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Thermakraft CoverTek 401 — Roof & Wall Underlay

Covertek 401 is an affordable lightweight roof and wall underlay designed to keep water out and allow moisture to escape. Covertek 401 is a more affordable option if the project does not require a fire-retardant underlay. It is stable, shrink resistant, easy to handle and easy to install.

Key Features
  • Tear resistant and strong
  • Affordable, lightweight synthetic roof and wall underlay
  • BRANZ Appraised
Scope of Use

Roof Application:

  • Suitable with masonry tile, metal tile and profiled metal roof cladding.
  • Suitable for timber or steel framed buildings.
  • Self-supporting in roof pitch application greater than or equal a 10 degrees (Refer to installation guide)
  • Will provide temporary weather protection during construction (maximum 7 days), same day coverage recommended.
  • Covertek 401 may be installed during adverse conditions (rain/snow) without affecting durability or performance. 
  • Suitable for use under dark coloured roofs. 

Wall Application:

  • Can be used with timber and steel framing, either direct or in conjunction with an 18mm minimum drained cavity.
  • Suitable with absorbent (e.g. timber, brick or fibre cement) or non-absorbent wall claddings (e.g. metal or plastic).
  • Suitable with masonry veneer in accordance with NZBC Acceptable Solution E2/AS1 or NASH Building Envelope Solutions.
  • Is suitable for use in Wind Zones of NZS 3604 up to and including ‘Very High’ when used as a standalone flexible underlay, and ‘Extra High’ when used as a flexible underlay over a rigid wall underlay.
  • Is suitable as an air barrier in unlined wall spaces.
  • Will provide some temporary weather protection during construction (maximum 60 days for wall application).

Refer BRANZ Appraisal No 943 (2021) for full details

Statement of Building Code Compliance

Covertek 401 Roof Underlay, if used, designed, installed and maintained in accordance with the statements and conditions of the BRANZ Appraisal, will meet, or contribute to meeting the following provisions of the NZBC:

  • Clause B2 DURABILITY: Performance B2.3.1 (a), not less than 50 years, B2.3.1 (b), 15 years and B2.3.2. Covertek 401 Roof Underlay meets these requirements. 
  • Clause E2 EXTERNAL MOISTURE: Performance E2.3.2. When used as part of the roof cladding system, Covertek 401 Roof Underlay will contribute to meeting this requirement. 
  • Clause F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1. Covertek 401 Roof Underlay meets this requirement and will not present a health hazard to people
Other Performance Attributes


Roof Application:
Designed for use as a roof underlay within the following scope:

  • The scope limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1,  with regards to building height and floor plan area.
  • Situated in NZS3604 Wind Zones up to, and including, 'Extra High' (ROOF ONLY).

Wall Application

  • Can be used as a wall underlay within the scope limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1, with regards to building height and floor plan area.
  • Or within the scope limitations of NASH Building Envelope Solutions, Paragraph 1.1 for steel framed buildings.

Refer BRANZ Appraisal No 943 (2021) for full details.

BRANZ Appraised
BRANZ Appraised
Data Sheet

Issue 8, Jun 2023

Quick Reference Guide


Thermakraft on Masterspec
BRANZ Appraisal 943

No.943 [2021] 25 Oct 2023

Installation and Operation

Issue 4, Jun 2023

Kingspan Thermakraft Warranty Statement

Issue 3, Aug 2022

Kingspan are New Zealand’s leading provider of high-performance insulation products and complementary Thermakraft range of premium wall & roof underlay products, flashings tapes & underlay mesh.

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