Under-tile waterproofing is the most important invisible element of a premium bathroom. Without it — even the most expensive tiles will not prevent a costly leak after 3 years.
Why waterproofing is the most critical element of a bathroom
A bathroom leak is one of the most costly building defects. Water that seeps through an unsealed grout joint or through a micro-gap around a drain does not stop at the floor — it penetrates the screed, destroys thermal insulation, reaches the slab structure and causes damp on the ceiling below. The cost of such damage — including tile removal, drying and re-execution — can be several times higher than the cost of proper waterproofing from the start.
At LOFTBAU, under-tile waterproofing is a standard part of every execution, not an optional extra. We use only certified systems from reputable manufacturers, selected appropriately for each project.
Schlüter-DITRA uncoupling mats — when and why
DITRA mat is a polypropylene membrane with a characteristic waffle structure, laid directly on the screed before tiling. It serves two functions simultaneously: it uncouples the ceramic cladding from substrate movements (eliminating thermal and mechanical stresses) and waterproofs the surface beneath the tiles.
We use DITRA wherever the floor has electric or hydronic underfloor heating, where the screed is relatively new, or where large-format tiles are particularly sensitive to micro-movements. The Schlüter system is compatible with Mapei and Kerakoll adhesives — we always create a coherent, system-based assembly.
Flexible waterproofing — Mapei and Kerakoll
For waterproofing shower enclosure walls, around bathtubs, in drain channels and at pipe penetrations, we use flexible sealant compounds: Mapei Monolastic or Aquaflex 360 for surfaces requiring elasticity, and Kerakoll Aquastop Elastic for zones of constant high humidity.
We apply a minimum of 2 coats — the first must be dry before the second is applied. Sealing tape is applied at corners and edges. These are the most critical points, where stresses concentrate most — without corner tape, the waterproofing is effectively incomplete.
Premium bathroom pricing — Kraków
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Sealing at Viega linear drains
A linear drain is an elegant solution, but technically demanding. If the seal at the drain housing edge is imprecise, water reaches below the screed. We use sealing collars dedicated to Viega Advantix drains, installed on the waterproofing layer before tiling.
Geometry also matters — the drain must be set with a minimum 1.5–2% slope towards the outlet. Errors at this stage justify stopping all works. We never cut corners on this process.
How to verify that waterproofing has been done correctly
During execution — before tiling — we carry out a water test: we flood the shower floor or bathtub with water for 24 hours and check that the ceiling below remains dry. It is a simple method, but it gives certainty before the waterproofing layer is covered by cladding.
After execution is complete, we document every waterproofing stage with photographs. The investor receives images of: uncoupling mats, sealant compound layers, corner tape and drain collars. This is proof of correct execution — important for any future insurance claims.
