Problems with balcony waterproofing usually have more than one cause. Leaking balconies can be caused by a failed or missing waterproofing layer, an unsatisfactory slope or clogged balcony drainage, unsuitable edging or leaks at connections. While simple regrouting might be carried out as an urgent measure, a proper repair can only be completed after the true cause of the problem has been established.

Signs your balcony may be letting water through

The following indicators can suggest a balcony waterproofing problem:

  • Damp patches, staining or peeling paint on the ceiling of the flat below, especially after rain.
  • Hollow-sounding tiles, or tiles that have lifted or cracked.
  • Cracking or breakdown of grout, especially at balcony edges and around drain outlets.
  • Water not draining off the balcony within a reasonable time.

A musty smell or visible mould on the balcony ceiling of the apartment below may also indicate condensation rather than a leak. These issues must first be investigated to establish whether water is entering through the balcony.

It’s best to investigate before the next heavy downpour.

Waterproofing versus tiles, grout and surface sealers

Water leaking from balconies is often addressed by regrouting or painting a surface sealer onto the tiles. In most cases, a more complete approach is required.

The balcony is made up of different layers: the substrate, waterproofing membrane, tiles, flexible tile adhesive and grout, movement joints and sealants. Waterproofing needs to be addressed as a complete system rather than by treating only the surface of the tiles.

SikaCeram tiling systems treat the balcony as a complete system, with components designed to work together. These include substrate preparation, waterproofing, flexible tile adhesives and grouts, and elastic sealants for joints and connections.

In practice, this means:

  • More grout is not necessarily the solution. Water can pass through joints or other vulnerable points in the tiled surface. If the underlying waterproofing has failed, regrouting alone will not address that failure.
  • A surface sealer is not always a long-term solution. It may reduce water penetration but can require reapplication.
  • Some systems can be installed over existing tiles. Combined waterproofing and adhesive systems are available, but a qualified contractor must assess whether the existing tiles and substrate are suitable.

Why slopes, outlets and edge details matter

Allowing water to flow off the balcony rather than accumulate on its surface is also important.

  • Slope: The balcony floor needs to fall towards the drain outlet so water flows away rather than standing in puddles.
  • Drain outlet: A blocked or poorly fitted outlet can leave water sitting where it shouldn’t. Our guide to autumn storms and empty homes in Greece covers the risks associated with blocked balcony and terrace drains.
  • Perimeter and movement joints: Connections between the balcony floor, building walls and door thresholds are vulnerable points. These joints may need flexible sealing rather than rigid repairs.
  • Thresholds and door sills: Inadequate threshold height or poorly arranged floor levels can allow water to flow indoors.

A repair to the waterproofing membrane that does not also address problems with the slope, drainage and edge details may only solve part of the problem.

What a proper inspection should establish

Before anyone proposes a fix, an inspection should identify:

  • Where water is entering. This is not always directly above the damp patch. Water can travel along a slab or other surfaces before appearing on the ceiling below.
  • Whether the problem involves the waterproofing membrane, drainage or joints.
  • The condition of the substrate beneath the tiles. Is it sound, or has it suffered cracking or other damage?
  • Whether the leak is confined to the balcony or comes from elsewhere, such as plumbing, another apartment or the roof. Responsibility for repairs may require a separate review of the building’s documents.

Can the proposed cause of the water ingress be explained and confirmed before repairs begin?

“Before comparing quotes for a repair, it would be helpful to have the proposed cause of the leak and proposed scope of works clearly explained. Then at least the cheapest quote will tell you something!”

Yanis, Founder of Home Watch Athens

Repair options and when tiles may need lifting

What a repair involves depends on what the inspection finds:

  • Local repairs: A specific joint, threshold or small damaged area may be repaired without affecting the rest of the surface, if the surrounding waterproofing remains sound.
  • Waterproofing over existing tiles: A suitable system may be applied over the existing tiles, provided the tiles and substrate are in an appropriate condition.
  • Full removal and re-waterproofing: Where the membrane has failed more widely or the substrate is damaged, tiles may need to be removed so the area can be properly prepared and waterproofed before new tiles are laid. This is more disruptive and expensive, but local patching may not resolve a wider failure.

This guide does not cover structural problems. Cracked or deteriorating concrete, exposed reinforcement and similar damage should be assessed by a structural engineer.

Questions to ask about a waterproofing quote

A useful quote should be dated, state the surface area in square metres and explain whether VAT is included. It should also answer:

  1. Diagnosis: What is the stated cause of the leak, and how was it identified?
  2. Preparation: Will tiles need to be removed? If not, why not? What substrate preparation is included?
  3. Drainage: Does the work include correcting the floor slope or repairing the drain outlet? Are those items included in the quoted price?
  4. Detailing: How will perimeter joints, thresholds and movement joints be treated?
  5. Products and finish: What waterproofing system and tile finish are specified?
  6. Warranty: What is covered, for how long, and does it cover workmanship, water ingress or both?

Don’t choose the cheapest quote when its scope is described only as “waterproofing and tiling.” Read the details and make sure potential contractors answer these questions before you decide. If you are obtaining several quotes, ask each contractor the same questions.

Checking the finished work from abroad

If you cannot be present in Athens, arrange for the condition and progress of the work to be documented:

  • Before work starts: Photograph drain outlets, thresholds, perimeter joints and movement joints. Mark the areas to be repaired and record failed coatings, cracked grout and other visible damage.
  • During the work: Obtain progress photographs, especially after tiles have been lifted. The substrate and waterproofing layers will be hidden once the work is finished.
  • After completion: Check that the balcony drains properly and monitor the area below for further damp.
  • Keep the paperwork: Retain the dated quote, invoices, product details and warranty terms in case problems return.

Greek Civil Protection guidance on flood preparation includes clearing drains and checking outlets. For a balcony, keeping the outlet clear between visits matters just as much as checking it after a repair.

For members, Home Watch Athens can help arrange checks before work starts and attendance during the repair. Technical work and attendance beyond a normal visit are charged separately. See our maintenance and technical oversight service for more information.

Last reviewed: 1 October 2026. This guide concerns balcony waterproofing. Falling finishes and structural deterioration require assessment by an engineer. Ownership and responsibility for a particular repair cannot be determined without reviewing the relevant building documents.

Frequently asked questions

Can rain leak through balcony tiles?

Yes. A tiled surface and its grout joints are not a complete waterproofing system. If the membrane underneath fails, water can enter even when the tiles appear intact.

Will new grout fix the problem?

It may help if the issue is confined to damaged grout and the underlying waterproofing remains sound. If the membrane has failed, regrouting is unlikely to solve water ingress into the area below.

Can waterproofing be installed over existing tiles?

Yes, suitable systems are available. A qualified specialist must assess the existing tiles and substrate on site before recommending this approach.

Why is the flat below showing damp?

A failed balcony membrane may allow water to reach the ceiling below. Other possible causes include poor drainage, a blocked outlet, failed joint or threshold seals, plumbing leaks or condensation.

What should a repair quote include?

The diagnosed cause, preparation work, whether tiles will be removed, drainage and joint treatment, specified products and finishes, VAT and warranty terms.

How can I verify the work from abroad?

Arrange photographs before and during the work, especially while the substrate and waterproofing are exposed. After completion, check drainage and monitor for damp, including after heavy rain.