Protection for Generations to Come
Rising damp in the masonry was threatening to damage a valuable fresco in a chapel in Upper Bavaria. WACKER experts developed a comprehensive, restoration plan that included chemical dampproofing to combat rising damp, and water-repellent impregnation with a silane/siloxane mixture. A new coat of silicone resin emulsion paint rounded out the plan.
Dr. Hartmut Ackermann uses a wetting test to check how much moisture has been absorbed by the wall coated with water-repellent silicone resin emulsion paint.
On the outskirts of Burghausen lies Bergerhof farm, where a chapel is located. The fresco inside the chapel was designed by an Italian artist in 2008.
“Il Soffio” – the breath – is the name of the fresco inside the family chapel at the Bergerhof farm on the outskirts of Burghausen. The farm chapel and its idyllic hillside location entice passersby to stop and linger, but the setting poses a constant risk of structural damage to the fresco inside the chapel: “Due to its location, the foundation is poor, allowing moisture to climb up through the masonry and make its way into the plaster and paintwork,” explains Dr. Hartmut Ackermann, a chemist at WACKER SILICONES and an expert in building protection. “We absolutely had to renovate the building if we were to protect the fresco.”
In 2008, Nunzio Di Placido, an artist from Burghausen’s sister city of Sulmona, Italy, created a painting for the Bergerhof chapel. For his fresco, he revived a forgotten technique from antiquity known as encaustic painting, in which pigments are bound in wax and applied to the surface while hot.
Brightly Colored Fresco
Extensive renovations to the tiny chapel began in the fall of 2013 in order to protect the painting and preserve the fresco’s luminous colors permanently. The project was sponsored by the city of Burghausen, which owns the Bergerhof, and Wacker Chemie AG. As a leading manufacturer of building protection agents, WACKER used the project as an opportunity to demonstrate the effects of its silicone resin emulsion paints and its hydrophobic (i.e. water-repellent) silanes and siloxanes – essentially in the company’s own backyard. “It was a four-step process,” explains Dr. Ackermann from the company’s Application Technology team. “After chemical dampproofing, we renovated the foundation and cleaned the exterior walls, applied an outer coat of silicone resin emulsion paint, and treated the interior walls to make them water-repellent.”
Workers drilled horizontal holes into the exterior wall ten centimeters above the ground and spaced ten centimeters apart. These holes were then used to inject SILRES® BS SMK 550 into the masonry. (see image below)
The first step was for workers from the municipal department of public works to drill horizontal holes into the exterior wall ten centimeters above the ground and spaced ten centimeters apart. They then injected SILRES® BS SMK 550 into these holes, each of which had a diameter of eight millimeters. This solvent-free, silane/siloxane concentrate had been diluted 1:9 to form a microemulsion. SILRES® BS SMK 550 has been specially designed for use in chemical dampproofing processes, where it suppresses rising damp.
Using pumping equipment from Desoi, the specialists injected the water-repellent agent into each hole for roughly five minutes at a pressure of two to five bar. In the process, the silane/siloxane mixture spread through the masonry,and the workers plugged up the holes with mortar one week later. Once the masonry is dry, a barrier forms that is impermeable to water – experts refer to this as a hydrophobic horizontal barrier – and reliably counteracts rising damp caused by capillary action.
Due to their very small particle size, silicone microemulsions are exceptionally well suited for this method of combating moisture – even in dense masonry. SEM images show that silicone microemulsions allow diffusion to continue and do not seal off or block capillary action. Instead, the agent reacts with capillary surfaces, rendering them permanently hydrophobic. “That effectively protects the wall from rising damp for generations to come,” Ackermann points out.
The diagram illustrates how silicone resin emulsion paint works: oxygen-silicon bonds (yellow) form a three-dimensional network, while the organic groups act as umbrellas, thus producing a water-repellent effect.
HYDROPHOBIC IMPREGNATION WITH SILANES
The aim of hydrophobic impregnation is to permanently reduce moisture absorption in the exterior or in other parts of a building, while retaining the ability of the building material to breathe. After application, the active ingredient of the water-repellent agent penetrates the surface of the structure and reacts with the silicate matrix of the building material, rendering its capillaries and pores water repellent. The formation of a hydrophobic zone reduces the surface tension of the building material to such an extent that water and the harmful substances dissolved in it can no longer penetrate in liquid form. The basic prerequisite is the selection of a suitable combination of active agents in terms of molecular size, mobility, reactivity and resistance to chemical and physical influences. Choosing the right water-repellent agent is a must for minimizing water absorption, allowing the active agent to penetrate as deeply as possible, and having it form a lasting bond with the building material matrix.
Renovation also included typical repairs to the foundation: workers from Burghausen’s department of public works removed the old paint with a high-pressure cleaner and filled cracks with mortar. A few days after removing the paint, workers repainted the entire building exterior with a silicone resin emulsion paint made by Sto – and based on SILRES® BS silicone resin from WACKER – giving the chapel’s render an efficient coating that is water repellent yet breathable.
“Silicone resins have a high affinity for mineral-based surfaces, which makes hydrophobicity an integral part of the paints – and that gives them a highly effective, lasting degree of protection,” explains Albert Hausberger, an applications engineer at WACKER who specializes in silicone resin emulsion paints.
Water Vapor Can Diffuse
Dr. Hartmut Ackermann in front of the Bergerhof chapel: this tiny place of worship also gives WACKER’s building protection experts an opportunity to demonstrate their high-performance products.
European standard EN 1062-1 categorizes silicone resin emulsion paints in the best possible class with respect to their permeability to water and water vapor. The unique properties of SILRES® BS silicone resins ensure that water from outside will bead on the building’s exterior, while still allowing evaporating water to diffuse out of the wall in the form of steam – a characteristic that prevents damage from accumulated moisture below the coating.
As a final measure, WACKER building protection experts also recommended hydrophobic impregnation of the chapel interior using SILRES® BS 290, a mixture of silanes and siloxane that has been diluted with organic solvents. A high-quality, general-purpose primer and water-repellent agent for mineral-based – and even highly alkaline – substrates, SILRES® BS 290 results in a lasting reduction in the amount of moisture that building materials absorb.
Thanks to this project, the interior, exterior and masonry of the Bergerhof chapel are now equally well protected from moisture, ensuring that subsequent generations will be able to enjoy the colorful fresco of Italian painter Nunzio Di Placido in all of its splendor.