The Most Important Part of a Bathroom Remodel Most Contractors Skip

If you’re planning a bathroom renovation, here’s the single most important thing to

understand: the tile you see on the walls and floor of your shower is NOT what keeps

water out. Tile and grout are not waterproof. The waterproof membrane system behind

the tile is what actually protects your home from moisture damage — and it’s the step

that too many contractors skip, rush through, or do incorrectly.

A properly waterproofed shower includes a waterproof membrane applied to all walls

and the floor (or shower pan) inside the shower enclosure. This membrane catches

every drop of water that penetrates through grout lines and tile joints and directs it to the

drain. Without it, moisture slowly soaks into the backer board, framing, and subfloor

behind the tile — leading to mold growth, wood rot, and eventually structural damage

that’s far more expensive to fix than the original renovation.

Industry-leading waterproofing systems like Schluter KERDI, Laticrete Hydro Ban, and

CUSTOM RedGard are specifically engineered for shower environments. They’re

applied as sheets or liquid coatings over cement backer board, creating a continuous,

watertight barrier behind the tile. Corners, seams, valve penetrations, and curbs all

receive special treatment because these are the most vulnerable points where leaks

develop.

Why do some contractors skip this step? It adds time and cost — typically $500 to

$1,500 depending on the size of the shower. Some contractors assume the tile and

grout will keep water out (they won’t). Others simply don’t know better or are cutting

corners to come in at a lower bid price. If a contractor tells you waterproofing isn’t

necessary for your shower, that’s a red flag.

This issue is especially critical in New Hampshire. Our cold winters create extreme

temperature differentials between the warm, humid shower environment and the cold

exterior walls behind it. This temperature difference drives condensation into wall

cavities and amplifies moisture damage if the waterproof barrier is missing or

incomplete. We’ve ripped out bathrooms that were remodeled less than five years ago

and found extensive mold and rot behind the tile — all because the waterproofing was

skipped.

When comparing bathroom renovation bids, ask every contractor specifically what

waterproofing system they use and where they apply it. If the answer is vague, or if

waterproofing isn’t mentioned at all, move on.

We use industry-standard waterproof membrane systems on every shower and wet

area we build — no exceptions. It’s not optional in our process, and it’s one of the

reasons our bathrooms last for decades rather than developing problems within a few

years. Free consultations throughout NH and within 75 miles.