Advanced Non-Vented RetroFit System is intended to be installed over existing roof structure.

• Dimond PIR insulation board is available in a range of thicknesses to achieve thermal insulation R values between R2.0 and R7.0.
• The control of moisture and condensation is achieved with the Dimond Vapour Barrier control layer on the existing roof sheet and a layer of breathable Dimond Underlay covering the PIR insulation ensuring no build-up of moisture within the system.
• The Dimond Top Sheet covering can be selected from Dimond's range of long-run roof profiles and coated metal materials to match performance to the environment. This includes the scope to use site-rolled, clip fastened decking profiles to achieve a continuous roof covering sheet in lengths up to 90m from ridge to gutter.
• Multi-layer skylights can be incorporated to achieve the required balance between natural lighting levels and thermal insulation.

Adding a new metal roof over an existing one increases the overall weight on the building’s structure. The load-bearing capacity of the existing structure must be assessed to ensure it can support the additional weight without compromising safety. 

Over time, the original roof structure may have weakened due to weathering, corrosion, or other factors. This could make it unsuitable for supporting an additional roof layer without reinforcement. Roof pitch meets the minimum required pitch for the selected top sheet product

• B1 Structure: Performance clauses B1.3.1, B1.3.2, B1.3.3 (a) (b) (c) (g) (h), B1.3.4 (b) (d): Dimond long run roofing and wall cladding has been tested in accordance with the NZMRM code of practice Section 17.1.
• B2 Durability: Performance clauses B2.3.1(b): Dimond long run roofing and wall cladding conforms to AS/NZS 2728 as stated in NZMRM code of practice section 17.4.
• C3 Fire affecting areas beyond the fire source: Buildings C3.4(a): Testing has been carried out material suppliers in accordance with the relevant standards stated in C3.4(a).
• E2 External moisture: Performance E2.3.1, E2.3.2: Is suitable for installation in accordance with Acceptable Solution E2/ AS1, NZMRM code of practice, RANZ installation guides and Dimond installation Details/Technical Manual. Installation details provided by other parties such as architects and engineers may also be suitable.
• F2 Hazardous building materials: Performance F2.3.1: The quantities solid particles emitted by Dimond long run roofing and cladding, shall not give rise to harmful concentrations at the surface of the material where the material is exposed, or in the atmosphere.
• G6 Airborne and Impact Sound: Performance clause G6.3. Specific design required using Dimond technical literature and Advanced Vented System details to reasonably meet the requires of NZBC clause G6.3.
• H1 Energy Efficiency: Performance clause H1.3.1 (a). Contributes to meeting this requirement.

Improved Health & Safety The existing steel roof sheets remain in position providing the contractor with a platform to work off. This significantly simplifies the fall protection plan required. Energy Efficiency Over-roofing with the Dimond Non-Vented Retrofit System creates an engineered, structurally defined cavity between the old and new roof coverings. When insulated this cavity dramatically improves the overall energy efficiency of the entire building and controls condensation issues with vapour control layer at the base. Acoustic performance Creation of an insulated cavity dramatically improves the acoustic performance of a roof, Additional Acoustic layers can be added to Advanced Non-Vented RetroFit. Acoustic performance is imperative when a conducive environment is required in places of learning, workspaces or the like.