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Permaphalt is a specially formulated mastic asphalt roofing, using advanced polymer technology to give the ideal combination of long term durability, increased fatigue resistance, improved temperature stability and ease of installation. Permaphalt is the result of extensive research and development, and the careful selection of polymers to provide improved performance, in all flat roof specifications. Permaphalt can be applied to form a continuous waterproof covering over flat, sloped or curved surfaces. It can be worked round pipes, roof lights and other projections to provide a completely seam free membrane. Permaphalt is suitable for insulated warm roofs, un-insulated cold roofs and inverted/ green roof configurations.

Features and benefits:

  • Fire resistance: When Permaphalt is applied onto a suitable substrate, it has an External FAA designation when tested to BS 476-3: 2004.
  • Odour: Permaphalt is odorless after laying.
  • Manufactured in the UK under BS ISO 9000 Quality Assurance Scheme.
  • Systems including Permaphalt have been approved by the Loss Prevention Certification Board. See current LPCB listing for full system accreditation.


  • Compressive strength: When Permaphalt is fully confined it has the same compressive strength as the containing material. When not confined, the compressive strength is dependent upon a number of factors including temperatures. Advice on individual cases should be sought from Permanite Technical Services.
  • Durability: Test data show that Permaphalt has improved high temperature stability and is more flexible at low temperatures that conventional mastic asphalt. On the basis of available data, Permaphalt should have a life expectancy in excess of that of conventional grades of mastic asphalt used in roofing applications.
  • Fire: Achieving BS 476-3: FAA.
  • Resistance to biological attack: Permaphalt is vermin proof and rot proof.
  • Thermal expansion: Permaphalt is thermoplastic and accommodates normal movement encountered in well-designed building structures.
  • Stability: Permaphalt will adequately resist the effects of wind suction and thermal shock likely to occur in practice.
  • Vapour resistivity: The vapour resistivity of Permaphalt is very high and can be assumed to be not less than 100,000 MN/g.


  • Permaphalt is supplied in nominal 20 kg blocks. Alternatively, Permaphalt can also be supplied directly to site in purpose built hot charge transporters capable of holding up to 19 tonnes of molten material.
  • Permaphalt should be installed generally in accordance with Permanite installation instructions, BS 8218: 1998 and BS 8000-4, on to a sheathing felt separating layer. Structural decking should comply with the recommendations in BS 6229: 2003 (flat roofs with continuously supported coverings) and be laid in accordance with the relevant codes of practice. Where using insulation in a warm roof configuration, the insulation should be laid on to a suitable vapour control layer.
  • On horizontal areas, Permaphalt is usually laid in two coats to a nominal thickness of 20 mm on a separating membrane of Black Sheathing Felt. In buried situations, such as roof gardens, the thickness is increased to 30 mm laid in three coats.
  • Detail work and surface finishes should be installed in accordance with the relevant codes of practice, client requirements and Permanite specifications.

Gold Guarantees:

The comprehensive Permanite one-point, insurance-backed Gold guarantees cover materials, workmanship and design, for up to 20 years. The guarantee can also include approved accessories, such as edge trims, outlets and rooflights. Consult manufacturer for details.

Related literature

The following content references this product:

NBS Specification

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This product is associated with the following NBS Create clause:
45-20-00/320 Mastic asphalt (MA)

Product specification

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+44 (0)1257 255 771

Product reference


Manufacturer details

Appley Lane North,
Appley Bridge,
Lancashire, WN6 9AB
Tel +44 (0)1257 255 771
Fax +44 (0)1257 252 514
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