The Nightmare Before Christmas: Why We Tore Out Our Brand New Shower

We thought we were crossing the finish line.

It was right before Christmas. The cabin finally had heat and hot water. We were staying in it as we renovated (a messy choice, but the only way we could keep working). The bathroom was functional, and we were just working on the drywall and trim to make it look finished.

Then I saw it.

A black area on the wood framing near the floor. I touched it, and my heart sank. It was wet.

I pulled back a piece of the purple rigid foam insulation we had installed months ago—before the shower was even installed. It was wet.  Dripping wet. And then I saw it: Mold. Not just a little bit, but a layer of it hiding behind the insulation all around the shower.

In an instant, our “finish line” moved far away. Here is how we messed up, what it cost us, and how you can remove mold if you catch it early enough.

The Setup: Why We Rushed

To understand the mistake, you have to understand the logistics of a new build.

We chose a one-piece fiberglass shower unit. (I don’t like grout) The one-piece unit is huge. In fact, it’s so big that once you frame the bathroom walls and door, you can’t get the unit into the room. Because of this, we had to install the shower early in the process—before the rest of the room (and house) was fully prepped.

The problem? The electrical wiring wasn’t done yet.  Why is that a problem?

We planned to use professional spray foam insulation for the whole house, but you can’t spray foam until the wiring is complete. However, the shower needed insulation in the surrounding walls before it was installed.

The Mistake: Mike (not to throw him under the bus, but he also saved the day) decided to use rigid foam insulation (the pink/purple board you see at hardware stores) behind the shower so we could get the unit installed. We cut and fit the pieces in from floor to ceiling where the shower unit would be placed.

We thought it was good. We were wrong.

The Perfect Storm

What we didn’t realize is that rigid foam insulation only works if it is air-sealed. We should have spray-foamed around every edge to create a barrier. We just cut it to fit and popped it in.

Combine that with:

• Radiant Floor Heat: Our floors are warm. 
• No Dehumidifier: We didn’t have one running yet because we didn’t know we needed one.
• Winter: Cold air outside, warm, moist air inside.

Because the insulation wasn’t sealed, warm, moist air got behind it, hit the cold exterior wall, turned into condensation, and sat there for weeks. (Lucky for us, the heat and hot water had only been on for a short time, or this could have been much worse).

The Tear Out

Finding the mold was just the beginning. To fix it, we had to go backward.

We had to remove the toilet. Then, the scariest part: We had to pull out the giant fiberglass shower unit. This is a one-piece beast. If we cracked it while wrestling it out, we’d be out almost $2,000 and would have no way to get a new unit into the bathroom.

(Spoiler: We didn’t crack it, but we did put a nice dent in it that I had to fix with a repair kit last weekend. It’s a permanent scar from this lesson.)

Once the shower was out, we pulled down all the wet insulation so we could see the rest of the damage. Luckily, it was mostly on the wall sections immediately above the shower unit and by the showerhead.

The Fix: How We Removed the Mold

We spent many days treating the wood and mitigating the mold until the wood was bone dry and clean. Here is exactly what we used:

The Treatment 

We used Concrobium Mold Control Spray.  Mike saturated the moldy areas and left it for at least 24 hours until completely dry.

The Drying Process 

Since our house was unusually humid (radiant heat + no fresh air exchange yet), we had to aggressively dry the space:

• Dehumidifier: We ran one constantly with a hose to drain.
• Space Heater: We only ran this while we were there.
• Heat: We turned the thermostat up to help dry the air.

Mold Removal 

Once the wall was dry, the mold started to look gray and dusty. That meant it was dead and ready to remove. This is tricky because you don’t want spores to escape. (and yes, you will notice Mike did this solo…the “gross duty” plus I’m allergic to mold)

• Safety First: Mike wore a mask and gloves.
• The Scrub: He used a hard nylon brush to scrape off the “dead mold dust.”
• The Catch: He used disposable handi-cloths on the floor to catch the flakes as they fell, then immediately bagged and sealed them.

He repeated this process—Spray, Dry, Scrub—over several days (interrupted by Christmas family visits) until the wood was clean.

The Re-Do: Insulation & Sealing

We didn’t take chances this time. Once the mold was gone, we bought a Spray Foam Froth Pack (and a Tyvek suit!) and Mike sealed the wall properly.

It is now airtight, watertight, and mold-free. We re-installed the shower, re-connected the plumbing, and finally—weeks later—we are back to where we started before Christmas.

The Cost

This mistake cost us:

Now that we are back on track, once the drywall is finished, what color should we paint it? It seems too white to me.