What is the best concrete thickness to use for your pool? You’re likely already looking into and comparing pool contractors in your local area if you ask this question. Concrete pools are too complex and technical for most people to DIY. Professionals will build it. Ask them all the questions in our Swimming Pool Builder vetting checklist to verify their competence and integrity.

River Pools is a specialist in a fiberglass pool, but we are experts at all three types of pools and want to ensure you have all the details.

Concrete pool contractors might tell you how thick their pool shells are to show that they’re better than others. However, this doesn’t help if you don’t know the standard.

The Best Concrete Pool Thickness

3500-4000psi is the average concrete strength. Concrete has high compressive strength (difficult to crush) but a low strength — it can be easily cracked if it’s bent or pulled apart by something. It would be best if you supported it with steel.

The concrete can be flexed by using a web made of steel (called “rebar”). Because the pool must be strong enough to resist the forces of nature (water inside and soil outside), the concrete and rebar thicknesses will vary depending on the environment.

A concrete pool shell must be 6 inches thick to be structurally sound. It may be higher depending on the engineer and soil conditions. The plaster interior finish should not be less than 3/8 inches thick.

Also, the ANSI/APSP standards will need to be met. Ask the pool engineer or builder for a copy of your pool specifications.

Concrete pool construction can take 3-6 months. It takes 3-6 hours to place the steel, plumbing, and concrete. This is usually done using the gunite method to see the pool thickness very early.

Concrete cracks can cause problems.

Cracks in concrete can either be within the structure or surface (crazing).

A structural crack is usually caused by poor design or construction. An engineer must design the pool to withstand uneven or expansive soil. After that, the construction crew must construct it according to the specifications. The pool could fail structurally if it is not correctly designed or constructed.

A craze cracked is a surface crack caused by shrinkage. These cracks are not likable but can cause staining and algae and calcium nodules.

A Better Alternative to Thick Concrete

Fiberglass pools are an option if a concrete pool seems too complicated.

Fiberglass pools are stronger than concrete in many aspects, and they’re only 3/8 inches thick. Although math is not my forte, I know that fiberglass pools are significantly thinner than concrete. How does this work?

River Pools has developed a manufacturing method called Cross-Lynx Composite Technology, allowing fiberglass pools to bend under environmental pressure without cracking or losing shape. Six layers made of fiberglass materials bond through a chemical process called Polymerization. We also provide support for walls and edges subject to greater stress.

A fiberglass pool is as durable and strong as a concrete one, requiring minimal refinishing. The pool shell is smaller… which means you can have more pools in the same area of your yard.

What are the differences between concrete and fiberglass pools?

This is only a brief overview. For a more detailed discussion of these contrasts, please visit the article “Concrete Pools vs. Fiberglass Pools – An Honest Comparison.”

Concrete pros and cons


  • You can customize
  • Durable
  • Pretty


  • Long startup (3-6 months)
  • Surface rough
  • Maintenance is very important
  • High initial cost (50,000+)
  • Long-term, significant savings in time and money
  • Frequent refinishing

Fiberglass pros and cons


  • Fast installation (3-6 weeks)
  • Durable
  • Low maintenance
  • Low cost of living
  • Attractive
  • Compatible with salt water systems


  • Limiting size and shape
  • The initial cost of a vinyl pool liner pool is higher ($35,000+).

River Pools offers freeform and linear fiberglass pools throughout Virginia and Maryland. Our distributors also offer these pools in other parts of the country. We are happy to answer your questions if you feel a fiberglass pool is the right option.

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