Damp proofing for old houses

If you’re considering whether to buy an older property, it can be beneficial to commission a structural survey to find out if there are damp issues.

Some common signs you can look out for are:

– Water coming in through walls

– Condensation on walls and floor

– Blistering on walls

– Groundwater on the floor

– Rotting columns, headers and joints

– Damp, humid air

Damp can cause a myriad of problems if left untreated including health issues, furniture damage and, on a surface level, a cold and unwelcoming feeling.

So what causes damp?

Issues tend to have a catalyst, but luckily it’s not too difficult to find out they are.

Here are potential sources:

Condensation

Older properties tend to have colder walls.

Why is this important?

When warm air touches a cold surface, it causes condensation – kind of like when you take a cold drink from the refrigerator outside in summer.

Condensation is common in older houses that aren’t well-insulated and that don’t have sufficient ventilation – for example, in period properties such as those from the Victorian or Edwardian eras that have blocked fireplaces.

You can recognise a condensation problem when there is mould on the wall, but it can also occur underneath the floor.

Interstitial condensation

As a rule, condensation occurs when moisture meets with cold surfaces such as windows and outside walls and causes black mould.

It is not the only kind though.

Sometimes, condensation happens when warm, moist air from inside attempts to move somewhere with lower vapour pressure.

If it becomes trapped, it can cause additional issues.

External walls should be airtight, allowing moisture to escape outside.

Usually this form of condensation occurs inside walls and under floors, causing a raft of additional problems.

The main way to combat them is to make sure the wall’s insulation has a temperature gradient.

Substandard ventilation

You need to make sure moisture in a wall has room to move. If it struggles to leave a property, it can be a potential cause of a damp problem.

Penetrating damp

Any structural issues, such as cracks and honeycombing concrete, or misplaced guttering can cause water and moisture to seep into a property.

Chimneys and rooves can also sustain damage, allowing water to enter the home and cause damp.

Breathability and walls

If you’ve purchased an older property, it’s to be expected some moisture will find its way inside.

The movement of air and moisture is more liberated because of the materials used, and the structure makes them less airtight.

This comes with its own issues.

When there is extreme weather, or if you need a warm and dry environment inside, it can become difficult to deal with dampness.

Traditional physical damp-proofing methods, such as a waterproof paint, will most likely cause issues with the vapour permeability of an affected wall.

That means you’ll have dry environment for a short while, but the moisture already in the property is going to have a hard time escaping.

That risks causing timber decay and damage in the long term.