Adibiatic moisture transport blamed on pets
August 2, 2006 9:20 PM   Subscribe

My landlord says my cats urinate near the front door. I don't think this is true because this is what I think is happening: The weather seal under the front door is missing, there was an old carpet remnant over a tile floor with no moisture barrier underneath and this combination of moist, cool air going under the door, condensing under the carpet and then rising through evaporation where it collected at the opposite end of the remnant and seeped through the carpet causing moisture damage to the wood floor underneath is the culprit (adiabatic moisture transport). This has happened over a period of years, by the way. Is this plausible? Calling all science and physics Ex Perts out there (persons in the construction trade welcome too.)

So how about it? Plausible cause or nonsense?
Just as an FYI, I live in a shared house and no one has ever mentioned the cats urinating anywhere in the house or any pet urine odors. Most of the time they are in fairly close proximity to me and are religious about using the litter box.

I was over at a house next door a few months back that was being restored and one of the construction guys blamed a couple of wet spots on an old wood floor on pet urination damage. What he wasn't aware of until I told him this is that where the moisture damage occured there were two large potted plants that were frequently overwatered causing the wood stains (I used to live there when this was going on).
posted by mk1gti to Science & Nature (11 answers total)
Wait 'til it's dark, flash a blacklight on the potentially offending spot, and see if you see glowing pee-stains... other things do glow in blacklight, but if you don't see a glow, you can at least say with relative certainty that it's not cat pee.

Failing that, get down on your knees and take a whiff.. the smell is very strong... if you can't smell much, it ain't cat pee.
posted by twiggy at 9:52 PM on August 2, 2006

Your argument seems preposterously thin, mk1gti. But, I'm a broad minded guy, and I've got time.

I do wonder how you'd explain that the discoloration/rot is not occurring in the very well defined lines your explanation would cause, if it, in fact, isn't. Because, if your door mat moves around like that of most people I know does, your mechanism kinda falls apart on randomization of day to day placement.

But, I'm willing to listen. Do go.
posted by paulsc at 9:54 PM on August 2, 2006

Response by poster: paulsc
I didn't tell anyone anything about exactly where this moisture line is. It is in fact a left to right line that very nearly matches the line where the carpet remnant was located.

The carpet itself has been replaced as has the tile. At this point the layout is like this: There is no more carpet remnant, I threw it out. The tile is all new and on the tile itself there is a rough-grass mat from Bed Bath and Beyond (how did we ever live without them) so at this point, moisture transport or cat pee, whatever was causing this I don't think it will happen again.

twiggy, do you know if a red light would work for your experiment or would it have to be a blacklight? As far as the odor, when the moisture was still there, it had a mildewy smell, definitly not cat urine (I do know what it smells like, being a cat owner as long as I have.)
posted by mk1gti at 10:19 PM on August 2, 2006

It would have to be a blacklight. You can pick them up cheap at one of those party stores.

I keep one around for the times when one of my cats goes on a peeing spree.
posted by zerokey at 10:25 PM on August 2, 2006

Response by poster: I just tried the blacklight experiment, no glowing, so currently there is no cat urine, however I'm still curious about the moisture transport theory. By the way, the carpet remnent is four by five feet, just inside the door over a well-worn tile floor about three by five feet, so about six inches of overlap near the front door and on the opposite entryway.
posted by mk1gti at 10:27 PM on August 2, 2006

If it doesn't smell of cat piss, it isn't cat piss. Case closed.
posted by flabdablet at 10:29 PM on August 2, 2006

OK, mk1gti, you've gone. And yet, I'm skeptical your problems are related to airborne condensation.

Only because it would take a whopping lot of airflow, presumably under your door, to carry in enough airborne moisture to condense in a carpet door mat, so intensely as to support discoloring mildew, or even worse, run out as dewed moisture or plain water. If you or roommates routinely tracked in wet water, that couldn't dry, maybe I'd see it as more plausible. But condensation? Tough argument to make.

Look, I live in Florida, 3 miles from the Atlantic Ocean. Average humidity here is 97%, seasonally adjusted. Running the air-conditioner on any given March day will generate condensation on the inside of the patio sliding door, and in August, I use a terry cloth towel over there a couple of times a day, to keep the carpet from getting dripped on. I can see a little daylight under the west facing front door in the afternoon, and I ought to fix the sill seal there.

But I've never, ever had any condensation form in the front hall doormat, sitting on a ceramic tiled front hall floor.

Color me hard to convince, but I can't quite see it. Is it possible you have some other source of water there? A radiant heat system going bad, a leaking outside gutter pooling water in front of the door, some kind of structural problem around the door leaking in, etc.?
posted by paulsc at 10:46 PM on August 2, 2006

Response by poster: I live in the pacific northwest, near the Puget Sound, Lake Union is a few hundred feet away and moisture in our little sea/lakeshore neck of the woods is definitly something to be aware of when one lives around here. Again, this is a scenario occuring over a number of years, and with the rainfall that occurs around here, the scenario of multiple housemates coming in and out with wet footwear over a period of days or weeks could certainly be part of that equation.
posted by mk1gti at 10:51 PM on August 2, 2006

Sometimes, cat piss doesn't smell (I wish that was always the case). I had a Siamese afflicted with kidney disease who soaked the corner of a little used dining room with quarts of pee (literally; his output over a relatively brief time warped the floorboards and subflooring and soaked up into the drywall to warp a window frame). We didn't have a clue until significant damage was done as a) the carpet (inherited from the previous owner) was an unfortunate shade of piss yellow, b) the wall was covered in wallpaper and c) Milo's (the pissing cat) output was so dilute it was odorless.

The blacklight caught him out though, afaik, that always works. BTW, black light bulbs, i.e. incandescent "black lights", do not work well for trace evidence detection--their UV output usually isn't strong enough. To be sure of your cats' innocence, you must use the UV tube kind.

You might try showing your landlord a article about UV lighting in piss detection + a demonstration of the afflicted area because I suspect you'll witness a great rolling of eyes when you launch into your adiabatic moisture transport theory, however scientifically plausible.
posted by jamaro at 10:56 PM on August 2, 2006

Yeah, jamaro's right. Don't focus on your alternative theory, which frankly sounds pretty thin even if it might be true.

Just show him the blacklight test, point out that it couldn't have been your cat, and leave it to him to figure out what's wrong. It's his house, after all. You just need to clear your [cat's] name.
posted by nebulawindphone at 4:16 AM on August 3, 2006

Response by poster: Thanks all, this has been a great help (^_^)
posted by mk1gti at 5:57 AM on August 3, 2006

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