Importance of water load for the planning

The right determination of actual water level is most important for the planning of water-proofing works and the choice of the waterproofing system. The conditions of the soil must be examined carefully and the existing water load be evaluated. From this, the planner can determine the loads acting on the basement structure. These water loads are basically divided into 4 cases (according to DIN 18533).

DIN 18533

Water load category W1-E: ground damp/ non-pressure water

Ground damp is a capillary-bound water present in the soil, e.g. water under suction, retained water, and capillary water. Water that can even drain away in opposition to gravity, due to the capillary forces. 

A case that is comparable to the case of ground damp, is generated by non-banking seepage water due to precipitation. Non-banking seepage water is surface water and seepage water in liquid dripping form, and it does not exert hydrostatic pressure on the water-proofing system. This case can only be prevailing if the ground in a sufficient depth under the foundation base and if the backfilling material of the excavation pit consists of highly permeable soils, such as sand or gravel. The accumulating water must be able to seep down to the free ground water level. Non-banking seepage water must also be assumed for low-permeability soil components in combination with functional drainage (according to DIN 4095).

Water load category W1-E

Water load W1-E

Ground damp and non-pressure water on concrete slab and earth-contacting walls

Water load category W1.2-E

Water load W1.2-E

Ground damp and non-pressure water on concrete slab and earth-contacting walls with drainage

Water load category W2.1-E case of banking seepage water

Water load 2.1-E

Moderate pressure water – Case of banking seepage water without drainage

Water load category W2.1-E case of ground water

Water load W2.1-E

Moderate pressure water – Case of ground water

Water load category W2-1.E: moderate solicitation of pressure water

Pressure water is water that exerts pressure on the external side of the building. The case of pressure water is differentiated in banking seepage water, flood water and ground water. In case of soils with a low level of permeability (≤ 10- 4 m/s), one must anticipate that the seepage water penetrating into the masonry will, at times, bank up in front of the building parts, and exert stress on them as pressure water. Likewise, pressure water should be assumed, if ground water stresses the structures

Easy determination of load case in accordance with standards

The part 1 of DIN 18533 describes the scope of application of the standard and defines the respective cases of water load, depending on the type of soil and water and the installation parts. The case of water load can be clearly assigned from these parameters. The above-described diagram helps planners and applicators in assigning the specific case of water load. The assessment of water level is an important factor for determining the load case for earth-contacting building structures. It defines the "highest ground water level or highest flood water level determined from years of observation, if possible". If sufficient information is not available, then an expert report on soil conditions must be drawn up.

Is a drainage required?

If the load case of non-banking seepage water (W1.2-E) should be avoided in case of cohesive soils, a drainage is then required under compliance with national guidelines/standards (for ex. DIN 4095) for proper execution and dimensioning of the drainage system.

Often drain water cannot however be drained as planned as suitable, when receiving water courses or storm water sewers are not present.

Given this situation an increasing number of new construction projects are planned according to the load case of pressure water. This requires a seamless and jointless tanking design and execution of the waterproofing system and a higher reliability of application.