If I had to guess what you think goes wrong with a shower door order, I'd guess glass. A chip on the edge. A seal that let go after six months. A hinge that sagged and pulled the panel out of alignment.
Those happen. But when I pulled our rejection log for last year — roughly 390 custom glass orders, the log says 386, I was working from memory — 43 of them got held before they ever left the building, and in only a handful was the glass itself at fault. The rest were the wrong size for the opening they were supposed to fill. Or the opening wasn't ready for the door.
That distinction matters, because a wrong-sized door isn't a fixable problem. It's a scrap problem.
The opening you measure isn't the opening you get
The core issue with bathroom shower doors is that they're built to fit a hole that doesn't exist yet at the time most people measure it.
On paper, a tub shower door opening looks simple: width, height, and which side the hinges land on. In practice you're measuring the distance between four planes — two side walls, the tub deck or curb below, a header or ceiling above — and none of those planes are where they'll eventually end up while the job is still open.
Tile is the big variable. Backer board plus thinset plus tile adds somewhere between a half inch and a full inch per side, depending on what's being installed. Measure a tub alcove before tile goes up and you can be off by an inch and a half, sometimes two, on width. On a standard 60-inch alcove, that's the difference between a door that installs in an hour and a door that goes in the dumpster.
Plumb is the other one. Framed shower doors buy you forgiveness — most framed units carry adjustment built into the track and header, which is why they're still the workhorse on rental and multi-family jobs. Frameless is a different animal. A frameless sliding shower door system wants walls plumb within about an eighth of an inch across its full height and a curb that's actually level. Miss that and the panels bind, the seals sit crooked, and water finds the one gap you didn't plan for.
Nobody owns the number
This is the part I keep coming back to after four years of reviewing these orders.
From the outside, ordering a shower door looks like a simple transaction: measure, order, install. The reality is that three different people usually touch that measurement, and none of them owns the final one.
The general contractor measures the rough opening because he's standing there. The tile setter changes it two weeks later. The homeowner places the order — often online, often at 11 p.m. — using a dimension someone texted them. Or the designer specifies from a catalog drawing without ever setting foot on site.
And the order usually goes in before the tile, because custom glass shower doors run four to six weeks and nobody wants a finished bathroom sitting doorless for a month. So the measurement gets taken against a wall that's still going to grow by three-quarters of an inch.
Here's the piece that doesn't get said at the sales counter: the only measurement that matters is the finished opening, taken after waterproofing and tile are complete. Everything before that is an estimate. Good estimators know what to add back. Most people don't, and there's no field on the order form that asks.
There's a reason some frameless suppliers insist on templating after tile is done and charge more for the privilege. They're not being difficult. They're removing the variable that generates most of their warranty claims. If a company lets you order a custom glass shower door from a web form and three numbers you typed in yourself, they've just handed the risk to you — and the terms of service usually explain that in the last paragraph nobody reads.
The other half of this problem is blocking. Frameless panels are heavy. A 3/8-inch panel in a 30-by-72 format runs around 85 pounds, and the hinges need to transfer that load into framing, not drywall. If the blocking isn't in the wall before drywall closes, your installer is going to have a bad day and your wall is going to have a worse one. We ask for photos of the open wall at every hinge location on frameless orders. Maybe half come in unprompted.
What a rejected door actually costs
Tempered glass can't be cut down. That single fact drives the economics of the entire category, and it's why a small measurement error turns into a large invoice.
Per CPSC 16 CFR Part 1201, glass in shower and bathtub enclosures has to meet Category I or II impact resistance, which in practice means tempered or laminated. Tempering happens after cutting, drilling, and polishing, so once the panel is made there is no trimming an inch off the edge. The unit is scrap. Verify current requirements at ecfr.gov, since local amendments vary, and ANSI Z97.1 is the other standard worth knowing if you're doing commercial work.
So the real cost of a bad measurement looks something like this:
- The original unit. Call it $400 to $1,200 for a typical tub shower door as of early 2025, more for a full frameless enclosure with a return panel.
- A second unit at full price, because it's a new order, not a warranty claim.
- Four to six weeks of lead time, which is usually the part that actually hurts.
- Whatever the delay costs downstream — a punch list that won't close, retainage held, a closing date slipping, or a family sharing one bathroom through the holidays.
Then there's the line item nobody budgets for: the temporary shower curtain that stays taped up for four months while the reorder is in production. Water gets past it. The curb and the subfloor around it don't love that.
I've watched this play out the cheap way, too. Saved $140 by having the homeowner take the measurements instead of sending someone out. The width was taken at the tub deck rather than above the tile, so it came in 1-3/4 inches wide. Reorder, freight both directions, plus a very uncomfortable phone call. In the neighborhood of a $1,100 lesson on a $620 door. That was the last time we accepted a measurement without a signature on the spec sheet.
The fix is boring and it works
None of this is complicated. It's just unglamorous, and it costs a little time up front.
- Measure the finished opening — after waterproofing, after tile, after the curb is set. Not the rough opening.
- Take three width measurements (top, middle, bottom) and three height measurements (left, center, right). Use the smallest number. If the spread exceeds a quarter inch, you have a plumb problem to solve before you have a door problem.
- Check plumb with a four-foot level, not a torpedo level. An eighth of an inch across 12 inches is nothing. Across 72 inches it's a panel that won't slide.
- Confirm hinge blocking before the drywall closes. Dated photos, filed with the order.
- Match the door to the opening, not the other way around. Wide spread, framed shower doors absorb it. Frameless sliding systems generally won't.
- Write the numbers on the order, have the person who measured sign it, and keep it. Thirty seconds of work that has settled more disputes than any warranty language we've ever drafted.
Five minutes of verification beats five days of correction. I would rather hold an order a week than eat a reorder and explain to a customer why their bathroom is finished except for the one part they look at every single day.
One caveat, and it's a real one: this all comes from the supplier and installer side, on residential and light commercial work in a region where tile over backer board is the default. If you're dealing with a prefab acrylic surround, or a curbless wet-room build with a linear drain, some of these numbers shift. I can only speak to what I've actually signed off on.
