I just noticed that the baseboard by my shower has significant water damage. The baseboard is white MDF with enamel paint, and has buckled and swollen for about 12-14 inches where the baseboard meets the shower. The drywall and paint above it are completely undamaged as far as I can tell.

Now, I swear it wasn't like that even a few days ago. Is there a way to test and see where the water might be coming from? My concern is that the shower is leaking under the floor. (Floor is slab with tile) It's very likely that water splashed out from the shower and sat on the baseboard/floor under the baseboard and we just didn't notice, but can MDF get that damaged from one incident? Because it has definitely happened recently and we've been using the shower daily for 5 years. It's not accumulated damage from years of splashes/leaks.

That wall is an exterior wall, if that makes any difference.

Pics are below, a closeup of the damage and then showing the shower. I appreciate any advice; I'm freaking out a little.

Thanks,
Jenn

MDF trim like that will show that sort of damage from excess humidity, too.

During the drier heating season this can be worse, too.

The buildingScience folks recommend running the fan for 15 minutes after every shower.

But, there is a possibility of water coming from elsewhere too.

Get the moudling out, clean and treat the problem. While, it's out, use blue shop towels as a poor-man's blotter paper and see if there's anything wicking under the or along the plate line.

But, I'll wager there's not liquid water there--wallboard is significantly more hydroscopic than that painted trim--you'd feel the "mush" in either material were they wet. (Unless the wallboard is cementitious, DensGlas or the like--but, the mdf would still show it, if liquid water.)

That's my 2¢, you'd need $4 for a happy meal.

Thanks! I will get the trim off and watch it. The sweeper on the glass door needs to be replaced and that could explain where the water came from too. The wall is basic drywall and it is completely solid, no mush or swelling at all.

I appreciate the help!

I had the same thing happen to me (MDF baseboard, swelling outward into room). I also though it was moisture from the inside of the room.

As it turned out, the toilet was leaking at the wax seal, however since the toilet was caulked to the floor, the water leaked UNDER the tile, into the wall behind/beside it. Water ran down the wall (on inside) and into the closet baseboards into other room.

So in my experience, the reason the baseboard swelled is because it was wicking moisture from INSIDE the wall. Since your is near your shower, your shower pan could be leaking or something. You won't know until you tear up the baseboards.

Hopefully for you it is moisture from the room/shower area and not coming from behind.

CapCity, I think I may be having this issue as well. Did you end up doing all repairs yourself or have to hire multiple contractors to do the fix? Or did you just replace the toilet and trim? Any advice is much appreciated.