Terrace waterproofing with hybrid polyurethane liquid membrane

Descripción sistema

Office buildings located at the end of the Rambla Nova (Tarragona) on the seafront next to the so-called Balcon de Europa at about 40 metres above sea level. These buildings are communicated by a terrace of about 200 m2 which is non-transitable and located above an office of the BBVA bank in which there are water leaks. The Property wanted to solve the problem of the leaks and to be able to reopen this passage between buildings for specific situations.

Broadly speaking, waterproofing systems based on membranes can be divided into two large groups: discontinuous waterproofing (asphalt membranes, etc.) and continuous waterproofing (cementitious, acrylic, polyurethane). For some time now, the market trend has been to waterproof with continuous membranes, as they offer a series of advantages over discontinuous membranes, such as the elimination of overlaps, not using welding, etc…

Although undoubtedly one of the great advantages of this type of waterproofing is the subsequent repair or rehabilitation, as we can quickly locate where the leak has occurred and repair it without having to remove the entire waterproofing.

Reason for the intervention

In the work we are referring to, the aim was to repair and solve the leaks that have occurred on the ground floor of the building and to recondition the terrace for moderate traffic use.

Challenges and constraints

“Repair and waterproof the terrace to prevent water seepage.
“Apply a continuous membrane, which allows for easy, quick and economical repair in future repairs.
“Apply a material resistant to ultraviolet rays that also has a high mechanical performance to allow moderate foot traffic.

Molins Solution

“Levelling with PROPAM® RECRECIDO PRONTO screed mortar to level the surface and generate the necessary slopes for water drainage.
“Half-grouting at all joints with PROPAM® REPAR TECHNO repair mortar.
“Application of BETOPUR HYBRID water-based polyurethane-acrylic hybrid continuous waterproofing membrane.

Execution

“Cleaning and cleaning of the substrate by mechanical roughing (rotary diamond grinding), until a firm, clean substrate is obtained, free of loose particles, compact, free of grease, oil, paint…
“Regularisation and levelling with PROPAM® RECRECIDO PRONTO (CT-C30-F6) normal setting mortar for the execution of quick-drying screeds in thicknesses of 10 to 80 mm.

“3. Creation of joints (expansion, perimeter and intermediate joints) with BETOFLEX MS single-component, high-performance elastomer sealant based on MS polymer, planned by the project management.
“4. Production of half-rounds with PROPAM® REPAR TECHNO repair mortar, thixotropic cementitious mortar with fibres, fast setting and compensated shrinkage (meets the requirements of EN 1504-3 class R4, EN 1504-2 and EN 1504-7). The morphology of the half-round allows the stresses on the membrane to be reduced at this critical point.

“5. Apply a first coat as a primer of BETOPUR HYBRID diluted with 5-10% water by brush or roller, to promote penetration of the product into the substrate and improve adhesion with the subsequent coat. Then apply a second coat of BETOPUR HYBRID over the touch-dry primer with a brush or roller until the entire surface is covered.

“6. 2 weeks after application of the membrane, the terrace shall be tested for watertightness to ensure that the waterproofing is working properly.

Technical note

It is practically impossible to consider a roof or terrace as watertight by visual inspection alone. Small defects that escape the naked eye can be the cause of leaks, so it is necessary to test its watertightness by means of a watertightness test.

In flat roofs, the watertightness test is carried out by flooding, keeping the roof flooded for 24 hours and observing, 24 hours after the end of the flooding, whether there are signs of leaks under the roof.

The process begins with the plugging of the evacuation points. Once sealed, flooding is started by filling with a hose up to about 5 cm below the lowest point of the vertical delivery of the waterproofing. If this level is exceeded, water can easily enter from behind the waterproofing, which would lead to errors in the assessment of its watertightness. To ensure that the roof is not overfilled, the drain can be plugged with a sealed standpipe as an overflow.

After emptying, the vertical drainage network is checked for leaks. The watertightness is never assessed by the final water level, only by possible leaks, although this level should remain more or less stable during the test.