Acrylic pans dominate replacements for a simple reason: they arrive pre-sloped, with the drain opening formed and the flange in place, and they weigh little enough for one person to carry. The trade is that the shell depends entirely on what is underneath it, which makes the setting bed the most important part of the installation.
How an Acrylic Pan Is Built
A moulded pan is a shell rather than a solid block. The visible surface is acrylic or a composite skin; behind it sit reinforcement ribs, a filled core or a sprayed layer that gives the shape its rigidity. Two pans with identical outside dimensions can behave completely differently depending on that layer, which is why section and weight tell you more than a photograph.
A gel-coated fiberglass pan is built the same way, with a different surface. Fiberglass tends to craze when it flexes, while acrylic marks and scratches; both fail for the same underlying reason when the bed is not continuous. That comparison is set out in our material guide to acrylic versus fiberglass.
Flex, Support and What a Setting Bed Does
When someone stands in the shower, load passes through the floor of the pan into whatever is directly beneath it. If the bed is continuous, the load spreads; if the pan is spot-bedded on lumps of adhesive, the skin spans the gaps and deflects with every step.
Flex announces itself in stages. First a spongy feeling underfoot, then movement at the caulk line where the pan meets the wall, then a crack starting at the drain or an edge. By the time the crack appears the cause has been present for months, which is why the installation instructions for a specific pan are worth reading before the bed is mixed rather than after.
Sizing and Drain Position
Acrylic pans are sold in a small set of footprints, and the drain position is a factory choice. The sequence that works is: measure the finished opening at three heights and take the narrowest; measure the depth at both ends; measure the trap from two reference walls; then choose the pan whose footprint and drain orientation match those numbers.
| Measurement | How to take it | What it decides |
|---|---|---|
| Finished opening | Three heights; use the smallest | Pan footprint |
| Depth | Both ends, front to back | Pan depth and door clearance |
| Trap position | From two walls, not a corner | Left, right or centre drain |
| Threshold height | Subfloor to intended base line | Door glass height and step-over |
Where the opening or the trap matches nothing standard, a made-to-measure pan is the alternative to a filler strip - the ordering route is described in the guide to custom shower pans.
The Subfloor and the Drain Connection
Under the setting bed the subfloor has to be flat, dry and sound. Wet plywood, sheathing that flexes between joists, or a drain opening cut generously all show up later as movement in the pan. Fix the subfloor before the pan, not around it.
The drain connection is made to the trap below, with trap arm, venting and the drain fitting itself governed by the adopted plumbing code published at iccsafe.org. Around the outlet, the membrane and flange details follow the same principle as any wet-area assembly, described in the methods published by the Tile Council of North America and catalogued on the Whole Building Design Guide.
Cleaning and Surface Care
Acrylic and composite surfaces tolerate ordinary bathroom cleaning but not abrasives. Powder cleansers, scouring pads and blades leave a dull track that cannot be polished out on site, and the same applies to the textured non-slip areas where dirt collects in the pattern.
The workable routine is a non-abrasive liquid cleaner with a soft cloth, a rinse afterwards, and early attention to mineral scale. Where cleaning products are selected for lower environmental impact, the EPA Safer Choice programme lists products that meet its criteria - and any product used on the pan should also suit the wall surround and the door seals.
Where Acrylic Is the Wrong Choice
Acrylic is the wrong specification where the subfloor cannot be made continuous and flat, where the pan will take heavy point loading - a shower chair, for instance, on a thin shell - or where the household expects a cast-iron-like solidity. In those cases solid surface, or a tile-ready pan over a properly built bed, is the better answer.
Where a previous pan has leaked into the floor assembly, the damage is beneath the pan rather than in it: the moisture guidance published by the EPA explains how far the repair has to go, and component test methods for receptors are published by ASTM International.
Ordering Checklist
Confirm five things before ordering: footprint and drain orientation against the measured opening and trap; threshold height against the intended step-over and door; the setting bed material the manufacturer requires; delivery access, including the crated dimensions; and the finish, since a pan that has to match a wall surround is usually ordered with it.
Order the pan before the door, because the door is measured from the installed pan. Where the pan and surround are being replaced together, specify them as a set: a 60 in. pan, a 60 in. surround and a 60 in. door line up at the jamb, while three components from three sources can each be dimensionally correct and still leave a taper at the seal line.
FAQ
Which type of shower pan is better, acrylic or fiberglass?
Acrylic is usually the more expensive of the two, holds its surface better and offers more finish options; fiberglass costs less and can be moulded into large one-piece shapes. Both depend on a continuous setting bed, and both fail the same way when that bed is missing.
Are acrylic shower bases any good?
Yes, provided they are supported correctly. Acrylic is non-porous, warm underfoot and light enough to handle, and it arrives with the slope and flange formed. Its weakness is deflection, so a continuous bed and a flat subfloor decide whether it performs.
What is the best material for a shower pan?
Match the material to the project: acrylic or composite for fast replacements and standard footprints, solid surface where a refinishable finish and colour matching matter, tile-ready pans where the floor finish continues into the shower, and cast iron where the structure can carry the weight.
Do acrylic shower pans need a mortar bed?
Most require a continuous setting bed - usually mortar or a purpose-made foam bed - installed so the underside is fully supported. Follow the manufacturer's instruction for the specific pan, because the requirement varies with the ribbing and thickness.
Send the finished opening at three heights, the depth at both ends and the trap position from two walls, and we will confirm the footprint and drain orientation that fits.
