Why can damage appear after summer in Madrid?

Madrid summers combine high temperatures, prolonged dry periods, intense solar radiation and significant temperature differences between sun-exposed and shaded surfaces. These conditions place repeated stress on roofs, terraces, façades, sealants and window frames.

Thermal expansion and contraction

Construction materials expand slightly when they become hot and contract as they cool. These movements are normal, but repeated cycles can weaken older joints, open small cracks or separate sealants from their supporting surfaces.

Sunlight and deterioration of finishes

Long exposure to sunlight can accelerate the ageing of external paint, plastics, membranes, mastics and flexible joints. South- and west-facing façades, terraces, awnings and windows are often subjected to the most demanding conditions.

Accumulated dust and debris

Dust can reduce airflow through air-conditioning filters and collect around terrace drains, gutters and downpipes. When autumn rain arrives, this debris may prevent water from draining correctly.

Sudden rain after a dry period

A damaged joint or small crack may remain hidden throughout the summer. The first substantial rainfall can reveal the problem through staining, blistered paint, dripping water or damp around window, façade and roof junctions.

Air-conditioning condensation

An air-conditioning system removes moisture from indoor air and produces condensate water. If the drainpipe is blocked, poorly connected or incorrectly sloped, the water may overflow and affect walls, suspended ceilings or furniture.

1. Air leaks and loss of energy efficiency

Why they occur

Window and door gaskets can harden, flatten or become detached because of heat and regular use. External sealant may crack, window leaves can become slightly misaligned and air can enter around roller-shutter boxes.

In penthouses, detached houses and properties immediately below a roof, accumulated heat may also reveal existing insulation defects or gaps around ducts and other building services.

How to check for air leaks

• Paper test: place a sheet of paper between the opening section and the frame. Close the window or door and pull gently. If the paper comes out with almost no resistance, the gasket may not be compressing correctly.
• Air movement: move a light tissue around the frame on a windy day. Movement in a specific area may indicate an air leak.
• Touch test: look for areas of the frame that feel noticeably warmer or cooler than the surrounding surface. This is only an initial indication and does not replace thermal imaging.
• Night-time light test: ask another person to shine a light from the opposite side of an external door and check whether light passes through its edges.
• Roller-shutter box: place your hand near the access panel and strap opening to detect noticeable draughts.
• Visual inspection: look for cracked sealant, flattened gaskets, detached corners or difficulty closing the window.

Safety note: avoid using a flame or burning incense near curtains, combustible materials, detectors or electrical equipment. A light tissue is usually a safer way to identify air movement.

What you can do immediately

• Clean the frame and replace visibly detached or hardened weather seals.
• Fit a temporary draught excluder if air is clearly entering below an external door.
• Seal small, non-structural internal joints with a product compatible with the surface.
• Only adjust window hardware if you understand the particular system.
• Do not cover drainage holes or permanent ventilation grilles.

The best long-term approach

A long-term solution should balance airtightness, insulation and controlled ventilation. Sealing a property indiscriminately without considering air renewal may increase the risk of condensation.

If the frames remain in good condition, renewing the seals, adjusting the hardware and improving the roller-shutter box may be sufficient. If the frames are distorted, the glazing performs poorly or significant thermal bridges are present, a more comprehensive upgrade may be appropriate.

The result will depend on the orientation, glazed area, ventilation, previous condition and way the property is used. Energy savings should not be estimated without inspecting and measuring the building.

DIY maintenance or professional work?

• Suitable for basic maintenance: cleaning, the paper test, straightforward gasket replacement and fitting a temporary draught excluder.
• Professional assessment recommended: distorted frames, water penetration, damaged glazing, uninsulated roller-shutter boxes, persistent condensation or work affecting the external façade.

2. Air conditioning after the cooling season

Why problems develop

During summer, a split unit or ducted system moves a large volume of air. Dust collects in the filters, while moisture may remain in drain trays and condensate pipes.

Without appropriate maintenance, the system may develop unpleasant smells, reduced airflow, unusual noises, internal dripping or biological contamination in damp areas. A heavily clogged filter can also make it more difficult for the equipment to operate under suitable conditions.

How to perform an initial check

• Switch off the equipment and isolate it as instructed by the manufacturer.
• Open only the user-accessible cover and inspect the filters.
• Look for drops, water marks or a damp smell around the indoor unit.
• Check whether the airflow appears reasonably consistent across the outlet.
• Inspect the accessible end of the condensate drain without dismantling fixed components.
• Review the thermostat schedule and remove cooling periods that are no longer required.

What you can do immediately

• Clean or replace filters in accordance with the manufacturer’s instructions.
• Wash only filters designed to be washable and allow them to dry completely.
• Remove visible dust from accessible grilles and external surfaces.
• Update the programme for autumn and avoid maintaining unnecessary cooling settings.
• Do not introduce tools into a drainpipe if they could damage or puncture it.

Setting the thermostat to an unnecessarily low temperature will not cool the property faster. Stable, appropriate settings are generally more useful than extreme adjustments.

The best long-term approach

Plan periodic maintenance covering filters, coils, drain trays, condensate pipes, fans and general system operation. In ducted systems, return-air grilles, supply outlets and maintenance access points should also be reviewed.

When renovating a property, efficient cooling should not be approached simply by installing a more powerful unit. Insulation, solar protection, air leakage, room distribution and zoning should be assessed first.

For further information, see our air-conditioning and climate-control service in Madrid.

DIY maintenance or professional work?

• Suitable for the user: cleaning accessible filters, removing surface dust and updating the thermostat, provided the manufacturer’s instructions are followed.
• Professional work required: refrigerant handling, electrical repairs, internal coil dismantling, deep disinfection, loss of performance, ice formation, abnormal noise or internal dripping.

Safety note: disconnect the electrical supply before opening any permitted cover. Do not handle wiring, refrigerant or internal components. Work on refrigerant circuits must be carried out by suitably qualified professionals where required.

3. Waterproofing and damp after the first autumn rain

Why water ingress occurs

Water may enter through façade cracks, parapet junctions, balcony thresholds, window perimeters or defects in a waterproofing membrane. It may also collect if a terrace has inadequate falls or if its drains are blocked.

Older ground-floor properties may experience rising damp. This happens when moisture from the ground moves upwards through the pores of walls and finishes. Applying anti-damp paint alone will not correct the cause.

Spain’s Technical Building Code includes requirements intended to limit inappropriate moisture caused by rainfall, ground water, runoff and condensation. However, identifying the correct repair still requires an assessment of the particular property.

Signs to look for

• New marks on ceilings or corners after rainfall.
• Blistered, peeling or discoloured paint.
• White crystalline deposits known as efflorescence, caused by salts transported by moisture.
• Swollen MDF skirting boards or furniture panels.
• Raised or distorted timber and laminate flooring.
• Persistent damp smells in cupboards and next to external walls.
• Open joints around windows, parapets, thresholds and wall-to-floor junctions.
• Blocked terrace drains, gutters or overflow outlets.

How to distinguish water ingress, condensation and rising damp

• Water ingress: usually appears after rainfall and close to roofs, terraces, façades or windows.
• Condensation: forms on cold surfaces, corners or behind furniture and is often associated with indoor humidity, limited ventilation and thermal bridges.
• Rising damp: normally begins near the bottom of a wall and rises irregularly, often accompanied by salts and deteriorated plaster.

These signs can provide useful guidance, but they do not always reveal the exact source. Water can move through cavities, slabs and junctions before appearing some distance from the point of entry.

What you can do immediately

• Clean accessible terrace drains, gutters and drainage points.
• Move furniture, textiles and stored objects away from the affected wall.
• Ventilate in a controlled way and use a dehumidifier if appropriate.
• Mark the edge of the stain lightly in pencil and record the date.
• Take photographs before, during and after rainfall.
• Do not repaint or cover the area until the source has been identified and the surface has dried.

The best long-term approach

The repair must address the underlying cause. Depending on the diagnosis, this could involve renewing joints, repairing junctions, correcting falls, improving drainage, repairing part of a membrane or replacing the waterproofing system completely.

Where rising damp is confirmed, physical barriers, injection systems or other solutions compatible with the existing wall may be considered. Their suitability depends on the wall material, thickness, salt contamination and ground conditions.

Recurring condensation normally requires a combined approach involving ventilation, insulation, thermal-bridge reduction and control of indoor humidity.

See our waterproofing and damp-treatment service in Madrid for further information about how these problems should be assessed before repair.

DIY maintenance or professional work?

• Suitable for the user: cleaning accessible drains, photographic monitoring, controlled ventilation and moving affected objects.
• Professional assessment recommended: active leakage, a growing stain, recurring mould, distorted flooring, façade cracking, a communal terrace, suspected rising damp or any work at height.

Safety note: do not climb onto roofs, parapets or unsafe ladders. Avoid working on wet surfaces. If water reaches sockets, lights or an electrical distribution board, do not touch the affected area and request professional assistance.

A 10-minute seasonal inspection

Minutes 1–3: doors and windows

• Perform the paper test.
• Inspect gaskets and sealants.
• Check roller-shutter boxes for draughts.
• Look for stains beneath windows and balcony doors.

Minutes 4–6: terrace or balcony

• Remove leaves and debris from accessible drains.
• Look for cracks, open joints and loose tiles.
• Inspect thresholds and parapet junctions.
• Identify areas where water could remain trapped.

Minutes 7–8: kitchen and bathroom

• Check for damp smells under sinks and washbasins.
• Inspect visible silicone joints and connections.
• Look at corners, suspended ceilings and MDF furniture.

Minutes 9–10: air conditioning

• Inspect the accessible filter.
• Look for condensation marks.
• Listen for unusual noises and assess the airflow.
• Update the autumn programme.

Preparing a Madrid property for autumn rain

• Keep terrace drains clear and accessible.
• Remove visible leaves from accessible gutters.
• Check that overflow outlets are unobstructed.
• Move planters and furniture away from drainage points.
• Inspect joints around parapets, doors and windows.
• Photograph the condition of the terrace before heavy rain.
• Inspect internal ceilings and walls after rainfall.

On a small terrace, a watering can may be used carefully to observe the superficial direction of water, provided there is no active leak and the area is not flooded. Water should move towards the drain without remaining in prolonged pools.

Do not carry out your own flood test. A formal watertightness test requires controlled sealing of the drainage points and an assessment of the risk to the properties below.

Autumn comfort adjustments

• Remove cooling schedules that are no longer needed.
• Use cross-ventilation when outdoor temperature and air quality are suitable.
• Do not leave windows open for extended periods when outdoor air is very humid or polluted.
• Adjust blinds, curtains and awnings to benefit from useful sunlight without overheating.
• Monitor relative humidity with a domestic hygrometer.
• Avoid drying large quantities of laundry in rooms without adequate ventilation.
• Leave some airflow behind large furniture positioned against cold external walls.

As a practical reference, a relative humidity level of approximately 40% to 60% is often comfortable in residential properties. This is not a rigid target: surface temperature, ventilation and insulation also affect condensation risk.

Indicative action plan by budget

The following figures are general indicative ranges. Actual costs vary according to the area involved, accessibility, materials, property condition, required permits, supporting work and the precise cause of the problem. A site inspection and itemised quotation are necessary before making a decision.

€0–€100: basic maintenance and monitoring

• Cleaning or replacing filters.
• Simple weather seals and door draught excluders.
• Compatible sealant for minor internal joints.
• Cleaning accessible drainage points.
• A domestic hygrometer and thermostat adjustments.

Expected impact: improved maintenance, reduction of certain draughts and better humidity monitoring.

Seasonal value: this level can provide useful preventive value, but it will not correct construction defects or significant water ingress.

€100–€500: targeted corrections

• Professional sealing of specific points.
• Improved gaskets and adjustment of several windows.
• A suitable dehumidifier.
• Technical air-conditioning maintenance.
• Minor, localised waterproofing repairs.

Expected impact: improved thermal stability, fewer odours or condensation problems and prevention of local damage.

Seasonal value: potentially worthwhile when it corrects a clearly identified defect. Its effectiveness depends on an accurate diagnosis.

€500–€2,000: partial remedial work

• Local waterproofing of a damaged terrace area.
• Repairs to parapets, thresholds or construction junctions.
• Partial renovation of window components.
• Minor insulation improvements around roller-shutter boxes or accessible areas.
• Repair of internal finishes after the source of moisture has been corrected.

Expected impact: potentially noticeable improvement when the intervention addresses the actual source.

Seasonal value: should be assessed in terms of comfort and damage prevention, not only annual energy savings.

More than €2,000: comprehensive intervention

• Window replacement.
• Complete renewal of a terrace or roof membrane.
• A combined insulation and airtightness upgrade.
• Comprehensive repair of drainage systems and junctions.
• Restoration of damaged finishes after the source has been resolved.

Expected impact: a substantial improvement may be possible where the property has widespread defects.

Seasonal value: should be considered over the medium and long term, taking account of durability, maintenance, energy use, property conservation and the owner’s plans. There is no universal payback period.

Illustrative example: a 1970s apartment with an enclosed terrace

This is a hypothetical example and does not represent a completed project or an actual client.

The property

An apartment of approximately 85 m² in a residential building dating from the 1970s, with an enclosed terrace, older windows and a split air-conditioning unit in the living room.

Signs identified in September

• A draught around the balcony door.
• A damp smell when the split unit is switched on.
• A recent stain near the junction between the former terrace and the façade.
• Slight distortion of an MDF skirting board.

Initial assessment

• Hardened gaskets and a misaligned closing mechanism.
• A heavily soiled filter and contamination in the condensate drainage system.
• A deteriorated external threshold joint.
• A need to monitor whether the stain reappears during rainfall.

Indicative hypothetical costs

• Split-unit maintenance and drain cleaning: approximately €100–€250.
• Balcony-door adjustment and joint renewal: approximately €150–€400.
• Local external junction repair: approximately €300–€900, depending on access and substrate condition.
• Replacement of the skirting board after the wall has dried: approximately €50–€200.

Estimated outcome

If these were the only causes, the likely result would be reduced draughts, removal of the equipment odour and stabilisation of the damp area. Any energy benefit should not be expressed as a percentage without measuring conditions before and after the work.

What to check according to the type of property

Apartments in older or mid-rise buildings

• Uninsulated roller-shutter boxes.
• Older or misaligned window frames.
• Internal courtyards with limited ventilation.
• Communal façades and rainwater pipes.
• Condensation behind furniture placed against external walls.

Penthouses with terraces

• Waterproofing membranes.
• Drains, overflow outlets and falls.
• Junctions with parapets, doors and service penetrations.
• Roof insulation.
• Movement joints in external paving.

Terraced and detached houses

• Flat and pitched roofs.
• Gutters and downpipes.
• Patios and junctions with the ground.
• External doors and garages.
• Rising damp in ground floors and basements.

Frequently asked questions

How can I distinguish condensation from water ingress?

Water ingress is normally associated with rainfall and often appears near roofs, terraces, façades or windows. Condensation forms on cold surfaces and is more likely when indoor humidity is high and ventilation is insufficient. Measurement and observation over time may be necessary.

How often should air-conditioning filters be cleaned or replaced?

This depends on the manufacturer, frequency of use, dust levels and the presence of pets. Inspect filters periodically during the cooling season and follow the equipment manual.

What relative humidity is comfortable in autumn?

Approximately 40% to 60% is a reasonable practical reference for many homes, but it must be interpreted together with indoor temperature, insulation and condensation risk.

Can I apply new silicone over a cracked joint?

The deteriorated material should normally be removed before the surface is cleaned, dried and resealed with a compatible product. Applying new silicone directly over a failing joint is usually a temporary and unreliable repair.

Will anti-damp paint stop water ingress?

No. It may improve the visible finish, but it will not stop water entering through a roof, terrace, façade or pipe. The source must be identified and repaired first.

When should I call an authorised air-conditioning technician?

Request professional assistance if the system loses performance, forms ice, leaks indoors, develops an electrical fault, produces unusual noise or requires refrigerant work.

Is a terrace always the owner’s responsibility?

Not necessarily. A terrace may be privately owned, communal or communal with private use. Responsibility can depend on the source of the defect, the building configuration and the community rules. Inform the property manager or homeowners’ association before work when communal elements may be involved.

Technical references

• AEMET: Spanish State Meteorological Agency.
• IDAE: energy-saving recommendations for households.
• Spanish Technical Building Code: DB-HS Health and Hygiene.

These sources provide climatic context, energy guidance and technical principles concerning protection from moisture. They do not replace an assessment of the individual property.

Inspect small warning signs before winter

An open joint, clogged filter or blocked terrace drain may initially appear minor. Combined with autumn rain, lower temperatures and reduced ventilation, however, these defects can affect comfort and accelerate the deterioration of finishes and materials.

Inspect the property, photograph any irregularities and observe what happens during the next period of rain. If you find active moisture, an unexplained draught or an air-conditioning problem, a professional inspection can help distinguish straightforward maintenance from a defect requiring technical repair.

Maceta y Cortafrío assesses apartments, penthouses and houses across the Community of Madrid, helping owners prioritise work according to urgency, scope and its likely effect on comfort.

To request an initial assessment, use our contact form or contact us on WhatsApp at +34 662 267 918.

A useful inspection does not begin by covering the visible mark. It begins by identifying where the problem comes from.