Exterior mineral wool boards: permitted support, fit, condition and cladding handover
A rental-building elevation has exposed mineral wool boards with uneven faces after a wet week. The cladding crew is booked, but the team has not assessed the board condition or confirmed the attachment and interface checks.
Exterior boards need a receiving check that covers both their condition and how they are supported. ROCKWOOL’s residential guidance describes its Comfortboard installation and distinguishes permanent support from temporary attachment. Use the actual product, framing and cladding detail on this job. A board that looks neatly pressed onto the wall is not evidence that its fastening, hidden fit or exposure condition has been accepted.
Check a complete first area, then follow the same received method
- Confirm the board and ready wall. Match the delivered grade and thickness with the specified exterior layer. Check the receiving membrane, openings, flashing and required trade reviews before boards hide them. Arrange suitable access and handling for the location. Keep a damaged or unfinished substrate area visible for correction rather than using the insulation layer to conceal a rough handover.
- Connect support with the actual cladding system. Identify the permitted temporary and permanent attachment, fasteners or retaining arrangement for the end use. Locate clips, strapping and backing with the responsible team. Do not make an adhesive used to hold a trial board the assumed permanent fixing or borrow a residential fastener count for a different height and cladding load. Refer gaps in the attachment detail before repeating the first bay.
- Fit the boards without losing interface details. Follow the specified course, joint and layer arrangement. Check cut pieces at clips, openings and penetrations, including hidden edges and required continuity. Avoid using a compressed scrap to disguise an unresolved clearance or forcing a board into a connection its detail does not permit. Confirm drainage and separate control-layer work remain functional under their own requirements.
- Assess exposure and receive the elevation. Record wetting, damage, looseness or displaced boards and obtain the required material response. Do not assume every wet board is ruined, or that water-repellent material makes every exposed installation acceptable. Protect remaining work using the actual product and site requirements. Retain the located fit, support and condition checks, the receiving review and any area still held before cladding closes access.
Common mistakes
- Using temporary adhesive as unreviewed permanent support.
- Compressing scraps to hide interface problems.
- Assuming water-repellent means every wet condition is acceptable.
- Covering an elevation before its held areas are resolved.
Checklist
Before the cladding handover, retain
- Actual board grade, thickness and receiving-wall status.
- Permitted temporary and permanent support.
- Located joints, cuts and connected control layers.
- Exposure assessment and received material response.
- Checked areas, review evidence and remaining holds.
Check your understanding
The boards look flat when the cladding crew presses on them. Does that complete the check?
