What Can Cause Dampness Under London Windows and Can It Be Fixed?

What Can Cause Dampness Under London Windows and Can It Be Fixed?

10th February, 2023

You are in the market for a home in London and upon doing a walk-through with the realtor, you notice dampness around the windows. Perhaps you never would have noticed this if you hadn’t gone over to see what the street view is from inside the home. At this point you find that the windows are all fogged up, preventing you from seeing anything until you get a cloth to wipe them up a bit.

You might think that someone had water boiling on the stove, causing steam to seep into nearby rooms. But what happens when you experience the very same thing when viewing the bedrooms upstairs? Do you actually think that steam is making its way up the stairs and around corners and through doors that are shut tightly?

In fact, it wasn’t boiling water. The fog is from leaky windows! However, what you may not be aware of is that fog is only one of the issues you could be dealing with. This is evidence in just how important a pre purchase survey is and how to go about damp proofing London homes so you will not need to deal with this if you buy and move into that home.

How to Assess Why This Is Happening

The very first thing to do is request an independent survey with the surveyors chosen by you. It is imperative that you have London damp surveys conducted by an independent surveyor that will be ethical in terms of their findings. You can probably trust all duly registered surveyors, but you will feel more comfortable if they are chosen by you. Bear in mind that if they are RICS certified, they are under the rules and regulations of the Royal Institution of Chartered Surveyors, meaning ethical surveys are absolutely required.

That said, you will almost always find that there are two common causes of dampness around windows but there are several ways in which that dampness can affect the home – none of which are pleasant! So, what will they find? You can bet it’s one of the two following underlying causes.

1. Improper Sealing Around Windows

Water is probably getting in around windows because they are improperly sealed. It doesn’t always mean that the right kind of sealant was used because age can wear sealants down as well. It could have been something the current owner missed, or didn’t understand, but it is something you need to be aware of before signing a purchase contract.

2. Lightweight Plaster Around Windows

The second reason why there is dampness around windows could be that whoever did the plastering job used a lightweight plaster that wasn’t ‘strong’ enough to withhold water during heavy rains or snow storms. Lightweight plaster can disintegrate quickly under those conditions because it wasn’t formulated to withstand significant amounts of water. It was either the wrong kind or insufficiently applied.

6 Most Common Concerns from Improperly Sealed Windows

This leads us to the most common concerns surrounding improperly sealed windows, the least of which is that fog. Yes, it’s a concern but you will find other, more pressing, concerns as outlined below.

1. Foggy Windows – Inability to See Out

Since you noticed those foggy windows already and your inability to see out, you know now from having that property survey completed that it can be a problem. However, in most cases that isn’t going to be your greatest concern and you’ll soon see why.

2. Draughts Getting In

One of the things that home surveying can apprise you of is the fact that improperly sealed windows can lead to draughts getting in. This can be extremely uncomfortable in the cold winter months but it will also cause your heating source to work harder and longer and that’s not something anyone is happy about. Those utility bills are high enough already without compensating for those draughts that can be avoided.

3. Water Getting In

Dampness in a house indicates that water is getting in somewhere and is not drying quickly enough to avoid this issue. Not only will it indicate that there may be spaces to allow draughts getting in but it also means that water can lead to other issues such as black mould behind walls. Not only is that a structural problem but it can lead to respiratory issues in the home’s inhabitants.

4. Timber Rot

A timber survey would also indicate if there is any structural damage to the home. Bear in mind that sometimes it can be easily corrected if the water infiltration was localised to a window or two and other times the entire structure could be compromised. This can be one of the reasons why you might want to look elsewhere for a home when in the market. However, if the problem is in terms of just a window in one room, it’s not something for a huge amount of concern but it must be dealt with nonetheless.

5. Inability to Open and Shut Easily

Another of the underlying causes of dampness under and near windows could be because of the inability to open or shut them easily. You would absolutely want condensation treatment in order to prevent any health-related concerns. But it will also help to eliminate any structural damage to the home. A damp specialist London can be relied upon to make the necessary repairs before issues progress. But it will also help you keep the costs of heating your home down as well if you are able to ensure they are tightly closed.

6. Higher Costs to Heat and Cool a Home

This leads us to the final issue that can result from improper sealing of windows and dampness in a house. The cost of energy is already high enough and expected to rise significantly in the near future. Rising damp treatment costs are reflected in so many ways. Not only in the repairs necessary to correct water and moisture infiltration but the cost of heating your house as well. That, in itself, is a major concern.

Who Pays for Pre-Sale Repairs?O

nce you’ve had an independent damp survey conducted, you may be wondering who would be responsible for paying pre-sale repairs. In most cases it would be the seller unless you, as the buyer, are willing to commit to that expense. As they would say in the world of sports, the ball is in your court, so what are you going to do with it? Will you pass it back to the seller or run with it yourself? It’s in your hands now, so what will you do? It probably depends on how badly you want that specific home, but you have the information you need to make a wise decision. What will that be?

Our Equipment

Damp Meter

Purpose:

Takes comparative surface moisture readings across accessible walls, floors, ceilings and building joinery.

Common Uses / Notes:

Maps surface moisture profiles to help identify rising damp, penetrating damp, condensation, or active plumbing leaks.

Deep-Penetration Damp Meter

Purpose:

Detects moisture changes deep below the immediate surface of structural materials without destruction.

Common Uses / Notes:

Evaluates dampness within wall cores, beneath floorboards, inside subfloors and behind finishes without removing plaster.

Non-Invasive Moisture Scanner

Purpose:

Scans surface planes non-invasively without inserting pins or probes into decorated finishes.

Common Uses / Notes:

Checks decorated walls, tiled surfaces and delicate floor coverings to trace sub-surface water migration non-destructively.

HD Borescope Inspection Camera

Purpose:

Provides high-definition visual examination inside enclosed, narrow, or inaccessible building cavities.

Common Uses / Notes:

Inspects subfloor voids, wall cavities, dry lining and enclosed pipework to locate leaks and defects with minimal disruption.

4K Inspection Drone

Purpose:

Captures high-resolution imagery and video of high-level external structures and rooflines.

Common Uses / Notes:

Inspects roof tiles, chimney stacks, lead flashing, parapet walls, valleys and gutters to locate water ingress sources.

Air Humidity Sensor

Purpose:

Measures ambient air temperature and relative humidity (%RH) levels within living areas.

Common Uses / Notes:

Determines whether atmospheric moisture, cold bridging, or insufficient ventilation supports surface condensation and mould growth.

Thermal Imaging Camera

Purpose:

Visualises surface temperature differentials across walls, ceilings and floors.

Common Uses / Notes:

Detects cold spots, missing insulation, thermal bridges, evaporative cooling zones and concealed water leaks.

Airflow & Ventilation Detector

Purpose:

Measures volumetric air extraction performance (L/s or m3/h) of mechanical extractor fans.

Common Uses / Notes:

Tests kitchen, bathroom and utility fans to verify compliance with UK Building Regulations Part F and control condensation.

Gas Screening Instrument

Purpose:

Screens indoor environments for sewer gas intrusion, combustible gases and combustion concerns.

Common Uses / Notes:

Traces foul odours, soil stack leaks and sewer gases (H2S, NH3, CH4, CO, O2). Does not replace Gas Safe registered safety checks.

Chemical Vapour Detector

Purpose:

Screens air for Volatile Organic Compounds (TVOC/VOC) and chemical substances like formaldehyde (HCHO).

Common Uses / Notes:

Investigates unexplained chemical odours, building material off-gassing, post-flood air safety and indoor air quality.

Airborne Particle Detector

Purpose:

Measures airborne particulate concentrations across precise micron size ranges (PM1.0, PM2.5, PM10).

Common Uses / Notes:

Assesses fine dust, smoke, airborne matter and environmental air quality following water damage or mould outbreaks.

Electrical Socket & RCD Tester

Purpose:

Provides basic safety and protective circuit screening in areas affected by dampness.

Common Uses / Notes:

Identifies socket wiring faults, tests RCD trip functions and checks AC voltage in wet areas. Does not replace an EICR.

Survey Levels & Package Specifications

Level 1

Standard Damp Survey

Standard price: £299 + VAT

Promotional Price: £199 + VAT (Limited Time Offer)

The Level 1 Damp Survey is a basic damp inspection designed to check the main accessible areas of the property for damp, leaks
and visible moisture-related issues.

Equipment Included

  • Damp meter

What Is Included

  • Inspection of walls
  • Inspection of floors
  • Inspection of ceilings
  • Leak inspection of drains and plumbing
  • Damp information and prevention guide

Best For

This survey is best for customers who need a basic damp check where only a damp meter is used. It is most suitable for simple

damp concerns, such as suspected rising damp, visible damp patches, minor moisture concerns or a general check of accessible
areas.

The Level 1 Damp Survey is suitable where the customer wants a straightforward inspection of walls, floors, ceilings, drains and
plumbing without the use of advanced survey equipment.

Level 2

Detailed Damp & Timber Survey

Standard price: £399 + VAT

Promotional Price: £299 + VAT (Limited Time Offer)

The Level 2 Damp Survey includes everything in the Level 1 survey, with additional timber decay inspections and deeper
moisture testing.

Equipment Included

  • Damp meter
  • Deep-penetration damp meter for all building materials
  • Non-invasive moisture detection equipment

What Is Included

  • Inspection of walls
  • Inspection of floors
  • Inspection of ceilings
  • Leak inspection of drains and plumbing
  • Dry rot inspection
  • Wet rot inspection
  • Woodworm inspection
  • Deep moisture detection in building materials
  • Non-invasive moisture testing under floorboards and subfloors where accessible
  • Damp information and prevention guide

Best For

This survey is best for customers who need a damp and timber inspection. It is suitable where there may be concerns about damp,

wood rot, dry rot, wet rot, woodworm or moisture hidden behind building materials.

The Level 2 Damp Survey uses equipment that can read deeper into building materials, including areas such as subfloors, under
floorboards, behind panelling and other accessible hidden areas. This allows us to get a better understanding of whether there may
be hidden damp within the property without dismantling or damaging materials.

This survey is very suitable for home buyers and sellers who want a more detailed damp inspection before purchasing or selling a
property.

Specialised Laboratory Diagnostic Add-Ons

Add-On 1

Laboratory Analysis of Plaster Samples

Price £299 + VAT

Small plaster samples are carefully taken from affected walls and submitted to an independent laboratory for salt analysis. The laboratory tests for the presence and precise concentration of hygroscopic salts, including nitrates and chlorides.

Diagnostic Value: Soluble ground salts are drawn up through masonry during rising damp and remain in plaster permanently. Salt analysis scientifically differentiates true rising damp from condensation or historic leak contamination.

Note: Plaster sampling requires minor material removal and is our only add-on involving minor invasive work.

Add-On 2

Mould Laboratory Testing & qPCR DNA Analysis

Price £299 + VAT

Surface swab or lift samples are submitted to an accredited laboratory for advanced qPCR DNA analysis.

Diagnostic Value: Accurately identifies exact mould species, measures contamination concentrations and detects hidden fungal growth inside cupboards or behind dry lining. Delivers impartial scientific evidence to guide safe environmental remediation.

Add-On 3

Gases, Chemical Vapours & Airborne Particle Testing

Price £299 + VAT

Comprehensive environmental air quality and gas screening tailored to specific property concerns.

Screening Suite Includes: IAQ air quality assessment, Volatile Organic Compounds (TVOC/VOC), Formaldehyde (HCHO), Particulate Matter (PM1.0, PM2.5, PM10), Sewer Gases (H2S, NH3, CH4), Combustion Gases (CO, O2) and ventilation performance.

Diagnostic Value: Air quality issues are often linked to damp, leaks and mould, but they cannot always be identified by a visual inspection alone. This testing helps detect hidden airborne contaminants, gases, chemical vapours and fine particles that may affect the property’s condition and indoor environment. It can also help identify problems such as poor ventilation, sewer gas ingress, off-gassing from building materials, combustion-related gases, or airborne particles following water damage, providing a more comprehensive understanding of the property’s condition.

It is also useful where a property has persistent unpleasant or unexplained odours. The testing can help investigate foul smells caused by damp, water damage, stagnant water, drains, sewer gases or chemical vapours, allowing the source of the odour to be identified more accurately.

Testing includes:

  • Indoor Air Quality Testing- IAQ
  • Volatile Organic Compound Testing- TVOC / VOC
  • Formaldehyde Testing- HCHO
  • Fine Particulate Matter Testing- PM1.0 / PM2.5 / PM10
  • Dust and Smoke Particle Testing- PM1.0 / PM2.5 / PM10
  • Sewer Gas Testing- H2S / NH3 / CH4
  • Gas Leak Screening- CH4 / C3H8
  • Carbon Monoxide Testing- CO
  • Hydrogen Sulfide Testing- H2S
  • Ammonia Odour
  • Testing- NH3
    Oxygen Level Testing- O2
  • Ventilation / Stale Air Assessment- IAQ / TVOC
  • Drain Smell Investigation- H₂S / NH3 / CH4
  • Chemical Odour Investigation- TVOC / VOC / HCHO / NH3
  • Post-Leak Air and Surface
  • Condition Assessment- PM2.5 / TVOC
  • Combustion Gas Safety Screening- CO / O2 / CH4
  • Building Material Off-Gassing Assessment- TVOC / HCHO
  • Airborne Pollutant Screening- PM1.0 / PM2.5 / PM10 / TVOC