Do You Have a Defective Slate Roof?

Do You Have a Defective Slate Roof?

Thursday 25th July 2019

Looking at a defective slate roof in Pinner

We at Tayross Associates Chartered Building Surveyors were recently asked to inspect a newly completed slate covered roof in London.

We visited site when the scaffold was still erected and we noticed that there were serious issues with the construction structure and slate covering of the roof.

Starting with the internal timber structure, we noted that straps had not been properly located at 2m centres to hold on the wall-plates for the main roof.

We also noted that many of the fixings connecting structural members had not been properly screwed. Fixings were missing in areas and also brackets missing to composite beams.

We also noted in areas that the felt had not been properly supported at the end of the roofs/verge areas.

Most importantly, we noted that the slates to the roof had been laid wrongly with no gap being left between adjacent tiles, which should have been in the range of 3-5mm. Also, slates were not laid straight and most likely would crack in the long term.

We also noticed lots of issues with the flashing details, such as not enough movement being allowed in the lead valleys and improper cleating details likely to cause flooding.

It occurs to me that lots of roofs are built without any proper consideration to the detailing required, ultimately leading to long-term issues for the building owner. Whereas proper consideration needs to be given to the longevity/installation/ventilation and maintenance of roofs to ensure they continue to deliver in the long term.


This article was written by Carl O'Boyle BSc MRICS FCIOB MFPWS. Carl is a full professional member of the Royal Institution of Chartered Surveyors, a member of the Faculty of Party Wall Surveyors and a Fellow of the Chartered Institute of Building for which he currently sits on the CIOB professional conduct committee and adjudications panel.

If you have a defective slate roof in London then please call us at our office on 0208 426 1448.