By Richard Walker, National Technical and Development Manager at Peter Cox

With leaves starting to fall and the daylight hours becoming noticeably shorter, we are starting to enter a period of colder mornings and evenings, or what we call in the remedial treatment industry, “the condensation season”.

Property managers can do a lot to minimise condensation and the risk it poses to a building. In this piece we go through these in a logical ‘step-by-step’ way to make sure we eliminate as many of the possible causes to help protect your buildings and tenants.

Keeping the building dry on the outside

It is important to keep as much of the moisture away from the outside of a building as possible. If masonry absorbs moisture and becomes wet then the level of thermal transfer is considerably increased. Tests undertaken at Portsmouth University in a recent experiment calculated that ‘wet’ solid 225mm thick brickwork could lose up to 29 per cent more heat than the equivalent section of ‘dry’ walling.

It is important to keep as much of the moisture away from the outside of a building as possible. If masonry absorbs moisture and becomes wet then the level of thermal transfer is considerably increased. Tests undertaken at Portsmouth University in a recent experiment calculated that solid 225mm thick brickwork could be up to 29 per cent colder if it is moist.

So what can property managers do?

Check gutter and down pipes, valleys and parapets, and ensure all rainwater is being safely discharged to the ground and into drains. Regular maintenance to unblock gutters and remove leaves should be undertaken after the last of the autumn leaves have fallen, and any defects repaired, or rainwater goods replaced.

Defective areas of pointing and flashings should be checked and replaced or repaired to prevent further water ingress. Seals around window and door frames must also be checked and repaired as necessary.

In some cases, despite all the above measures being undertaken, the walls will naturally absorb moisture due to their natural porosity. Normally this would not be an issue, as heavy sustained periods of rainwater are normally quite infrequent and rarely cause sufficient damp penetration to spoil decorations. However, the loss in thermal efficiency can be significant and will lead to a damp wall being cold and a form a ‘condensation trap’ on the inside of the property.

One solution to dealing with porous masonry is to use a ‘vapour permeable masonry protection cream’. These ‘waterproof’ the outside of buildings while still allowing it to breathe. They can penetrate as far as 10mm into the masonry surface and are not degraded by UV light or erosion. The cream consists of a combination of Silane and Siloxane, and is white in colour, but dries to a completely clear finish 48 hours after application. If applied correctly it can also last for over 10 years.

Keeping the building dry on the inside

This aspect of the process involves doing an internal check around the property to ensure the property is well protected. An electrical moisture meter can help, but a word of caution – these do not give accurate ‘quantitative’ results. They simply show areas of concern for a suitable qualified surveyor, such as a CSRT Certificated Surveyor to diagnose and recommend the correct remedial works.

High meter readings could be a result of either:

1. A ‘bridged’ damp proof course – by external render or blocked cavities. Bridging can simply be dealt with by removing the offending material, though damp as an underlying issue may remain
2. Lateral damp penetration – as a result of moisture entering masonry from the exterior, e.g. through faulty gutters, flashings and so on
3. Lateral damp penetration from high ground – this can be prevented by moving the problem such as flower beds/driveways/paths etc, away from the house. If the ground cannot be lowered (perhaps a pavement or if the room is a basement), then specialist advice from a Waterproofing Specialist should be sought
4. Rising damp due to a failed damp proof course – needs to be checked and dealt with by a CSRT Certificated Surveyor and again Waterproofing Specialists can help here

Condensation prevention

The key to preventing condensation is ensuring the humidity in the property never gets to the level where the atmosphere becomes saturated with water vapour. Ventilation is therefore crucial to managing a potential condensation problem.

Once the air temperature in a property begins to drop, the ability for air to hold moisture in suspension reduces. Where the ‘humidity’ level gets to the point where the air is saturated then ‘condensate’ (water droplets) form on the coldest surfaces. This is especially common as occupants start to turn on central heating BUT fail to ventilate the living space. After a few days naturally occurring spores in the atmosphere can start to germinate and create black spot mould (Aspergillus niger) on the water droplets.

To control condensation an even air temperature is required as well as plenty of ventilation. To many householders this advice seems counter intuitive, especially if the heating is on and you don’t want to open the windows. This is where whole house ventilation systems (innovative fans) are useful. They control the humidity levels in houses by increasing air pressure and forcing out moisture laden air through small gaps around windows and doors and use very little energy, making them cheap to run.

Final words

Given the complexity of damp-proofing a building, a specialist should always be involved. Getting the process wrong can lead to the building’s structural integrity being compromised and therefore it will cost you far more in repair and damages if experts aren’t involved in the early stages.