Single-ply roofing has a significant presence in the commercial roofing industry and can offer advantages in many applications. However, recovering an existing metal roof with a single-ply membrane requires careful evaluation of the building, roof structure, drainage, attachment method, and existing roof conditions.
A system that works well on one type of commercial building may not automatically be appropriate for a pre-engineered metal building. Before any recover system is installed, the existing structure and roof assembly should be evaluated to make sure the proposed system is compatible with the building.
Why the Existing Metal Roof and Structure Matter
Pre-engineered metal buildings are designed as complete structural systems, with components such as purlins, framing, metal panels, and drainage paths working together.
When a new roofing assembly is installed over an existing metal roof, the contractor should consider how the added system may affect drainage, attachment, loading, movement, penetrations, and other conditions specific to the building.
Proper drainage remains essential to the performance of both the roofing system and the building. Any recover system should be designed and installed so that water is directed to appropriate drainage points without creating unintended ponding or other conditions that could contribute to roof deterioration.
Roof Coatings as a Restoration Option
Finding the right roofing solution for a pre-engineered metal building is key to its long-term performance. When the existing metal roof is structurally sound and otherwise suitable for restoration, a roof coating system may provide an alternative to a complete tear-off or recover system.
Some potential benefits of a properly selected and installed roof coating include the following.
Reflective performance: White and other reflective roof coatings can reduce the amount of solar heat absorbed by the roof. The effect on overall building energy use will depend on factors such as climate, insulation, building use, HVAC efficiency, and the specific coating system.
Improved appearance: A coating system can provide a more uniform finished appearance while adding a protective surface to a properly prepared roof.
Extended useful life: When an existing roof is a suitable candidate for restoration, a properly installed coating system may extend its useful life. The actual service life depends on the existing roof condition, preparation, coating type, installation, weather exposure, drainage, and maintenance.
Recoating options: A roof that has been coated and properly maintained may be eligible for recoating later. Whether recoating is appropriate, and what preparation or reinforcement is required, depends on the condition of the existing coating system and manufacturer specifications.
Reduced tear-off: In suitable restoration projects, coatings can often be applied over the existing roof after necessary repairs and preparation. This can reduce tear-off, disposal, and disruption compared with a complete roof replacement.
Potential cost savings: When a roof is suitable for restoration, coating may cost less than full replacement because less existing material may need to be removed and replaced. Actual project costs depend on roof condition, preparation, repairs, materials, labor, and project requirements.
Maintaining the existing roof profile: A coating follows the general profile of the existing metal roof rather than creating an entirely new membrane assembly over it. However, drainage conditions should still be evaluated and corrected where necessary before restoration.
Determining the Best Option for Your Roof
Finding the right roofing solution for your pre-engineered metal structure requires looking at the entire roof and building rather than choosing a system based on one factor alone. A commercial roofing contractor should evaluate the existing metal panels, seams, fasteners, flashing, drainage, moisture conditions, structural concerns, and any previous repairs before recommending a solution.
Roof coatings are not appropriate for every metal roof. Wet insulation, severe corrosion, structural deterioration, drainage problems, extensive damage, or other conditions may need to be corrected first or may make another roofing approach more appropriate.
Choice Roof Contractor Group members are independent commercial roofing contractors that perform their own inspections, provide their own recommendations to customers, and perform their own roofing work.
A member can evaluate the existing roof and discuss repair, restoration, coating, recover, or replacement options based on the conditions present.
