The Ultimate Guide That Explains Damp In A Property

One of the worst issues that can impact a property investor is damp in the property. Specifically, if the investor is unaware of the ins and outs of damp. Typically, my refurbishment budget is higher whenever there is a damp issue identified and has to be fixed.

It also gets tricky, given that there are 4 different key types of damp and it can either be one of those 4 types or a combination of them within a property.

There was only one way to learn property for me and that is take every issue that I come across and start exploring the issue to as much detail. Even better, write about it so others can synthesize the summary of learnings.

What will you learn?

  • What is damp
  • How to identify damp in a property
  • Reasons to take damp seriously
  • Type of damp explained to detail
  • Fixing damp: Flavours of damp proofing
  • Damp prevention and best practices

What is damp?

By definition damp is unwanted moisture accumulated in the structure of building due to various reasons including condensation, leaks or others.

Damp can affect any building and can have serious consequences if left unattended. Fixing it is not easy either and has significant impact on cashflow/ROI numbers you work through as an investor.

How to identify damp in a property

Firstly, beware of those properties which appear like distressed but are newly painted or wallpapered to give an impression that minimal work is required to refurb the property. These are increasing in numbers to secure a higher sale price for the property.

However identifying dampness is not that difficult. If you come across any of the following then you know you are in for some serious refurbishment work.

  • Musty Smell
  • Brownish stains appearing on walls
  • Nails or Screws that appear rusty
  • Powder deposits on walls as patches
  • Mushroom growth on walls
  • Discoloured areas or tide marks on walls
  • Deteriorating paint and Loosened wallpaper
  • Visible moisture deposits on surface
  • Mould infestation
  • Leaky roofs and Porous walls
  • High humidity levels

There are damp meters in the market that can help you identify damp too which mostly builders and surveyors rely on heavily.

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It is important to identify the root of damp and fix it than action a cello tape fix.

It’s not about realizing that there is a damp in the property but understand that fixing it also involves going back to brick to fix and replaster and repaint. All of that will cost money. If the source or root of damp is not fixed you do this process all over again until it’s fixed.

Reasons to take damp seriously

There are two key reasons why an investor or a home owner should take damp issues seriously.

One being, ignoring damp can lead to eventual structural damages which are difficult to not just identify but also fix them.

Second being it’s a health hazard too. Damp conditions are breeding ground to bacteria causing health issues to anyone living in the property.

Types of damp explained

There are following types of damps and don’t you worry, they are explained to just enough detail to digest

1. Rising Damp

Rising damp is slow movement of water upward within the lower sections of the walls and typically this movement can go up to 1.5 meters.

This is caused when water at the ground level moves via pores within the walls and will rise until it evaporates or there is no more moisture to move further.

Rising damp is most common in ground floors or basements.

Things to look out for if you come across a rising damp while viewing a property are

  • Source of standing water at the ground level
  • Rotting of wooden floors and skirt boards
  • Brown tide marks or salt deposits on lower walls
  • Wet patches on walls and sometimes resulting in wallpaper peeling off

2. Condensation Damp

Condensation damp occurs when warm air containing water vapour travels horizontally or vertically and gets in touch with cooler surface. When this happens, the air cools resulting in water vapour converting into water droplets hanging on to the surface.

Condensation damp is most commonly found in kitchens, bathrooms and wet rooms typically where hot water is used like cooking, dish-washing, bath or others.

This can be frequently and easily seen within winter season between October and February of the year.

Things to look out for if you come across condensation damp while viewing a property are

  • Visible droplets of water on walls
  • Mildew (surface fungi) on walls
  • Musty smell in the room or from any contents within the room

3. Penetrating Damp

This probably is most common type of damp found in properties and usually is a result of water from outside somehow penetrating into the house. This could be due to rain water leaking into house via walls, roofs or through even faulty windows.

Some of the root causes for penetrating damp are leaking roofs and gutter pipes, defective pointing, cracks within walls, lack of cavity trays, faulty joints between windows and walls or defective bricks themselves used in construction.

Things to look out for if you come across penetrating damp while viewing a property are

  • Water drips on walls
  • Burst water/gutter pipes
  • Cold rooms with Stained damp patches
  • Faulty roofs outside resulting in stained patch inside on opposite side

4. Chemical Damp

Salt deposits can exist while construction of the building or otherwise which are mostly invisible. When these salt deposits absorb moisture directly from air they cause damp.

Salts can also result from combustion of gases within chimney, de-icing salt, from rain or simply constant leakage of water focused at one place.

Often this causes accumulation of chloride or nitrate salts of sodium in other words, hygroscopic salts (substance that can absorb moisture).

Things to look out for if you come across penetrating damp while viewing a property are

  • Brown stains on the wall
  • Mostly on plastered surface
  • Growing stains with time and weather
  • Common on chimney breasts

Beyond above types, damp can also occur due to human error like bad masonry or plumbing resulting in leaks and leaving moisture to escape through pores on bricks.

Fixing Damp: Flavours of Damp Proofing

1. Damp Proof Course

Damp proof course (DPC) is a damp treatment where a linear strip of water resistant material is laid on top of bricks at the base of the walls. This material assures that the rising water from ground is stopped in its path right at the source.

Damp proof course can be applied in varieties of ways including

  • Just applying a linear strip of water resistant material on top of bricks at the base of walls. This method is more useful if the building is being constructed. This method may be a tedious work if it needs to be applied on a building which is already in existence.
  • Damp proofing can also be done via injecting a silicon fluid into an appropriately spaced holes drilled horizontally into the affected wall. This fluid then spreads to form the resistance layer to moisture rising up from ground.
  • There are damp proofing rods/tubes which are comparatively easier to install into pre-drilled holes within affected walls. This is a liquid free option and allows drying up of damp quickly than other options.

2. Damp Proof Membrane

Damp proof membrane is similar to damp proof course but with a difference that a sheet of material (resistant to water) is inserted beneath the concrete floor of a property to prevent any moisture escaping upwards from the ground.

3. Cavity Wall Construction

This is a mechanism where a cavity wall is constructed forming an external and internal wall preventing damp transmission from exterior environment to interior walls.

4. Condensation Damp Cure

Fixing condensation damp can be little simpler than a rising damp or a penetrating damp. In first instance a good enough ventilation or dehumidifying the rooms can be an option to get rid of dew formed due to condensation.

Usage of anti-condensation materials within construction or painting walls can be useful to avoid condensation at-least in the near future.

Prevent Damp and Best Practices

Prevention is better than cure. Here are few easy to follow measures to prevent damp or at-least minimize the possibility of being hit by a damp issue. Some of them could be included as clauses in tenancy agreements given that they are more of life style than anything.

Damp prevention revolves around three key elements which are

  • Insulation
  • Ventilation
  • Heating

Insulation is better way to prevent damp right from the start and will include loft insulation, doors and windows proofing, cavity insulation, secondary glazing and others. Periodic verification of leaks from roofs, cracks on walls, identifying any damp patches early on are few best practices to avoid damp.

Ventilation can sound very simple way to avoid condensation and other types of damp, however is one of the highest rated reason why damp appears in a property. Simple lifestyle change to open up doors and windows for few hours in a day can only do good.

Heating that little bit extra specifically in cold seasons is a sensible way to prevent damp. It is also realistic to request people living in the property to ensure that the guttering pipes are always clear or just review them as part of quarterly checks of the house.


Damp is not as bad an issue if you are equipped with right knowledge to know and identify it early on, either when you are viewing the property or within periodic reviews. You may have to ensure you have right cover within your estimates to fix it and ensure it does not throw the deal into a liability.


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