In many of the UK’s cities space is at a premium and in particular parking. It is, therefore, not uncommon to find parking spaces or loading bays located on the roofs of commercial buildings such as offices or shopping centres. Our client, a property management company, had been experiencing a leak beneath a roof car park construction such as this and procured our Building Leak Detection Service to accurately locate the source of the water ingress.
The building consisted of a concrete frame with brick facades with the roof space predominantly used for parking. The roof comprised mastic asphalt waterproofing with rolled asphalt (Tarmac) finishes.
In this situation the mastic asphalt is the waterproofing layer and the rolled asphalt provides a wear course. Since rolled asphalt is porous it is possible to undertake an electronic test of the waterproofing layer beneath to give an indication of any potential breaches. As the waterproofing layer is not exposed any breaches it cannot be inspected but it allows further tests to be focused in the right place. (It should be noted that testing in such circumstances provides an indication of potential breaches only and is not as accurate as testing an exposed waterproofing layer as earthed structural items are not visible and cannot be excluded from the test.)
A number of readings were obtained from the test and where these corresponded with internal leaks localised water tests could be undertaken, incorporating trace dyes where necessary. All tests undertaken resulted in water ingress internally, confirming the source of the leaks to be associated with the asphalt waterproofing beneath. Results such as this provide invaluable information for our clients, enabling further works, such as opening up of the structure or removal of finishes, to be target effectively, often without the need for extensive remedial works.
On a return visit, when the waterproofing had been exposed, a further electronic test was undertaken. Numerous splits were indicated in the asphalt waterproofing and repairs undertaken accordingly by the clients Asphalt Contractor.
This is a useful technique for locating breaches in membranes but can also be used to confirm the integrity of the waterproofing systems, allowing testing to be undertaken to other structural items which could equally be the source of a leak.