Where is the mold? Smells a lot but can't be seen.

[Back83]

Right now is the driest period so it's not surprising that it's dry and nice right now. There could very well be issues with moisture and mold growth during late summer/fall that still smells.

Once it's set in the boards, I don't think airing it out will help for a couple of decades when it's against the concrete.

Took over the house in October, then it rained quite a lot. We planned to tear out the floor at the end of the month. Just got so surprised when it looked so dry, nice, and mold-free.

 

[Back83]

It's certainly possible to seal and fix it, but eventually, the material will give way or smells will come up anyway.

I would have at least started planning a renovation, comparing different solutions. It is a risk construction, the inspection report from when you bought it should have clearly shown that.

The easiest is to install a ventilated floor, like Nivell or something similar. The best, especially if there's low ceiling height like there often is in basements, is to break up and pour a new slab with proper insulation and a capillary-breaking layer underneath. But it's a significantly bigger and messier job.

Yes, the inspection showed moisture, but I know others with this problem without any mold smell. They just use dehumidifiers. It didn't smell when we bought it, but it was summer and well ventilated.

We were planning to tear it down at the end of January. So you can't just tear everything out and lay tiles directly on the slab?
Dad laid something like Styrofoam, then concrete and tiles on it in the house we lived in when I was a teenager. He didn't break it up as far as I understood. He was also a concrete worker. Admittedly, he drained around the house too during that time, I think.

Was just thinking of tearing everything away and laying tiles directly on the concrete slab, but I suppose some insulation and moisture protection is needed?

Was mostly wondering if the parquet flooring on the upper floor can be reused after airing out? Or will it smell there too?

 

[Snigla]

Smells like mold from the basement floor spreading throughout the house. Took a photo in the hole to see how bad it is but can't see anything. Possibly at the top right of the first photo, between the beam and the outer wall? The particle boards are lying directly on the concrete slab and look damp. Could it be that?
I expected massive amounts of mold. [image][image][image][image]

I can tell you that it doesn't take much to odor-wise contaminate an entire house!

Our first house had a basement with "odor problems" (i.e., mold).. we re-drained and were trying to locate the mold on the inside.. there were wooden studs on the walls and floors (mixed surfaces.. but the floor mainly wooden floors and vinyl).

Not all rooms smelled the same, and eventually, you could identify which rooms actually had mold.

The funny thing was that we tore down two rooms (like two storage rooms) and opened up walls and floors.. and it turned out to be a WHOLE 10 CM moldy/rotten floor beam along one outer wall.. the rest was great.. not a "spot" anywhere!

It felt both tragic and comical that such a small damage caused so much odor and problem...

BUT one should keep in mind that the damage had been there for a while.. the moisture had existed.. and all the surrounding materials (like insulation, etc.) had absorbed the odor.. even the concrete slab.

However, we sold the house before we had the chance to renovate/check all rooms.. but the new owners had to strip everything before taking possession so it could air out for a couple of months.. We took the opportunity to have a look when we were there.. (before they would officially take possession) and there was not much bad actually! (of what we could see)

So the lesson is.. that it's not always something big you're looking for and it makes it very difficult to "just tear a little" because it's very hard to find where that little damage is...

 

[klaskarlsson]

Yes, the inspection showed moisture but I know others with this problem without any mold smell. They just use dehumidifiers. It didn't smell when we bought it, but it was summer and well-ventilated.

We plan to tear it down at the end of January. So you can't just tear everything out and lay tiles directly on the slab?
Dad used something like Styrofoam, then concrete and tiles on top in the house we lived in when I was a teenager. If I understood correctly, he didn't drill. He was also a concrete worker. I believe he also drained around the house during that time.

I thought about just tearing everything out and laying tiles directly on the concrete slab, but I guess some insulation and moisture protection might be needed?

I mostly wondered if the parquet flooring on the upper floor can be reused after it's been aired out? Or will it smell up there too?

If the parquet isn't affected, it can certainly be reused, you'll see when you take it up - but it might need airing out/ozone treatment.

Tiles directly on the slab are fine in themselves, tiles and grout are permeable to moisture so they don't trap any moisture, and it's inorganic so no growth should occur. However, it might result in a fairly cold floor.

 

[Snigla]

Yes, the inspection showed moisture but I know others with this issue without a mold smell. They just use a dehumidifier. It didn't smell when bought but it was summer and well-ventilated.

We plan to demolish at the end of January. So, can't you just tear everything out and lay tiles directly on the slab?
Dad put down foam, then concrete and tiles in the house we lived in when I was a teenager. He didn't drill, as I understand it. He was also a concrete worker. I believe he also drained around the house at that time.

I was just going to remove everything and lay the tiles directly on the concrete slab, but I guess some insulation and moisture protection might be needed?

I was mainly wondering if the parquet flooring on the upper floor can be reused after airing? Or will it smell there too?

Don't reuse any wood that's been in the "scent" in the basement of the house again. I wouldn’t risk it anywhere considering how the smells stick and mold spores live.

Tiles directly on the slab is the best. It ventilates itself in the grout and thus allows the floor to "breathe." You shouldn't have any moisture protection; you want the moisture to "travel" and not get trapped underneath. BUT... the second option (which can sometimes be recommended if there are major scent issues) is to build up the entire floor and have mechanical ventilation on it/the floor (that is, ventilate the slab and remove moisture and scent).

Regardless, you must address the original issue, i.e., why there is mold and where! It’s not worth doing anything inside until external problems related to the issue have been addressed (classic problems are downpipes, that is, the corners of the house, exterior walls if the slope of the ground outside is a bit off, lack of gutters, etc., and of course, the drainage itself).

A basement will always be a bit damp, and it will always have a basement smell, but there’s a big difference between the pungent "mold smell" and a slightly damp earth cellar smell.

The important thing is to get a functioning ventilation system going and start the heating (if you have a finished basement). Ventilation is key.

 

[Back83]

I can tell you that it doesn't take much to scent-wise pollute an entire house!

Our first house had a basement with "smell problems" (i.e., mold).. we re-drained it and then we tried to locate the mold on the inside.. there were wooden studs on the walls and floor (mixed surfaces.. but mainly wooden floors and wet room floor).

Not all the rooms smelled the same, and eventually, you could pinpoint which rooms actually had mold.

The funny part was that we demolished two rooms (two storage spaces) and opened up walls and floors.. and it turned out to be WHOLE 10 CM mold/rotten floor joist along one outer wall.. the rest was perfectly fine.. not a "spot" anywhere!

It felt both tragic and comical that such a small damage caused so much scent and trouble..

BUT you have to keep in mind that the damage had been there for a while.. the moisture had been present.. and all the surrounding material (like insulation, etc.) had absorbed the scent.. even the concrete slab.

However, we sold the house before we had the chance to renovate/control all the rooms.. but the new owners had to tear everything out before moving in so it could stand and air out for a couple of months.. We took the opportunity to peek a bit while we were there.. (before they were to officially take over) and there wasn't much bad at all! (from what we could now see)

So the lesson is.. it's not always something big you're looking for and that makes it very difficult to "just tear a little" because it's really hard to find where that small damage is...

I can imagine it doesn't take much. I know how the trash can smell after a few hours if you've thrown something moldy in there.

So even the slab itself can smell? 😭 I understand now why you have to break it up. Ugh, what a job! I was hoping to rip everything out, dry it, and just lay tiles directly on the slab.

I thought about starting to tear out a room where we can close the door and throw things out the window. That way, you can see how everything looks underneath without spreading the mess throughout the rest of the house. The remaining floor is open to the rest of the house.

 

[Back83]

If the parquet is not damaged, it can certainly be reused; you'll see that when you lift it - but it might need to be aired/ozonated.

Tiles directly on the slab are fine in themselves, tiles and grout are permeable to moisture so they don't trap any moisture, and it's inorganic so no growth should occur. However, it does create a rather cold floor.

Yes, we were thinking of doing ozone cleaning too. However, most of it is open plan, so we'll need to stay somewhere else during that time.

1/4 of the basement is tiles and so cold. The boiler room is quite ok and there's only concrete and paint there. Maybe we should just sand it and paint? It doesn't look very nice though. Otherwise, we'll have to use rugs on the tiles.

 

[Snigla]

I can imagine it doesn't take much. You know how the trash bag can smell after an hour if you've thrown something moldy in there.

So even the slab itself can smell? 😭 then I understand why you need to break it up. Ugh, what a task! I had hoped to just tear everything out, dry it, and lay tiles directly on the slab.

I'm thinking of starting in a room where we can close the door and toss everything out through the window. That way we can see what everything looks like underneath without spreading the mess to the rest of the house. The remaining floor is open to the rest of the house.

You have to take it step by step..
First, tear out everything bad.. and then clean/dry off the slab.. and let it air out (not just for a day..). In the meantime, you have to be a bit attentive.. and see if the smell improves or not (it could be a problem if you have mold somewhere else too.. it's hard to determine where the smell is coming from, you know).

In most cases, it usually hasn't set into the slab (especially if the damage is minor) and then it's perfectly fine to do as you suggested (tiles directly on).

Because if you do it over and do it right.. meaning fixing the core issue (the reason why mold developed in the first place) and ensuring you have proper ventilation.. the air will change at a reasonable pace and any trapped odors will disappear by themselves

Perfect to be able to close off the room and start in one room..!
Remember to take off/change clothes before running around the rest of the house, hehe (at least at the beginning when you need to throw out all the "junk").

 

[Back83]

Do not reuse any wood that has been in the "scent" in the basement again.. wouldn't risk it anywhere considering how the odors attach themselves and mold spores survive..

Tile directly on the slab is the best.. it aerates itself in the grout and thus allows the floor to "breathe".. you should not have any moisture barrier.. you want the moisture to "travel" and not get trapped underneath BUT.. option two (which can sometimes be recommended if you have significant odor problems) is to build up the entire floor.. and have mechanical ventilation in/on it (i.e., ventilate the slab and remove moisture and odor)..

Regardless, you must address the original problem.. that is, why the mold occurred and where! It's not worth doing anything inside.. until you've addressed any outdoor issues related to the problem (classic issues are downspouts.. i.e., corners of the house type.. exterior walls if the slope of the ground outside is slightly wrong.. lack of gutters etc etc - then of course the drainage itself..)

A basement will always be a little damp and it will always smell like a basement.. but there's a big difference between the sharp "mold smell" vs a slightly damp root cellar..

The important thing is to get ventilation working.. and turn on the heating (if you have a finished basement).. ventilation is key.

Well explained, thank you!

No wood or organic material in the walls on the basement level, built in concrete, so it should be what is on the concrete slab causing the smell.
Still no sense in fixing the floor before drainage outside around the house? If we choose tiles, that is.

Poor ventilation in the house. Only natural draft and no openable windows or even ventilation holes in the half of the basement that smells. No fire has been used in the cassette for at least 10 years and switched to a geothermal heat pump in 2013. So, in other words, poor ventilation. No wonder it smells.
Considered installing mechanical ventilation in the attic but poor finances and the smell of mold make us choose to tear up the floor and new windows instead.
Large house, so everything costs extra. Over 50 sqm of floor to tear up, so tiles directly on the floor seem more reasonable than building up a vented floor.

We've never owned a house before, so we mostly listened to friends and fell for this house but didn't understand the extent of the renovation needed as everything looked incredibly well-kept.

 

[bollen]

Yes, we're planning to do ozone cleaning too. However, most of the space is open plan, so we'll need to stay somewhere else during that time.

1/4 of the basement is tiled and so cold in there. The boiler room is quite okay as it's just concrete and paint. Maybe we should just sand and paint? It won't be that pretty, though. Otherwise, we'll use rugs on the tiles.

Yes, mold smell can unfortunately really permeate different materials. We have a continental bed (spring mattress + cold foam mattress) that was first stored for a couple of years in a damp-damaged basement of an old relative (but no moisture damage to the bed itself), and then for a couple of years in a fresh and well-ventilated apartment. After this, it moved into our house, and I (but not my partner) was immediately bothered by a mold smell that I really couldn't stand. The solution was ozone cleaning - we taped up the bedroom and rented a generator that ran in there for a few days. The house didn't smell great during that time either, and it took another couple of weeks for the ozone smell to vent out properly - but it solved the problem!
(However, we had to throw out the latex foam mattress - it was damaged by the ozone and started to smell strongly of "old rubber" afterward)
So a round of ozone in the basement after clearing out all damaged material sounds like an excellent idea!

 

[Totte56]

I myself had a small water collection in a WC in the basement, which came from a minor pipe break.
Wiped up everything, it was half a bucket.
Fully tiled WC, but a little water found its way down by the door, later reflection.
The mold smell came after about 2 weeks.
Started looking and smelling, but it was very difficult to find the source.
Removed the threshold after a while, the threshold was on a 12 mm chipboard 45 mm wide, which then lay on a 45x70 frame.
It was completely intact and dry.
But when I removed it, there were mold spots on the side facing down towards frame 45x75.
Some water had probably gotten down at one end by the threshold.
There weren't many mold spots (maybe around 20 fly droppings) but it smelled strong....

 

[GregerRil]

Yes, we plan to tear it out at the end of January. It can dry for a month and then tiles and re-drain around the house by summer.
Why jackhammer? Isn't it enough to remove all the material on top of the concrete slab and lay tiles?

Yes absolutely that is a solution! It will be cold on the floor then, thought you wanted parquet if it will be a bedroom or similar.

 

[Anna_H]

Good to tear out first, then drain again, then decide how you want to proceed. A luxury option is to break up the floor, insulate properly, and then install underfloor heating when you re-cast.

 

[Kardan79]

Well explained, thank you!

No wood or living material in the basement walls, built in concrete, so it should be what is ON the concrete slab that causes the smell.
Still no point in fixing the floor before drainage outside around the house? If we choose tiles, that is.

Poor ventilation in the house. Only natural ventilation and there were no openable windows or even ventilation holes in the half of the basement that smells. No one has lit a fire for at least 10 years in the fireplace, and the heat pump was switched to a geothermal one in 2013. So, poor ventilation, to say the least. No wonder it smells.
Thought about installing mechanical ventilation in the attic, but poor finances and the smell of mold mean we have to choose to tear up the floor and get new windows first.
Big house so everything costs extra. Over 50 sqm of floor to tear up, so tiles directly on the floor seem more reasonable than building up a ventilated floor.

We never had a house before, so we mostly listened to friends and fell for this house but didn't understand the extent of the renovation needed since everything looked incredibly well-kept.

Note that tiles directly on the slab (likely neither insulated nor heated) will be freezing cold. Maybe obvious, but since you seem to rely on what others say and then blame them if everything doesn't turn out as you intended, it's best to be overly clear.

I don't know why it's urgent to replace windows, how dependent you are on the basement, or to what extent the "scent" spreads in the house. However, I would have chosen to take measures to get rid of the significant mold smell indoors and postponed the window replacement a bit unless the replacement is for some reason urgent.

If the money isn't enough (or one doesn't dare trust craftsmen), one might need to learn something new and roll up their sleeves.

 

[klaskarlsson]

Well explained, thank you!

No wood or living materials in the basement walls, built in concrete, so it should be what's on the concrete slab that's causing the smell.
Still no point in fixing the floor before drainage outside around the house? If we choose tiles, that is.

Poor ventilation in the house. Only natural ventilation, and there were no openable windows or even ventilation holes in the half of the basement that smells. No fires have been lit in the fireplace for at least 10 years, and we switched to a geothermal heat pump in 2013. So, as bad ventilation as it gets, in other words. No wonder it smells.
We were planning to install mechanical ventilation in the attic, but poor economy and the smell of mold make us have to choose to tear up the floor and get new windows instead.
Big house, so everything costs extra. Over 50 square meters of floor to tear up, so tiling directly on the floor seems more reasonable than building a ventilated floor.

We have never owned a house before, so we mostly listened to friends and fell for this house, but didn't understand the extent of the renovation needs since everything looked incredibly well-kept.

If you have moisture problems, you should absolutely look into drainage, but if you use inorganic materials in the basement, and especially if you use it as a basement and not living space, then the drainage can probably wait a while (in the past, basements were built as just basements, not as "rooms").

Ventilation in the house is also important to look at for your own health.
New windows: Is it urgent?
If the old ones aren't completely rotten, they should hold a bit longer.
If they are at least double-glazed, you can reduce drafts with new seals and let them stay a while longer. Of course, replacing windows can improve the insulation in the house, but there are many other things that can be done before that (and attic insulation gives even better results than new windows). Additionally, if the windows are good but old, you can install an inner pane (for example, Grundels do this) to get better insulation at a lower cost and much less intervention than new windows.