Fix Damp Walls: Advice & Tips for Rented Flats

[Ryan_m_b]

I live in a rented second floor flat, been here nearly a year now. In the past couple of weeks a huge damp section has appeared in the corner of my bedroom (picture attached). It almost looks like a leak but there's not one there. I've spoken to my landlord who said this happened last winter (I moved in in feb) and that he had people into look at it but they couldn't do anything. His advice is to buy a dehumidifier and send him the bill.

Thing is my room is pretty well ventilated and there never seems to be too much condensation. My landlord also advised putting the heating on more but PhD stipend vs heating bills isn't exactly a fair fight.

Anyone have any advice of what this could be or how to fix it? :(

 

[Bandersnatch]

Move some furniture to that corner?

 

[Doug Huffman]

Look above, another flat, rain gutter, ice dam? I second the motion for a dehumidifier, particularly when he has offered to pay for it (an admission against interest in a suit).

A year ago I had an odd little drain pipe freeze and back-up under the floor and freeze. I ran a dehumidifier all summer to get the moisture content (by conductivity) down to comparable with known dry locations. I have discovered that the dehumidifier keeps the bedroom cozy warm and prevents the ice forming inside the double pane windows. I shopped for triple and more pane windows and am really impressed that the Finlanders can afford to use five-pane thermal glass, they're mind boggling expensive.

 

[Ryan_m_b]

Move some furniture to that corner?

I much prefer the room the way it is at the moment, also was hoping to get rid of the damp rather than just live with it.

Look above, another flat, rain gutter, ice dam?

There's five flats in the block so another two above me. Outside that wall is the stairwell to the block, it's open to the air but protected from any rain or anything like that.

I second the motion for a dehumidifier, particularly when he has offered to pay for it (an admission against interest in a suit).

A year ago I had an odd little drain pipe freeze and back-up under the floor and freeze. I ran a dehumidifier all summer to get the moisture content (by conductivity) down to comparable with known dry locations. I have discovered that the dehumidifier keeps the bedroom cozy warm and prevents the ice forming inside the double pane windows. I shopped for triple and more pane windows and am really impressed that the Finlanders can afford to use five-pane thermal glass, they're mind boggling expensive.

Ok I'll get a dehumidifier as fast as possible. Hope I can find one that isn't too energy intensive. I guess Nordic countries have affordable windows because it's a much bigger market, making and installing in bulk is probably cheaper.

 

[Doug Huffman]

A dehumidifier is a short-circuited air conditioner, short-circuited on the air side so that warm humid room air passes over the evaporator coils, condensing the moisture as a cold trap, then the cooled dry air passes over the cooling coils to recover some of the heat.

My impression is that as the room air dries to the dew point of the evaporator coils, then the heat output increases. As I say, it keeps the b'room warm and cozy. We do not heat this room as there are no pipes associated and we DO use down comforters, electric mattress pad and electric robes.

 

[edward]

Is the stairwell outside of that room a covered stairwell? Covered or not Is the stairwell attached to the outside wall right at about the height of, or just above the height of your ceiling?

 

[Ryan_m_b]

The stair well is covered and meets the wall about halfway up the height of my room. There is a banister that meets the wall at roughly the same height as fas as I can tell, not sure how much of a difference that may make.

 

[Borg]

If a leak has definitely eliminated then I would think that it's outside air getting behind the wall and condensing when it hits the warm wall. Can you check various areas of the walls to see if that one is colder than the rest?

Since there is a stairwell outside that wall, I would look for a gap outside that is either at your level or above. I would check all of the places where the stairwell connects to the building and look for gaps. Otherwise, air could be coming down from the roof and stopping at your level for some reason. I would also check to see if anyone else has been affected in order to look for patterns that may point to the culprit.

 

[Ryan_m_b]

As far as I can tell all of this wall is equally cold, the insulation in this flat is atrocious. I'll check the stairwell again to see if there is anything but I've not seen anything before.

 

[russ_watters]

Wet walls from condensation are a really bad thing. They mean that the inside of the wall is totally covered in mold. Very unhealthy. If you can find an excuse to poke a hole in the wall to verify, your landlord will probably be required by law to remediate it properly (vapor barrier outside, insulation inside).

Otherwise, paint the wall with a few thick coats of waterproof paint.

 

[Borg]

I would check for gaps all the way to the roof. The moisture could be condensing several floors up and running down to your flat where it manages to get to the drywall. Since the insulation is so poor, it's a good bet that there isn't a vapor barrier installed either.

From the looks of the picture, it looks like you have standing water on that part of the ceiling where it's darkest. It looks like it's then running down the corner of the wall. The lighter stains are probably capillary patterns as the water soaks across the wall. I'm betting that whole area is pretty mushy to the touch. Russ beat me to it - if you can poke a hole, you can at least get some of the water to drain out.

I'm not sure what the thin blobs are on the right, but if it's mold or algae, I wouldn't stay for long.

 

[Ryan_m_b]

I've looked quite closely and there is some mold, but not too much at the moment. I'm not sure how feasible it is to poke a hole in the wall. Drywall isn't a common building technique in the UK, the wall is a double layer of brick plastered on the inside. I'd have to drill into make a hole. Better insulation seems like a good idea. I know there are types of wallpaper that are designed to keep walls suffocated and insulated.

 

[zoobyshoe]

I'd smash through with a sledge hammer. There's a certain probability the dampness is a time portal opening up back to the age of the dinosaurs.

 

[russ_watters]

I've looked quite closely and there is some mold, but not too much at the moment.

Er...sorry, but you are looking at the wrong side of the wall.

I'm not sure how feasible it is to poke a hole in the wall. Drywall isn't a common building technique in the UK, the wall is a double layer of brick plastered on the inside. I'd have to drill into make a hole. Better insulation seems like a good idea. I know there are types of wallpaper that are designed to keep walls suffocated and insulated.

One good way to retrofit with insulation is by poking a hole and spraying foam in. It isn't too expensive and your landlord really owes it to you.

[edit] Oh, and a dehumidfier? In winter? That makes no sense. If it is humid inside, just bring in more ventilation and compensate with heat. It'll be cheaper and more effective than a dehumidifier.

 

[Ryan_m_b]

Er...sorry, but you are looking at the wrong side of the wall.

I meant across the whole wall, there is mold in the area I've photographed :/

One good way to retrofit with insulation is by poking a hole and spraying foam in. It isn't too expensive and your landlord really owes it to you.

That's certainly something I'll look up, hopefully the fact that this is a block of separately owned flats won't be too much of an issue.

 

[Medicol]

Break that area then rebuild it. True! :)
Covering it with any waterproof paint will not be helpful at all in the long run.

 

[Danger]

a huge damp section has appeared in the corner of my bedroom

Do you walk in your sleep...?

 

[edward]

So if it is condensation, consider that condensation first forms on the coolest portion of the wall or a cool portion of the wall with the little air movement. If the stains are not from seeping water evidently the bricks in the wall behind that plaster are getting colder than ones behind the rest of the room.



I don't think that you should try the idea in the video. It is only an example of whacko things that I might personally try. Could you put a lamp in that corner?

 

[lisab]

I'd be careful about heating the area. You probably already have mold on the other side of the wall, heat could encourage it to grow on the inside, too. The only good solution is to stop the water at its source.

Are there laws where you live stating renters' rights? Mold is a serious health issue and shouldn't be taken lightly. Also, if you can't use that room you should get a reduction in your rent.

IMO, the landlord is making a stupid decision by ignoring this. When it comes to building materials, water is the enemy! A slow drip, drip, drip can result in expensive repairs.

 

[Astronuc]

I agree with Russ and lisab, and if I were in your situation, I'd probably do as zooby suggested - knock out the plaster.

A dehumidifier will not help the moisture (or dampness) on the backside, where serious mold can grow. It could be a significant respiratory threat.

Do the upstairs flats (apartments) have dampness problems in the same corner? Does either have a leak, or is there a leak in the roof (or joint in the outer wall) such that the water drains down to that corner? Or does the above flat have a leaking lavatory or loo in the vicinity of the corner? It could be that the ceiling will also be damaged.

 

[zoobyshoe]

...and if I were in your situation, I'd probably do as zooby suggested - knock out the plaster.

I was pretty much joking, though. The drips reminded me of T-rex teeth.

He's got two layers of brick behind the plaster, he says, and I suspect that's acting as a heat sink causing warmer, moister air to condense right there, as Edward suggested. He might test that corner with a sensitive thermometer and compare it to other walls in the flat that aren't having this problem. If it's not significantly cooler, then I'd suspect there is a leak above somewhere. It could be the water supply pipe to the toilet in the flat directly above is leaking, like this:

https://www.physicsforums.com/threads/stupid-science-tricks.785958/

Or the source could be far removed. As the Romans knew, water can travel long distances sideways, so to speak, with a very small drop in elevation along the way. Not that I'm suggesting the two layers of brick are part of an old Roman aqueduct, but we are talking about a country where kings of yore are found tucked under parking lots.

 

[RonL]

I don't think it is your problem, but check the AC collection and drain system, I have seen some weird problems in connection with blockage and overflow, some have shown up as long as two months after the units have had little use.

 

[Ryan_m_b]

First off thanks to everyone for replying, it's good to have a wealth of opinions about what to do.

I'd be careful about heating the area. You probably already have mold on the other side of the wall, heat could encourage it to grow on the inside, too. The only good solution is to stop the water at its source.

Are there laws where you live stating renters' rights? Mold is a serious health issue and shouldn't be taken lightly. Also, if you can't use that room you should get a reduction in your rent.

IMO, the landlord is making a stupid decision by ignoring this. When it comes to building materials, water is the enemy! A slow drip, drip, drip can result in expensive repairs.

There are renter's rights but I live in London where it's very much a sellers market, having problems with your landlord maintaining things is unfortunately common. They can get new tenants the next day whereas finding a decent affordable place to live with good transport links is much harder. My landlord is good at dealing with things, he just signed off on buying a £140 dehumidifier but it is looking like I need to find someone to come take a look at it and sending on the bill.

I agree with Russ and lisab, and if I were in your situation, I'd probably do as zooby suggested - knock out the plaster.

A dehumidifier will not help the moisture (or dampness) on the backside, where serious mold can grow. It could be a significant respiratory threat.

Do the upstairs flats (apartments) have dampness problems in the same corner? Does either have a leak, or is there a leak in the roof (or joint in the outer wall) such that the water drains down to that corner? Or does the above flat have a leaking lavatory or loo in the vicinity of the corner? It could be that the ceiling will also be damaged.

Upstairs as far as I know are fine, it's been a while since anyone checked though so I'll knock on the door and see if I can have a look myself. It is looking like I need to get a professional in.

I don't think it is your problem, but check the AC collection and drain system, I have seen some weird problems in connection with blockage and overflow, some have shown up as long as two months after the units have had little use.

I don't have any air conditioning (less than two weeks of the year that might be desirable) and no drains. I'm suspecting that where the stairwell banister is drilled into the wall might be causing an issue.

 

[OmCheeto]

First off thanks to everyone for replying, it's good to have a wealth of opinions about what to do.

There are renter's rights but I live in London where it's very much a sellers market, having problems with your landlord maintaining things is unfortunately common. They can get new tenants the next day whereas finding a decent affordable place to live with good transport links is much harder. My landlord is good at dealing with things, he just signed off on buying a £140 dehumidifier but it is looking like I need to find someone to come take a look at it and sending on the bill.

Upstairs as far as I know are fine, it's been a while since anyone checked though so I'll knock on the door and see if I can have a look myself. It is looking like I need to get a professional in.

I don't have any air conditioning (less than two weeks of the year that might be desirable) and no drains. I'm suspecting that where the stairwell banister is drilled into the wall might be causing an issue.

Have you done as Zooby recommended, and measured the temperature of the wall?
Moplin sells the fancy ones for £14.99.
Also, what is the source of your heat?
A friend of mine has an internally venting natural gas wall mounted fireplace, and it generates a lot of moisture. She has problems similar to yours.
I heat with electricity, and, although we only live 2.5 km apart, I have never had a problem with moisture.
A third question is, do you sleep with your bedroom door closed?
According to NPR, we lose 1/2 kg of moisture during the night.
This might all be your fault.

 

[russ_watters]

Yeah, I would measure the humidity in the apt.

 

[Doug Huffman]

There are useful subjective measures of room humidity, mold being just one. The most obvious one to me is the area and density of condensation on the the window glass. My confirming objective measure is how many hours are required to fill the water reservoir on the dehumidifier.

 

[OmCheeto]

Moplin sells the fancy ones for £14.99.

This morning, I picked up the even fancier gun type for just a little bit more, and got an extra 115°C of range.
It seems to work on everything, with the exception of polished stainless steel.

Yeah, I would measure the humidity in the apt.

I just built a dew point tester out of my new infrared thermometer, a paper towel, and a spare muffin fan.

dry temp: 19.4°C (66.5°F)
wet temp: 13.6°C (56.0°F)
dew point: 8°C (48°F) from a fancy chart

I can't figure out how to get relative humidity from that, but I decided that I don't really care.
All I want to know is, at what temperature water vapor will condense in Ryan's apartment.

Checking various spots around my house, nothing is lower than 11.6°C (53.0°F). (A single pane window)

I also filled a glass with tap water and ice cubes. After about 15 minutes, the exterior of the glass fogged up.
I measured the surface temperature at 7°C (44.5°F), which is very close to the eyeballed dew point temperature.

Success!

I also did some rough estimates on how much this brick wall is costing Ryan.
I of course, given that he didn't use the homework template, made some assumptions:

Wall area: 8.28 m² (based on the dimensions of my bedroom wall: 11.5ft wide x 7.75ft height)
Standard UK brick length: 0.214m (8.46 inches)
R value per inch thickness of brick(SI): 0.03 m² K / (W * in) (I'm not sure why wiki mixed inches into the SI system.)
effective R value: 0.25 (SI) (1.44 Imperial)
Average temperature today in London: 3.3°C (38°F)
Interior temp: 20°C (68°F)

Watts lost through wall: 545
kwh/month: 398
cost of electricity in London: 12 pence/kwh
monthly cost for this wall alone: £47.73

Cost of 3 polyisocyanurate foam panels (1/2" thick) which will completely cover the wall: £24.90
aggregate effective R value with brick & foam: 0.85 (SI) (4.85 Imperial)
monthly electric cost for this new improved wall: £14.19

Return on investment: 22.6 days

And of course, no more condensation.

Fancy wallpaper extra.

 

[russ_watters]

This morning, I picked up the even fancier gun type for just a little bit more, and got an extra 115°C of range.
It seems to work on everything, with the exception of polished stainless steel.I just built a dew point tester out of my new infrared thermometer, a paper towel, and a spare muffin fan.

dry temp: 19.4°C (66.5°F)
wet temp: 13.6°C (56.0°F)
dew point: 8°C (48°F) from a fancy chart

I can't figure out how to get relative humidity from that.

Try this fancier chart: http://www.captiveaire.com/CATALOGCONTENT/EVAPCOOLER/PSYCHROMETRIC.asp

 

[OmCheeto]

Try this fancier chart: http://www.captiveaire.com/CATALOGCONTENT/EVAPCOOLER/PSYCHROMETRIC.asp

Thank you.
But I really would rather have had a set of equations to plug-and-chug through.
Which, after several hours of googling, I think I may have found.

Dewpoint Formulas

From which, I was able to come up with a dew point temperature of ≈9°C.
So, I think I transcribed the equations correctly.

Saturation Vapor Pressure at Dry Bulb (mb)__Es = 6.108 * (e^((17.27 * T) / (237.3 + T)))________22.53
Saturation Vapor Pressure at Wet Bulb (mb)__Ew = 6.108 * (e^((17.27 * W) / (237.3 + W)))________15.58
Actual Vapor Pressure (mb)__________________E = Ew - (0.00066*(1 + 0.00115 * W) * (T - W) * P)__11.65
Relative Humidity in percent (%)____________RH = 100 * (E / Es)_________________________________51.72
intermediate value (no units)_______________B = (ln(E / 6.108)) / 17.27__________________________0.04
T = Air Temperature (Dry Bulb) °C____________19.4
W = Wet Bulb Temperature in °C_______________13.6
P = Barometric Pressure in millibars (mb)__1009.47__[mm mercury PDX 2014.12.09.09:42__759(shamelessly stolen from the local weather forecast)]
e (natural log number thingy)_________________2.718281828
1 mm mercury = 1.33 mb (google is my friend)
Dewpoint in °C______________________________D = (237.3 * B) / (1 - B)__9.22
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Yay!

I spent my youth calculating this kind of stuff on paper. Computers, spreadsheets, and infrared thermometers, make me want to cry.

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