Condensation Problems London

Condensation Problems London

If you’re here you have condensation problems London in your home, or because you’re a landlord and you have tenants who are complaining about mould in your rental property.

We can help.

My name is Kevin Reid, BSc ISSE (Institute of Specialist Surveyors & Engineers) and I am the principal surveyor of City Damp Surveys.

Tel 07949763671

I have now undertaken over 5,000 damp surveys and I have helped thousands of London home owners and landlords solve their condensation problems.

Landlords and Damp

Every day I get calls from distressed landlords who have tenants who are complaining about mould and condensation in their rental property.

We can help.

When does condensation occur?

Condensation occurs when warm wet air has contact with cold surfaces, like windows and external facing walls.

Obviously it’s much more common in winter, and this is when we get the majority of enquiries.

The air naturally contains water, and inside an occupied flat, more water vapour is generated by everyday activities like cooking, showering, drying clothes and even breathing.

When this moisture-packed warm air comes into contact with a cold surface, it cools down quickly and releases the water, which turns into liquid droplets on the walls.

Because of the pollution in London’s air, the condensation will appear as black dots on the walls. Imagine dirty water condensing on the white painted walls.

If it’s not cleaned, black mould can start growing on walls, ceilings, and around windows.

condensation problems London

In my experience, the worst affected areas are always on external facing (cold) walls, under and around windows, and around external facing doors.

One of the biggest myths (and mistakes) about treating condensation is that’s it’s caused by a lack of ventilation. This is simply not true and leads to homeowners adding useless and redundant wall vents to their property.

condensation problems London

Have a look at the photo below. This is from a house I surveyed recently in Hounslow.

Mould has formed on the cold (left wall). The warm wall on the right has no mould.

The wall on the left with the black mould is the street facing (cold) wall. The right side wall is an internal (warm) wall.

Both walls are exposed to the same air.

Mould has formed on the cold wall.

These are not strictly ventilation problems, and fans and wall vents only make the mould worse as they make the wall colder.

condensation problems London

Condensation is simple physics: wet air condensing on a cold surface.

The solution is to eliminate the cold surface – not too make them colder by installing useless vents.

Condensation Problems London

Condensation and mould will form on the coldest parts of the property. Putting holes in your walls will make the wall and room colder – and make the condensation worse.

Ground floor, and especially lower ground floor flats are naturally colder and these are the flats where we see it most often.

Mould inside wardrobes seems to be the place most cited by tenants when they contact the landlords, followed by the areas behind sofas and beds (the headboard).

The presence of UPVC plastic doors and windows make the mould and condensation worse.

When we super seal our properties to fight heat loss, we also trap all the wet air inside the property.

The most common call I get from landlords is ‘I lived in the flat myself for years and we never had any problems‘.

The most important thing I’ve learned after carrying out over 5,000 surveys in London is that rarely is there a defect with the property.

Most of these condensation problems can be managed to some extent but they are never going away forever, unless you move the building to Spain.

There is no magic bullet.

The other thing I’ve learned is that there are no bad tenants and no bad landlords.

The solution for landlords and tenants with condensation problems is education. Learning about the cause of the problem and the potential solutions.

And there are solutions.

Condensation Problems London


We offer condensation surveys in London for landlords from £149 which includes a full survey of the property and a written report with solutions and recommendations.

Click here to go to our website: City Damp Surveys.

We do not carry out any works so I have no commercial interest in the outcome of the survey.

I insist that the tenants be present during my survey so I can explain to them how condensation occurs and explain to them that I am there to help them,  and the landlord, solve the problems.

I am very flexible and often do these surveys on Saturdays and even Sundays to accommodate the tenants’ schedules.

Most of the solutions are straight forward and easy to implement.

Tenants need to be made aware that condensation happens in properties all over the UK and it is their responsibility to wipe down the walls and windows before black mould occurs.

I will explain how improving the heating in winter months will make a huge difference. Sometimes I will advise landlords to add wall mounted electric heaters (on timers) which can help keep the walls from getting too cold without running the gas boiler all day.

Things as simple as rearranging furniture can help prevent mould from occurring.

In extreme cases, we sometimes recommend installing thermal plasterboard on some external facing walls to permanently eliminate the cold surface.

Proper ventilation in the kitchen and bathroom are important but I never recommend adding wall vents. They simply make the room colder and condensation gets worse.

And I have never, not once, in 5,000 surveys, ever recommended chemical injections to solve these problems.

Condensation Problems London

If you’re a London home owner or landlord, feel free to contact me for more information, advice, or to book a survey.


Tel 07949763671

We are available from 930am to 6pm Monday to Saturday.

City Damp Surveys

Registered Address:

Damp Survey London Ltd
1 Rocks Lane
SW13 0DB

Company number 11756005