mushrooms in the shower

jackson2348May 30, 2007

No, I'm not kidding. And not the good kind. We are in new construction, moved in right before Christmas. It is on a crawl space, with Icynene sprayed under the house, so we can't see anything under there. This morning, I go in the bathroom and there are real live mushrooms on the outside of the shower curb, between it and the floor. There is NO grout or caulk there (we won't go into how bad my tile guy was). Builder says we just need to caulk it up good. My thoughts are that caulk would just be a band-aid, I think the shower is not water tight.

The tile guy did put some type of membrane under the tile, but water is coming from SOMEWHERE. The shower does dry up, but the tile outside is slightly darker and the veining in the tile is much darker, indicating (to me) moisture.

Don't think the builder is going to be happy about taking it all out and starting's all marble, and was expensive. I'm concerned that it is going to rot out after the builder has no more liability if we don't.

Any ideas on how to approach this, or if I may be wrong about what's going on? TIA.

Thank you for reporting this comment. Undo

I'm sorry I have no helpful advice. I'm just dumbfounded at the thought of finding mushrooms growing in one's shower :o Hope everyone involved is agreeable to fixing the problem and not just putting a band aid over it.

    Bookmark   May 30, 2007 at 4:56PM
Thank you for reporting this comment. Undo

My thoughts are that caulk would just be a band-aid,

Your thoughts are right. All mushrooms are, are another kind of fungus-- in the same family as mold. They live off wet rotting wood. Time for a new shower pan and curb.

As for where the water might be coming from, there are several possibilities. One, if the tile guy didn't preslope the pan, and didn't hold the cement board off the bottom of the pan, it could be that the weepholes are clogged and water is holding in the shower pan, and whicking up the cement board, up and over the pan liner. Another possibility could be that the installer put nails thru the pan membrane way too low when he was nailing up the cement board. Another possibility could be the curb-- either he didn't sufficiently waterproof the corners of the curb, or didn't wrap the liner far enough over the top of it.

it could be a bunch of different things, but from what you're telling me, it sounds like installer error, having to do with the pan membrane, and/ or shower construction.

Is there a built in seat in this shower? I mean one that's framed out, waterproofed, etc.?

    Bookmark   May 30, 2007 at 5:15PM
Thank you for reporting this comment. Undo

Oh wow.

Ya gotta laugh, crying would be too painful.

    Bookmark   May 30, 2007 at 5:26PM
Thank you for reporting this comment. Undo

Bill, thanks for chiming in...I was hoping you would. Yes there is a seat, but it is in the back, opposite the door and curb. We do have to squeegie it, as it is not sloped for drainage. I have no idea if he ran the membrane up that far or not; i seem to remember him putting the membrane about 8 or 10" up the other walls, then using some semi-liquid bright blue goop on the remainder of the walls. And yes, that is a techinical term.

Monica, dumbfounded does not even begin to describe my reaction. Thanks for the sympathy!

    Bookmark   May 30, 2007 at 5:28PM
Thank you for reporting this comment. Undo

Sounds like Laticrete's Blue 92 (9235 liquid waterproofing). if he didn't slope the seat, then I can almost guarantee you he didn't preslope the pan. ( put a slope UNDER the pan membrane, as well as over, to get the water to gravity feed to the weepholes)

This is NOT optional, and if your GC or tile guy tries to tell you it is, show em these specs:

IRC Preslope code:
2000 IRC:
P2709. 3 Installation. Lining materials shall be pitched one-fourth unit vertical in 12 units horizontal (2-percent slope) to weep holes in the subdrain by means of a smooth, solidly formed subbase, shall be properly recessed and fastened to ap-proved backing so as not to occupy the space required for the wall covering, and shall not be nailed or perforated at any point less than 1 inch (25. 4 mm) above the finished threshold.

Uniform Plumbing Code related to shower pan construction.

"412.8 When the construction of on-site built-up shower receptors is
permitted by the Administrative Authority, one of the following means shall
be employed:
(1) Shower receptors built directly on the ground:
Shower receptors built directly on the ground shall be watertight and shall
be constructed from approved type dense, non-absorbent and non-corrosive
materials. Each such receptor shall be adequately reinforced, shall be
provided with an approved flanged floor drain designed to make a watertight
joint in the floor, and shall have smooth, impervious, and durable surfaces.
(2) Shower receptors built above ground:
When shower receptors are built above ground the sub-floor and rough side of
walls to a height of not less than three (3) inches (76 mm) above the top of
the finished dam or threshold shall be first lined with sheet plastic*,
lead* or copper* or shall be lined with other durable and watertight
All lining materials shall be pitched one-quarter (1/4) inch per foot
(20.9 mm/m) to weep holes in the subdrain of a smooth and solidly formed
sub-base. All such lining materials shall extend upward on the rough jambs
of the shower opening to a point no less
than three (3) inches (76 mm) above the top of the finished dam or threshold
and shall extend outward over the top of the rough threshold and be turned
over and fastened on the outside face of both the rough threshold and the
Non-metallic shower sub-pans or linings may be built-up on the job site
of not less than three (3) layers of standard grade fifteen (15) pound (6.8
kg) asphalt impregnated roofing felt. The bottom layer shall be fitted to
the formed sub-base and each succeeding layer thoroughly hot mopped to that
below. All corners shall be carefully fitted and shall be made strong and
watertight by folding or lapping, and each corner shall be reinforced with
suitable webbing hot-mopped in place. All folds, laps, and reinforcing
webbing shall extend at least four (4) inches (102 mm) in all directions
from the corner and all webbing shall be of approved type and mesh,
producing a tensile strength of not less than fifty (50) psi (344.5 kPa) in
either direction. Non-metallic shower sub-pans or linings may also consist
of multi-layers of other approved equivalent materials suitably reinforced
and carefully fitted in place on the job site as elsewhere required in this
Linings shall be properly recessed and fastened to approved backing so
as not to occupy the space required for the wall covering and shall not be
nailed or perforated at any point which may be less than one (1) inch (25.4
mm) above the finished dam or threshold. An approved type sub-drain shall be
installed with every shower sub-pan or lining. Each such sub-drain shall be
of the type that sets flush with the sub-base and shall be equipped with a
clamping ring or other device to make a tight connection between the lining
and the drain. The sub-drain shall have weep holes into the waste line. The
weep holes located in the subdrain clamping ring shall be protected from

*Lead and copper sub-pans or linings shall be insulated from all conducting
substances other than their connecting drain by fifteen (15) pound (6.8 kg)
asphalt felt or its equivalent and no lead pan or liner shall be constructed
of material weighing less than four (4) pounds per square foot (19.5 kg/m2).
Copper pans or liners shall be at least No. 24 B & S Gauge (0.02 inches)
(0.5 mm). Joints in lead pans or liners shall be burned. Joints in copper
pans or liners shall be soldered or brazed. Plastic pans shall not be coated
with asphalt based materials."

    Bookmark   May 30, 2007 at 5:48PM
Thank you for reporting this comment. Undo

The order of things, as best I can recall...

Hardie board all over bathroom. Cement for shower pan and curb. Membrane over that to about 8" up, then the blue 92 above. Thinset or mortar, not sure which, then tile.

I know that he sloped the cement (is this the pan?) to the drain, but then installed the tiles unevenly so we got humps in the floor. made him re-do the worst of it, but still we have small uneven places. under the cement is hardie board, so that was flat. are there supposed to be two layers, a pre-slope and a slope? I'm not understanding the code.

Talked to builder again and he said they are coming to look tomorrow, and that tile store guy (who subbed it out to the installer) said he would warranty it if there is a problem, so that was somewhat of a relief. Now to convince them there is a problem.

Oruboris, Hubby laughed, I cried. He had the better idea.

    Bookmark   May 30, 2007 at 6:14PM
Thank you for reporting this comment. Undo

He put the liner OVER the cement board? I hope that was Kerdi!! It's the only sheet membrane that I'm aware of that can go OVER the cement board, and if he DID use Kerdi, it should have been used THROUGHOUT the shower-- not just for the pan. It sounds to me like they used two idfferent systems, which means there's no chance of a manufacturer's warranty. No big deal, so long as the showroom's willing to back up the installation.

Now to convince them there is a problem.

Leave the mushrooms. If you've removed them already, hopefully you got pictures, or they grow back. DO NOT accept caulking the joint. That won't last a month.

    Bookmark   May 30, 2007 at 9:35PM
Thank you for reporting this comment. Undo

You're frightening shower will be built soon.

I guess we could become vegitarians....I'm going to watch my guys install like a mushroom hating vulture!

I'm sorry you're going through this. What a nightmare!

    Bookmark   May 31, 2007 at 1:26AM
Thank you for reporting this comment. Undo

SO sorry to hear - what an awful situation -
Have final payments been made? Money has power so continue to hold back if final payments have not been made.

Bill V has offered sound advice -I'd follow it to the T he is the expert.

In addition I would make careful documentation regarding any communication on the issue - date/time/discussion etc... Pics of mushrooms would speak volumes on this new construction

Don't accept the "band aid" remedy and it may be advisable to get another contractor in there to offer their opinion - remember your builder & his subs are biased - so a contractor who has no vested interest may shed some light.

good luck!

    Bookmark   June 1, 2007 at 9:24AM
Thank you for reporting this comment. Undo

Ok, so I haven't checked the boards for a week or so and got to the third page and was reading messages. I clicked the "home" button to check the news and just as the page is changing, "mushrooms in the shower" catches my eye... What the #!@$?!? I was astounded... Do you have a resolution from your builder/tile store yet? Good luck... I would be completely flabbergasted and sooo upset


    Bookmark   June 7, 2007 at 11:04PM
Thank you for reporting this comment. Undo

Thanks to everyone for responding. We've been on vacation for a week, and come back to more mushrooms, so not a fluke. This is where things stand.

Builder came and looked...we let the shower run for about 30 min. and NO LEAKS!!!! Nothing under the house, nothing outside the shower, NOTHING. Builder thinks that since the outside of the curb is not grouted or caulked where it meets the floor, when we open the door and get out, we are dripping water that's getting in there and that it causing the problem. Hence the caulk fix.

I think there is no way we are dripping enough to saturate the wood enough to rot. Builder agreed to take off the curb so we can see what's going on, and that should happen this week.

One other possibility, is that when we first moved in 6 months ago, we did have a leak in the plumbing in the shower. It soaked the wall between the shower and the master, and the hardwoods in the master on that wall. It was fixed, but I'm wondering if the wood framing they built the curb out of could have gotten saturated and not dried out (in 6 months????)

I'm concerned we're not seeing any water...even the floor grout is not wicking it and getting wet. But obviously there is a problem, and at least builder acnowledges that, and seems willing to fix.

Bill, is there a site somewhere with step by step instructions an building a shower in layman's terms? I think that this is going to have to be redone, and I'd like to be able to check that it is done correctly this time. Alternatively, wanna come to Mississippi in the dead of summer?

    Bookmark   June 10, 2007 at 7:59AM
Thank you for reporting this comment. Undo

Here's a site for the shower pan:

Here is a link that might be useful: Building a shower pan

    Bookmark   June 10, 2007 at 9:19AM
Thank you for reporting this comment. Undo

Thanks Bill...looking at that, I can see he did not do a pre-slope, as you suspected. All the mortar was put down at once. Sigh.

    Bookmark   June 10, 2007 at 12:41PM
Thank you for reporting this comment. Undo

"letting the shower run for 30 leaks"

That showed no evidence of water flowing during the 30 minutes. The mushrooms? That shows you have a wet curb.

How the curb got wet is the mystery.

You mentioned "going under the house." Is this a crawl space? What is the "ground" of the crawl space? Dirt? A thin rat slab? A membrane of some sort over the earth, with the membrane covered by stone or something else? If there is any membrane, how is it detailed, or sealed, to the perimeter walls of the crawl space, or is this open pier and beam construction.

You mentioned "in the crawl space you can't see anything because icynene is sprayed under the house...".

Here's a concern. Crawl spaces are moist. Thus the need for vapor barriers of some sort to protect the underside of the house from excessive moisture/humidity build up in the crawl space. If there is a vapor barrier, it needs to be properly sealed against the mudsill (or some other part of the foundation's perimeter) of the house.

That prevents any damp air from beneatht eh vapor barrier from getting to the bottom of your first floor.

Back to the icynene. Icynene is an OPEN CELL foam. Meaning, it's like a sponge. A particle of air, on a microscopic level, could pass right through a thickness of icynene.

On the bad siade, moist air can pass into and/or through icynene, and the icynene can hold the vapor from the moist air, with the foam eventually becoming saturated. Not "saturated" as a spnge, where water will drip out of the pores, but "saturated" in terms of the foam holding moisture against the bottom of your house's subfloor.

If Icynene is to be used in an application like this, is need to be sealed with a topical sealer that will serve as a vapor barrier, that prevent the open-cell icynene from becoming saturated and promoting rot.

A better foam is a closed-cell type of foam like polyisocyanurate, or "polyiso". While not technically correct, think of polyiso as being a bunch of microscopic sealed spheres. Air can't pass from one, through one, or around one sphere to another, so polyiso is "closed cell" and does not allow air or wate vapor to pass through it. Polyiso in and of itself is a vapor barrier. It does not need a topical coating to seal it.

So...could there be a leak in the shower that is saturating the curb, that is in turn manifesting itself as mushrooms growing through the one unsealed area between the curb and the floor? Yes.

Or could the icynene under the house be saturated and holding moisture against the bottom of your house's subfloor...and it's showing itself by coming into the living space through an unsealed area at the curb? Possibly.

You have a history of the leak in the shower iteslf. That's a smoking gun.

Your tile guy apparently wasn't the greatest. You have evidence of moisture outside the shower with the darker colored marble. those are a couple more bullets loaded in the already smoking gun.

You have icynene under the shower. That can hold moisture, either vapor coming through the foam from the crawl space below, or liquid water soaking the fowm from a leak in the shower above.

My first reaction is that at a minimum the curb needs to be demo'd, as that's the source of the 'shrooms, and the area under the curb needs to be dried out and repaired.

Depending on the extent of the damage, it my then be prudent to go under the house and cut out a small section of foam to expose the area of subfloor unde the curb. Start small, as you may find no damage at all.

From there, you'll have visual access to the damaged area from above as well as from below. It'll be like peeling back the layers on an onion. Go only as far as you need to, for like cutting into an onion, the further you cut into your house, the more it'll make you cry.

Regardless, check out the combo of the crawl space and the icynene. Make sure you have proper detailing of botht he crawl space and the underside of the open cell icynene.

Sorry for the long post...but moisture damage can be insidious, and the combo of crawlspace and open cell foam made me want to reply with a little more detail than I might otherwise offer.

It might just simply be a bad shower, or it might be more. But you just need to have your eyes wide open so you can actually process what you see when you try to make repairs to the damage that you have.


    Bookmark   June 10, 2007 at 1:21PM
Thank you for reporting this comment. Undo

Mongo, Thanks so much for the information. We are pulling off the curb this week, and will see what we can find.

Under the house is a crawl space, with vents around the perimeter. There is plastic on the ground, but it is not sealed to the concrete block of the foundation walls. That is certainly something we could do, should we just use duct tape, or it there something more specialized? Also, there is no seal where the pieces overlap, I assume that needs to be sealed as well? And is there a special product used to seal Icynene?

Another factor (not sure if it matters) is that we are in a drought here. The crawl space is dry as a bone.

We will also cut back some of the Icynene under the shower and check for evidence of moisture from underneath. If you don't mind, I'll print your post, along with the code Bill gave me, for my builder. Thanks again for your help.

    Bookmark   June 10, 2007 at 2:15PM
Thank you for reporting this comment. Undo

That the crawlspace is dry, that's great news.

A dry crawl, coupled with the newness of your home, leans the argument towards the water coming from the shower itself. That's good.

As to sealing the icynene, hold off on that for now, as it may not be appropriate due to the desired location of a vapor barrier within your structure. But a good quality latex primer/sealer is what would normally be used.

Were your crawl space a damp wet hole, that'd be one thing. But again, with it being dry, take this step-by-step.

I'd start the demo from the curb. Only if the damage seemed to extend down THROUGH the thickness of the subfloor, or if for some reason you just couldn't isolate the source of the moisture and you needed another perspective, then and only then I'd cut into the foam from below.

Regardless, it'd still be a good thing to tighten up the vapor barrier in the crawl space.

You can use simple and inexpensive 6-mil polyethylene sheeting, available in 10' by 100' long rolls at home centers, to something better reinforced and more substantial...and more expensive...made just for crawl spaces.

Typically, seal the liner to the concrete wall of the crawl space just below the wood sill plate. Run a bead of polyurethane caulk along the concrete, and press the liner into the caulk. You can reinforce that with fasteners, it'll prevent the liner from being pulled down.

An easy way is after the liner is caulked to the concrete, place a strip of pressure treaded wood over seam and nail or tapcon screw the strip of wood to the concrete every few feet or so.

Any overlapping seams in the liner should have a few inches of overlap. Seal between the two sheets of liner with another bead of polyurethane caulk, mash them together, then use something like Tyvek tape to seal the edges of the sheets.

Remember, you're trying to keep moisture (liquid and vapor) from BEHIND the liner from getting onto your crawl space, so all overlaps should be done so a drop of water running down the liner (think between the liner and the crawl space wall) will not be trapped in any overlap.

This would mean that the walls would be draped with liner first, then the floor liner would go on top of the wall liner.

I hope that makes sense!

Back to the curb. In a properly built shower, the membrane will be on top of a deck mud preslope, so by the time the membrane gets to the curb, the membrane should be a couple inches above the subfloor.

So when you demo the curb and you can see the cross-section of the shower pan, from the bottom up you should see a couple of inches of deck mud, then the membrane, then more mud on top of that, then yout tile.

If the membrane is down low to the floor, then you don't have a preslope.

If you find any nails on the shower side of the curb securing the membrane or the wire lathe over the membrane to the curb, that may be the source of the leak.

Time will tell, though. Water can take interesting paths in its travels.


    Bookmark   June 10, 2007 at 4:43PM
Thank you for reporting this comment. Undo

Mongo, makes perfect sense. Thanks so much to you and Bill for lending your time and expertise to help. I'll keep ya'll posted!!

    Bookmark   June 10, 2007 at 6:57PM
Thank you for reporting this comment. Undo

Ok, so SOME good news (I think)

Had some people out with an infared camera. The moisture under the curb seems to be comfined to the curb, none showing under the tiles in the shower floor itself. There is also moisture showing in the wall behind the shower valve.

So the current game plan is to fix the leak in the valve, demo the curb so we can assess the wood and subfloor, leave it open until it's dry, fix it all, use the shower for a week or so and then get the infared back out and HOPE LIKE H*** that there's no more moisture. If there is, builder says they will demo pan at that point.

    Bookmark   June 21, 2007 at 10:49AM
Thank you for reporting this comment. Undo

I'm curious to see how they pull and replace the curb without demoing the pan.

    Bookmark   June 21, 2007 at 6:29PM
Sign Up to comment
More Discussions
Tile sizes and!
My husband and I are about to tear our hair out. We've...
Has anyone seen an interior door handle like this in the States?
Sorry for the link but I couldn't find an image to...
40" for double vanity, any suggestions?
Hi, We are remodeling our bathroom and would like a...
Walls are blue with red and royal blue towels white...
extra tile decisions
It turns out I have more grey crackle tile than I needed...
edwina 1330
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™