Most of the stuff I’ve been doing on the house has involved removing waterproof paint. That’s not for eco or idealogical reasons but because waterproof paint has caused some very expensive damage very quickly.
The problem is it is waterproof. When it cracks water will get in but can’t get out again (because the paint is waterproof). This isn’t just an old house problem – it’s also the reason why wooden windows don’t last more than 20 years any more, where previously they were good for hundreds of years.
For some reason I have the ends of oak beams sticking out of the north wall. The ends were clearly fairly flat before they were gummed up with cement and waterproof paint maybe 20 years ago. The paint was still flat on the outside until I prodded with a screwdriver and made a hole.
Underneath the paint the oak has rotten. Fortunately it’s only the outer inch that has gone. Oak is a wonderful material and resistant to abuse. But even oak can’t stand up to being sodden wet for 20 years.
Let’s just be thankful I don’t also have a 17th century timber frame under the modern paint (which was rendered in 1910 in an early use of cement just for good measure).
Oh wait, hold on – it turns out I did have one.
I wonder if the people who peddle waterproof paint as the solve all for preserving your building will offer to pay for the repairs. Of course they won’t – the guarantee on the most posh ones is only for 6 years, and that only covers the paint not what it damages underneath.
The building did perfectly well for the previous 400 years using breathable materials like lime and linseed oil. Modern paints and cement have turned the original wood to dust.