grout is not waterproof. there needs to be a waterproof pan under the grout. you have deeper problems.

We once had grout fail in an upstairs shower. Couldn't figure out what was leaking onto the ceiling below whenever my third child would take a long shower. The leaking never happened with the other three children, just number 3 son. We finally discovered that he directed the spray of the shower to the back wall and the grout had failed. Yeah there was a lot of water on the ceiling of the room below.

xracer is correct. A properly built shower is waterproof before the tile and grout are put in.

My best guess is it is a slow leak in the copper pipe joint,likley at the "on valve" or where shower head comes thru...bad solder...

We had a similar problem, the joint between the shower pan and tile was caulked... with painters caulk instead of plumbers. It failed and a leak below.

A preformed shower base does not require a waterproof pan. Backerboard is not water proof (just like a concrete wall isn't), and wherever you have joints in backerboard to the shower base you can get leaks if the tile and grout aren't watertight. Even though the shower base should have a lip that the backerboard laps over.

As others wrote, a properly built shower is waterproof even without tile (so the grout is definitely not the issue). We used the Kerdi system. You could have a pipe leak, a valve leak or an improperly built shower.

Depending on your piping material you could have a small pinhead leaks in the pipes. This is primarily a problem with copper pipes and certain kinds of water chemistry. I'm sorry, I forget at the moment which water factor predisposes copper to develop these leaks. But once they develop, the only reliable cure is to cut out the damaged part and insert a piece of repair pipe. And even then you might find it more economical to replace a larger section since these little holes will often develop in the remaining parts of the same material and age.

HTH,

Molly

I'm in the process of buying a house. Just had a follow up inspection by a plumber today (I couldn't be there, but my realtor was). She said the plumber claims that the leak is due to the fact that SOME of the tiles in the shower surround have grout that is gone. And therefore, when the shower is run, the water goes behind the tiles, and down into the basement below, which is where we saw the leak.

From what I've read in the other posts, this doesn't sound like a very good plumber if he thinks that grout is causing a leak when the shower should be waterproof prior to tiling. Either that or your realtor is minimizing the issue to get you to continue with the deal.

I would definitely get a second opinion and this time, be in attendance. I'd also hire the plumber yourself in case you used the realtor's plumber.

Some old-time plumbers would only waterproof the shower base and put the wall tile directly over greenboard (basically drywall). On that case, they are relying on the grout to prevent total collapse of the shower. I had a friend whose father actually fell through the back wall of their shower. Water had eroded the wallboard and one day when he leaned against the wall he went through, his arm going into the closet next to the shower.

Now it is more common (well, more correct) to use a waterproofing system, like Kerdi, on the walls as well. Some tile guys will tile over cement board (NOT greenboard) without an additional waterproofer. A friend of ours does it that way, but used the Kerdi when I insisted. In a house older than 10 years old it is very possible you have greenboard.

Regarding the copper pipe eroding, the well guy we used said (I think I'm recalling this correctly) hard water will erode copper. I have also been told that the quality of copper is declining. We used PEX to prevent copper erosion. It also has the advantage of not bursting when frozen. We also have a (very expensive!) water treatment system.

Sue -- that's what our shower was like, tile placed directly over green board and when the grout failed, water below. We ended up ripping the whole thing out and replacing tub, shower and tile. What a mess and expense.

We just had a situation with a leak below the two bathrooms in our house. The plumber's analysis was that the copper piping had been laid into concrete and steel mesh when the house was built (1950). Over time, the steel caused the copper piping to corrode. The fix was fairly simple in our case: To get to the pipes, they cut through the garage ceiling and knocked out a small area of tile in the wall of one bathroom, sealed off the old water supply piping, and redirected it with new piping. It took them less than a day, cost less than $2k, and immediately fixed the problem. Luckily, the two bathrooms are over the garage and we noticed it right away, so damage was minimal.

Update: Managed to get a plumber to come in to perform a second opinion. I wasn't able to be there again (I live 7 hours drive away) unfortunately, but on short notice, and a looming inspection contingency deadline I thought it was the best option. Plumber isolated different areas of the bathroom to see what would generate a leak. It is, in fact, the grout (or lack thereof). I suspect that the tile is placed directly over green board. The sellers have offered to give us a credit at closing for the repair work on the tiles ($350), but I am insisting that they do it themselves. I can imagine that this could turn into a much bigger/more expensive repair once tiles are removed and greenboard uncovered. So, I don't think their credit at closing is sufficient. We'll see if they go for it.

Thanks for the help everyone!

Stretchad,
You probably need to rebuild the shower, not just grout the tile. There could also be significant moisture inside the wall.

Just remember that grout is NOT waterproof!

There is a sealant you can put on grout to make it waterproof, however it is not permanent and has to be reapplied about once a year. It also makes the grout more stain resistant. If you are fastidious about noticing stains on the grout you'll know when its time to reapply the sealant.

Also they make some premixed waterproof grout but I don't know well it works.

Also they make some premixed waterproof grout but I don't know well it works.

Pre-mixed products should never be used in showers or other wet areas.

That's just a bandaid fix. You really need to get money to correctly redo the entire shower.

Plan on tearing out that shower after you take title in order fix it right. As others have posted, if the water is leaking through the grout (or where the should be grout), the shower is not built correctly.

I wouldn't let the sellers fix it, it won't be a lasting fix. I would take the cash and put it towards doing it right.

You likely need to tear things out and get it dried out and make sure there isn't mold growing or it gets sealed before dried out to let mold grow.

stretchad, in all of the inspections did anyone have a guess how long this leak has been going on?

If not, the water is leaking into the basement, did one of the inspectors see the joists and floor under the shower and inspect for mold?

I wouldn't take the sellers $350.00 offer unless you plan on redoing the bathroom soon anyway. That price says it will be a patch job. $350 is grout and labor to make it pretty for a sale.

The big expense will still be behind the walls.