Drainage

Drying - Drying refers to the structural removal of moisture from buildings, particularly in basements, foundations, and walls in contact with the ground. Causes of moisture include rising damp (capillary water transport through porous masonry), water penetrating from the sides (defective or missing exterior waterproofing), and condensation (insufficient ventilation combined with low wall surface temperatures). Drying out is one of the most common and costly renovation measures for existing properties - and one where a misdiagnosis can be particularly expensive.

Drying-out Methods

The choice of the right method depends crucially on the cause of the moisture:

Horizontal barrier (against rising damp): Inserting a water-impermeable layer into the wall to stop the capillary rise of ground moisture. Traditionally done using the wall sawing method - mechanically inserting stainless steel sheets or bituminized fabric layers into a sawed-through wall joint. More modern and less invasive: injection method - injecting a silicone, silicate, or acrylic resin solution into horizontally drilled holes, which form a water-repellent barrier after curing. Effectiveness: well-documented for the wall sawing method; for the injection method, it depends on the homogeneity of the masonry.

Vertical waterproofing (against water penetrating from the side): Exposing the exterior wall down to the foundation footing and applying a new waterproofing layer. Materials: Bituminous waterproofing (primer and welded membranes), synthetic waterproofing membranes (KMB), mineral-based waterproofing slurries, or combinations thereof. Always combined with drainage at the base of the foundation to divert accumulated pressurized water. This is the most labor-intensive solution but, when properly executed, the most durable.

Internal Waterproofing (when external waterproofing is not possible): Mineral waterproofing plasters or slurries applied to the interior of the damp wall. This method keeps the water out but does not eliminate the cause-hydrostatic pressure remains on the exterior. Suitable as a temporary solution or for basements used solely for storage.

Electro-osmosis: Electrical methods in which weak direct current fields are intended to influence moisture movement within the masonry. The scientific efficacy is controversial; recognized professional associations (WTA, Fraunhofer IBP) do not recommend this method as a primary remediation procedure.

Costs and Cost-Effectiveness

Costs vary greatly depending on the method, extent of damage, and accessibility of the building:

• Injection method (horizontal barrier): approx. 150-300 euros/linear meter of wall length
• Wall sawing method: approx. 250-400 euros/linear meter
• External waterproofing (exposure + waterproofing, including earthwork): approx. 500-1,200 euros/linear meter
• Drainage (in addition to waterproofing): approx. 100-200 euros/linear meter
• Internal waterproofing (mineral-based): approx. 50-120 euros/m² of wall surface

For a typical single-family home with a damp basement (basement perimeter approx. 40 running meters), the total cost is approx. 10,000-50,000 euros - depending on whether only a horizontal barrier or complete exterior waterproofing with drainage is required. This significant range in costs underscores why a precise preliminary investigation is essential.

Common Misdiagnoses and Their Consequences

A widespread mistake is confusing rising damp with condensation. Both lead to damp walls, but require completely different measures:

• Rising damp is caused by capillary transport of ground water into the masonry - typical pattern: moisture starts at the floor and rises upward; salt efflorescence is characteristic
• Condensation occurs when warm, humid air meets cold wall surfaces - typical pattern: Stains primarily in corners and behind furniture, more pronounced in winter, no connection to proximity to the floor

A horizontal vapor barrier is an expensive misinvestment for a pure condensation problem. Conversely, better ventilation does not help if groundwater is pushing through the exterior wall. A building moisture diagnosis by a certified expert is therefore mandatory before any dehumidification measures are taken.

Practical Tip for Homeowners in Nuremberg

We recommend that homeowners in the Nuremberg metropolitan area with damp basements-particularly common in post-war buildings in Langwasser, Schweinau, Gibitzenhof, and the Südstadt, but also in Wilhelminian-style houses in Gostenhof and Johannis-have a professional damage assessment conducted before beginning any dehumidification work. The expert should perform moisture measurements (CM method for wall moisture content), salt analyses (to identify the source of the moisture), and, if necessary, a thermographic survey.

In Nuremberg, specialized companies (ISOTEC, Getifix, local waterproofing firms from the DHBV network) offer free initial inspections-though these are naturally not impartial. For an independent diagnosis, we recommend an independent building expert (IHK-certified or publicly appointed) whose assessment is not influenced by a vested interest in a particular method. Upon request, we can connect you with suitable experts from our network.

Frequently Asked Questions

How can I tell if there is moisture in the basement?

Typical signs include: damp spots on walls and floors, salt efflorescence (white, crystalline deposits indicating the presence of chlorides or sulfates in the masonry), peeling plaster and flaking paint, a musty, earthy odor, mold growth in corners and shady areas, condensation on pipes and windows, and bulging or lifted flooring. With a simple moisture meter (electrical-capacitive, starting at 30 euros), you can take initial measurements yourself; for a professional diagnosis, a building inspector with a CM meter (calcium carbide method) is recommended.

Is drainage advisable for an old building’s basement?

That depends on the planned use. If the basement is to serve only as storage space, a simple horizontal barrier with injection and improved natural ventilation is often sufficient. If the basement is to be converted for residential use (bedroom, hobby room, office), complete exterior waterproofing with perimeter insulation and drainage is required-a significantly more expensive undertaking that is only worthwhile if the additional living space justifies the added cost. For very old basements (built before 1900) with natural stone or fieldstone masonry, complete drainage is often technically difficult and economically unfeasible-in such cases, restricting the use of the space is often the more pragmatic decision.

Who pays for the drainage in a condominium association?

The basement is generally considered common property-the drainage is therefore financed through a resolution of the owners’ meeting, either from the maintenance reserve fund or via a special assessment. All owners bear the costs in proportion to their share of co-ownership. If only a single basement unit is affected and the cause lies within the common property (e.g., defective exterior waterproofing, inadequate drainage), the condominium association must still bear the costs. If, on the other hand, the cause lies within the individual property (e.g., defective basement waterproofing due to improper DIY work), the affected owner pays. In case of doubt, an expert determines the cause.

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