(This page was automatically translated from German. Feuchtes Mauerwerk)

Humidity in the brickwork -

5/2008 -

Exactly at old buildings, the financial recovery of moist walls is a problem. In many cases, one assumes a "ascending humidity", underestimates the hygroscopic quality of the salts and the dew-water on that occasion at the cooler wall-surface. In this contribution, the concept is expounded humidity nearer. Still, the causes are shown and are compared with the individual insulation as well as desiccation-methods.

Dampness brickwork
Form 1: At this facade, the outside-finery is missing since already many years and it could get precipitation unhindered into the brickwork.

1. General references to the humidity
2. Causes of the dampness in the brickwork
3. Possibilities a Trockenlegung
4. Vertical law cases to the interruption of the capillary transportation
5. Horizontal law cases about the interruption of the capillary transportation
5.1. Mechanical Law cases
5.1.1. Sectional Aufstemmen per hand
5.1.2. Sectional sawing open
5.1.3. Wall-separation between slanted separation-cut, automatic
5.1.4. To hit of steel-sheet metal, automatic
5.1.5. Unterfangungsverfahren
5.2. Cross section-insulation through pressure-unmounted and pressure-afflicted injection-law cases
5.3. Elektrophysikalische respectively electro-kinetic law cases
5.3.1. Principle of the electro-chemical desalination and reduction of the capillary conveyance by water
5.3.2. Passives Law cases
5.3.3. Committee Law cases
5.3.4. Electrode-batches Electro-osmosis
6. Salt in the brickwork and the role of the finery
6.1. Salt in the brickwork (broadly)
6.2. Mode of action of the victim-finery or compress-finery
6.3. Cementgebundene finery (so-called close finery)
6.4. Finery for the recovery
7. Desiccation-law cases
7.1. Snifter insertion
7.2. Desiccation-appliances
7.3. Sensor steered ventilation
7.4. Desiccation with infra-red-radiation
7.5. Microwave-principle
7.6. Temperature regulated Heizstabtechnologie
      Literature Leaflets and norms

1. General references about the humidity

Humidity or dampness understand by the concept one the content at water vapor of the atmospheric air. Each construction-material stands by its surroundings in a dampness-balance. The practical dampness-content (table 1) becomes for itself according to the location, whether cellars, roof, in the bath, South-page and other put in and is influenced by this.

Table 1: Practical dampness-salaries of construction-materials and component parts

MaterialPractical dampness-content
volume-covered [Vol%]
BricksAbout. 1,5
Lime-sandstoneCirca 5,0
Emphasize with closed structure with dense or porigen surchargesCirca 5,0
Easily-concrete with haufwerksporigen structure with dense surcharges after DIN 4226 part 1Circa 5,0
Easily-concrete with haufwerksporigem structure with porigen surcharges after DIN 4226 part 2Circa 4,0
Gypsum, anhydriteCirca 2,0
Full-bricks1 ... 2,5
Concave-bricks1,5 ... 4,0
Inner-finery1 ... 10
Outside-finery1 ... 7
Inorganic materials in unmounted Schüttung; Expanded rock-glass (for example expended perlit)5,0 (claim-covered)
Mineral fiber-heat insulation-materials of glass, stone, blast furnace-cinder - fibers (cottages -)5,0 (claim-covered)
Yeast-glass0 (claim-covered)
Wood, plywood, chipboards, fiberboards, excelsior-easily-construction-plates, reed-plates and - weak, organic fiber-heats insulation15,0 (claim-covered)
Vegetal fiber-heats insulation from kelp, wood, - peat - and coconut-fibers and other fibers15,0 (claim-covered)
Cork-heats insulation10,0 (claim-covered)
Yeast-synthetic material from polystyrene, polyurethane (hard)5,0 (claim-covered)
[12, 14]

In all capillary-porous component part, humidity is stored. The storage proceeds dynamically and within the same component part often very unevenly. With capillary-porous component part, an average term-moisture-content appears. Wood is marked by a balance-humidity, humidity however also can bind hygroscopic out of the air. One distinguishes
Water vapor-diffusion:  The transportation of water vapor from the construction-material
Capillary Conductivity: The transportation of fluid (water) from the construction-material
Hygroscopic: The ability of a construction-material, to pick up waters and to bind.

Form 2: Dampness-performance of different construction-materials /6/

Well qualified capillary-system with capillaries of different diameter:
Big water-reception-capability, big dampness-delivery-capability for example bricks gypsum

Shot cells structure with few capillaries between the cells:
Big water-reception-capability, low dampness-delivery-capability, for example gas-concrete

Structure with small, closed pores and capillaries:
Low water-reception-capability, low dampness-delivery-capability, for example heavy-concrete, Blähton-Beton
Form dampness-performance of different construction-materials

From the above named ones, shows itself very easily, that water has another meaning 5 per cent of bulk-volume in each construction-material. One must each construction with it, even component part with the respective ones would use separated construction-materials assesses.

The binding agents would use at the house-construction, like cement, lime and gypsum, requires for its chemical water curing process and the mortar even for its processing water. This must escape also again to the largest part and is taken away. Earlier, one therefore had "ausgewintert"(over dne winters empty abandons) the buildings. Through the stand-time, the building could dry up well. Or in the first 1 to 2 years, poorer families lived in the new apartments. They had the task the apartment to live drily. Even squatters provide a dry building in the winter through the inescapable opening of the doors and window menus and heating. If the building becomes unused longer time, so it increasingly disintegrates. An essential cause for this is the humidity, that is not led sufficiently away. Yielding a return considerations shorten the construction-times without, to keep to the necessary technological desiccation-times. With it interconnected is one much too high humidity of the ambient air, that often leads to mold-formation, with the initial utilization. 80 per cent relative atmospheric humidity and could already often be determined more at redevelopment-works for the lived in status. Unfortunately it is no particular case that old facades with high pressure are cleaned and a heat insulation system are found directly after it. During this time, the window menus with metal leaves are covered. It cannot be pointed out to sufficiently urgently that the evaporation is that mechanism, which counteracts the water-reception, in the undisturbed dampness-household of a wall. Only so, the more extrinsic wall-work periods dry off. Deeper wall-work periods can serve as its humidity after the legalities of the steam-diffusion.
Bricks, clay and wood have especially favorable physical qualities and are to be recommended for that reason as space-enclosing construction-materials. Its essential advantage is that they can reduce short-term moisture-apexes as they perform with the douche, for example.
Find gypsum and gypsum-lime-finery a wide application-field with the financial recovery and at the new construction. For its processing, however, also a large volume is required at water, which must be carried off again until on the crystal-water. The inner-walls with new gypsum-lime-finery became in an object, partially until 4 cm firm, plasters. The insufficient ventilation changed some spaces into downright caves with an interesting ginger mold-cover. The processor put the whole blame on the material. It didn't want to hear anything about a processing-mistake, insufficient ventilation.

In principle, gypsum-containing construction-materials belong, as not plasterboard-construction-plates (also they become green) or gypsum-finery in a normal cellar! Lime or lime-cement-finery can be abandoned in the comparison of a higher dampness-encumbrance without that damaged the construction-materials, and a high mold-concentration occurs. However, borders also are placed here.

vollständig falsche KellernutzungBut also by wrong utilization, damages can virtually be promoted. Here a picture (2005) from a cellar (BJ 1910) in NRW. Virtually a classic example of the mistakes. The tiles (barrier layer) prevent the dampness-adjustment between wall and ambient air. The wall-dampness therefore rises upward on and on. It salts - and dampness-damaged finery already came off, sees defective tiles. The dry the washing in the closed building is to be omitted and really in the cellar. (A washing-base is airy and is always led away the dampness.) Neither the tiles nor the cover can pick up the dampness. Not only the window menus are closed and something here in the picture not recognizable is, the cellar-doors are flat closed and leave zund no cross-ventilation or an air-replacement with the other cellar-spaces so

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Contributions to the wall-humidity

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