"IF ONLY SOMEONE HAD TOLD ME
ABOUT ROOFING UNDERLAY WHEN
I WAS BUILDING MY HOUSE..."

How Roofing Underlay’s Work; 

New Zealand has a temperate climate and widely varying construction techniques. Humidity is generally high, significant portion of building construction is close to the coastline, and in some parts of the country have sub zero temperature condition exist for several months. The Roofing Underlay design, specification and installation has a critical effect on the building moisture management system, and should allow water vapour to pass freely through, and prevent water penetration into the building structure and insulation.

A roofing underlay is required to;

• Hold accumulated condensation formed overnight on the underside of roofing materials, released as vapour during the day
• Be a secondary layer of protection, should the roofing material allow water egress;
• Be able to manage construction moisture, and allow the building structure to fully dry;
• Reduce dust infiltration;
• Reduce wind loading and pressure fluctuations within the building;
• Protect the insulation, and maintain thermal efficiency of insulation materials;

Underlay Types;

• Bituminous or Fire Retardant Kraft based Roofing Underlays
• Fully Synthetic polyolefin based Roofing Underlays

Bituminous & Fire Retardant Roofing Underlays;

These Kraft based Underlays have been successfully used for many years in the building and construction industry. These products are a cost effective solution, which have proven to perform in most climatic conditions, and construction types, both commercial & residential.

Thermakraft Industries (NZ) Ltd offers a range of Kraft Based Roofing Underlays. The Thermakraft 215 Bituminous Self Supporting Roofing Underlay, and the ThermoKraft 368 Solvent Free Fire Retardant Self Supporting Underlay can be used in most Concrete tile applications. Refer to Designer and User Guidelines or call the Thermakraft Technical Helpline on 0800 806 595.

Fully Synthetic Roofing Underlays

Synthetic Roofing Underlays provide the latest in polymer technology, developed in Europe for demanding climatic conditions, and support all roof construction types. These products provide unparalleled water penetration resistance, with exceptional water vapor tramission rates. Synthetic Roofing Underlays are constructed of a water resistant breathable film, laminated between fire resistant UV stabalised non-woven spun bonded polyolefins. This laminate structure provides for a light, shrink-resistant, tough and extremely durable Roofing Underlay.

Due to the water absorbency, and fire resistant requirements in New Zealand, many of the European and North American Synthetic Roofing Underlays cannot be used. Thermakraft Industries have developed, and manufacture Synthetic Roofing Underlays designed specifically for New Zealand requirements and conditions. The Covertek™ 407 or 403 Absorbant Breathable Synthetic Roofing Underlays are the premium in Roofing Underlays and are recommended in all concrete tile roofing applications. Refer to Designer and User Guidelines or call the Thermakraft Technical Helpline on 0800 806 595.