Have you ever considered just how heavy a swimming pool really is?

A standard residential pool, measuring 34’ x 16’ and 5’ deep, can hold around 20,000 gallons of water,  which is roughly equivalent to 166,000 pounds. Add concrete and steel, and the structure can exceed 300,000 pounds.

That’s nearly double the maximum takeoff weight of a Boeing 737.

For architects, engineers, and homeowners, this isn't just trivia; it's a structural challenge. Building pools on rooftops, hillsides, or above existing structures requires materials that can handle weight without adding to it.

This is where structural foam, specifically Expanded Polystyrene (EPS), becomes a practical solution. EPS offers the compressive strength required for full-scale pools while reducing total structural weight by up to 90%.

In this article, you’ll learn what EPS is, how it’s applied in pool construction, and why it's shaping the future of complex pool builds.

What Is Structural Foam (EPS) and Why Does It Matter?

EPS (Expanded Polystyrene) is a lightweight, rigid foam made up of 98% air. While commonly associated with packaging, construction-grade EPS is engineered to meet structural load demands.

It provides the same base support as traditional fill materials, such as gravel, but at a fraction of the weight. That reduction is critical when you're building a pool above a garage, on a slope, or in locations where soil conditions can't handle heavy loads.

Quick Definition: EPS foam is a lightweight, load-bearing material used to replace gravel or soil fill beneath concrete pool shells, reducing stress on foundations without sacrificing strength.

Why EPS Is Stronger Than It Looks

Lightweight doesn’t mean weak 

To put the numbers in perspective:

• Pool Size: 34’ x 16’ x 5’

• Water Weight: ~166,000 lbs.

• Concrete & Steel Shell: Adds another ~130,000+ lbs.

• Total Weight: Over 300,000 lbs.

Without careful weight management, that load can overwhelm rooftop slabs or undermine hillside stability.

EPS provides structural integrity by:

• Distributing weight evenly

• Reducing the need for deep foundations or soil reinforcement

• Meeting ASTM D6817 standards for compressive strength

When used correctly, EPS helps form a solid, watertight, and long-lasting pool structure.

How EPS Foam Supports Custom Pool Designs

Because EPS blocks can be cut and shaped on site, they offer more flexibility than rigid materials. Whether it’s a tanning ledge, spa bench, sloped floor, or a curved wall, EPS makes it easier to form the structure without adding stress to the underlying soil or slab.

For builders and designers, this means more design freedom without compromising stability.

Faster Installation Without Cutting Corners

Construction timelines matter, especially in complex projects.

EPS streamlines construction by:

• Reducing excavation time

• Replacing heavy fill that requires transport and compaction

• Allowing faster forming and reduced concrete use

With the proper layout and engineering, EPS can save days to weeks on complex pool projects.

A More Sustainable, Cost-Effective Material

EPS offers environmental and budget benefits beyond its weight advantage:

• Less material transport: It’s lightweight and often fabricated locally.

• Lower fuel and labor costs: Fewer truckloads, less equipment.

• Reduced waste: Precision cuts = minimal excess.

• Recyclable: Construction-grade EPS can be reused or recycled.

In short, it reduces both upfront project costs and ongoing operational impact.

Built-In Thermal Insulation

A lesser-known advantage of EPS is its natural thermal performance.

Its insulation properties help:

• Keep pool water warmer in winter

• Reduce heat gain in hot climates

• Lower heating and cooling energy bills over time

For homeowners in regions with seasonal temperature swings, this is a quiet but valuable benefit.

Durability Over Time

EPS is not exposed once the pool is complete. It sits beneath the concrete shell, protected and stable.

It won’t rot, compress under load, or degrade when properly installed, and when combined with a concrete pour, it forms a strong, watertight structure with lasting performance.

EPS has been used in civil and structural projects for decades, including highways, bridges, and embankments, all of which demand long-term reliability.

Code-Backed Safety Standards

EPS used in structural applications must meet strict code and material guidelines.

These include:

• ASTM D6817 – regulates density and compressive strength

• ISPSC & IBC – international and state building codes for structural performance

When engineered and installed to code, EPS is not only safe; it’s a preferred method for complex construction where traditional fill is not feasible.

Real-World Example: Protecting Structures with EPS Pools

Imagine trying to build a pool on top of a vaulted parking garage, basements, or living spaces.

With a total weight exceeding 300,000 pounds, traditional fill materials like gravel could place dangerous stress on the structure below. But with EPS:

• The weight is reduced by up to 90%

• Loads are evenly distributed

• Concrete forms a stable, secure shell over the foam

This method is now a standard approach for rooftop pools, hillside installations, and builds over underground structures.

Your Next Step: Learn How EPS Works With Caissons

EPS solves the weight problem, but it’s only one part of the equation. On sloped or soft-soil sites, it often works in conjunction with deep foundation systems, such as caissons.

👉 Read next: Caissons: The Key to a Stable and Secure Hillside Construction

Frequently Asked Questions About EPS Foam in Pool Design

Q: Is EPS foam strong enough to support a full-size pool?
A: Yes. Structural EPS foam is engineered to meet ASTM standards and can safely support the compressive loads of concrete and water when installed correctly.

Q: What makes EPS better than gravel or fill dirt?
A: EPS weighs up to 90% less, distributes loads more evenly, is easier to install, and often includes thermal benefits. It’s also better suited for projects with weight-sensitive foundations.

Q: Is EPS foam waterproof?
A: EPS does not absorb water when sealed and encased in concrete. It contributes to a long-lasting, watertight shell when appropriately used.

Conclusion: Lighter, Safer, More Flexible Construction

At J Designs, we’ve seen firsthand how EPS opens doors for creative pool design — without sacrificing structural safety.

• EPS reduces the single biggest challenge in pool construction, weight.

• You may be building over garages, slopes, or soft soil.

• Next Step: Learn how EPS integrates with caissons for complex sites.

• Since 2008, we’ve helped homeowners, engineers, and builders create safe, structurally sound pools using advanced materials, such as EPS foam.

Considering EPS for Your Pool Project?

Let’s discuss whether it’s the right fit for your site.

📩 Contact the J Designs Team