My client had a mortgage survey done by an RICS Chartered Surveyor. As always, this idiot went around the house with a ping prong 'damp' meter and diagnosed rising dampness all over the place. In particular, he highlighted one room which he said was 'very damp' and on the basis of this, he would not allow the mortgage to proceed. He also requested a 'timber and damp survey from a Property Care Association timber and damp surveyor'
At this point my client smelt a rat and asked me to check the house out. It's Georgian - brick built, with most of its original features intact. Quite old fashioned inside, but in good shape. One end of the main range obviously had the servants quarters - a big chimney with open inglenook where the range used to be. Next to it the cellar entrance. The walls of the rooms downstairs that surrounded this chimney stack showed obvious signs of salts - staining to the wallpaper, a bit of white fluffy salt here and there, rusty nails to the skirtings - all the typical things that happen in a well used chimney.
To digress a bit - they used to make ammonia from coal.. Heat coal, get the tar and gas that comes off, there's yer ammonia. Chemical formula Nh3 - or dissolved in water - NH4OH. Now this stuff likes to react with things and produce nitrates - salts - so when NH3 goes up a chimney over many, many years of cooking for his lordship, it reacts with the bricks and mortar in the chimney, and produces a lovely chemical soup. It's that soup that travels around in the chimney and creates all that brown staining and white fluffy stuff in and on the walls. It's also like the salt on yer kitchen table - leave it in the air, and it gets damp - so the wall attracts moisture and looks damp. It's not really - the water is bound into the crystal structure of the salts for the most part...
Now - when I went upstairs to the housekeeper's room, the old dear had a little fire, and a tiny kitchen - now an ensuite, attached to the room with the chimney breast. This showed all the classic signs of salts - damp stains, a bit of brown staining, peeling wallpaper and so on. A bit more wallpaper peeling than normal for a chimney - but next to an unventilated ensuite it became obvious - condensation from the bathroom.
I tested the wall for salts using the 'damp' meter - which of course went off the scale. Aha! Our idiotic RICS Chartered Surveyor had stuck the prongs in, and behold - there were his little pin marks in the wallpaper.. Instant diagnosis of damp. He called it 'The Wettest Room In The House'
So now out came the Thermal Imaging Camera. Hum... no dark spots to indicate evaporation taking place - just a smooth expanse of wall, even temperature. That you'd expect from a dry wall with salts in it..
Then I got out the thermo hygrometer. And carefully lifted the wallpaper. And pushed the probe underneath. Now normally at this point hygrometer probes go into orbit - wallpaper traps moisture. But no... the probe was resolutely fixed on the room moisture levels. Nothing increased. Hmmm. Re-Name the room - the Driest Room In The House.
So why was the wallpaper peeling off in great chunks? For that you had to look next door into the ensuite.. A great big shower, big bath, and a window that hadnt been opened in years.. All that lovely steam, billowing into the room and soaking the wallpaper until it peeled.. And then, after the last Great Shower, the room had lain undisturbed for years until our village idiot, the RICS Chartered Surveyor turned up from the mortgage company and stuck his damp meter into it.
So what to do? Well for a start, treat any surveyor who produces a damp meter with complete contempt. Strong words maybe - but when I see the misery this causes on a daily basis, it's a justifiable comment. (Except me of course - mine is a 'salt meter' :-) ) Remember - chimneys = soot = salts = damp meter off the scale. And it's dry.
And finally, here's a video I did on the day - The Wettest Room In The House which I've renamed the Driest Room In The House...
And here, for comparison, is another video I did in another house - which graphically shows how gypsum plaster traps these salts and forces them to come out of the lime plaster above. The lime looks awful until you clean it off, and you realise that it is perfect. It's so porous that it lets the salts come out, and you can wipe them away. Ain't lime just great? Gypsum just gets wet and manky, and you then have to remove and replace it.
