdoor cushions, you've probably come across terms like 1836 foam, high-density foam, HR foam, reticulated foam, ILD, Dacron wrap, or densified fiber. Unfortunately, many of these terms are poorly explained, making it difficult to compare products or understand what you're actually purchasing.

At Cascadia Outdoor Cushions, we believe customers deserve more than marketing buzzwords. Understanding how cushion materials work can help you choose the right replacement cushions for your furniture, your comfort preferences, and your budget.

This guide explains the most common cushion filling materials, how foam is measured, what the numbers really mean, and why comfort depends on much more than simply choosing the highest-density foam.

What Does Foam Density 1836 Mean?

One of the most common questions we receive is:

"My manufacturer says they use 1836 foam. What does that mean?"

The answer is surprisingly simple.

Most polyurethane upholstery foams are identified by a four-digit code.

Example:

1836

The first two digits represent the foam density.

18 = 1.8 pounds per cubic foot

The last two digits represent the foam firmness.

36 = 36 ILD (Indentation Load Deflection)

So a piece of 1836 foam is:

• 1.8 lb density

• 36 ILD firmness

Once you understand those two measurements, foam specifications become much easier to compare.

Foam Density vs. Firmness: What's the Difference?

This is probably the biggest misconception in the furniture industry.

Many people assume that high-density foam means a firmer cushion.

That isn't true.

Density and firmness measure two completely different characteristics.

Foam Density

Density measures how much polyurethane material exists within one cubic foot of foam.

Higher density generally means:

• Longer life

• Better durability

• Greater resistance to sagging

• Better recovery after repeated use

• Improved long-term support

Density is primarily a measure of quality and longevity, not comfort.

Firmness (ILD)

Firmness measures how soft or firm the foam feels when you sit on it.

This measurement is called ILD (Indentation Load Deflection).

Higher ILD numbers create firmer cushions.

Lower ILD numbers create softer cushions.

Example

These three foams may all feel very similar when new:

• 1536

• 1836

• 2536

Each has:

36 ILD

The firmness is essentially the same.

The difference is durability.

The 2.5-density foam contains considerably more material than the 1.5-density version and will typically maintain its support much longer under heavy daily use.

What Is ILD and Why Does It Matter?

ILD stands for Indentation Load Deflection.

It measures how many pounds of force are required to compress a piece of foam by 25% of its thickness.

Lower ILD:

• Softer

• Easier to compress

Higher ILD:

• Firmer

• More supportive

Typical upholstery ranges include:

Most quality outdoor seating falls somewhere between 30 and 40 ILD, providing a comfortable balance between softness and support.

Understanding Common Foam Codes

Keep in mind that manufacturers may use slightly different coding systems, but the basic concept remains the same.

What Is High-Resiliency (HR) Foam?

High-Resiliency foam, commonly called HR foam, is considered one of the highest-quality polyurethane foams available for upholstered furniture.

Compared to conventional foam, HR foam generally offers:

• Greater resilience

• Faster recovery after compression

• Better support

• Longer lifespan

• Improved comfort over years of use

HR foam achieves these characteristics through a different cell structure rather than simply increasing density.

It is commonly found in premium indoor furniture and commercial seating where long-term performance is critical.

Because HR foam costs significantly more than conventional polyurethane foam, it is less common in standard residential outdoor cushions.

Why a 6-Inch Cushion Isn't Always More Comfortable Than a 4-Inch Cushion

Many shoppers assume thicker automatically means better.

It doesn't.

Comfort depends on the complete cushion design.

A properly engineered 4-inch cushion using quality foam may outperform a poorly constructed 6-inch cushion.

Comfort depends on factors including:

• Foam density

• ILD

• Cushion dimensions

• Dacron wrap

• Seat construction

• Fabric tension

• User weight

• Cushion design

Simply adding thickness without changing the foam characteristics does not necessarily improve comfort.

How Dacron Wrap Changes the Feel of a Cushion

Most quality foam cushions include a layer of polyester fiber wrapped around the foam core.

This material is commonly called Dacron wrap or polyester batting.

The wrap serves several important purposes.

It:

• Softens the feel of the cushion

• Helps eliminate sharp foam edges

• Creates a fuller appearance

• Improves fabric fit

• Reduces wrinkling

• Makes cushions appear more luxurious

Without Dacron wrap, many foam cushions would feel noticeably firmer despite using exactly the same foam.

Why Two Cushions with the Same Foam Can Feel Completely Different

This surprises many customers.

Two cushions built with identical 1836 foam can feel completely different.

Why?

Because foam is only one part of the cushion system.

Comfort is influenced by:

• Cushion thickness

• Cushion size

• Fabric tension

• Dacron wrap thickness

• Foam contouring

• Cushion construction

• Seat support underneath

• Individual body weight

Even the way a cushion fits within a furniture frame changes how it feels.

This is why experienced manufacturers evaluate the entire cushion design rather than focusing on a single foam specification.

The Truth About Reticulated Foam

Reticulated foam, sometimes called dry-fast foam, is frequently promoted as the ultimate outdoor cushion material.

It certainly has advantages.

Because the cell walls have been removed during manufacturing, water flows through the foam extremely quickly.

Benefits include:

• Excellent drainage

• Fast drying

• Good airflow

• Reduced water retention

However, reticulated foam is not automatically the best choice for every application.

It also has tradeoffs.

Compared to conventional polyurethane foam, reticulated foam generally:

• Costs significantly more

• May double the price of a finished cushion

• Often requires special ordering

• Is unnecessary for many residential applications

For covered patios, screened porches, or furniture protected with covers, traditional upholstery foam combined with quality outdoor fabrics often provides excellent comfort and long service life.

The best choice depends on how and where the furniture will be used.

Foam, Densified Fiber, or Loose Fiber: Which Cushion Filling Is Right for You?

There is no single "best" cushion filling.

Each material is designed for different applications.

Polyurethane Foam

Best for:

• Deep seating

• Sofa cushions

• Club chairs

• Chaise lounges

Advantages:

• Excellent support

• Comfortable seating

• Available in multiple firmness levels

• Widely used throughout the furniture industry

Densified Fiber

Densified fiber consists of compressed polyester fibers bonded into firm slabs.

Advantages include:

• Excellent moisture resistance

• Does not crumble like aging foam

• Good dimensional stability

• Lightweight

• Often used in outdoor dining cushions and occasional seating

Many commercial outdoor cushions have successfully used densified fiber for decades.

Loose Polyester Fiber

Loose polyester fiber is commonly used in:

• Pillow backs

• Decorative pillows

• Knife-edge pillows

• Lumbar pillows

Advantages include:

• Soft feel

• Excellent loft

• Comfortable support

• Easy shaping

Unlike foam, loose fiber allows pillows to maintain a plush, casual appearance.

Choosing the Right Cushion Filling

The best cushion depends on how the furniture will be used.

For deep seating:

• Polyurethane foam remains the industry standard.

For dining cushions:

• Foam or densified fiber both perform well depending on the desired feel.

For decorative pillows:

• Loose polyester fiber provides the softest appearance.

For constantly exposed commercial pool furniture:

• Reticulated foam may be worth the additional investment because of its rapid drainage.

Final Thoughts

Foam specifications such as 1836 are useful, but they represent only one piece of the overall cushion design.

A quality replacement cushion is the result of many components working together, including the foam core, firmness, fiber wrap, construction methods, fabric selection, and overall engineering.

Rather than focusing on a single number, consider the complete cushion system and how the furniture will actually be used. The right combination of materials will provide lasting comfort, dependable support, and years of enjoyment outdoors.

At Cascadia Outdoor Cushions, we build replacement cushions using carefully selected materials designed to balance comfort, durability, performance, and value. If you're unsure which cushion filling is right for your furniture, our team is always happy to help you choose the option that best fits your needs.