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Mildew smell - suggestions?

We are in the Northeast and it’s been a damp humid summer. We are experiencing a strong smell of mildew in our guest room and don’t know what to do. We just got negative private feedback about it. We have many guests scheduled for the next couple of months and I dread bringing them in there.

What we are trying:
Using dehumidifier including in the cellar below the room.
Using an ionizer.
Putting a saucer of baking soda in the room.
Opening door and windows in between guests.

We get great reviews and are superhosts, but I think this issue threatens our status and is, at the very least, unpleasant to some or most guests.

Ideas?

I think you will first have to find the source of the smell:
What is the construction of your house like? Materials / construction method?
Do you have airconditioning?
Do you have a ventilation system?
Did you already check for visible mildew?

Hmm, I don’t know much about the construction method, it’s a solid house built in the 70s. No AC, no ventilation system and we don’t see any mildew. We did have the carpet replaced but it didn’t help. I’d love to have a mildew expert come in and investigate but can’t find one in the area.

Thanks for responding to my question.

Some builders may well have one of those ‘taser’ looking damp detecting tools that they push into a wall…that may at least point you in one direction or another

Solid house, do you mean it’s a brick or concrete house? The walls and floor are brick / concrete? The roof is a wooden structure?
Since there is no visible mildew and the problem only started this summer it’s unlikely to be moisture creeping up the wall. Most likely, due to hot humid summer the moisture balance in your roof went wrong, read: Due to an internal condensation problem the roof’s ability to loose moisture to the outside was less than the moisture that was coming in. This can happen if the damp proofing is insufficient, in some houses it’s even absent.
In case the room is on the ground floor, and it’s a wooden floor (floor joists) on top of a void in the ground, it could also be the floor.

EDIT: I just read you have a cellar beneath the room. Does the cellar smell like mildew too?

Sorry Barns, those things don’t do anything. They give totally wrong measurements.

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Oh well, perhaps a different builder with a different way of detecting damp.

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Interesting! Thank you.

@Rachael52 We are in the tropics so this is a constant challenge. While you can’t see any mold or mildew, the slight smell is there and if we were to keep the rooms closed up, especially now in the rainy season, it wouldn’t be long before we would start seeing black spots.

Apart from the obvious of keeping the rooms aired out, I have found a small bowl of vinegar in each room does wonders to kill the smell. We remove the bowls before check in of course.

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I am on my way to the refrigerator to get some vinegar now. Thank you!

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Keep up with the dehumidifier and check the humidity readings on it and how much water it extracts each day.
Make sure windows are open or an extractor is on every time someone cooks or has a shower. It’s better to install a humidistat extractor which turns itself on and off according to the humidity.
Ultimately you will need to check there is no penetrating or rising damp or condensation. There should be a damp specialist in your local town. However most damp is caused by human behaviour.

I would use a dehumidifier in the room itself for a day or so and then move it to the space below. I would also do a deep clean of every hard surface, every soft surface.

The damp smell is a challenge in the Catskills, too, and this was a VERY wet summer. I had to put a dehumidifier in the basement and run its hose line into the sump hole. It helped a lot. A little bit of that old woody “cottage” smell is the classic cottage smell - which I love. More than a little and it is not good.

Another long term solution can be closed cell foam under the room in the floor bays.

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If you smell mildew, you have mold hiding somewhere. I would definitely invest in a moisture meter.

I don’t think that’s true at all. Our home inspector uses that kind, and it works great. I bought one that you just set on a surface and it takes a moisture reading, and it gave exactly the same results as his professional kind that sticks into the wall. It has been REALLY helpful in finding hidden water damage at our old house.
eta: We had massive water damage under our laminate floor because we didn’t realize that water was seeping in around our front door which wasn’t sealed properly.

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I want to thank each and everyone of you who is giving me advice on this topic. Believe me, I will be following up on this and I have hope now.

Do you have central AC? if there are air returns in the room, or near the room, if you leave the furnace fan ON it will circulate the air.

Hi @Rachael52: How timely this post is. I was about to post on this subject as well. I have, I hope. some helpful information for you. First, if you are not finding mold, chances are that smell is leftover from the mold drying up. It is harmless, but yeah, kind of embarrassing. So many people equate it with not clean when, in fact, you place is very clean. I have a 72 year old home built of extremely old redwood timbers (reclaimed from a train station in fact) and the walls are plaster not drywall. There is no mold in the house, we have checked and rechecked, I work my butt off trying to get rid of that odor. Most of my guests have no issue with it, they are generally of an age that they understand that older homes in a foggy coastal area have an “old house smell” and they are fine with that. They can see the house is clean. It is the uneducated early 20 something females that I have issues with. No offense if any are hosts here please. But they seem to think they know just everything about why things are they way they are and they are just going to educate you right now AND punish you for not being perfect by giving you a not so great review. Who cares that they are messing with someone’s income. :roll_eyes:

In my research I ran across this information on the Realtor.com site https://www.realtor.com/advice/home-improvement/old-house-smell-removal-whats-causing-get-rid/

I have already done most of it but I am going to try their cleaning solution on the walls. I will post to its effectiveness but it won’t be for a day or two. Here is the wall cleaner “recipe”. I have found it numerous places other than this site, so I am hoping that means it is effective.

½ gallon hot water
½ cup borax
2 cups distilled white vinegar
16 ounces of hydrogen peroxide

Right away, wipe down your walls and let them air dry. This will remove grease, dust, and mildew, and also remove smells that have embedded into wall surfaces or wallpaper,

I hope this helps. Good Luck!

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I would spray the walls with a solution (half water & half Clorox bleach). Then put fans in the room to dry the walls. Open the windows and put fans in the windows as well.

My house is 135 years old in a damp part of the UK. I have zero smell of damp (I ventilate so no internal humidity or condensation for me). If I had any lingering damp smell I would definitely contact a specialist. A damp smell is not healthy and a sign of something being wrong.

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A lot of posts are tackling the smell, not the cause of the smell…are you sure that the perfect air freshener will solve the problem, or do you suspect there’s something that will still cause the smell. I had a flat once, and if I was away for more than a day, I’d really notice the damp smell upon return. Turns out the was a wooden beam above my window that was absorbing a leak from a crack in the outside wall slightly higher up…AND water from the shower was going behind some of the wall tiles, and rotting an entire wall and some timber underneath the floor. Had to have the middle of the flat/apartment rebuilt!

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I too am in the Northeast and yes it was hot and humid summer for extended periods. Since you have dehumidifier in basement you might want to put a window unit a/c in the room with the mildew smell. If you don’t want to purchase on maybe you could borrow one. Air conditioners also remove humidity from the room as well as moisture. By using the dehumidifier in the basement and a/c in the room the you might just get a handle on it vs removing the dehumidifier from the basement and then having to catch up there.

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