The green roof of Smailholm Tower, Scotland.

This is an interesting twist on a 100% natural green roof by using a thick bed of clay and turf...

 

   
 

 

The Pringles, who built the tower around 1450, were a prominent Border family and land owners. The tower is a 20m (65ft) fortified house with walls 2.5m (9 ft) thick. In its shadow lie the ruined foundations of an outer hall and kitchen block, discovered during excavations in 1979. The tower house was the main residence for the laird. The ground-floor has cellars, the first-floor a hall and the second-floor a bedchamber with additional rooms in the roof arch; a stone catenary.
 
   

In 2011 the tower suffered from severe damp in the roof. It was fixed with a soft cap of 4 tonnes of clay and living plants, a technique called 'soft capping' [ discussion], which completely cured the leaking roof and gave a 60% reduction in rainwater running onto the walls.

 
 

Watch an aerial tour of the tower and the hills around it in the video above
 

 
           

The plants were a special mix of pre-grown Sedum alba and Sedum acre, wild Festuca rubra grass and plantago lanceolata (plantain, to help the tower recover from its cold) laid at angles of up to 75 degrees. You can find out more about Smailholm Tower on Historic Scotland's website.

You can find out more about clay caps in this online publication from page 50 of the research report: Soft capping in Scotland: the content and potential of using plants to protect masonry (volume 1)

 

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