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The Granite City’s secret weapon against building decay is… granite

The granite of Marischal College. Image: Shutterstock
The granite of Marischal College. Image: Shutterstock

One of Scotland’s top conservation experts has said Aberdeen is one step ahead of many other cities in the race to save crumbling buildings – thanks to its iconic granite.

Craig Frew, the director of Fife-based Frew Conservation, recently gave a talk to owners of historic houses in the city to advise them on how best they can be maintained.

Ferns, trees and weeds can be seen sprouting from facades on Union Street, adding to the sense that it’s seen better days.

At his presentation, Craig cycled through picture after picture of wonky walls, tatty windows and leaky pipes.

He’d taken around half of them on a walk around Aberdeen the day before.

Craig Frew offered his advice to owners of historic buildings in Aberdeen. Image: Craig Munro/DC Thomson

“Often we don’t pay very much attention to our homes,” he told the attendees, many of whom had come along to his previous talks.

“And if you take anything away from today, it’s to look up.”

Looking up in Aberdeen

Craig’s talk was organised by the Union Street Conservation Area Regeneration Scheme (Cars), which was set up to halt the physical decay of Aberdeen’s main thoroughfare.

A survey from earlier this year found that repairing damaged buildings on the Granite Mile could cost £11 million.

The expert said walking along Union Street highlighted the same issues as a walk on any other Scottish main street.

The most common problem is one that makes a significant impact but is “actually quite an easy thing to resolve”.

Algae and plant life on walls at Castlegate. Image: Craig Munro/DC Thomson

Blocked gutters and downpipes can cause water to dribble down a wall, leaving a green streak of algae.

It’s such a common sight in Aberdeen that it can be difficult to register.

But leaving the blockage intact for too long can lead to damp or rot problems inside the building.

In a slightly embarrassing moment for his hosts, Craig even showed an example from the exterior of Aberdeen Arts Centre – the very building he was talking inside.

Green evidence of a leaky downpipe on the wall of Aberdeen Arts Centre. Image: Craig Munro/DC Thomson

Granite to the rescue?

However, there was one reason to be cheerful for Aberdonians.

Among the pictures on the slideshow were countless examples of sandstone wear from different parts of Scotland: vast holes carved into chimney stacks over a matter of decades by rough winds and rain.

But the hardy rock of the Granite City has no such issues.

The detail on this sandstone carving in Arbroath has been lost over the years. Image: Paul Reid

Craig said: “If you’re a stonemason working in Aberdeen, you’re probably not going to be doing much stonework.

“You might be doing lots of pointing, rendering, harling, but actually you’re not going to be replacing much granite.

“Marischal College is a perfect example. You look at the quality of granite, and in its refurbished state it looks pretty much the same as it would have looked when it was built.

“It hasn’t changed at all.”

The walls of Marischal College were given a deep clean in 2010. Image: Kenny Elrick/DC Thomson

And when it comes to the nasty business of cleaning the green streaks from blocked pipes, Craig’s advice surprised many in the room.

“Just use warm water and a stiff brush,” he said.

Plant life can sink deep into more porous rocks like the sandstone of Edinburgh, Glasgow and Dundee, but can’t penetrate further than the surface of Aberdeen’s granite.

Igneous issues hard to ignore

Granite isn’t all sparkle, though, and its toughness does come with downsides.

All buildings need a certain amount of ‘breathability’, for example, to ensure moisture doesn’t build up inside.

Because granite doesn’t have that quality, it’s the mortar between the bricks that must serve that purpose.

Weeds grow out of the mortar on a Union Street building. Image: Kenny Elrick/DC Thomson

Craig told the story of a house in Aboyne that had a “waterfall” coming down the stairs every time it rained.

The culprit was loose pointing between the granite blocks on the chimney stack, which was letting in all the precipitation blown against it.

Like sandstone, mortar can wear away and host the roots of trees, bushes and ferns like the ones on the side of Union Street buildings – making it extra fiddly to sort.

According to the Savills survey, three buildings on the street are in “significant disrepair”, while work on 63 would bring “significant benefits” to the area’s overall appearance.

Craig’s top tips for looking after your historic building

  • If you’re going to have a look at your home, do it in really heavy rain. You’ll see what’s working and what’s not
  • Remember to clear your gutters regularly. It’s a simple solution that can prevent some very serious problems
  • Carry out regular checks around the property. You can catch minor issues before they become disasters
  • Ensure your building is wind and watertight. It’s the best way to ensure future generations will be able to enjoy it too

Who owns Union Street? Here’s how finding the answer could bring the tired thoroughfare back to life