Corrosion Protection Guarantees - Metal Roofs & Roof Coatings!

Like most guarantees or warranties, the 'devil is in the detail!'

In the world of roof refurbishment or building restoration, there is a vast array of solutions that satisfy the requirements to extend the life of the building envelope without having to demolish and rebuild.

This article is focused on the options of metal roofing solutions vs roof coatings.

With this in mind, let's consider what SANS 10400-L: 2020 Clause 4.2.1.2 States:

"Products used in roof coverings and waterproofing systems shall preserve their properties satisfactorily when used in accordance with the manufacturer’s recommendations and with normal maintenance specified by the manufacturer for at least 15 years:

NOTE (from 10400B 4.2.1.1) The design working life of a building other than a category 1 building shall be not less than 30 years in respect of the structural system and non-accessible components, and 15 years for repairable or replaceable components and materials, such as claddings, roofing materials, exterior trims, and integrated components, such as windows and doors."

Summary of the intent of the SANS clauses:

1. Design working life of the building NOT to be less than 30 years – Structural & Non- Accessible Components.
2. Design working life of repairable & replaceable components NOT to be less than 15 years.
3. Preservation of roof coverings and waterproofing properties for at least 15 years with normal maintenance.

Questions to consider:

• What is the implication of a 10-year metal roof, waterproofing or roof coating guarantee?
• Are building owners maintaining their roofs with recorded maintenance?
• If a 10-year guarantee is accepted, then as it is deemed to be replaceable, is the cost of replacement twice factored into the cost of the project? i.e. twice to get to the 30 years of design working life.
• Does a 5-year system warranty from a roof sheet manufacturer satisfy the requirements of the above SANS clauses?

Components that make up a Metal Roof Guarantee

There are a number of components that make up a metal roof guarantee, as follows:

1. Corrosion Protection Guarantee - Issued by the Coil Manufacturer subject to terms & conditions including maintenance of washed and unwashed areas. Length of term typically, 0 to 20 years, is determined by the material and its environment and corrosion zone.
2. Roof System Warranty - Issued by the Roof Sheeting Manufacturer subject to terms & conditions including maintenance. Length of term, typically 5 years.
3. Workmanship warranty - Issued by the Roofing Contractor. The length of the term is typically between 2 and 7 years.

The Maintenance clause of a Metal Roof

Just like a car, regular cleaning and maintenance is required to keep the validity of the service plan, so it is for a metal roof.

There are two categories of areas on a building envelope: washed and unwashed.

Washed areas are typically washed by natural rainfall, however, if there is no rainfall, the metal roof will need to be cleaned as per the manufacturer's recommendations.

• Coastal or High Corrosion Zones - Washing or rainfall typically every 3 months.
• Inland Zones - Washing or rainfall typically every 6 months.

Unwashed areas are typically areas of a building envelope that are not impacted by rainfall and need to be cleaned according to the recommendation of the material supplier.

Without recorded maintenance, the validity of the corrosion protection guarantee can be brought into question, and the guarantee can be invalidated.

Components that make up a Roof Coating Guarantee

There are a number of components that make up a roof coating guarantee, as follows:

1. Corrosion Protection Guarantee - Issued by the Coating Manufacturer subject to terms & conditions, including substrate preparation & maintenance. Length of term typically, 0 to 20 years, is determined by the material and its environment and corrosion zone.
2. Workmanship warranty - Issued by the Roof Coating Contractor. The length of the term is typically between 2 and 10 years.

The Maintenance clause of a Roof Coating

The maintenance regime of a roof coating system is very different from that of a metal roof. To satisfy recorded maintenance, an annual inspection is to be undertaken, and any mechanical damage is touched up accordingly.

Whilst it is seen the operational cost benefit of the maintenance of a roof coating system vs a metal roof system, several key considerations should be built into any roof coating guarantee:

• Adhesion of the coating onto the substrate - A guarantee of adhesion can only be provided if the substrate is prepared as per ISO 8501-1: 2007 St2 preparation or better. Many roof coating guarantees do NOT include adhesion.
• Roof coating guarantees are corrosion protection and, in general, do NOT guarantee waterproofing guarantees. Seals, tapes, fasteners and flashings provide a waterproof seal. The roof coating guarantee should include a waterproofing seal for the same term.
• ISO 12944 clearly states what roof coating products should be used at what thicknesses in the given corrosion zone. All roof coating guarantees should reflect this.

According to ISO 12944, acrylic roof coating systems should not be used for long-term performance in a C4 - C5 corrosion zone.

Summary of Guarantees

In general, metal roof and roof coating guarantees are similar in that the long-term is associated with the guarantee regarding corrosion protection.

The major benefit of roof coating from a guarantee perspective is significantly less maintenance to maintain the validity of the product guarantee.

Choosing the correct installer or applicator will significantly impact the longevity of the building envelope solutions.

How to choose the correct installer or applicator is more than a manufacturer's recommendation. Confidence in the contractor's ability to deliver to a high quality will reflect in the Contractors Warranty and should include the following:

1. The term of the workmanship should mirror the term of corrosion protection.
2. The waterproofing seal, including flashings, seals, fasteners and closures, should reflect the same length of term as the corrosion protection.
3. The recorded maintenance scheme should be included in the system warranty.
4. The operational life of the building envelope solution, supported by evidence in the same corrosion zone, should be woven into the system warranty.

Contact Us:

E: [email protected] or [email protected]

W: https://mrc-group.co.za or https://mrcsolutions.co.za

T: +27 (0)86 167 2476

Keep up to date and follow us:

Click on ONE or ALL: LinkedIn Company | Facebook | Pinterest

Services: Inspection |Design | Supply | Install | Maintain

Offices: Johannesburg | Durban | Cape Town | UK - London

#buildingenvelope #buildingrefurbishment #construction #buildingdesign #remedialsolutions #buildingrestoration #technicalspecifications #turnkeyconstruction