What you should have said is that the buildings were probably capable of handling the British weather when they were built. A hundred years or so down the line things can be very different. Lime mortar that no doubt did its job back in the day is now little more than sand with a handful of chalk mixed in, which offers zero resistance to rain.
You insistence that all damp comes from within is faintly ridiculous
I've never claimed that. Come back with some real content.
NT
Your assertion that
"damp moves from inside to outside a building, not vice versa, ie from warm air containing water vapour from breathing, showering, washing etc to lower temp and thus lower water vapour outdoor air"
would be a start. You appear to be living in some kind of pre central heating time warp.
OK, a closer look at that...
The air in a house begins as outside air - it can't come from anywhere else . Heating warms it, reducing RH, but it hasnt changed the water vapour conten t any, its only increased its vapour carrying ability thus reduced RH.
Now add humans: breathing, washing, cooking all add more water vapour to th e air. In a well functioning house none of this condenses out. So we have i nterior air that contains more water vapour, feels drier as its lower RH, a nd is warmer than outside.
So across exterior walls there are 2 gradients: temperature and water vapou r. RH is lower indoors, but water vapour content is higher indoors. So wher e a wall is permeable, as they ever are, water vapour cant help but very sl owly permeate from the higher water vapour content side to the lower, ie fr om indoors to out. Central heating doesnt change that fact.
Central heating does change what happens as the vapour heads outdoors. As w arm high vapour content air very slowly permeates outward, it also cools, s ometimes to dew point, condensing out water. Old buildings usually handle t his fine, it simply evaporates and the water content of the walls remains l ow enough to not cause problems.
Now, if you add a water blocking external membrane, ie modern masonry paint , that very gradual movement of water is mostly blocked from evaporating... and it builds up. The wall very gradually gets a damp problem.
NT
I'll take your word for the science (I'm feeling generous), but penetrating damp is mostly a simple case of rain pissing through walls which don't dry out quickly enough. As I've said, I don't doubt the buildings were reasonably water resistant when they were built, but I've seen enough lime mortar in 9" brickwork to convince me that it performs no function 100 years down the line. You can dig the stuff out with your little finger, and replacing the top layer by repointing doesn't work because it soon turns to chalk and sand on exposure to the air. So, you either rebuild the wall or you resort to surface treatments. In my case pliolite paint has performed very well on cracked render that 20 years ago was leaking like a sieve. I should have taken pics to show what the inside looked like at the end of a wet winter. I wasn't in the mood for academic discussions about the movement of air I can tell you :-)
Certainly its a problem sometimes, like where hoppers block or downpipes ru st through.
same as it was originally, when it worked ok. Lime's quite porous, but it d oes dry after rain.
a complete nonsequitor.
Render, if cement, reduces evaporation. Cracked render lets rain in deeper too. Pliolite stops rain going in and blocks evaporation, so its only going to raise water content in the long run to higher than the wall would have if not cemented or pliolite painted.
NT
So the pliolite stopped bucket loads of rain coming in but prevented a relatively minor amount of vapour going out (let's assume we have no windows, and that a coat of paint is actually able to create a total vapour barrier on masonry,.... and also that interior vinyl paint has not already formed such a barrier). The "long run" must be long indeed if no symptoms have been experienced for 20 years. What symptoms are future generations going to experience, and when are these likely to manifest themselves? Does it never occur to you that sometimes you might be wrong? And even if the theories are right, what chance does the average house owner have of complying with SPAB ideals in the real world? Yes, I could knock the render off my gable end wall. Yes, I could repoint the brickwork, but actually the bricks themselves are not that great-that's why they were rendered by the original builders in 1900. Ever considered religion? You can spout stuff, be wrong most of the time, and still come up smelling of roses.
If bucketloads of rain was coming in something was wrong, and needed fixing
if you follow my explanation its clear that evaporation exceeds rain ingress
You can get away with a lot in some cases. How much depends on the building, its maintenance and its situation.
damp
Stuart, at the risk of stating the obvious a) you are unfamilair with the basic theory, haven't followed it and haven't even read up on the subject b) obviously everyone is wrong c) a) means your position here is... based on basic errors
in most cases its straightforward. In a minority compromises are a logical choice
Those measures are not usually necessary. If they are, lime render evaporates much better than cement.
Well, the position I agree with makes sense, yours is based on failure to understand parts of the topic. So I'll stick with the school of thinking I believe, unless you can come up with something better.
NT
You have no idea what degree of rain ingress exists in any given situation yet you assert it is always exceeded by evaporation. Mad as a hatter
If it didn't you'd end up with a flooded wall, so its a bit obvious it does. Silly boy.
NT
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