Thermakraft Roof Underlays for Skillion Roofs

Previously commonly used for extensions and sheds, skillion roof designs are now regularly seen in new subdivisions and house designs. At the same time, the performance of modern buildings has also increased, with improvements to glazing, window and door design, and insulation ratings. Together these elements make for greater airtightness in modern homes.

With all these changes, one of the things that hasn’t yet been addressed fully is the provision for ventilation and moisture movement — especially in the roof space. Skillion roof designs in particular have a greater risk of condensation due to low air volumes and restricted air movement. If the roof design and roof system does not allow for ventilation of any uncontrolled moisture, this could not only be detrimental to the structure, but also to the occupants.

When getting involved in skillion roof projects, Thermakraft asks:

Has ventilation being considered and have provisions being made to provide ventilation to the roof space?
Does extra ventilation need to be considered?

Roof underlays cannot be considered in isolation when allowing for ventilation, and will only work in conjunction with good building design. A Skillion roof, teamed with a good building design and the correct installation of a high quality roof underlay will mean all the products can work together.

When specifying underlays for skillion roofs, Thermakraft's technical team works with designers to select an underlay suitable for the project. Options which may be suitable for skillion roof designs include:

Covertek 407: A fire-retardant, absorbent and breathable synthetic self-supporting roof underlay
Vapor-Shield 101: A polythene underlay suitable for roof construction where condensation and moisture control is required
Thermabar 344 and 346: Fire retardant foil insulation that can be used as a vapour control layer
Thermakraft 215: Highly water vapour permeable bituminous underlays

Talk to Thermakraft about upcoming projects and which Thermakraft underlay is best for specific skillion roof designs.

Thermakraft 215 Building Paper

Kingspan Thermakraft

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Thermakraft 215 Building Paper is a bitumenous self supporting wall and roof underlay for use in residential or commercial walls and roofs.

Suitable as a roof and wall underlay with all cladding types, where fire retardancy is not required
Can be used as an air barrier

Complies with NZBC E2/AS1 table 23 as an Acceptable Solution for use on roof and wall systems.

Thermakraft CoverTek 407 — Roof & Wall Underlay

Kingspan Thermakraft

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Thermakraft CoverTek 407 is a fire retardant self supporting synthetic building underlay for the use under all claddings.

Thermakraft CoverTek 407 Fire Retardant Self-Supporting Roof Underlay has been appraised for use as a self-supporting roof underlay on buildings within the following scope:

The scope limitations of NZBC Acceptable Solutions E2/AS1, Paragraph 1.1 with regards to building height and floor plan area; and,
With masonry tile roof cladding; and,
With metal tile and profiled metal roof cladding; and,
Situated in NZS 3604 Wind Zones up to, and including Extra High

Clause B2 Durability: Performance B2.3.1 (a), not less than 50 years, B2.3.1 (b), 15 years and B2.3.2. Thermakraft CoverTek 407 meets these requirements.

Clause E2 External Moisture: Performance E2.3.2. When used as part of the cladding system, Thermakraft CoverTek 407 will contribute to meeting this requirement.

Clause F2 Hazardous Building Materials: Performance F2.3.1. Thermakraft CoverTek 407 meets this requirement and will not present a health hazard to people.

Thermakraft CoverTek 407 Roof Underlay has an AS 1530 Part 2 flammability Index of not greater than 5 and therefore meets the requirements of NZBC Acceptable Solutions C/AS2 to C/AS6, Paragraph 4.17.8 b), for the surface finish requirements of suspended flexible fabric used as an underlay to exterior cladding that is exposed to view in occupied spaces. It may therefore be used with no restrictions in all buildings.

BRANZ Appraised

CodeMark

Thermakraft Thermabar 344

Kingspan Thermakraft

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Thermakraft Thermabar 344 is a fire retardant light diffuser foil insulation.

Suitable for roofs and walls
Commercial and industrial buildings
Fire retardant light diffuser foil insulation
Suitable as a vapour control layer

Thermabar 344 will meet the performance requirements of NZBC Clauses B2, Durability (B2.3.1[b] 15 years), E2 External Moisture E2.3.2, F2 Hazardous Building Materials F2.3.1

Thermakraft Vapour Shield

Kingspan Thermakraft

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Vapour Shield is intended for use as a vapour barrier layer ideally for skillion roof construction where condensation and moisture vapour control as required behind internal cladding.

Underlayment for roof construction, where condensation and moisture control is required
Acts to keep sarking dry until roof is fixed
Acts as vapour control layer during serviceable life of roof
Can be laid either side up

Thermakraft Vapour Shield Moisture Control Barrier, if correctly installed, will meet the performance requirements of NZBC:

Clause B2, Durability (B2.3.1[a] 50 years), and B2.3.1 (b) 15 years
Clause E2, External Moisture

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