Waterproofing and CTE DB-HS1: warranties and how to choose a contractor in Madrid

Waterproofing is not just “installing a membrane”: in Spain it must meet the CTE DB-HS1 (Protection against moisture) requirements, and you should also secure clear warranties to avoid leaks, disputes, and repeat repairs. This guide explains what to ask for and how to choose a professional in Madrid (and Toledo) using practical criteria.

What CTE DB-HS1 is and why it matters for waterproofing

Spain’s Building Technical Code (CTE) sets minimum performance requirements. DB-HS1 focuses on reducing moisture risk (rainwater, rising damp, condensation, ground water) in elements such as:

• Flat and pitched roofs
• Terraces and walkable roof decks
• Basements and below-grade walls
• Junctions, parapets, drains, and other critical details

Meeting DB-HS1 is not “just paperwork”: it means designing and installing a system that matches the use, slope, drainage, mechanical protection, and detailing.

If a critical detail (drain, parapet junction, pipe penetration) fails, the whole waterproofing system often fails.

Common failure points that cause leaks

Without turning this into a full specification, these are the most frequent issues behind waterproofing defects:

• Insufficient slope and chronic ponding
• Poor drain detailing (no clamping ring/flange, no reinforcement, wrong height)
• Parapet upstands with inadequate height or no proper coping/protection
• Poor compatibility between primers, membranes, and finishes
• Lack of protection against puncture (traffic, gravel, pavers)
• Untreated joints and junctions

What warranties to request (and how they should be written)

When you request a quote, make sure the warranty is clear and documented. Practical recommendations:

• A written warranty stating duration, scope, and exclusions (maintenance, third-party damage, later works).
• Identification of the system (brand/model), layers, and included critical details.
• Use conditions: walkable/non-walkable, planters allowed, whether drilling is permitted, etc.
• What counts as a repair (patch) vs. a full replacement.
• A photo report of the installation (especially before covering layers).

For homeowners associations, it’s essential to define exactly which areas are covered (roof, common elements, junctions with façades) to prevent disputes.

Minimum documentation a serious contractor should provide

To align workmanship, warranty, and compliance, ask for:

• An itemized quote (substrate prep, primer, membrane, reinforcements, detailing, protection layer).
• Technical data sheets for the specified system.
• A critical-details plan (drains, parapets, joints, façade junctions).
• A completion record (depending on scope).
• A maintenance proposal (annual inspection, drain cleaning).

How to choose a waterproofing contractor in Madrid (quick checklist)

Madrid combines intense rain events with large temperature swings, which stresses joints and detailing. When choosing:

• Proven experience with roofs and terraces like yours.
• A complete approach: diagnosis + system + detailing + protection.
• A quote that does not ignore critical details.
• Clear explanation of alternatives (e.g., liquid-applied membrane vs. sheet membrane) and why.
• Clear responsibility on site (in-house team or identified subcontractor).

Red flags in a quote

• “Waterproofing” with no layers, brands, or detailing.
• Very low price with no mention of protection or drain treatment.
• Either skipping necessary removals or proposing demolition without justification.
• “Verbal” warranty or warranty with no conditions.

Useful questions before you sign

• How will you detail drains and parapet junctions?
• What final slope will remain and how will it be checked?
• What protection layer will you install (pavers, gravel, geotextile, screed)?
• What maintenance do you recommend, and what voids the warranty?

Conclusion

Long-lasting waterproofing depends on the right system, correct installation, and having the work aligned with CTE DB-HS1 and a clearly defined warranty. If you’re planning to waterproof a roof or terrace in Madrid or Toledo, Impermyna can help you diagnose the moisture source, specify the right system, and deliver everything with clear scope and written warranty.

If you’d like, request an assessment and we’ll recommend the best solution for your case, with scope and warranty in writing.