Sale fell through after survey - damp?!

[Worrywart]

Newbie here and wish I’d found this forum a lot sooner! Grateful for any help you can provide.

I am selling my stone walled Victorian house, we have lived here 10 years and no damp was ever reported on our level 3 survey, however, we now suspect a dehumidifier used by the previous owner may have ensured that was the case…

We are now selling and while we noted things like furniture drawers in one room starting to stick and a bit of bubbling in odd spots on the windows recesses, we never thought we had damp - so no peeling paint or wall paper . Plus we didn’t heat one room much and it had a gas fire - so no working fireplace, which we thought was why the furniture stuck. Naive I know!!

Anyway - ten years on and following our buyers survey we discover that he said the house was riddled with rising damp, penetrating damp- the whole shebang! The buyer pulled out.

We now have a new buyer and true surveyor is coming next week. We got a damp survey guy out, who told us to just get a dehumidifier in - which was fair of him given he could have sold us a DPC.

I am worrying constantly and so bought a protimeter to check the walls myself. I know these are to be taken as only aspect of damp measurement, but the level two survey which is booked will surely use one.

Can anyone tell me what level the surveyor will deem as being damp? My dehumidifier is giving a reading of between 40 and 59 and the protimeter between 0 and7 on the walls as as high as 17 on the base of the chimney breast .

I can just see another sale falling through because people hear the word damp and don’t put it in context with the age of the house and the surveyors are so risk averse they treat the house like a new build! Can anyone help please?

 

[88v8]

Dehumidifier... 40-59 is that the RH?
59 is on the high side, but not really what I would call damp. However, we live in a C17 cottage where the summer RH is in the 70s. In a C20 house, 59 would be rather damp and raise questions..

The protimeter readings, if they are reliable... taken like this and this with some drilling into the wall and a dry reference material to sample, will tell the tale whatever it may be.

A high proportion of the topics on here are damp problems, so it's understandable that buyers may be nervous.

I think that advice to get a dehumidifier is good, we have two running 24/7.

Hopefully you will eventually find someone who doesn't commission a full survey.

Sorry I can't give you any great reassurance.

 

[Lacan07]

My dehumidifier is giving a reading of between 40 and 59 and the protimeter between 0 and7 on the walls as as high as 17 on the base of the chimney breast .

Lol, most owners of an old house would kill for readings like that! RH is a complex subject and some people take it far too seriously. How do you know you're not the cause of the moisture in the house - washing, kettle, breathing, etc? I bet most new builds are far worse with their air tight insulation. And those damp readers are next to useless, even if they were a reliable tool how do you know they aren't just reacting to condensation on the wall?

None of this is any help to you though of course if people are going to send stupid surveyors round with they're crappy gadgets. Most of them no nothing about old houses. If you've no physical indications of damp, like peeling paint, etc, I'd say you've been very unlucky to be labelled as a damp house. If all you need do is stick a protimeter on to the wall and take a reading to determine whether something is damp or not I'm guessing the majority of old housing stock in the UK will suddenly be deemed unliveable overnight. I mean you've lived there for 10 years and never been aware of any issues.

As 88v8 has said above, ramp up the dehumidifiers before the survey, they're not that expensive these days and you can always sell them on if you need to afterwards. Who cares, people have done far worse in order to sell a house in the past.

 

[Worrywart]

Thanks to you both for your replies . Forgive my ignorance - I don’t know what RH means? Is it relative humidity? I am just using the reading of the digital display on the dehumidifier . I have a protimeter but it’s not that expensive so not sure how accurate it is. It shows % only. Most walls go between 2 and 7 % after using the dehumidifier and the worst is the bottom of the chimney breast at 19%. Again even at the bottom of the chimney there is no peeling wallpaper

 

[Lacan07]

Thanks to you both for your replies . Forgive my ignorance - I don’t know what RH means? Is it relative humidity? I am just using the reading of the digital display on the dehumidifier . I have a protimeter but it’s not that expensive so not sure how accurate it is. It shows % only. Most walls go between 2 and 7 % after using the dehumidifier and the worst is the bottom of the chimney breast at 19%. Again even at the bottom of the chimney there is no peeling wallpaper

Yes, RH is relative humidity.

Those meters are not a reliable source of damp measurement, there's lots of Youtube videos out there about it.

Chimney's are often areas that can contain or seem damp, the soot interacts with the lime mortar to create salts and of course those salts sucks the warm moisture out of the air.

 

[Zebra]

My RH is consistently 75, and it's not damp...I have a dpc and breathable walls.
But relative humidity is fairly meaningless - as it refers to the humidity in relation to the total amount of moisture which would saturate the air at that temperature. Warm air can hold much more moisture than cold air. Therefore the 100% humidity point is very different at 15 degrees compared to 20 degrees. With no moisture added or taken away, the RH will drop considerably as the temperature rises in a space (as the 100% point gets further away) and were the temperature to ever drop to zero, the RH would show almost 100%. So the same amount of moisture in a space will show vastly different readings depending on whether you're heating the space. My RH is 75...but my internal temperature is currently 16 degrees. So that's normal. You just can't take a RH reading as being an absolute indicator of the level of dampness in a space.
Anyone please feel free to correct me on my physics!

 

[Lacan07]

My RH is consistently 75, and it's not damp...I have a dpc and breathable walls.
But relative humidity is fairly meaningless - as it refers to the humidity in relation to the total amount of moisture which would saturate the air at that temperature. Warm air can hold much more moisture than cold air. Therefore the 100% humidity point is very different at 15 degrees compared to 20 degrees. With no moisture added or taken away, the RH will drop considerably as the temperature rises in a space (as the 100% point gets further away) and were the temperature to ever drop to zero, the RH would show almost 100%. So the same amount of moisture in a space will show vastly different readings depending on whether you're heating the space. My RH is 75...but my internal temperature is currently 16 degrees. So that's normal. You just can't take a RH reading as being an absolute indicator of the level of dampness in a space.
Anyone please feel free to correct me on my physics!

I'll pass on the physics but you're idea that RH is meaningless is spot on. I've been monitoring RH for years now, you can have a dry period and the RH be low but as soon as rain threatens it shoots up even before rain hits the house.

It certainly should never be used as a basis for not buying a house.

 

[CliffordPope]

I've never really understood why we measure relative humidity rather than just humidity. What does it matter how much moisture the air could hold - why not just how much it does hold?
We don't usually want to know the relative temperature - how hot or cold it could be - but how hot it actually is. The oven's at gas mark 6, but it can go up to 12. Similarly, air pressure, direction, sound volume, light brightness, calorie content, etc etc.

Don't we normally want to know what things are, not what they theoretically could be?

 

[Worrywart]

I'll pass on the physics but you're idea that RH is meaningless is spot on. I've been monitoring RH for years now, you can have a dry period and the RH be low but as soon as rain threatens it shoots up even before rain hits the house.

It certainly should never be used as a basis for not buying a house.

I wish someone would tell the RICS surveyor that! I have heard that anything over 15% on the protimeter is the measure used to indicate damp. Does anyone know? Most walls are now showing much lower than that after using the dehumidifier so I’m hopeful!

 

[Worrywart]

I've never really understood why we measure relative humidity rather than just humidity. What does it matter how much moisture the air could hold - why not just how much it does hold?
We don't usually want to know the relative temperature - how hot or cold it could be - but how hot it actually is. The oven's at gas mark 6, but it can go up to 12. Similarly, air pressure, direction, sound volume, light brightness, calorie content, etc etc.

Don't we normally want to know what things are, not what they theoretically could be?

I don’t really understand any of this and it’s so unfair that the surveyor can use such unreliable instruments without allowing any challenge from the vendor.

 

[stuart45]

R/H and temperature are useful to know when combined with a surface thermometer. Any surface at and below the dew point is going to attract condensation. Walls with hygroscopic salts will do this at even higher temperatures. Once a wall becomes damp, it tends to be a cold spot on the wall, and gets worse. Thermal cameras can also help pick out damp areas.