Is this condensation or damp ?

[JohnD]

I've seen reports about rising damp in Venice going up a few metres. Said to go higher in thicker walls.

Which may be stone walls with a rubble core. The same thing happens in cavity walls when the cavity is full of absorbent builders waste.

Not comparable to nine inch wall of clean coursed brickwork or a clean cavity or one containing non-absorbent or hydrophobic material

Which has resistance to capillarity at every boundary between brick and mortar due to the changes in pore size.

As we know, render or plaster can defeat the natural resistance of clean coursed brickwork to capillarity.

 

[blup]

Rising damp is usually diagnosed at the base of the structure where the dpc has been bridged or isn't present. But capillary action must also occur at any point in a building where damp has penetrated, it's just more convenient to refer to it by source e.g. penetrating damp. At several metres up it could be a combination of both.

Blup

 

[JP_]

I believe "rising damp" doesn't exist.

But it has been observed many times, and the process explained. How can it not be real?

 

[JohnD]

But it has been observed many times, and the process explained. How can it not be real?

It is pretty sure to have a cause, that can be addressed.

Unless it is a rubble filled wall.

Which in this country is not normal.

"Rising damp" is not normal on an ordinary wall, of clean brick, exposed to the air. Within a few courses, water evaporating from the surface equals that passing through the boundaries of brick and mortar below. In my house it is two courses above the ground. It does not even reach the DPC.

 

[stuart45]

Which may be stone walls with a rubble core. The same thing happens in cavity walls when the cavity is full of absorbent builders waste.

Not comparable to nine inch wall of clean coursed brickwork or a clean cavity or one containing non-absorbent or hydrophobic material

Which has resistance to capillarity at every boundary between brick and mortar due to the changes in pore size.

As we know, render or plaster can defeat the natural resistance of clean coursed brickwork to capillarity.

A lot of the Venitian buildings affected are brickwork.

 

[JohnD]

Show us the evidence you have seen.

 

[RandomGrinch]

A lot of the Venitian buildings affected are brickwork.

I think we can probably all agree that Venice is pretty much a 'worst case' scenario!

 

[stuart45]

Rising damp in historical buildings: A Venetian perspective - ScienceDirect
I have been to Venice and noticed a lot of brickwork.

 

[stuart45]

I think we can probably all agree that Venice is pretty much a 'worst case' scenario!

It obviously is, and it's said that the height it will rise is greater the thicker the wall is. It the UK most houses don't have 6ft thick walls, although some of the stone farmhouses in my area are 3ft.

 

[^woody^]

I have been to Venice and noticed a lot of brickwork.

LOL. Goes to romantic Venice, surveys the walls.

 

[mrrusty]

Rising damp in historical buildings: A Venetian perspective - ScienceDirect
I have been to Venice and noticed a lot of brickwork.

Thanks for this - that's interesting. I think it goes to show how complex this subject is, and no wonder there are differences of opinion. Also interesting how this study relates so much of the analysis to salt content within the walls; I have long suggested that we do not take enough notice of salt poisoning caused by decades of coal fires in old houses where the combustion products react with the building products causing acids and hygroscopic salts.

I also think that the relationship between condensation, attracted moisture due to salt contamination and the subsequent cooling caused by evaporation (i.e. same cooling effect as the reason we sweat) lowering temperature and exacerbating condensation on the lowest/wettest parts of a wall is not considered enough.

https://www.wcp-architects.com/the-problem-with-condensation/

My own view, FWIW is that the majority of so called "rising damp" in UK houses, is actually caused by condensation and/or lack of ability to evaporate caused by impermeable renders and finishes, with another high proportion caused by leaking gutters/windows/pipes/drains, and very few cases by true "rising damp" where the wall is so saturated by standing in water and regular flooding that water retention and capillary progression is even a factor.

Perhaps it is flippant to say rising damp doesn't exist, but based on my own experience, if you take remedies to control condensation and ventilation, and consider any salt poisoning, and check/correct any broken plumbing, "rising damp" seems to disappear which suggests it wasn't "rising" in the first place.

 

[JohnD]

Unsurprisingly, walls standing in seawater for 500 years have a salt content different from most British houses.

 

[blup]

The myth of rising damp is actually the misdiagnosis of rising damp, by getting it wrong, exaggerating it or ignoring other causes.

blup

 

[^woody^]

Moisture can travel up, down and sideways to varying extents depending on various factors and various materials.

I recall that old Softus was the anti-vaxxer of the rising damp debate, and the topic has been done to death already

 

[JP_]

Rising damp is determined by type of brick, type of water, and time. Over time salt deposits block the capillaries in the bricks, and as they narrow, gravity & evaporation lose the battle and water rises higher, depositing more salts to further narrow passages for water, making it possible for water to "climb" higher. You can't test it by putting a brick in a bucket of water and saying "look, no rising damp", which some people did once. In some areas rising damp will never be a problem.

Even the Stephen Boniface (the building surveyor who does not believe in rising damp) says "in my experience rising damp is probably the rarest form of damp whilst condensation is probably the most common"

Rare, not non-existent.