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Bitumized Perlite Roofing Base

A unique roofing base material that is produced and used extensively in Europe is bitumized perlite which offers several distinct advantages to the user. Among these advantages are:

  • Provides roof insulation
  • Can be sloped to drain
  • Requires no curing or drying time
  • Provides a monolithic base for roofing
  • May be roofed immediately
  • Is a lightweight, dry granular material
  • Suitable for reroofing or new construction


Bitumized perlite is dry, granular material consisting of perlite particles coated with bitumen. The lightweight material is ready to use as poured from bags and requires no mixing; nor does it require the addition of any additives.


Bitumized perlite can be applied directly over hard surfaces such as concrete that have been treated with a cold bituminous adhesive layer. When the bitumized perlite is to be applied over a wood base, an asphalt underlayment is nailed to the wood before the cold asphalt adhesive layer is applied. Built-up roofing may then be immediately applied by flood coating the surface with hot asphalt.


Bitumized perlite is an excellent material for repair of existing roofs as it can usually be applied over structurally sound roofs that have been swept clean of loose debris and coated with a cold asphalt adhesive layer. Not only does the new roofing base provide additional insulation but water ponding conditions may be corrected by sloping the new roofing base toward internal drains or to the perimeter of the roof.


Roofs are prepared by applying a coat of cold asphalt that acts as an adhesive layer to bond the bitumized perlite to the structure of the building. Dry, granular bitumized perlite is poured from bags, spread and screeded to the desired slope and to a thickness 40% greater than the final desired thickness. Sheets of plywood are laid over the dry material and a 400 lb(180kg) roller is used to compact the material. Final compaction is achieved by rolling the bitumized perlite directly without benefit of the plywood sheets.

With bitumized perlite, roof grades can be easily established, low areas filled and a monolithic roofing base produced. As no curing or drying cycle is necessary, roofing material may be immediately applied. Built-up roofing is secured to the bitumized perlite base by flood coating the base with hot asphalt

If protection from ultraviolet radiation or mechanical damage is desired, ballast may be spread on top of the roofing material.

When bitumized perlite is used as a roofing base for rooftop parking areas, the parking surface may be applied directly on top of the built-up roofing.

Information given herein is from sources considered reliable, but no guarantee of accuracy can be made or liability assumed.  Your supplier may be able to provide you with more precise data.  Certain compositions or processes involving perlite may be the subject of patents.
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