THE construction of a £4m monstrous metal shed to encase Charles Rennie Mackintosh’s Hill House in Helensburgh for the next ten years, we are told, is the only way to save the building (“Restorers’ giant cage will protect Mackintosh masterpiece”, The Herald, December 7). But is this really so?

There are 10 Grade A Listed houses in Helensburgh, built within the same period and including the Hill House. They represent a golden age of architecture in Scotland, with buildings by William Leiper, Baillie Scott and “Greek” Thomson as well as Mackintosh. All of the houses have suffered from the effect of weather and the years. Sandstone and lead can become porous over time and the climate in the west of Scotland is a lot wetter than 100 years ago. Yet none has required the construction of a giant shed for many years to keep the weather out.

The National Trust’s architects have described their shed plan as “radical and experimental”. No doubt it is but it would also be a giant, ugly lump on the landscape for a decade. Should we be spending £4 million on an “experiment”? Or should we spend it on something tried and tested? The plans for this huge shed offer no solutions for the Hill House’s issues – just the possibility that experts might be able to do something in the future.

Having been involved in restoration and building projects over the years, I have found architects to be ingenious, imaginative and helpful. And sometimes I have found them prone to offer over-large “Rolls-Royce” schemes when pro-active maintenance and repairs, mastic, conservation coatings, fitting deep-fill gutters and improved drainage might do just as well.

The problem with the Hill House is well-known – it is the concrete harling specified by Mackintosh. Helensburgh catches the brunt of Atlantic storms, even to the point of “upward rain” sweeping under the eaves occasionally. If modern conservation coating treatments cannot cope with the weather at the Hill House, then there is a very obvious solution – replace the concrete with a look-alike modern material. Yet, though Mackintosh himself acknowledged that the concrete harling was a poor choice, there are purists who insist that its removal would be sacrilege. One even likened it to scraping the paint off the Mona Lisa.

As a member of the National Trust for Scotland (NTS) I will no doubt be asked to contribute to this £4m. I think that the NTS has to do much more convincing before it can expect a good response. It could start by offering a comparative costing for replacing the concrete.

Russell Vallance

4, West Douglas Drive

Helensburgh