Can a basement be waterproofed retrospectively?

Yes. A basement can be waterproofed retrospectively with ALLESDICHT, either externally or internally. The appropriate method depends on the level of water exposure and whether the basement wall is accessible.

External waterproofing is the more reliable option because it stops water on the positive side of the basement wall. The wall is excavated, cleaned and prepared to provide a sound substrate. ALLESDICHT is applied in several coats and, once cured, forms a seamless, crack-bridging rubber membrane that adheres to concrete, masonry and bitumen while bridging minor settlement cracks. Reinforcement fabric is embedded at the wall-to-floor slab junction and around service penetrations. The required dry film thickness depends on the water exposure: around 3 mm is sufficient for ground moisture, while approximately 4 mm is required where there is perched water or hydrostatic pressure.

If the outside of the wall is inaccessible, for example because of adjoining structures or pavements, internal waterproofing on the negative side may be considered. It is particularly suitable for protection against ground moisture and non-pressurised water, provided the substrate and service conditions are appropriate. Where hydrostatic pressure is present, the requirements for internal waterproofing are significantly more demanding. The suitability of this waterproofing approach for the specific loading conditions should therefore be assessed before work begins. Once completed, the waterproofed surface can be plastered or clad.

In both cases, careful substrate preparation is essential. Loose plaster, efflorescence and all contamination must be completely removed before application.