If you're considering an oval above-ground pool, you will likely come across two variations of structural options: buttress and buttress-free.
What Is a Buttress? 
In the above-ground pool world, a buttress is what was originally used as the pool's support brace (can also be referenced as an A-Frame). Its purpose is to counteract the water pressure pushing against the walls since the water in oval pools isn’t evenly distributed. These support systems extend outwards from the long sides of the pool, about 3’+ feet on either side.
So, what supports Buttress-Free pools? 
To evenly distribute weight in a buttress-free pool, oval models use compact angled supports that extend about 1’ foot or less on each straight side. Buttress-free models are equally capable of withstanding the pressure of thousands of gallons of water, but rely on internal engineering, using pressure plates attached to beams that run beneath the pool, instead of relying on large external braces.
These are typically referred to as Buttress-Free, Trimline Space Savers / Trimline Side Support, and more.
Let’s Compare:
Buttress Oval Pool
Structure: A-frame angled side braces that evenly distribute the water's outward pressure.
Space Requirement: Requires additional space around the actual pool frame, typically 2’ to 4’ feet extra on either side.
Design: A classic, time-tested design that offers strong, dependable support using external braces.
Buttress-Free Oval Pool
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Structure: These systems rely on pressure plates and heavy-gauge beams beneath the pool to support its lateral pressure.
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Space Requirements: Designed with a more compact footprint, supports typically stick out 1’ foot or less.
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Design: Modern design that delivers the same dependable support with a more compact footprint.
Whether you choose a traditional buttress oval pool or a modern buttress-free design, the real difference lies in how each model fits into your space. Both accomplish the same end goal, supporting the outward pressure just in two different ways.
Regardless of which you choose, both designs are structurally sound and built to handle the demands of daily use, so you can feel confident in your pool's strength, stability, and long-term security.