What a Pan Actually Is
Under the tile of a built shower sits a waterproof assembly. In older Boulder homes it is a lead or copper pan or a hot-mopped membrane. Mid-era work used a vinyl liner folded up the walls and clamped at the drain. Modern builds run a bonded sheet or liquid membrane under a mortar bed. All of them do the same job. Tile and grout above are decorative and porous; the pan below catches everything that soaks through and delivers it to the drain's weep holes. A shower floor is, by design, a lined pond that empties itself. When the liner fails, the pond empties into your house instead.
How Pans Die
Each generation fails its own way. Metal pans from the older housing corrode through at the folds after decades, a slow pinholing that no one sees. Vinyl liners crack at corners where they were folded too sharply. Some were punctured by the original tile installation and take years to show it. Others fail at the drain clamp, where hair and movement work the seal loose. Weep holes clog with mortar and silt, forcing the water that reached the liner to sit and find the corners. And curbs, the dam at the shower's edge, leak at their tops where liners were nailed through instead of wrapped. None of these repairs from above. The tile is a roof over the failure.
The Flood Test: Proof Before Demolition
Pan diagnosis has a definitive test. We seal the drain with an inflatable plug, fill the pan area with a measured couple of inches of water, mark the level, and wait. A sound pan holds the line for the duration; a failed one drops the level and, in upstairs installs, produces the stain below on schedule. Moisture meters and, where useful, thermal imaging read the surrounding floor and ceiling to map how far past the shower the damage has traveled. The result is certainty. No shower floor should ever be demolished on suspicion, and with a flood test none has to be.
Rebuild Scopes, Priced Honestly
A failed pan means rebuilding the floor assembly: tile up, bed out, new membrane or pan in, proper slope, clean drain connection with open weep holes, curb wrapped correctly, then new tile. We scope it three ways where the situation allows: floor-only rebuild preserving the wall tile, floor-plus-lower-walls where the liner's wall flange is implicated, and full-stall renewal where age argues for it, each priced flat. Adjacent damage gets addressed in the same opening, and any question about whether the tub next door shares the problem gets settled with its own tub-side check while everything is accessible. Stains that survive a passed flood test are not the pan's fault, and those route onward as a ceiling leak investigation rather than an excuse to rebuild a healthy floor.
Remodels: Where New Pans Go Wrong
A surprising share of failed pans are young ones. Remodel-era failures come from preventable sins: membranes without a flood test before tile, curbs pierced by fasteners, pre-slope skipped so the liner holds standing water, weep holes mortared shut on day one. If you are mid-remodel, insist on a 24-hour flood test after the membrane goes in and before a single tile is set, and keep the photos. If you are buying a home with a recent bathroom renovation, that flood-test documentation is worth asking for, and its absence is worth a pre-purchase test of your own. A pan verified once, in writing, is a decade of stains that never happen.
And if your shower is on a slab rather than over a ceiling, do not assume a failed pan is harmless because nothing stains below. The water goes into the slab edge and the walls instead, where it works quietly. Ground floor pans deserve the same test on the same schedule.
Older stalls in Louisville Victorians, mid-era liners across Boulder's post-war blocks, or a remodel that never quite dried right: the flood test tells the truth in an afternoon. Schedule one at (303) 552-3896.