Waterproofing flat roofs in Malta – from specification to execution

Ing. Karl Borg Regardless of whether you are a seasoned expert in the field of waterproofing, a developer, or simply an oblivious home owner with no knowledge whatsoever about how the roof keeps the elements above it out, the only common denominator which is of equal concern to everyone is: Does water come in or not?

Traditionally the Maltese roof has always been flat. We are not accustomed to pitched roofs like Northern countries since our wet season is a relatively short and mild one. Consequentially somehow, at least in the domestic mentality, we have also inherited the misconception that we need not worry so much about waterproofing, and in some magical way, the water will find its own way out.

Experience teaches otherwise! Standing (stagnant / undrained) water will always drain through cracks and crevices following the passage of least resistance, and unless we give waterproofing its deserved attention, our roof will invariably leak. Sometimes the water ingress may manifest itself in wall / ceiling stains, mold growth, or literally running water, and at other times this will go un noticed for many years as the layers in the roof absorb the humidity until eventually the damage will affect the structural elements (rusting steel beams / spalling reinforcement in concrete).

Unfortunately therefore, waterproofing has generally been an afterthought which came to mind when water damage has already been visually experienced. Additionally, we have found ourselves seemingly comfortable to uphold the yearly ritual of maintaining the roof; patching up and painting over with whatever product we manage to get our hands on

But what is waterproofing exactly? Waterproofing is the process / system which makes a structure resistant to the passage of water, such that it remains unaffected by the ingress of water. Waterproofing should in itself be designed, specified and executed by professionals. It follows therefore that at every stage of the process, the experts involved in the process need to be educated on the various waterproofing systems available and on the various construction methods found locally, knowledgeable about the related building trades which directly affect or follow waterproofing (e.g. construction, plumbing, drainage, plastering, tiling), trained (and ideally certified) in the products applied, and last but not least, experienced!

Clearly, waterproofing is not simply a question of choosing a product or a brand. The classification tree of waterproofing materials is too vast a labyrinth to enter unless you are educated and trained in the subject! The list is endless; concrete admix- tures, injectable materials, brushable slurries, sprayable resins, bituminous membranes, synthetic membranes, mastic joint sealants etc. A professional waterproofer (or waterproofing engineer) is primarily concerned about the system, not the material. The selection of the material is a function which follows the specifications of the system.

Luckily, the European Organisation of Technical Assessment (EOTA) provides a scientific and technological knowledge base in order to ensure fitness for use of a construction product. The organization provides technical approvals (ETAs) for products after assessing all characteristics and aspects for the use of the product, such as packaging, storage, transport, instal- lation and maintenance. The specifier can therefore give his system a solid foundation by assuring that the end products are covered by an ETA.

Following the specification of the system, a major loophole in the process can be encountered when the applicator is uncertified, or worse – untrained. The perfect system is often a victim of a poor application. Locally, market leaders in the waterproofing sector have taken the initiative by training applicators in order to ensure that the best practice is always delivered.

The end client therefore must always ask the right questions; Which waterproofing system is being proposed by my engineer and why was it chosen in favour of others? Will this waterproofing specification meet my requirements without failing (e.g. entertainment area, green roof, tiled area, BBQ area etc). Is the applicator a trained / certified applicator in the product selected? Is the product being specified backed by a European technical approval (ETAG)? At the end of the day, all we want is peace of mind that when the rain hits, no water comes in. Every time however, to have a waterproof building, the approach to waterproofing must not leak either!

Karl Borg is from the Technical Consultancy Department at JMV Building Solutions and JM Vassallo Vibro Steel Ltd.