What is Condensation?

What is Condensation?

Part 1 in a series of guides about how to stop condensation in loft space, attics and roofs.

This article focuses on:

Condensation is one of the most common problems found in UK properties today. Although more prevalent in the colder autumn and winter months, moisture can build up at any time of the year. Finding damp in loft space, moisture on insides of windows, or black spots on your walls are all signs that its present and causing problems.

It is estimated that 1 in 5 UK homes are affected. While you may think that draughty older properties are more likely to succumb, it is just as common in well insulated new builds. In fact, insulation, which makes our homes more energy efficient, can have a negative effect by reducing ventilation and the property’s ability to ‘breathe’. This may lead to high levels of humidity inside the home, and ultimately, condensation.

What is Condensation?

Condensation occurs when warm air full of moisture, comes into contact with cold surfaces. When the warm air hits the colder surface, it is unable to retain its moisture levels. Small droplets of water (‘dew’) are released.


This is particularly noticeable on windows during winter months when outside temperatures are much colder than our heated interiors. If left untreated, condensation may cause all kinds of damp-related health problems such as asthma, bronchitis, and allergies. It can also damage the fabric of your building through creating the ideal conditions for rot and rust to take hold.

What Causes Condensation?

In addition to temperature differentials caused by the weather, it can also be created by everyday activities. Cooking, showering, boiling the kettle, using the tumble dryer, drying clothes next to radiators, and even breathing help contribute to this menace. This is why it can be found in all areas of the home including lofts, living rooms, kitchens, bathrooms and bedrooms.

During warmer summer months, when windows are left open and the home is well ventilated, it is much less of a problem. As soon as temperatures start to drop, these activities can contribute to the build-up of warm moisture-laden air in the home. This may result in common problems such as damp in loft, mouldy windowsills, black spots on the walls, and eventually, structural damp.

Where Condensation Occurs?

Condensation can occur just about anywhere in the home, workplace, or even the car where humidity levels are high. A fine film of water on windows and mirrors, or condensation in the loft is a sure sign that there is too much moisture in the air. This is when you must take steps to control humidity levels, monitor air temperatures, and improve air circulation.

In addition to windows, it may occur on walls, floors, ceilings, attics, and roof spaces, and so it is important to check the whole house. As with most things in life, prevention is always better than cure. You should always take preventative steps as soon as you see water gathering.

Fortunately, this is normally a seasonal problem that can disappear altogether in the warmer summer months. If you can create a well-balanced environment in your home year-round, you could eradicate the problem for good.

How to Stop Condensation?

With a prevention plan, it is possible to reduce or eradicate it from your home and prevent mould or rot from developing.

Our top 6 tips for stopping condensation:

• Ventilating your Home.

One of the easiest ways to combat condensation in your loft space is by keeping your home well ventilated. You can do this by ensuring all air vents are unobstructed (or install loft ventilation products if none are present). Open windows every day, especially bathroom and kitchen windows where condensation is known to be a problem, and by airing your home often. If you have window vents, leave them open, even in the colder months to ensure a constant flow of fresh air.

• Install Extractor Fans in Bathrooms & Kitchens.

Extractor fans are relatively inexpensive and easy to install, yet they are highly effective at stopping condensation in kitchens and bathrooms. By using extractor fans when cooking or bathing, you will significantly reduce the amount of moisture released into the air, and keep it at bay.

• Check Loft Hatches and Light Fittings.

If your loft hatch doesn’t seal correctly or your light fittings are loose, moist warm air generated in your household could easily travel up into the colder loft space. Here it will instantly condense. Small upgrades or repairs to your loft hatches can put an immediate stop to your problems. Consider the excellent range of Manthorpe Loft Hatches from Manthorpe Building Products.

• Do Not Dry Clothes Inside.

It can be tempting to take advantage of the central heating during the winter months and use radiators to dry clothes. This, however, is one of the easiest ways to fill your home with condensation.  If you are unable to line-dry your clothes outside, use a well-ventilated tumble drier. It may not be as energy-efficient, but it could save on expensive damp repairs in the future.

• Open / Close Doors.

If you are heading out for the day, leave interior doors open so that the air can circulate naturally. When taking a bath or shower, close the bathroom door to contain the condensation generated, and open a window or use an extractor fan. Likewise, when cooking you should close the kitchen door to contain any moisture and use an extractor fan to expel condensation outdoors.


Position furniture (or boxes in your loft) at least 5 cm away from walls. This will allow air to circulate and helps prevent mould on walls.

In many instances, problems can be solved quickly, and without a huge investment. By implementing the top tips listed above, you could improve air circulation in your home and significantly reduce condensation levels without calling on the professionals. But if your problems are critical, it is important that you find the underlying cause and make the necessary home improvements to prevent the onset of damp.

If you have damp in loft or attic and need advice, please contact the Roofing Specialist at Ashbrook Roofing Supplies. Alternatively, read our other articles in this series to find out more.

What causes condensation in roof, attics and lofts?

What causes condensation in roof, attics and lofts?

Part 2 in a series of guides about how to stop condensation in loft space, attics and roofs.

This article focuses on:

Finding condensation in attic is surprisingly common. It is estimated that at least 1 in 5 homes are affected by this issue. First tell-tale signs include finding damp in loft or water accumulation on the inside of roof tiles or roof membrane. This can quickly escalate into unsightly black spots on the ceiling and walls. In advanced cases you may find mould spores on furniture, clothes, and linens stored in your loft space or attic.

Fortunately, condensation in attic and roofs is normally easy and inexpensive to treat. In many cases you can often do so without employing the costly services of roofing professionals. It is however essential that you find the underlying cause of your condensation problem before establishing a treatment plan.

Primary causes of condensation in attic:

  • Condensation in Loft after Insulating.

It is especially common in homes where modern loft installation has recently been installed. The benefits of loft insulation are well documented. You can save money on your energy bills. Your home will be warmer in the winter, and the Energy Performance Certificate rating of your home will improve. All these could add value to your property, and so it is a wise investment for any homeowner.

However, loft insulation has one disadvantage in that it can restrict your property’s ability to ‘breathe’. Your house may be warm and cosy, but if the air doesn’t circulate properly, it is unable to get rid of excess moisture held in the air. When that moist air comes in to contact with your cold roof tiles or breather membrane, it will condense into water and cause condensation.

Condensation in loft after insulating is a primary complaint. Homeowners and contractors need to ensure that loft insulation is installed correctly.

  • Wet Trades Drying Out: New Builds

condensation causing plaster
Wet Trades – Plastering

In newly built properties, wet trade building materials such as cement, plaster and mortar can cause condensation problems in the home.  As wet trade materials are mixed with water, they release large amounts of moisture into the air during the drying process. When that moisture-rich air collides with a colder surface, be it a wall, a window or the roof, condensation appears.

It is therefore essential that new builds are well-ventilated, especially in their first years of occupation. If you have just moved into a newly built property, and are already seeing signs of condensation, then wet trades could well be the cause.

  • Un-insulated loft hatches

Poorly insulated or badly fitting cheap loft hatches allow moisture laden air to enter the loft space. If the loft space is unable to breathe this moisture laden air will accumulate. On contact with the cold roof slates or breather membrane, this warm air will condensate. Typically the water will then flow down the inside of the roof, and form pools of damp in loft space.

  • Poor ventilation caused by poor design, over-filling the loft space or boxes too close to walls.

Manthorpe Roof Vent
Manthorpe Roof Vent

Modern roof designs now incorporate ventilation along both eaves and ridge which encourages the free circulation of air. Water laden hot air (the primary cause of condensation) rises and is allowed to escape through ridge vents, whilst colder air (at the same temperature as the roof, replaces it through the eaves.

Many older buildings may only use the odd tile vent to ventilate the roof space. Many roofs may not have any ventilation at all.

In other cases, it may be the hhomeownerat fault. It is all too easy to fill the loft with so many boxes, that air is unable to circulate. Or it could be that one or two boxes are obstructing vents, effectively rendering them useless.

How to Stop Condensation in the Loft Space.

Two processes must be in place to effectively stop condensation in the loft space. Firstly there must be adequate ventilation. Secondly , you must remove or reduce as much as possible warm moisture laden air rising into the loft.

To prevent warm air rising into the loft, ideally, a vapour barrier would be fitted. This should be installed under the loft insulation. Don’t forget that poor fitting or cheap loft hatches also allow warm air to enter the attic. A well-insulated loft hatch does not cost the earth, and most are easily fitted.

You will also need to ensure that your loft has adequate ventilation.

First, remove any obstructions to the loft ventilation in your attic. Ensure that your loft insulation does not go all the way into the roof eaves. A gap should exist here to enable eaves ventilation, and the insulation should not contact the roof itself. Secondly consider moving boxes to ensure that there is a 5cm gap between them and the walls, and that they are not blocking any ventilation points.

Loft Ventilation Products

Simple roof vents, such as those by EasyVent and Manthorpe, are highly effective at ventilating roof spaces, and they start at just a few pounds each. Designed to improve ventilation, roof vents really do work, and they come in a variety of shapes, sizes and designs to suit every loft and project.

Manthorpe Felt Lap Vent. Perfect for Loft Ventilation.
Manthorpe Felt Lap Vent. Perfect for Loft Space Ventilation.

Fascia vents, slate vents, soffit vents and roof tile vents are some of the many roof ventilation options available. Perhaps the easiest of all to install are Felt Lap Vents, which you can install yourself in seconds, without the use of tools, scaffolding, or machinery.

Felt lap vents are compact plastic air ventilators that slot neatly between the overlap of your roofing felt. Once installed, they instantly improve air circulation, and prevent warm humid air being trapped under the roof.  When the warm air is expelled, it takes any excess moisture with it, and condensation is no longer a problem.

All loft vents come with easy-to-follow installation instructions, and they are available in multi-size packs to suit homes of every size.

If you have damp in loft or attic and need advice, please contact the Roofing Specialist at Ashbrook Roofing Supplies. Alternatively, read our other articles in this series to find out more.

Felt Lap Vent, Loft Vents and other Loft Ventilation Products

Felt Lap Vent, Loft Vents and other Loft Ventilation Products.

Part 3 in a series of guides about how to stop condensation in loft space, attics and roofs.

This article focuses on:

In this final section of our complete guide on how to stop condensation in loft spaces, we will give you all the tips and professional advice you need to banish condensation from your home.

What causes condensation in your attic?

Commonly found in bathrooms after a long hot shower, or kitchens after boiling the kettle, condensation is a daily occurrence in most homes. In some instances, it doesn’t cause any issues at all. But if it is left to build up in your attic or loft, it could lead to both serious health problems and structural damage.

So how does condensation occur? Well, put simply, condensation forms when warm air comes into contact with cold air or cold surfaces. The water vapour within the air liquefies to form water droplets or dew. These droplets cling to walls, windows, furniture, ceilings, lofts… just about any surface, and this is what we refer to as condensation.

It’s easy to ignore condensation in the loft or attic. Most people only visit their attic once or twice a year. The weeks running up to and following Christmas is one example as many people visit their lofts to bring Christmas decorations down from storage.

However, if you do spot it, it’s important that you take quick action to stop in turning into a major issue.

Loft vents come in all shapes and sizes. Our top 5 Loft Ventilation Products to stop condensation in your attic are listed below:

Felt Lap Vents
(DIY solution for modern and period properties):

Felt Lap VentsFelt Lap Vents are considered by many as the most popular and easy-to-fit products available on the market today. Inserted on the inside of the roof, they are a DIY product that can be easily and cheaply installed. They are extremely effective at treating condensation problems in attics and lofts.  Manthorpe and Easy Vents for Lofts are widely considered to be the best on the market.

Manthorpe Felt Lap Vent.

Specifically designed to improve ventilation in existing loft spaces, Manthorpe lap vents are manufactured from robust polypropylene plastics. Designed to slot right into your breather membrane or roof felt, they are simple to install. Each vent is equipped with 3 felt clips to keep it securely in place and generates up to 3,000mm2/m of ventilating airflow.

The Manthorpe Vent can be fitted to any loft with joists ranging from 400mm to 600mm, and they are fully recyclable after use.

EasyVent for Lofts.

The EasyVent is both innovative, inexpensive and inconspicuous. Just like Manthorpe vents, they are installed on the inside of the roof, in between the overlap and underlap of the felt lining or membrane.

Each EasyVent Loft Vent comes with a spring attachment that you position inside the vent before installation to create an airflow outlet.  This allows warm, moisture-rich air to escape through the roof and instantly helps to stop condensation in lofts.  It’s such a simple solution, but it works.

Other Products to Help Ventilate your Attic.

There are many products available to help you stop loft condensation, and most of them are inexpensive. Remember that they require a lot more work to fit, and work is often undertaken on the outside of the building. Here is an overview of 3 other roof vents that may help you:

Roof Vents

(Fascia, Soffit and Eaves Panel Vents).

Roof vents are inserted into the inside of the roof, usually in the eaves. They improve airflow, aid ventilation, and prevent the build-up of condensation. Available in a variety of specifications, colours and sizes to suit every property. Roof vents are affordable, quick to install, and effective at reducing loft condensation in buildings of every size. They are best installed on new roofs or when an old roof is being refurbished.

Roof Tile Vents.

Roof tile vents are applied to the exterior of the roof, just like regular roof tiles. Each tile is fitted with an inconspicuous air vent that draws warm air up and out of the roof while keeping bugs and debris out of your roof space. Any rainwater entering the vent is funnelled straight back out onto the tile, and so your loft remains dry and condensation free. Roof tile vents come in various colours and sizes, so matching them up to your tiled roof is easy.

Slate Vents.

Products are also available for slate roofs in the form of slate vents. Compact, easy to install, and discreet, these vents are ideal for period properties and stone houses, where they promote airflow and keep roof spaces free from condensation. They slot in place just like regular roof slates and blend in seamlessly with the rest of the roof.

If you have damp in loft or attic and need advice, please contact the Roofing Specialist at Ashbrook Roofing Supplies. Alternatively, read our other articles in this series to find out more.

Key changes to BS5534: Code of Practice for Slating and Tiling

Back in 1978 BS 5534, the Code of Practice for Slating and Tiling, was first introduced as a British Standard. There are various updates that have taken place over the years.

Changes to BS5534 (the British Standard / Code of Practice for Slating & Tiling) came into full effect on the 28th February 2015. Against a background of worsening weather conditions, the new standards are designed to improve the overall quality and strength of the roof structure.

Whilst there have been significant updates across the entire standard, there are 5 key changes to BS5534 that every roofer should be aware of:

1) All bedded ridge and hip tiles must now be mechanically fixed.

2) Roof underlay meeting British Standards will be classified as to where in the country, and at what maximum batten gauge, it may be installed.

3) Laps should be secured by a naturally occurring batten course. Where necessary, the lap of the underlay should be adjusted to coincide with the nearest slating or tiling batten. Laps may alternatively be sealed with a manufacturer approved glue strip / tape.

4) All single lap tiles must be mechanically fixed (e.g. clip or nail) with two fixings at the verge (one of which may be an adhesive).

5) Timber battens and counter battens should be factory graded to BS 5534.


changes to BS5534 are designed to stop mortar falling out of ridge
Failure of mortar accounts for over 60% of all insurance claims related to roofing. Changes to BS5534 are designed to prevent this.

1) All bedded ridge and hip tiles must now be mechanically fixed.

Why the change?
Failure in mortar accounts for 60% of all insurance claims related to roofing.

How do I comply / What’s the solution?
Use of a dry ridge fixing kit, or the use of the correct type (as defined in the new standards) of mortar with additional mechanical fixings.

Mechanical Fixings that meet the standard include:
Universal Dry Ridge System: Manthorpe Dry Ridge System

The Manthorpe Universal Dry Ridge System will fit most roof coverings.

For Angle Cap Ridge: Manthorpe Ridge Fixing Screw

natural slate blow of a small roof
slate blown off roof after strong gale

2) Roof underlay meeting British Standards will be classified as to where in the country, and at what maximum batten gauge, it may be installed.

3) Laps should be secured by a naturally occurring batten course. Where necessary, the lap of the underlay should be adjusted to coincide with the nearest slating or tiling batten. Laps may alternatively be sealed with a manufacturer-approved glue strip/tape.

Why the change?

A combination of the availability of lightweight membranes and worsening weather conditions (especially higher wind-speed) has led to an increased number of roof blowouts caused by the ballooning of underlays against the underside of tiles and slate.

How do I comply / What’s the solution?
a) Choose membranes tested to BS 5544, which are suitable for the region you are working and the battening gauge of your roofing slate or tile.

map detailing wind zones associated with BS 5534
Choose breather membranes according to your region and batten gauge

Roofing underlay tested to BS 5534 and suitable for use with a 345mm batten gauge (most single lap / large format concrete tiles):

Klober Permo Forte (Zone 1 to 2)*
Suitable for zone 1 to 5 if used in conjuncture with Permo TR Tape to seal laps

Roofing underlay tested to BS 5534 and suitable for use with a ≤ 250mm batten gunge (most plain tiles and slates):

Klober Permo Forte (Zone 1 to 5)

b) Use sealing tape for overlaps: Klober TR Tape

A large section of roof tiles have been blown off this roof
Roof tiles blown off roof

Fixing Specifications on Single Lap Tiles
4) All single lap tiles must be mechanically fixed (e.g. clip or nail) with two fixings at the verge (one of which may be an adhesive).

Why the change?
Higher wind speeds have led to an increased number of tile blow-outs.

How do I comply / What’s the solution?
Roofing Nails – as specified by the tile manufacturer
Tile Clips – as specified by the tile manufacturer
Adhesive specified by the manufacturer

roof showing high quality roofing batten
High quality battens make sense for both build quality and health and safety (image supplied by SR Timber)

Roofing Battens:
5) Timber battens and counter battens should be factory graded to BS 5534.

Why the change?
Both structural strength of the roof and Health & Safety of staff are affected by the use of poor quality batten.

How do I comply / What’s the solution?
Use graded battens, manufactured to BS 5534.

Previously, those working to BS 5534 were allowed to self-grade batten for roofing purposes (also see NFRC Technical Bulleting 33 dated Nov 2012). Opinion on whether self-grading of Roofing Battens is still allowed under the updated version of BS 5534 is divided.
The new British Standard does not state that self-grading is an acceptable practice, whilst stating at the same time that no changes have been made to the standard in regards to battens. Ashbrook Roofing has asked for qualification from the NFRC on this matter.

Frequently asked questions about the changes to BS 5534:

Q: Does this standard apply to new build only?
A: BS5534 covers new and re-roofing projects. It applies to all roofs but those with special details and certain aspects of heritage and conservation works.

Q: Does this change affect me?
A: BS5534 will be the main document against which work is judged with regards to queries or disagreements over the contract specification. It will be for the roofer responsible for the works to prove that what they have done is as good as or better than the standards required by BS 5534.
Additionally, work undertaken and insured by the NFRC, as well as work self-certified under the Competent Roofer scheme, must be compliant with BS 5534.

Q: Why have there been so many changes?
A: The standards have been completely updated since the last review in 2003. This brings together guidance on updated work practices, new materials and adoption of European Standards related to building design. At the same time, this new standard on slating and tiling responds to worsening weather conditions and high levels of insurance claims (in particular those related to mortar).

Q: Has BS 5534 replaced BS 8000 – the Code of Practice for Workmanship for Slating and Tiling?
A: No. BS 5534 (which relates more to design) and BS 8000 (which relates more to workmanship) should be read in conjuncture with one another.

Q: Is there a British Standard for Dry Fix Roofing Products?
A: A British Standard for Dry Fix Roofing Products is in the course of preparation (Jan 2015)