Waterproofing: under roof terraces, which system?
Batirama.com 04/01/20160The Rooftop is not just a trend among hipsters looking for trendy addresses. A real ground swell, the roof becomes a space to be conquered as a terrace
Admittedly, the outdoor waterproofing market is suffering like so many others, weighed down by the poor construction figures that persisted until last summer. “But it benefits from an architectural trend that is once again growing in housing, which is that of the flat roof. It is also supported by the home extension market to nibble square meters. These movements are particularly favorable for sealing,” reveals Gaël Laude, Sales Director France at Firestone Building Products.
The one that became a fifth facade with functionality by becoming green with the addition of solar or vegetation, “also becomes a space that we reclaim, and which is no longer camouflaged under gravel. It is now a real ground swell both collectively and individually,” confirms Benoit Steiner, Deputy Managing Director at Meple.
Each configuration has its own waterproofness
First consequence for this waterproofing: “we can no longer design it on a terrace today without imagining the immediate function of the roof on which it will be placed. We must also integrate its future development,” continues Benoit Steiner.
Will it be transformed into an accessible space, with a pedestrian area and another green area? “We are working on notions of complex to pull the seal up,” adds Benoit Steiner, without revealing the content.
The fact remains that, faced with a still comfortable bitumen market with 75% market share because it is easy to implement, other products are developing, in particular for the benefit of single-layer synthetic membranes.
The proof: historical bitumen manufacturers are also investing in this niche. Hence this other consequence for waterproofing: “today, the answers are diverse and adapted according to the configuration of the site.
PVC membranes being, for example, more suitable on steel decking for weight reasons, EPDM facilitate extensions which will not always be carried out by waterproofers, and bitumen makes it easy to deal with a complex case”.
And if the implementation of a membrane is impossible or it distorts the work, liquid waterproofing systems (SEL) will be the solution.
Solution 1: Bituminous membrane: the traditional
© Soprema
75% of the flat roof waterproofing market is still dominated by bituminous membranes.
Particularly suitable on concrete substrates or when it is necessary to carry out surveys on the periphery or on a skylight for example, bituminous waterproofing remains the best controlled. Bi-layer but also single-layer, the upper part of the structure must resist UV attacks, mechanical and thermal stresses.
As a result, she will be armed with a veil, most often in polyester. These membranes often decried for the necessary use of a gas torch can now be freed from it by using hot air.
They also benefit from good resistance over time thanks to their thickness. However, due to temperature variations, they may undergo shrinkage phenomena. Consequently, water infiltration may appear, the membrane may also tear, or even damage the peripheral masonry.
Advantages: traditional and controlled installation, economical, independent or mechanically fixed method of connection, suitable for all desired finishes, allows the renovation of bituminous waterproofing; exist with the possibility of not having to use a flame.Limits: most often torch welding which requires heavy equipment, and which presents risks, especially on flat roofs of wooden frame houses .
Solution 2: Synthetic monolayers: an offensive challenger
© Firestone
In PVC, EDPM, TPO… Modern, technical, durable and easier to install than traditional bituminous membranes, they are eating away at market share.
These pre-designed systems facilitate implementation on site, and the treatment of singular points (raised, parapets, skylights, etc.). Monolayers, these synthetic membranes are easier and faster to implement than bituminous waterproofing.
In addition, their installation method, which varies according to the processes and materials used, does not require welding with a flame. So no specific tools, no fire permit. In addition, these membranes make it possible to work on large surfaces without joints.
They are therefore less sensitive to leaks, like TPO (thermoplastic polyolefin or FPO) which is becoming an alternative to PVC, with the advantage of not containing any plasticizer. Thus, this sealing does not pollute the rainwater which can be recovered.
And in general, these single-layer membranes open up the field of waterproofing to other trades than that of waterproofers. But on condition of having been trained specifically for the process implemented.
Advantages: implementation that does not require a flame, thus excluding the risk of fire, especially on wooden supports; lightness; sustainability; possible in the treatment of large surfaces.Limits: a workforce to be qualified; single-layer system therefore requiring particular care when assembling the lengths when necessary.
Solution 3: SEL: waterproofing that fits all shapes
© Mapei
Little thumb of terrace waterproofing, liquid waterproofing systems (SEL) remain the most suitable solution for dealing with complex shapes.
Based on synthetic resins, liquid waterproofing systems (SEL) form after drying and by incorporating a reinforcement, an adherent and waterproof elastic membrane, which resists in the event of cracking of the support.
Avoiding the problems of junctions between the lengths, they are applied cold, without flame or hot air, by spreading the resin over several layers using conventional tools: roller, brush and even airless machine.
But above all, and because they are liquid, these waterproofing systems are the answer to waterproofing various surfaces and complex shapes, with for example corbels. What remains more complicated with bituminous or synthetic membranes.
Advantages: seamless, continuous and homogeneous sealing over the entire surface; can be drivenLimits: high price when the terrace does not require the use of these systems; a highly skilled workforce; is implemented only when the atmospheric conditions are particularly favorable.
Co-branding for SEL with integrated isolation complex
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Manufacturers Recticel Insulation and Kemper System have combined the thermal insulation panel of the first and the SEL in solvent-free polyurethane resin of the second. The result: Kempertherm Iso-SEL. The flat, bubble-free finish of the panels allows the waterproofing to be applied directly to the insulation.
An adapted response in renovation that does not require removal of the old waterproofing, to be implemented on traditional vapor barrier, masonry or wooden frame.
Source: batirama.com / S. Lacaze-Haertelmeyer
