Facade with waterproofed granite plywood

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Created on Wednesday, 02 April 2014 18:27

There is a common use of repellents for waterproofing granite plywood facades. The water repellents used are mainly silicones, formulated as a mixture of silanes and siloxanes. On a plywood facade, the repelent has to be alkaline in the mortar PH of the joints as the attached to the stone. It also needs to have good penetration and hydrophobically resistance to the rainfall with strong winds, high resistance to solar radiation, etc. It also needs to have good penetration and hydrophobically resistance to the rainfall with strong winds, high resistance to solar radiation, etc.In addition to precipitations associated with adverse weather conditions, the water condensation as well as the hygroscopic absortion of the granite and mortar must be considered.

The repellent with a good behavior on the granite, does not resist the chemical action of the mortar. On the other hand, the repellent that has a good behavior in the mortar is not valid on the granite plywood.. There are several reasons for that, but it requires a chemistry explanation and it is related with the hybridization type Sp3, which adopts the silicon atom in the silanes, generating unstable compounds. However this hybridization Sp3 in the quartz (SiO2) is ordered spatially in a three­dimensional network (crystallized). This amorphous silica is also a desiccant, i.e. it removes the humidity.

Over more that 15 years ago we started to develop alternative techniques to the use of silanes and sixolanes basing on the precipitated amorphous silica capillary network, first in a experimental level and since 8 years ago applied on waterproofing and consolidated granite. The consolidated chemical processes we formulate for sealing the capillary network have allowed us to overcome the difficulties that the conventional silicone water repellents can not solve.

The following pictures were taken in facades with waterproofed granite plywood and the joints were taken with polyurethane caulk. In all of them the repellent degradation is appreciated on the granite plywood and the grout of the joints does not prevent the filtration trough the granite plywood. The instability of the silicones often induce structural and surface stains in the granite, accelerating the feldspar oxidation and degradation associated to the degradation of the proper water repellent.

The waterproof treatment has a hydrophobically resistance of a few years. As the ignorance is bold, many companies apply the products ignoring completely the chemical products they use for their treatments and they guarantee with audacity the longevity of their work for 10 years or more, when they waterproof a facade. I have never understood that guarantee, since the own repellent manufacturers do not assume the responsibility.

I've also seen plywood granite facades waterproofed with silicone resins, varnishes, paints, etc..

In my humble opinion, there are no miracle products that solve the leaks these facades present and that are directly related to the capillarity, the granite type and the construction defects of the building. To seal the joints with putty, to waterproof the facade, etc. could be effective treatments in a short term, but after a few years the humidity will show up the same way as before the treatment.

The chemicals used to correct these problems can not be handled by people without sufficient knowledge of chemistry, as its management and application could be very dangerous. Every chemical applicator in a construction context, should have a management background as well as in the usefulness and duration of the treatments. I can not imagine a chemical cleaning handled by untrained staff, with stain removals, repellents, paint, etc. The most common cleaning methods used by these companies are usually mechanical, by granulation, milling, sandblasting, etc. Other daring ones use products such as bleach, soda, etching, etc. In any case the final result will be minimally satisfactory, but they will keep doing it.