What can we do about the sagging roof?

John Conlin / 25 October 2016

A reader asks chartered surveyor John Conlin how to repair a sagging roof.


The roof of our Victorian terrace cottage has always sagged along the ridge but lately seems to be getting worse. Is there any way to repair it?


It sounds as if you have what is called a ‘banana roof’. In the 1950s the Government gave grants to replace old slates with interlocking concrete tiles. 

Unscrupulous roofers retiled vast numbers without reinforcing the rafters to carry the extra weight of concrete tiles. This may have happened to your house. 

The sag cannot be cured but a competent carpenter can stabilise it by installing timber purlins and struts within the loft. 

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