Waterproofing quote: what it must include and how to compare offers

A waterproofing quote shouldn’t be just “a price per m²”. To avoid surprises (leaks coming back, unexpected extras, or warranties that don’t really cover you), it helps to know which line items and conditions must be written down—and how to compare offers fairly.

What should be stated before the price

A solid quote starts by describing the issue and the substrate:

• Exact area: terrace, flat roof, gutter, parapet junction, etc.
• Surface and measurement (m² plus linear meters for upstands/flashings).
• Substrate condition: cracks, moisture, ponding, weak points.
• Proposed solution and system (not just “waterproofing”).

If the quote doesn’t explain the system and its layers, it’s hard to enforce quality later.

Must-have line items (checklist)

When comparing offers, make sure these are included (as applicable):

• Substrate preparation: cleaning, repairs, crack treatment, primer.
• Falls/levels correction to remove ponding.
• Waterproofing system: membrane type (EPDM, TPO, polyurea, bitumen, resin, etc.), thickness/weight, number of coats/layers.
• Reinforcement at details: drains, joints, parapet junctions, penetrations.
• Flashings/terminations: coves, termination bars, sealants, drip edges, coping if needed.
• Protection layer: geotextile, screed, drainage board, gravel, pavers on pedestals, protective coating, etc.
• Waste removal and final cleaning.
• Testing: a controlled flood test where feasible.

Measurement: it’s not only m²

Two quotes with the same “price per m²” may be impossible to compare. Check:

• Linear meters of parapets and terminations (often the real cost driver).
• Number of drains and how they’re treated.
• Upstand height on vertical surfaces (e.g., 15–20 cm or more depending on the case).
• Access, temporary works, and safety measures.

Warranty: what to ask for so it’s meaningful

The warranty should state:

• Duration and what’s covered (labor, materials, call-outs).
• Exclusions (maintenance, impacts, third-party works, blocked drains).
• Conditions to keep it valid (inspections, drain cleaning, etc.).
• System documentation and technical datasheets.

For multi-owner buildings, it’s best the warranty is issued to the homeowners’ association and the covered areas are clearly defined.

Standards and accountability (CTE DB-HS1)

Without getting too technical, a professional quote should align with proper watertightness and correct detailing. In Madrid, many refurbishments on existing buildings require extra attention to:

• Parapet junctions and penetrations.
• Rainwater evacuation (falls and drains).
• Material compatibility with the existing substrate.

Red flags in a quote

Be cautious if:

• It only says “waterproofing” with a lump sum—no system, no layers.
• Details/flashings aren’t included (they later appear as “extras”).
• Substrate preparation is missing.
• It promises a “full warranty” with no written conditions.
• There’s no protection layer for walkable areas.

How to compare offers (quick method)

Ask every contractor to price the same scope:

• Same measured area and same terminations.
• Same system—or, if different systems are proposed, full layer build-up and protection.
• Written warranty and a test where applicable.

Then compare in a simple table: preparation, system, details, protection, schedule, warranty, and price.

Key questions before you sign

• What happens if hidden moisture is found once finishes are removed?
• How will drains and movement joints be handled?
• What maintenance is required to keep the warranty valid?
• Will you provide progress photos and a watertightness test record?

A note for Madrid and Toledo

In many Madrid buildings, leaks often come from shared terraces with multiple junctions (parapets, stair cores, chimneys, HVAC units). In those cases, the quote must include specific line items for detailing—because that’s where failures most commonly start, more than the “m² of membrane”.

Want us to review your quote?

If you have multiple offers—or you’d like a detailed proposal for a terrace, flat roof, or garage in Madrid or Toledo—Impermyna can review the scope, recommend the right system, and document line items and warranties clearly so you can compare with confidence.