Factors considered in project-specific thickness review:
Water depth
Defines the load condition the engineering has to satisfy.
Panel dimensions & unsupported span
Longer spans generally mean higher bending demand.
Geometry
Flat, curved, and tunnel segments carry the same pressure through different shapes.
Support & boundary conditions
How a panel is held matters as much as how big it is.
Resolved inside the project-specific review — the initial enquiry needs only the acrylic dimension, water depth, and drawings if available.
Why water depth matters
Water is heavy, and it pushes on everything that holds it back. The deeper the water above and against a panel, the greater the pressure acting on it — which is why depth is the single most informative early number in a panel review. It defines the load condition the engineering has to satisfy.
Depth also separates two very different kinds of project. A shallow feature carrying a few hundred millimetres of water and a deep structural viewing panel are not the same engineering problem, even if the panels look similar on a drawing. Getting the depth on the table early — even as an estimate — tells the review which kind of problem it is dealing with.
Why water depth does not determine thickness alone
Pressure is only half of the question. The other half is what that pressure is acting on: how large the panel is, what shape it takes, and what holds its edges.
The same water depth produces very different demands on a small framed window, a long transparent wall, and a curved tunnel segment. Their dimensions differ, their geometry differs, and their support conditions differ — so their engineering differs, even though the water pushes on each of them with the same pressure at the same depth.
That is why final acrylic thickness is the result of project-specific review, not a number selected before the geometry and support conditions are understood.
Panel dimensions and unsupported span
Size changes behaviour. As a panel gets longer or taller, the pressure acts across a larger face, and the distance the panel has to carry that load between its supports — the unsupported span — grows with it. Longer spans generally mean higher bending demand, which is one of the main reasons a long wall and a small window at the same depth end up with different thicknesses.
This is also why a thickness that worked on one project cannot simply be reused on another. The depth may match; the dimensions rarely do.
Flat, curved, and tunnel geometry
Geometry changes the engineering basis. A flat viewing panel spans its opening and carries load primarily in bending. A curved pool wall or an underwater tunnel segment carries the same pressure through a different shape, which changes how the load travels through the material and into the supports.
None of this means one geometry is automatically thinner or stronger than another — curvature helps in some configurations and complicates others, depending on the radius, the segmentation, and the boundary conditions. What it does mean is that a flat panel, an aquarium window, a curved wall, and a tunnel segment at the same water depth are four different design problems. Application type alone doesn't set the thickness either; the specific geometry does.
Support and boundary conditions
How a panel is held matters as much as how big it is. A panel supported on all four edges behaves differently from one supported on two; a continuous rebate behaves differently from local support points; a stiff frame and a flexible one place different demands on the acrylic; and every panel needs room to move as temperature and load change, without losing its seal.
These are the questions a serious supplier asks before talking about thickness — not because the process is complicated for its own sake, but because the answers change the result. Interface tolerances belong on this list too: the panel meets a structure built by another trade, and the review has to know what that interface will actually be.
Why generic thickness tables are risky
A depth-to-thickness table has to collapse all of the variables above into one column — which means it has quietly assumed a panel size, a geometry, and a support condition the reader cannot see. If your project matches those hidden assumptions, the table is redundant; if it doesn't, the table is wrong. There is nothing careless about consulting one for orientation — the risk is building a design or a budget on it.
We don't publish a universal thickness rule — an indicative range can frame early budgeting, but no table replaces the project-specific review that sets the final figure. Completed projects show the variation rather than a rule: an oversized viewing panel in a Macau casino aquarium used 150mm at 2.5m of water depth, while the 10.6m × 1m pool viewing panel at Velero Doha used 100mm. Both figures are completed-project outcomes, resolved for their own dimensions, geometry, and support — not reusable templates.
Thickness is confirmed in project-specific engineering review before fabrication. PG's structural engineering is independently verified by the Tongji Architectural Design Institute. For the methodology behind that review — how span, depth, support, and casting constraints set the figure — see our thick PMMA panel thickness note.
What changes can trigger a thickness review
A thickness that was right for one version of a project may need review when the project moves. Typical triggers:
- the water depth changes;
- the panel dimensions or the opening change;
- a flat panel becomes curved, or the geometry is re-cut;
- the support arrangement, frame, or rebate changes;
- joints are added or moved;
- the deflection criteria or project requirements change.
None of these automatically changes the thickness — but each one changes the engineering basis, so each one requires review, and each should be coordinated before fabrication rather than discovered after it. Thickness revision after quoting is common enough that it has its own entry among the problems we see on almost every project.
What to send for an initial review
An initial thickness review does not need the full design package. It can begin with three inputs:
- acrylic dimension — the approximate panel or opening size;
- water depth — even as an estimate;
- drawings, if available — a section or sketch sharpens the review, but its absence doesn't prevent it.
Approximate values are acceptable; the review defines what the project-specific stages will need next. If you want the fuller picture of what those three inputs allow, see what a useful acrylic panel review needs.
Thickness and water depth — frequently asked questions
How does water depth affect acrylic panel thickness?
Water depth sets the pressure condition the panel must carry — the deeper the water, the greater the load, which makes depth the most informative early number in a review. But depth defines the load, not the answer: the final thickness also depends on the panel's dimensions, geometry, and support conditions, and is resolved in project-specific review.
Why can two panels at the same water depth need different thicknesses?
Because the same pressure acts on different structures. A small framed window, a long transparent wall, and a curved tunnel segment at the same depth have different dimensions, spans, geometry, and support conditions — so the engineering demand on each is different. Depth matches; almost nothing else does. That is why thickness is reviewed per project rather than copied between them.
Does panel length or unsupported span affect thickness?
Yes, significantly. As a panel gets longer or taller, pressure acts across a larger face and the unsupported span between supports grows, which generally increases bending demand. This is one of the main reasons a thickness that worked on one project cannot be reused on another at the same depth. The specific span and support arrangement are resolved in project-specific review.
Are curved acrylic panels designed the same way as flat panels?
No. A flat panel spans its opening and works mainly in bending; a curved wall or tunnel segment carries the same pressure through a different shape, changing how load travels into the supports. Curvature helps in some configurations and complicates others — there is no universal rule, which is why geometry is part of the project-specific review rather than a preset answer.
Can an online acrylic-thickness table be used for final design?
No. Any generic table has quietly assumed a panel size, geometry, and support condition that may not match your project — it can orient an early conversation, but it cannot carry a design or a budget. Final thickness is confirmed in project-specific engineering review against the actual dimensions, geometry, support, and interface conditions before fabrication.
When should acrylic panel thickness be reviewed again?
Acrylic panel thickness should be reviewed whenever the water depth, panel dimensions, geometry, support arrangement, frame or rebate, joints, or project criteria change. None of these changes automatically requires a thicker panel, but each changes the engineering basis. The review should take place before fabrication so the panel, supporting structure, sealing interface, and installation details remain coordinated.
Depth is the starting input — thickness is the output
Water depth tells the review what the water will do. The dimensions, geometry, and support conditions tell it what the panel can do about it. The first is a number you already have; the second is what the project-specific review exists to resolve — which is why the review, not a chart, sets the final figure.
Cast Acrylic (PMMA) Viewing Panels 20–600mm, reviewed project by project.