The Holy Mosque Expansion, Saudi Arabia

The King Abdullah Haram Expansion project is the largest expansion of the Grand Mosque in history.


The Grand Mosque is the largest and oldest mosque in the world and surrounds one of the world's holiest places, the Kaaba. The "King Abdullah Haram Expansion" Project is the largest expansion of the Grand Mosque in its four thousand year history. At a cost of US$22 billion, the new expansion will comprise new pray-yards, walkways, tunnels and the development of existing service facilities to increase capacity of the mosque to more than 2 million people.

The new buildings, including all related facilities, will be at a non-stop service throughout the year. They require an extremely durable waterproofing system especially for the walkways, service rooms, and water network channels. The waterproof membrane must be environmental friendly and has to be compatible with potable water.


Fosroc Proofex OFB, a fully-bonded Thermoplastic Polyolefin (TPO) membrane was selected due to its high flexibility, long-term durability and practicality. It has no VOC’s and has no harm to water for human consumption.

Unlike Loose-laid membranes, Proofex OFB, with its fleece-backed surface, bonds to the concrete substrate via Proofex OFB Adhesive to produce a fully-bonded waterproof system that prevents water tracking between the membrane and the concrete in case of any leakage. To ensure water tightness, adjacent rolls are overlapped using hot air guns, producing a seamless and continuous waterproof system. For the large areas walk-ways, automatic welding machines were used, making the application extremely fast and easy.

In addition to the waterproofing systems, Fosroc provided solutions for various applications such as tile adhesives, joint sealants and protective coatings; giving the client comprehensive solutions at all stages of the construction works.


The high flexibility of Proofex OFB made its application extremely versatile especially when dealing with the various intricate details such as trenches, corners and joints. It is UV resistant and is not affected by the aggressive UV exposure in the days of application, a feature that brought peace of mind to DAR engineers, the consultant, who confirmed that "Proofex OFB was an excellent waterproofing system for this application".

The first phase of the project has been completed successfully, and Proofex OFB system remains the ideal solution for waterproofing the roofs, the walkways and the service channels in the new buildings of the expansion project.


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