Electronic Leak Detection of a Supermarket Roof, Surrey

Project Overview

Thornton Consulting was instructed to carry out an electronic leak detection survey to assess the current performance of an aged PVC waterproofing system on a supermarket roof in Surrey. The existing single-ply PVC membrane was approximately 12 years old and, although there were no major visible signs of widespread failure, the client required a detailed assessment to confirm whether the waterproofing remained watertight and to identify any localised breaches that could present a risk to the building below if not addressed.

The Importance of Roof Integrity

A roof forms a critical part of any building envelope, but it is particularly important in commercial buildings such as supermarkets to maintain a watertight roof to protect stock, mechanical and electrical services and customer spaces. Even relatively small breaches in a waterproofing system can allow moisture to enter the roof build-up, potentially leading to internal leaks, insulation saturation, disruption to operations and increased repair costs if left unresolved.

Why Electronic Leak Detection Was Required

Given the age of the PVC waterproofing, the client required more than a general visual inspection. While visual roof inspections remain an important part of condition assessment, they can be limited where defects are small, located around complex details, or due to poorly bonded laps.

Electronic leak detection was therefore selected as a suitable method for testing the integrity of the waterproofing and helping to locate any points of water ingress with greater accuracy.

Survey Methodology

The survey was undertaken across the accessible roof areas using electronic leak detection techniques appropriate to the roof construction and membrane type. The purpose of the testing was to identify breaches in the waterproofing layer, including punctures, splits, failed laps, damage around details, or other breaches that could compromise the performance of the roof.

Survey Findings

During the inspection, the roof was systematically tested and any areas of concern were marked on the roof surface. In total, ten small breaches were indicated in the waterproofing from the test which were also marked on a plan of the roof and included in the report of findings to assist the client and their roofing contractor with targeted remedial works.

The Benefits of Early Detection

The survey provided the client with a clearer understanding of the current condition of the PVC waterproofing system. It helped establish whether the roof was continuing to perform as intended and highlighted any localised defects requiring attention. Although the breaches were minor, by identifying them at an early stage, the client was able to reduce the risk of future water ingress.

Supporting Planned Roof Maintenance

Regular roof maintenance is essential to maximising the service life of any waterproofing system. Roofs are exposed to weathering, temperature changes, foot traffic, plant maintenance, wind-blown debris and general ageing, all of which can affect performance over time.

A planned maintenance regime should include routine visual inspections, cleaning of outlets and gutters, removal of debris, review of roof details, and periodic electronic leak detection. Incorporating electronic leak detection into maintenance planning provides a more detailed assessment of waterproofing integrity and can help identify defects before they develop into active leaks.

This proactive approach can reduce emergency call-outs, limit disruption to building users, protect the building fabric and support a more cost-effective programme of long-term planned roof maintenance.

Outcome

For this supermarket in Surrey, electronic leak detection provided a valuable and non-disruptive method of assessing the performance of the existing PVC waterproofing. The findings enabled the client to address defects in a targeted manner and supported a practical maintenance strategy which could extend the serviceable life of the roof.

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