Wondering what happened to flat surfaces and Xypex, the writers explain what Xypex actually is, how it works, its benefits and applications.

An 8M Construction survey reveals that of all the originally flat roofs in Kampala, about 95% were replaced with iron sheets in a lean-to or other roofing styles, thus losing out on the useful purpose of such roofs to act as meeting places for business and leisure.  Take an example of Embassy House on King George VI Way, Kampala. It was built in 1968 by the defunct Uganda Consolidated Properties Limited (UCPL). UCPL was owned by the Uganda Development Corporation (UDC) by about 85%.

The last and ninth floor was flat, finished with a waterproofing adhesive, probably similar in action to Xypex.  It was glued with concrete tiles of 300mm by 300mm together creating a waterproof surface. The concrete tiles were pasted on top of the load-bearing slab. There were a strong safety-banisters around the 10m by a 36m rectangular flat surface, which gently sloped towards the down-pipes to fast-drain the rainwater.

With an external fire-fighting escape staircase, the place was complete as an exquisite and fully furnished bar. It was known as the UDC Executive Club, trodden by the directors and management executives of the UDC fraternity who mixed with the elite of Kampala. A lot of dancing, drinking, and other merriments went on there.

With the Ugandan poor maintenance culture, 34 years down the road around 2002, a Ministry of Education department as the beneficiary of the premises decided to do away with the leaking place and created an archive for decaying files, putting an end to the better use! Why? It would appear that the wonder-waterproofing material, Xypex, was either no longer known or anywhere nearby.  Yet, for more than 45 years in more than 80 countries including Uganda, Xypex crystalline technology has set an international standard of excellence in concrete waterproofing, durability, and protection. Continued worldwide research shows that no other ‘comparative’ product has its equivalent.


Xypex is a non-toxic chemical treatment for the waterproofing and protection of concrete. Its primary and most distinguishing performance feature is its unique ability to generate a non-soluble crystalline formation deep within the pores and capillary tracts of the concrete; a crystalline structure that permanently seals the concrete against the penetration of water and other liquids from any direction. Xypex crystalline products are dry powder compounds composed of Portland cement, silica sand, and many active, proprietary chemicals.


Crystalline waterproofing is a capillary waterproofing formulation of proprietary blends of chemicals, quartz sand, and cement. The chemicals contained in the crystalline waterproofing materials require the presence of moisture to set off a chemical reaction from within the matrix of the concrete.

Concrete is porous. Its tunnel-like capillaries are a natural part of its mass and permit the passage of water and other liquids. By means of diffusion, the reactive chemicals in Xypex products use water as a migrating medium to enter and travel down the capillaries of the concrete. This process precipitates a chemical reaction between Xypex, moisture and the by-products of cement hydration, forming a new non-soluble crystalline structure. This integral structure fills the capillary tracts rendering the concrete waterproof. It can also self-heal cracks up to 0.4mm.


The crystalline nature of the Xypex waterproofing system provides many application advantages over traditional barrier products.

It does not require a dry surface or dry weather to be applied; in fact, a wet surface is necessary.

There is no need for priming or leveling prior to application.

It cannot puncture, tear, or come apart at the seams

It does not require protection during backfilling or during placement of steel, wire mesh or other materials.

It can be applied on either side of a concrete surface – the negative or the positive (water pressure) side.

Xypex does not require sealing, lapping and finishing of seams at corners, edges or between membranes.

It is less costly to apply than most other methods.


Protecting wastewater treatment infrastructure

Protecting water treatment structures

Water-holding structures

Protecting foundations and flat roofs

Protecting tunnels

Protecting power & utility structures

Protecting marine structures

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