Zoom in. Can you see the drill holes?
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Zoom in. Can you see the drill holes?
Erm... if I were in Venice doing drill and inject I would rather do it from the side of the property rather than wearing a wet suit.
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You'll need a lot of time. Rising damp does not happen immediately, it can take decades before the salt deposits have built up enough to mean capillary action overcomes gravity.
A crack would destroy capillary action, but only where the crack is. And you can't have all the wall be cracks, or it will no longer exist ... so still plenty of scope for rising damp in a cracked wall.
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... you wouldnt see those buildings, as they are in Bruges.
Here's some houses in Venice. They must have had a very high tide that morning for the penetrating damp to get that high!
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That is the cause of rising damp, as far as I understand. And why experiments with putting new bricks in water fail to demonstrate it.
In any wall with moisture at its base there is a constant fight between capillary action, being driven by water pressure, and gravity. In new bricks the gaps in the brick are larger and gravity pulls water down quicker than capillary action can push it up. But, where the water does get, after evaporation, it can leave mineral / salt deposits, and over time this reduces the size of the gaps in the bricks, and the pressure increases and gravity loses, so slowly the damp keeps rising up. After every wet period, the water gets a little higher, more minerals are deposited, allowing more rising damp next time.
A long process, but one seen in many old buildings all over the world. The only way to stop it is to effectively stop the moisture at the base. This is why we have dpc in the first place.
When people were building these old buildings on canal sides etc. they were never meant to be used to live in. Probably temporary storage for loading cargo etc. and nothing more. More like a porch / garage than a living room.
Some types of stone, eg slate, is impermeable, so some old houses that were built with impermeable stone won't suffer rising damp (unless rendered, I guess), which is why you don't see it in all old properties. Shale, marble, mudstone, slate and well-packed sandstone are all examples of impermeable rocks.
The brick in the photo was in about an inch of water and rose up a few inches in a couple of hours. Went up a thermalite even quicker.
The mortar was lime. However in an old piece of brickwork it wouldn't get past the first bed joint, so your theory might be right George.
mortar and bricks have different pore sizes
the water rises by capillarity
the smaller the pore size, the more it attracts the water
water will easily travel from large pores to small,but resists going from small to large.
so each course provides an obstacle
very often the water can only get one or two courses up from the source
unless there is rubble in the cavity, or plaster or render on the bricks
in my house, it will only go up one course from the paving; it doesn't even reach the damp course
(0the bricks in the bottom course look full of hard water limescale, they even have a visible crust of it
this has presumably reduced the pore size in the bottom course, making it harder for the water to get into the larger pores above)
when the structure of the wall enables it to go higher, it will stop at the point where evaporation from the surface equals or exceeds water rising from the source. so hacking off plaster or render, exposing clean bare brick, and maximising ventilation (e.g. under floors or in disused chimneys) can dry out damp. Some people mistakenly apply cement render, or bituminous paint, to the bottom of walls thinking it will reduce damp, but it has the opposite effect
I don't know the pore size in lime mortar, so it may behave differently, I have only observed post-Victorian clay bricks and cement mortar.
there are some excellent photos of clean brickwork built in test labs, with the plinths standing in basins of water, and the water refuses to rise more than a couple of courses.
the water rises by capillarity
the smaller the pore size, the more it attracts the water
water will easily travel from large pores to small,but resists going from small to large.
so each course provides an obstacle
very often the water can only get one or two courses up from the source
unless there is rubble in the cavity, or plaster or render on the bricks
in my house, it will only go up one course from the paving; it doesn't even reach the damp course
(0the bricks in the bottom course look full of hard water limescale, they even have a visible crust of it
this has presumably reduced the pore size in the bottom course, making it harder for the water to get into the larger pores above)
when the structure of the wall enables it to go higher, it will stop at the point where evaporation from the surface equals or exceeds water rising from the source. so hacking off plaster or render, exposing clean bare brick, and maximising ventilation (e.g. under floors or in disused chimneys) can dry out damp. Some people mistakenly apply cement render, or bituminous paint, to the bottom of walls thinking it will reduce damp, but it has the opposite effect
I don't know the pore size in lime mortar, so it may behave differently, I have only observed post-Victorian clay bricks and cement mortar.
there are some excellent photos of clean brickwork built in test labs, with the plinths standing in basins of water, and the water refuses to rise more than a couple of courses.
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