Is damp usually condensation?

[stuart45]

Were you surprised to learn the effect of the different pore size in mortar and in brick, limiting rise by capillarity?

No

 

[opps]

I used to use a cheap Plasplug damp meter. I soon discovered that historical damp would change the salt levels in plaster and give false positives.

Damp meters for timber- yeah, for plaster- nope.

If you want to find out whether you have damp or condensation, tape some silver foil to the wall. If the surface of the foil gets wet, it is probably condensation.

 

[JohnD]

No

So you understand why good clean brickwork is so resistant to "rising damp"

 

[stuart45]

So you understand why good clean brickwork is so resistant to "rising damp"

It's new brickwork and cement mortar that's more resistant. It's why Jeff Howell thought it was a myth because the tests he did were on new brick piers standing in trays of tap water. As brickwork ages the ground salts affect it's ability to desorb moisture, so the damp is able to rise instead of evaporating. This can take many years, and only happens in the right conditions.
Jeff Howell's book contains a number of errors. His theory about the introduction of the DPC in 1875 was that it was to do with sanitation and not rising damp. He claims to have gone right through the 1875 Public Health Act, and can't find any reference to rising damp. Peter Ward says the same, adding that rising damp was invented in 1962. Actually they are partially correct, rising damp isn't mentioned there, it was in the British Medical journal in 1875 which was the reason the DPC was introduced into the regs.

 

[JohnD]

only happens in the right conditions.

As you say, "rising damp" is rarely seen.

There is generally a cause for damp, which needs to be rectified. Silicone injections do not repair the causes of excess water.

 

[George_engineer]

Total nonsense, cherry-picked evidence. One daft study that defies common sense in every way.

Any bricky knows that building a wall with wet bricks is a nightmare because... they absorb water, shock horror. Because they're made of porous material.

Instead of staring at a screen, pick up a brick and put it in a puddle. You don't need 400 pages, just try it for yourself.

It's not the 'damp' bit which is controversial - it's the 'rising' bit. There's many things that look like rising damp but are far more likely (high ground level, rain splashing off the ground, condensation, broken gutters), but diagnosing rising damp offers the opportunities to grifters to sell products and labour.

I've seen hundreds of examples of retrofit docs drilled into bricks above a slate dpc, or above three courses of blue engineering bricks. Completely pointless.

 

[stuart45]

As you say, "rising damp" is rarely seen.

There is generally a cause for damp, which needs to be rectified. Silicone injections do not repair the causes of excess water.

I didn't say rarely seen. I said it needs the right conditions.

 

[mrrusty]

My 2p based on my own experiences and my training in condensation control (merchant navy).

Rising damp does exist to some extent, BUT with the dew point of "comfortable" room air (say 20 degrees, 60% relative humidity) being as high as 12-13 degrees, a heck of a lot of damp is actually condensation on cool surfaces. Where there is no air movement to re-evaporate this condensation it sticks around building up moisture content, and of course evaporation causes cooling so there is an element of self-perpetuation.

 

[stuart45]

My 2p based on my own experiences and my training in condensation control (merchant navy).

Rising damp does exist to some extent, BUT with the dew point of "comfortable" room air (say 20 degrees, 60% relative humidity) being as high as 12-13 degrees, a heck of a lot of damp is actually condensation on cool surfaces. Where there is no air movement to re-evaporate this condensation it sticks around building up moisture content, and of course evaporation causes cooling so there is an element of self-perpetuation.

Condensation is a major cause of dampness in houses, so it's important to correctly diagnose the cause of any damp patches first.
Have you changed your views on rising damp? You used to agree with Peter Ward's website, that rising damp was a myth.

 

[WalksWithTurkeys]

Condensation is a major cause of dampness in houses, so it's important to correctly diagnose the cause of any damp patches first.

The biggest cause is the occupants breathing and cold walls. You only have to see how quickly an unventilated car fogs up in winter when someone is inside.

 

[^woody^]

You only have to see how quickly an unventilated car fogs up in winter when someone is inside.

Equally, you see the external face of car glass, greenhouse glass and even double glazed house glass with condensation on it - and you don't get any better ventilation than the outdoors!

 

[WalksWithTurkeys]

Equally, you see the external face of car glass, greenhouse glass and even double glazed house glass with condensation on it - and you don't get any better ventilation than the outdoors!

Not equally. When my car fogs up inside, I see no sign of condensation outside. Condensation will occur outside on cold surfaces when air saturated with moisture meets a colder surface but it needs the right weather conditions. I haven’t seen that since winter. Inside a house, the occupants will raise the humidity significantly, assuming poor ventilation and no dehum.

 

[stuart45]

Equally, you see the external face of car glass, greenhouse glass and even double glazed house glass with condensation on it - and you don't get any better ventilation than the outdoors!

That's rising damp woody.

 

[mrrusty]

Have you changed your views on rising damp? You used to agree with Peter Ward's website, that rising damp was a myth.

No not really - I've experimented myself and yes a brick in water gets wet so there is an element of truth, and maybe the next brick up the wall also gets wet through absorption, but to imagine that water creeps up a wall several feet jumping across the mortar layers......

Very difficult to argue it exists through capillary action to the extent that some people suggest it does against this photo

 

[stuart45]

It's worth reading the report carried out by Salford Uni a few years ago. It's goes into detail about how moisture gets through the mortar joints after a number of years. They had the finance to carry out a number of surveys on older, damp properties. Rising damp has always been difficult to reproduce in the lab.
The problem with Peter Ward's site for me is that he makes stupid statements, such as ' rising damp was invented in 1962' and the UK is the only country with a rising damp industry'.
Even Jeff Howell, who wrote the book, has had to come round to the fact he was wrong.