10/04/2026
Hence why portland does not make the best breathable products. Lime is and always will be the best!
A famous house is wearing a raincoat the size of a building. It has been inside it since 2019.
Charles Rennie Mackintosh designed Hill House in Helensburgh for the publisher Walter Blackie. It was built between 1902 and 1904. Blackie later recalled that the rooms were settled first, and only then did Mackintosh show him drawings of the outside.
The outside is where the trouble started. Mackintosh covered the walls in Portland cement harling, a newer and harder material than the traditional lime. Lime lets a wall breathe. Cement does not. Rain soaked in and could not get back out, and the damage built up over decades.
In 2019 the National Trust for Scotland, which has cared for the house since 1982, wrapped the whole building in a giant chainmail-mesh structure called the Box. It keeps the rain off while letting air move through, so the walls can slowly dry out. The Box is expected to stay up for years, and the house has remained open to visitors.
An architect built a house to last forever.
Now it needs a raincoat to survive.
What is the oldest building you have ever stood inside? Tell us where below.
