Case Study:
Flat Roof Replacement

Project Overview

The roof of a mill building was leaking and a recent EPC had found the building did not meet the minimum energy rating in accordance with the Minimum Energy Efficiency Standards (MEES).  Dabinett specified the works, tendered the project and contract administered and oversaw the project.

Project Requirement

The existing roof to the building comprised of a timber roof, with timber joists, sterling board/OSB and a single layer of felt.  The roof had begun to allow water into the building, which was causing disruption to tenants.

The single felt layer was poorly adhered to the timber roof deck, the laps of the felt were poor and the felt deteriorating with age.  As a result at the joints water was ingressing and beginning to cause the timber roof deck to deteriorate.

If left without any works then the issue of water ingress would continue and the roof structure would deteriorate.  Whilst patch repairs had been undertaken for several years the problems had become more regular and the risk of significant costly damage was likely.

A new roof was required to give a long life and to improve the thermal performance.

The existing roof contained no insulation; there could have been scope to omit insulation to the new roof to save money.  However, this would have created a cold roof form and would have required the void to be ventilated to guard against condensation.  We have acted, on several occasions, where roofs have deteriorated due to a lack of ventilation where new roofs have been installed without due care.

Project Outcome

Works were competitively tendered to four contractors, typically we find a difference of 20-30% between projects which are competitively tendered compared to those where a single contractor is appointed directly.  The specification allows for a level playing field, where the quality of the finished project is known from the outset.

In order to save money the existing roof was retained and overboarded.   This required site visits to inspect the condition of the existing roof deck and where there was damage repairs carried out.

The system specified was a three layer built up felt system with 120mm of insulation.  At the perimeters new upstands were formed, with chamfers to improve durability.  The roof had an existing fall to a uPVC gutter which was in good repair.

The project benefited from excellent weather which allowed for the work to progress without delay, the roofing works being carried out in a little over two weeks.

The project delivered a roof with a 20 year guarantee, fully insulated and meeting the minimum energy efficiency requirements and competitively tendered.

At Dabinett we have decades of experience in detailed design and specification of roofs, providing independent advice and working to achieve the best value for the client.  For further information do contact us and look at our project management and repair and maintenance pages.

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