Preservation of the basement area of historical houses, Praha - Old Town, Czech Republic


Husova 19-21, 110 00 Praha 1 – Staré Město
Description of work:
Drying out the basement after flood
Conservation work
Restoration of argillite masonry
Contractor: GEMA ART GROUP a.s.
Implementation: 05-11/2003 









  • History
  • Restoration work
  • More information

 Historic houses in Husova Street belong to the oldest burgher dwellings in the Old Town Quarter of Prague. The three houses which comprise the premises of the gallery are of Romanesque and Gothic origin. The gallery's exhibition spaces are within the House At the Keys (also known as House At the Golden Serpent), the oldest of the three. The stone-built Romanesque dwelling from the 12th century forms the core of the house. The square shaped living quarters, which have a central pillar decorated with a cubic capital, are the best preserved. The masonry is lined with small regularly-shaped argillite panels. During the 13th century, when the house was rebuilt in the Gothic style, the terrain was elevated and the original Romanesque living area became the basement. In the course of the following decades the Gothic appearance of the house was replaced by a Renaissance one. The other two houses, Gothic in origin, had over the centuries been rebuilt in the Baroque and the Classicist style respectively.
The houses had been in decline since the 19th century and during the clearance work, undertaken in Prague at the turn of the 19th and 20th century, their demolition was under consideration. By 1957 the dereliction of the buildings had reached such a critical stage that they had to be stabilized by temporary structural supports. Extensive reconstruction work took place between the years 1965 and 1973. The premises of the houses were afterwards used for short-term exhibitions organized by the Gallery of the Central Bohemian Region. The gallery was founded in 1963 and had several sites within the region, such as Nelahozeves Castle, and premises in the towns of Mladá Boleslav, Roztoky near Prague, Kladno and Průhonice among others. The gallery focuses on Czech art of the 20th and 21th century. It was temporarily renamed the Czech Museum of Fine Arts in Prague in 1989 but returned to its original name, the Gallery of the Central Bohemian Region (GASK), in 2009. Reconstruction of its premises took place after the August 2002 floods, when the original Romanesque basement had to be dried out and conserved by experts, and again in 2009. After this reconstruction the gallery was again renamed as the GATE Gallery and functioned as a branch of the Gallery of the Central Bohemian Region, which has been permanently accommodated in the former Jesuit College in the town of Kutná Hora since 1998. The three houses in the Husova Street were used as an information centre, art shop and stylishly refurbished café; they also had gallery spaces for temporary exhibitions and a permanent multimedia exposition in the Romanesque basements. The Gate Gallery ended its activities during 2014.

 The devastating floods of 2002 did not spare the three old houses in the Husova Street, whose history reaches back to the Romanesque and Gothic era. The basement areas were entirely under water. The first rescue efforts after the floods involved pumping out the water and basic cleaning of the walls. The premises were then ventilated for five months and at the beginning of 2003 specialist work commenced to return the historic basements to their original appearance.

Drying out of the basement area after the floods:
Before the clearing work could commence the wiring of the premises had to be replaced and new cables encased in concrete. GEMA ART GROUP a.s. workers then embarked on their specialist tasks. The entire surface of the masonry was still damp. The level of dampness was highly variable and the most affected was the masonry near the staircase. The flooring made from non-porous glazed tiles had also been found to be in a very poor state, as was the stone masonry. The experts found many cracks and instances of stone pulverization and separation of layers. In places the pointing had been washed away from the surface and the residual mortar continued to crumble away and lose its cohesion.
Prior to the drying procedure the exact levels of dampness and the salinity of the surface layers of the stone had to be established. Argillite is highly sensitive to climactic variations and sudden changes in temperature could cause it to disintegrate. For this reason the drying out process, which lasted several months, had to be carefully controlled and minimal losses of the stone mass ensured. In some locations, where there was a danger of argillite layers peeling off, the stone was reinforced during the drying out process.
The restorers preferred the natural method of ventilation of the basement and decided to utilize for this purpose the shaft of the heating ducts located in the north wall of the gallery premises. The shafts were cleaned and ventilation windows were installed in the bricked-up original openings. A new ventilation system was also established in the part of the premises leading to Husova Street. New waterproof ventilation windows built here were covered with grilles to prevent their obstruction with dirt and debris.
Another step in achieving the natural drying of the stone was to remove the residual pointing. The basement was afterwards left to dry for 4 months, during which time the process was monitored by the restorers. The actual restoration work could then follow.

Restoration of the argillite masonry:
After the 4 months all moisture was eliminated from the stone and the exposed masonry could be reinforced with organosilicate consolidate containing acrylic co-polymer. Great care was taken to maintain the porousness of all surface layers, which ensures a long lifespan of the stone.
All the original pointing was then replaced, again using porous materials.
The original Romanesque stone pillar is also located in the basement. All later cement repairs, found mostly on the base of the pillar, had to be removed and replaced with argillite-like artificial stone material.
All the masonry to the height of around one metre was also treated with an agent which reduces the effect of the dampness level fluctuations in the basement. Finally, localized retouching of the surfaces of the stone masonry was carried out.