Description

Thermakraft Covertek 403 Roof and Wall Underlay is a non self-supporting underlay for use in internally lined areas under roof and wall claddings.

Thermakraft Covertek 403 Roof and Wall Underlay is a synthetic, fire retardant, absorbent, breathable building underlay for use under roof and wall claddings.

The product consists of a micro-porous water-resistant film ultrasonically bonded between two layers of non-woven spunbonded polyolefin.

Thermakraft Covertek 403 Roof and Wall Underlay is coloured white on the top and bottom faces with green Covertek 403 branding on the exposed face.

Scope

1. Thermakraft Covertek 403 Roof and Wall Underlay use is certified

• a. as non-self-supporting roof underlay on buildings:
  • i. within the scope limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1 with regards to building height and floor plan area; and,
  • ii. with
    • 1. masonry tile roof cladding; or,
    • 2. with metal tile roof cladding or
    • 3. profiled metal roof cladding; and,
  • iii. situated in NZS 3604-2011 and NASH Standard Part 2:2019 light steel framed buildings Wind Zones up to, and including Extra High.
  • iv. with a roof pitch of 10° and above
• b. as flexible wall underlay for buildings:
  • i. within the scope limitations of
    • 1. NZBC Acceptable Solution E2/AS1, Paragraph 1.1 for timber-framed buildings; or,
    • 2. NASH Building Envelope Solutions: 2019-Light Steel Framed Buildings, Paragraph 1.1 for steel-framed buildings; and,
  • ii. with absorbent or non-absorbent wall claddings either direct fixed or installed over an 18 mm minimum drained cavity; or,
  • iii. with masonry veneer in accordance with
    • 1. NZBC Acceptable Solution E2/AS1 for timber-framed buildings or
    • 2. NASH Building Envelope Solutions for steel-framed buildings; and,
  • iv. situated in
    • 1. NZS 3604 and NASH Standard Part 2:2019 - light steel framed buildings Wind Zones up to, and including, Very High; or,
    • 2. NZS 3604 and NASH Standard Part 2:2019 - light steel framed buildings up to, and including, Extra High when used over a rigid wall underlay in accordance with NZBC Acceptable Solution E2/AS1 or NASH Building Envelope Solutions Paragraph 9.1.7.2.

2. Thermakraft Covertek 403 Roof and Wall Underlay shall be used and installed in accordance with all relevant technical information relating to the products use contained within Kingspan- Product data Sheet - Thermakraft Covertek 403 Non self-supporting Roof and wall underlay (Issue 8.0, May 2025) and Kingspan- Installation Guide - Thermakraft Covertek 403 Non self-supporting Roof and wall underlay (Issue 5.0, May 2025) and the BRANZ Appraisal No. 917 (2025) Amended 1 July 2025 Thermakraft Covertek 403 Roof and Wall Underlay (refer to www.branz.co.nz).

3. Thermakraft Covertek 403 Roof and Wall Underlay must not be exposed to the weather or ultraviolet light before being covered for a total of more than:

• a. 7 days when used as a roof underlay
• b. 42 days when used as a wall underlay.

4. Thermakraft Covertek 403 Roof and Wall Underlay must not be used in any unlined applications (except in spaces without any permanent openings to allow entry of natural light e.g. attic spaces at gable ends), including but not limited to sheds, warehouses, garages, canopies, soffits and lean-to designs.

5. Thermakraft Covertek 403 Roof and Wall Underlay must be separated or protected from heat sources such as fireplaces, heating appliances, flues and chimneys. 

6. When used as a roof underlay, Thermakraft Covertek 403 Roof and Wall Underlay can be installed vertically or horizontally and must span no greater than 300 mm in one direction between framing supports without additional underlay support. All underlay supports must be corrosion resistant material.

7. When used as a wall underlay, in cavity installations where the cavity battens are installed at greater than 450 mm centres, Thermakraft Covertek 403 Roof and Wall Underlay must be restrained between the battens to prevent the underlay bulging into the cavity space when bulk insulation is installed in the wall frame cavity.