To develop a suitable restoration concept, the cause and the scope of the structural damage need to be recognised, measured, recorded and documented. The focus is primarily on aggressive salts and building material moisture, as well as physical underlying conditions. In connection with the object-specific conditions, economic restoration can be planned, be it a cellar of a detached house or an historical vaulted cellar.
Relevant investigation results require a targeted sampling process. Samples of the various damage types, building materials and parts are examined. The samples must be of an adequate size to allow the inhomogeneous state of a brickwork cross-section to be recorded. The samples are taken at the measuring axes at various heights (heigh profile) and depth (depth profile). This allows statements to be made about distribution of the moisture and damaging salts; the causes of the damage become evident.
Neither method discloses the cause(s) of the moisture or the degree of moisture saturation.
Further measuring data and reference variables are necessary for this:
One important indicator is the maximum capillary water absorption. This is the maximum quantity of water that a dried building material sample can absorb based on its pore contents and/or pore geometry when water is retained in capillaries.
To determine the maximum water absorption, the entire pore space is filled with water under pressure.
Moisture saturation levels do not allow reliable conclusions to be made about the cause of the degree of moisture saturation. It is not clearly evident whether the moisture from the fluid phase penetrated through capillaries or whether it was absorbed, at least partially, hygroscopically from the ambient air. An assignment is only possible here by ruling out certain options: The hygroscopic moisture is measured at one or more points; this involves exposing the dried construction material samples to a special relative humidity for a longer time at a constant temperature in a climate chamber. The hygroscopic moisture is determined by the observed weight increase.
In certain cases condensation should be taken into account as a further cause of moisture. Its impact can be estimated by recording the room-climate conditions (relative humidity and air temperature) and the surface temperature. However, precise statements are only possible if the climate data is recorded for longer periods.