Rising damp

Alfster

stuart45 said:

Alfster said:

stuart45 said:

Out of interest and with nothing better to do now the crickets been rained off I stuck an old brick with a lime bed joint into an inch of water for an hour and it rose about an inch. So by my calcs it would be 1.38 miles in ten years.

I don’t think you can extrapolate this result linearly. Rising damp is real but seldom the cause of the damp the OP is talking about in period homes unless it’s sitting in a lagoon 24/7 like Venice as you mention. Even in Venice the average rising damp level in buildings is 1.5m and some these buildings are 800 years old:

Venice is a fascinating example of rising damp. The rising damp itself directly isn’t really the cause of decay; it’s the evaporation of that water out of the masonry and the remaining salts that wreck the building. A sad story for such an incredible city. 

I wasn't really serious about the 1.38 miles. Usually stops around a mile.
Jeff Howell was probably one of the first to study rising damp when he built a load of brick piers and stood then in water. He couldn't see any signs of rising damp and since then has written the book about the rising damp myth. 
However if you stand a brick pier in water the change in the pore structure of the mortar bed is different to the brick and this is thought to slow down the rise and allow the moisture to evaporate before it goes any further.
You normally find that moisture will go up the wall though the render or plaster as the pore structure is the same. There used to be a damp problem when membranes were first used under the slabs and the bricklayers used to cut them flush with the inner wall. This left a weak spot between the DPC and the DPM which allowed moisture to creep up the plaster.

I guess you meant stops around a metre 🤣
Yeh that’s interesting. I think people get confused with rising damp being a myth. It’s not a myth as you can see from Venice; it’s just a myth in the sense that it almost is never the reason for damp in a period house. So much extensive research has been done and so many journal articles have been written on Venice to show us what rising damp really is and what it does to old buildings. The myth comes in when your local PCA ‘damp specialist’ tells you that you have rising damp in a period home. Anyone wanting some more detailed advice on rising damp here is a good seminar from Dr Robyn Pender:

https://m.youtube.com/watch?v=Jo8oF9ubvtI&list=PLEtvbsQ08cB-WIH8hYHv0f4lZTPqVXjcx

She does a lot of work for Historic England (formerly English Hertiage); a body who have arguably the most extensive knowledge on preserving and looking after older buildings in UK. So always worth checking them out if you want advice looking after such buildings. 

lookstraightahead

daveyjp said:

Victorian houses are damp because they weren't built for modern living.

The damp has probably been an issue since the house was built, but we come along and block up chimneys, fit windows and doors which don't let in a howling gale, cook in kitchens with doors closed, dry clothes indoors, raise external ground with patios, decking etc so the conditions mean the damp can't evaporate.

If you put a wet item into a sealed plastic bag it will never dry out.  We have made Victorian houses into the equivalent of a sealed plastic bag.

This is so true. We've bought an 1860s house and I treat it with tlc. It's all one room downstairs apart from a cellar and a laundry room, and I've got the doors open most of the time which I love, but it's not for everyone!