Sizes, heights, and how to measure

Measure three times, and do not average

The single most useful habit in this entire project is measuring each wall at three heights — just above the pan, at about chest height, and near the top — and writing down all three numbers separately.

Almost everyone measures once, in the middle, and orders from that. It works in new construction where someone set the framing recently and checked it. It fails in remodels, because houses settle, framing twists, and the wall you are measuring may have been out of plumb since 1974.

The spread between those three numbers is the whole decision. Under an eighth of an inch and you can order exact-size panels. More than that and you want oversized panels you can scribe to the wall. Averaging the three numbers destroys exactly the information you needed, and produces a panel that fits perfectly at one height and leaves a visible gap at the other two.

Check your fit

Enter your numbers. The drawing exaggerates any out-of-square condition six times so you can actually see which way the walls lean, and the verdict below tells you what to order.

If that came back telling you to order oversized, that is the normal result rather than bad news. Most remodels land there, and the fix costs almost nothing at the point of ordering — it only becomes expensive if you discover it after the panels arrive.

Standard sizes worth knowing

Being on a stock footprint is worth more than it sounds. It means the widest choice of finishes, the shortest lead times, and the cheapest panels, because you are buying something the manufacturer already makes rather than something they have to set up for. If you are within a fraction of an inch of a stock size, that is a good position to be in.

Choosing a panel height

Heights run 72, 78, 80, 84, and 96 inches, with 108-inch panels available from a small number of manufacturers for nine-foot ceilings.

• 72″ — the traditional height. Leaves roughly a foot of painted wall above the panel on an 8-foot ceiling, and that band is exactly where steam damage shows up first.
• 78″ and 80″ — more coverage, still leaves a strip. A reasonable middle ground and a common stock height.
• 84″ — matches a standard door height, which reads as deliberate rather than arbitrary. Still a painted band above.
• 96″ — reaches the top of a standard 8-foot ceiling with no painted band at all. This is why it has become the default choice for anyone remodelling specifically to reduce maintenance.
• 108″ — for 9-foot ceilings. Rare, expensive, and heavy enough that getting a sheet up a staircase is a genuine planning question. Cultured marble and solid surface are the realistic materials at this height.

The jump from 80 to 96 inches typically costs a few hundred dollars in material and removes a strip of wall that will otherwise need repainting every few years. It is one of the few upgrades in this category that reliably pays for itself, and we would take it over a material upgrade if the budget only stretched to one.

How square is square enough

Houses are not built to the tolerances that manufactured panels are made to, and after demolition the situation frequently gets worse rather than better.

The last row is worth taking seriously. Panels are flat and rigid; they do not disguise a leaning wall, they announce it, because a perfectly straight panel edge against a leaning ceiling line draws the eye straight to the problem. Furring out and re-plumbing a wall is not a large job compared with what you are already spending, and it is much cheaper before the panels arrive than after.

Check the corners too. Hold a framing square into each inside corner and look for daylight. A corner that is out of square by any meaningful amount affects how the side panel meets the back panel, and it is a different problem from a wall that leans.

Exact-size versus oversized

Most manufacturers offer both. Exact-size panels arrive finished on all edges and ready to install with no cutting. Oversized panels arrive deliberately large, with one or more unfinished edges intended to be trimmed on site.

The one genuine downside of oversized panels is that the trimmed edge is a cut edge rather than a factory edge, so it needs the trim profile or the silicone bead to cover it. In practice that edge is almost always in a corner or against the pan, where it is covered anyway.

Valve clearance, the thing people forget

Here is a problem that only exists with panels and only when going over an existing surface: every layer you add pushes the finished wall outward, and the valve does not move.

A valve stem projects a fixed distance from the framing. The original tile used some of that projection; a panel bonded on top of that tile uses more. If the total exceeds what the stem projects, the trim kit will not seat, and the fix is a valve extension kit or moving the valve forward, which means opening the wall.

Check this before you order the panel, not after. It can legitimately change which material you should buy — if clearance is tight, a 0.22-inch SPC panel and a 0.625-inch cultured marble panel are not interchangeable choices, regardless of which one you prefer.

The same arithmetic applies at three other places worth measuring: the shower door jamb, which may no longer sit flush; the pan edge, where the panel needs to lap the upstand; and any existing niche or shelf, whose opening gets smaller by the panel thickness on every side.

The measuring protocol

Twenty minutes with a tape, a level, and a framing square. Do it in this order.

1. Back wall, three widths

   Just above the pan, at chest height, near the top. Corner to corner each time. Write down all three — do not average, do not round to the nearest half inch.

2. Each side wall, three depths

   Same three heights. Side walls are frequently more out of square than the back wall, because they are shorter and often built against something else.

3. Height, in two places per wall

   From the pan or tub deck up to where you want the panel to stop. Floors slope, pans slope, and ceilings are not always level relative to either.

4. Check plumb and square

   Level on each wall vertically. Framing square into each inside corner. Note which direction anything leans, because that determines which edge gets scribed.

5. Valve and showerhead positions

   Measure the centre of each from the pan edge and from the nearest corner. Use the pan as your reference, not an adjacent wall that may not be plumb. Note the valve stem projection with the trim removed.

6. Test the substrate

   Press and tap across every wall. Soft, hollow, or moving means repair before surface. This is the step that changes budgets, so do it before you order anything.

7. Photograph everything

   Corners, pan edge, valve, and any damage. When you send measurements for a quote, photos of the corners and the pan edge are far more useful than a wide shot of the room.

Tub surrounds measure differently

Two things change. First, measure the height from the tub deck, not the floor — tub heights vary by several inches between models and the deck is the reference the panels actually sit on. Second, the tub deck itself is rarely level, because tubs are set to drain.

Standard tub surround kits are built around a back wall up to 60 inches with returns to about 36 inches. Heights from the deck run 60, 66, 72, and 84 inches. As with showers, going taller removes the painted band that steam damages, and the material cost of doing so is modest.

The joint where the panel meets the tub deck is the most important one in the installation and the one most likely to have failed in whatever you are replacing, so inspect the substrate there closely before covering it. More on tub surrounds here.

Corner and neo-angle showers measure differently

An alcove is a rectangle with one open side, and it is forgiving because two of its three walls are held square by the walls of the room. A corner shower has only one corner formed by the building; the other edges are defined by glass, which means the panels have to be right rather than merely close.

Three differences worth planning for:

• Only two walls get panelled. The return edges are exposed rather than tucked into a corner, so the edge finish becomes visible and matters far more than it does in an alcove. This is where an integral or bullnose edge earns its money over a plastic trim profile.
• The glass has to land on something flat. A frameless panel or door sits against the panel face, so any bow or lippage in that panel becomes a sealing problem. Measure the flatness of those two walls with a straightedge, not just their dimensions.
• Neo-angle geometry is not obvious from a tape measure. A neo-angle has a clipped corner at 135 degrees, and the angled face has to be dimensioned along its own length rather than derived from the two side dimensions. Measure the diagonal directly.

If you are working with a neo-angle, send us the pan model number along with the measurements. Pan manufacturers publish exact wall dimensions for their bases, and matching the panels to the published pan geometry is far more reliable than measuring a rough opening.

Ceilings, niches, and benches

Ceiling panels

A ceiling panel closes the top of the enclosure and removes the last painted surface in the wet zone. It is worth considering in two situations: a steam-heavy bathroom with marginal ventilation, where the ceiling above a shower is the first thing to grow mould, and any enclosure where you have gone to 96-inch walls and a painted ceiling would undercut the effect.

Measure the ceiling as its own rectangle, at all four edges, because a ceiling that looks square rarely is. Note that a ceiling panel needs mechanical support during curing, not just adhesive — gravity works against you in a way it does not on a wall, and this is one of the few parts of a panel installation that genuinely benefits from a professional.

Niches

Two options exist and they have very different measurement consequences. A pre-formed niche is a moulded unit that the panel cuts around, and its opening dimension is fixed by the manufacturer, so you are designing the wall around the niche. A site-built niche framed into the wall and then panel-lined needs each of its five faces measured individually, and each face loses the panel thickness on every side — which means the finished opening is meaningfully smaller than the framed opening.

That shrinkage catches people out. A niche framed at 12 by 24 inches, lined with half-inch solid surface on all faces, finishes at roughly 11 by 23. Frame generously.

Benches and seats

A bench changes the panel layout because the back panel now has to be cut around it, or stop above it, and that cut line has to be dead level or it will be the most visible line in the shower. Measure the bench height at both ends and at the front and back, since benches are usually sloped slightly for drainage.

If a fold-down seat is going in later rather than now, the relevant measurement is not the seat — it is the blocking behind the wall that the seat will anchor into, and that has to exist before the panel goes on. Same principle as grab bar blocking: decide it before the walls close, or take them apart later.

Take this to the bathroom

Six expensive mistakes

1. Measuring once, in the middle. The most common error and the most expensive. It produces a panel that fits at one height and gaps at the other two.
2. Averaging the three numbers. This throws away the exact information you took the trouble to gather. Record all three.
3. Ordering exact-size for a remodel. Unless you set the substrate yourself and checked it, order oversized. The premium is small; the reorder is not.
4. Measuring the valve from an adjacent wall. If that wall is out of plumb, so is your hole. Always reference the pan edge.
5. Forgetting the panel thickness at the valve. Every layer added pushes the wall out. Run the clearance check before you order.
6. Not testing the substrate first. Discovering soft wall after the panels arrive means either delay or covering a problem. Tap the whole wall before you spend anything.

With numbers in hand, the two things left are choosing a material and understanding what it should cost. If you would rather just read your measurements down the phone, call 1-888-779-2284.