Simon Robertson, Technical Team Manager for Sika Liquid Plastics discusses specification considerations for metal roof remediation projects
Metal roofs offer an excellent roofing option for many environments. However, when corrosion occurs, it must be addressed with an appropriate metal roofing refurbishment system.
For many roofs in the early stages of corrosion, a cut-edge corrosion metal roofing system, such as Sika Pro-Tecta CE, may be sufficient to treat the affected areas.
Often, however, a full waterproofing system, such as Sika Pro-Tecta WP is required. This combines the innovative Sika Joint Tape SA to reinforce laps and fixings, with a choice of Sika Liquid Plastics’ proven cold-applied liquid roofing membranes; Sikalastic 625 or low-odour Decothane Ultra.
Corrosion Risk
The cut edge of the metal sheets used to construct metal roofs is the area most vulnerable to corrosion and this is sprayed with a protective layer to seal it. However, this protective layer can peel away, exposing the untreated metal edge to moisture and the risk of corrosion.
If surface rust can be manually removed and the integrity of the metal sheet beneath has not been compromised a cut edge corrosion treatment is usually sufficient. Following treatment with a suitable system, regular inspections will help ensure any future corrosion risk is managed proactively.
If the corrosion has penetrated the metal sheets or is likely to be compromise the integrity of the metal roof, a full waterproofing system will be necessary.
Specification Considerations
It is important to work with a supply chain partner that will carry out a full condition survey of the roof and offer expert advice on the most appropriate metal roof system. This should be aligned to the physical properties and current condition of the roof, geographical conditions, the function of the building, the planned service life for the building and the level of guarantee required.
Different metal roof structures require varying approaches to cut edge corrosion and waterproofing treatments so the survey must identify the type of metal roof and consider its fundamental properties.
Exposure to a range of different conditions, coatings previously applied as part of refurbishment schemes and surface contamination can all affect adhesion of the metal roofing system. Consequently, adhesion testing should be carried out as part of the condition survey to ensure that the proposed system will adhere effectively to the roof and deliver its intended service life.
The survey should also consider the internal roof structure and the activity within the building. This is because condensation due to moisture inside the building could become trapped within the roof structure if an inappropriate system or installation technique is specified.
Inspection of the fixings should form and integral part of the condition survey too, because the fixings need to be in sufficiently good condition to fix the roof to the structure and avoid wind-uplift. Pull-out test results will indicate whether fixings need to be replaced, reinforced with a full waterproofing system or can be left untouched as part of a cut edge corrosion treatment.
Proactive Maintenance
Regardless of the type of metal roof or the business case for refurbishment, the use of a specialist cut edge corrosion or metal roof waterproofing system from Sika Liquid Plastics’ Sika Pro-Tecta range will extend the roof’s service life as part of a proactive maintenance regime.
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