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St, Eunan's Cathedral Case-study

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St. Eunan's Cathedral or the Cathedral of St Eunan and St. Columba as it is also know is a Roman Catholic Cathedral located in the parish of Conwal and Leck, Letterkenny, Co. Donegal. It was built in the years 1890 - 1900 in Victorian Neo-Gothic style on a site overlooking the town.

In May 2010 we were contacted by local Architect Denis McGinley and asked if we could carry out an inspection of the lead gutters and flat roof areas throughout the Cathedral as they had been leaking for many years.

During our inspection we discovered how poor the original design and workmanship had been.The gutters did not have adequate falls and in most cases were installed level. There were widespread fatigue cracks which were a result of incorrect thickness of lead sheet for the distance between drips. The drip heights were insufficient with some drips only 30mm. Catch pits were of insufficient size with no provision made for overflows and risked surcharging in storm conditions.
The absence of sacrificial flashings had resulted in circular corrosion at the drip-off points and had actually penetrated in some areas. Cover flashings were over-long, inadequately fixed and clipped with insufficient side laps.

We also discovered that some of the lead gutters had been renewed in the past twenty years, but unfortunately the original design issues were not addressed and this lead sheet had also failed prematurely.
To meet the current code of practice for leadwork BS6915 a total redesign of the gutter system throughout the Cathedral would be required. Drip height would need to be increased to 75mm.
1 in 80 falls would be required and therefore the width of the gutters increased. Catch pits would need to be re-designed and 80mm over-flows installed. Because of the increased falls and drip height, new chasing for the cover flashings would be needed. To prevent corrosion from acidic run-off, sacrificial flashings will need to be installed.

M&I lead won the order and began work on the Cathedral in August 2010. A temporary work-shop was set up on site where the lead bays were fabricated and then lifted into position by crane. The project was completed in 16 weeks with some sixty tones of code 9, 10 and 11 rolled lead sheet used. The project was registered under the LCA guarantee scheme, inspected on three separate occasions by a member of the LCA Council and a certificate of guarantee issued to the client.