The Various Types Of Damp

Condensation

Condensation accounts for approximately 70% of reported domestic damp. It is a condition that affects millions of homes in the UK and is particularly common in houses which are poorly heated and insulated i.e. has more cold surfaces and usually gets worse in winter. This problem can lead to staining and mould growth damaging wallpaper, wall surfaces, window frames, furniture and clothing.

The following areas are particularly prone to condensation:

• Cold surfaces such as mirrors, single glazed windows and metal window frames
• Kitchens and bathrooms
• Walls of unheated rooms
• Cold corners of rooms
• Wardrobes/cupboards and behind furniture against an outside wall

An average household of 4 to 5 people can produce up to 17 litres of water vapour a day. This can be from drying clothes on radiators or using the tumble dryer, hot baths or showers, kettles, cooking and breathing. That’s a lot of water vapour being stored by the warm air in a typical centrally heated, double glazed home. The heating goes off at night and the air temperature inside the home drops. Cool air cannot retain the same amount of water vapour as warm air and when the warm air comes into contact with a colder surface, such as an outside wall or a window, it will deposit the moisture it cannot hold onto that surface. This results in streaming or misting of windows and in extreme cases, walls that are wet to the touch and black mould growth.
Some of the most effective courses of action you can take are simple:

• After a bath or shower, to ventilate the room to the outside, not to the rest of the house - just opening a window (and closing the door to that room) will help.
• Dry clothes out of doors or in a cool area of the premises - this latter suggestion may sound strange, it will take longer but less moisture will be held in the air at any one time.
• While drying clothes indoors, ventilate the room.
• When people come in with wet coats, hang them outside the living area to dry. A good reason for a porch.
• Increase the change of air in the premises - increase ventilation. Add forced ventilation/extraction to areas which produce a lot of moisture (kitchen, bathroom). Extractor fans are available with an air-moisture switch so that they operate automatically while the moisture in the air is above a set amount.
• Consider using a dehumidifier - domestic types are now available and can remove a surprising amount of water from the air. Striking a balance between ventilation and heating is the key.
• Increase ventilation so that the moist air produced can escape; simply opening a window will do. A suitable level of ventilation will allow this without making occupants uncomfortable by causing draughts and making the room cold. It may be quite difficult to strike the right balance however. It is for this reason many houses have built in ventilation measures such as trickle ventilators and extractor fans.
• Adjust the heating - condensation is most likely to be a problem in homes which are under heated. Keep temperatures in all rooms above 15°C as this will reduce condensation forming on external walls.

Penetrating Damp

Penetrating damp is caused by moisture which penetrates through the roof or walls, usually from an external fault or poor housekeeping. Penetrating damp can affect almost any area in the home and is usually the result of a building or plumbing fault allowing water to enter into the property. A brown stain normally occurs on the affected surface, which grows in size as more water penetrates. If the fault is not rectified plaster will start to perish and, in the case of ceilings, could even collapse. If you think you have a problem with penetrating damp you should have the fault repaired as soon as possible.

Identifying possible Penetrating Damp causes:

• Check all gutters for leakage, blockages and overflow. A constantly damp wall will suck moisture in.
• Check your overflow pipes for the same reason.
• Check any abutments to the wall and the joint it creates.
• Check for holes made in walls for hanging baskets etc.
Get your drains checked for broken or blocked pipes and manholes.
• Check all lead flashings for correct sealing at the point where they are chased into the wall and correct coverage to the surface and joint they are protecting.
• Check outside taps for leaks.
• Check external rendering for signs of ‘blowing’ or cracks, missing or damaged decoration.

Rising Damp

Rising damp is a form of dampness caused by the upward movement of ground water through a permeable masonry wall having no effective damp proof course by which to stop damp from rising. The water rises through the pores in the masonry via a process called capillarity.

Capillarity is an electrochemical action which attracts water molecules to mineral surfaces, enabling water to move vertically through pores of a certain size despite the counteractive force of gravity. The same process is responsible for the movement of moisture from tree roots to tree tops via intricately stacked hollow cells. Fortunately the pores in masonry are not as fine as those in trees and rising damp in walls rarely ascends more than about 1m in height though in extreme cases it has been noted to rise to approx 1.5m.

Rising damp only becomes a problem if it affects vulnerable materials or finishes that are in contact with the damp wall. For example if it affects timbers such as joists, skirting boards or the bottom of door frames causing wood rotting potential or if it causes wall plaster or wall coverings to deteriorate or become damp stained.

Once rising damp has been identified, remedial action will be required in the form of a new damp proof course (DPC) installation.

Chemical injection to the mortar course of the masonry or a cementitious based slurry membrane applied to the masonry are the two most recognised remedies. See our fact sheet “Rising Damp Remedial Action” for more information.

Rising Damp Remedial Action

Installation of a chemical injection damp proof course is the most common remedial action for the rectification of rising damp. However, it is not always the most efficient.

A chemical ‘tanking’ membrane is often used as an alternative and in certain situations it is the most comprehensive.

Chemical injection is an effective way of lining the pores of the mortar joint with a silicone resin water repellent. The mortar presents the only continuous passage ascending up a wall through which water is able to rise. Therefore a mortar bed joint is the only layer that can function as a damp proofing layer. Introducing a chemical DPC into just each brick or block unit along a stretch of wall will not stop the water rising through the joints between.

Chemical tanking is an alternative form of a damp proof course. It is used, mainly, in below ground situations or where injection is not possible. Due to the regulations of the Party Wall Act 1996, tanking is often used where damp proof remedial action is required on adjoining walls. Tanking is a cementitious based slurry, mixed and applied to a substrate to form a water tight membrane which is impervious to water.

In both instances, existing decoration and plaster removal is required to allow the installation to meet government standard BS 6576:1985.

Positive Pressure Units

Condensation dampness is a condition that affects millions of homes in the UK and is particularly common in houses which are poorly heated and insulated i.e. has cold surfaces and usually gets worse in winter. This problem can lead to staining and mould growth damaging wallpaper, wall surfaces, window frames, furniture and clothing.

Condensation occurs when the water content of air rises above a level called the ‘dew point’. At such time, water droplets form on the coldest surfaces e.g. windows, external walls etc.

On average, a family of four will produce about two gallons of water vapour per day from activities such as cooking, bathing, breathing and the washing and drying of clothes.

It is also a fact that nowadays most properties are insulated to prevent warm air from escaping. This reduction in ventilation allows the air contained within the property to reach a higher relative humidity.

This can be resolved with the installation of a positive pressure unit to the loft space.

Positive pressure units sited in the roof void draw in fresh air from the eaves. The air is warmed by Solar Gain in the loft space and is filtered and passed through ducting to discharge at landing ceiling level. The fresh air mixes with warm air rising up the stairwell and redistributes it throughout the entire property.

Each room is slightly pressurised and the continual air movement eliminates any stagnant pockets of moisture-laden air, which is eventually expelled through natural leakage points (window and door crevices, flues, air grilles etc) reversing the tendency towards cold draughts entering the property.

• Low Running costs – equivalent to a 60W light bulb on boost and 40W light bulb on background trickle (approx 1p per day).
• Low Maintenance
• Security (no need to open windows)
• Health Benefits - Improves indoor air quality
• Quiet Operation
• Heat Energy Dividend (Solar Gain)
• eets Building Regulations

After Installation

• Where condensation is a severe problem, it is recommended that once installed, the unit should be left on Boost speed for as long as possible over a 2 week period to allow the property to dry out.
• Supply and exhaust grilles should be kept clear at all times.
• Air grilles should be cleaned regularly.
• Filters within the unit should be cleaned or changed at least once a year. Through time the filter may become clogged, this indicates it is working correctly. If this occurs, you may notice a reduced airflow or an increase of noise from the unit.
• The unit should never be covered over.

Instructions for Cleaning or Replacing the Filter

• For routine maintenance, isolate the unit from the electrical supply.
• Wait a minimum of five minutes for the fan blades to stop rotating.
• Where possible the unit should be serviced in its fully installed location. If the unit has been suspended, the means of suspension will have to be released carefully. If the unit has been mounted, the restraints may prevent access to the filter, thus the restraints may have to be released.
• Now the four discs on the unit can be removed from the unit - careful use of a screwdriver may help lever them off quickly.
• Carefully remove the lid from the base unit noting its orientation; it should be replaced in exactly the same manner. The dirty white filter should then be visible.
• Remove filter from the unit and clean by one of three ways:
  a. Clean using a vacuum cleaner to remove dust - just like cleaning a household carpet.
  b. Having removed the frame, wash the filter material either by hand, or in a normal washing machine. Note: The filter must be completely dry before replacing in unit.
  c. Remove the filter and replace it with a completely new piece that covers the wire frame.
• If required the motor plate may be removed and brushed down using a soft brush.
• Once the servicing of the filter is completed, the filter and wire frame must be tightly held in the lid, before the lid is replaced. Do not use excessive force to replace the lid onto the unit; it may not be aligned correctly.
• Replace the four coloured discs.
• Now switch on the electrical supply. The fan should now operate

Passyfier Vents

Condensation dampness is a condition that affects millions of homes in the UK and is particularly common in houses which are poorly heated and insulated i.e. has cold surfaces and usually gets worse in winter. This problem can lead to staining and mould growth damaging wallpaper, wall surfaces, window frames, furniture and clothing.

Condensation occurs when the water content of air rises above a level called the ‘dew point’. At such time, water droplets form on the coldest surfaces e.g. windows, external walls etc.

On average, a family of four will produce about two gallons of water vapour per day from activities such as cooking, bathing, breathing and the washing and drying of clothes.

It is also a fact that nowadays most properties are insulated to prevent warm air from escaping. This reduction in ventilation allows the air contained within the property to reach a higher relative humidity.

Installation of Passyfier ventilation units will aid ventilation and reduce moisture vapour.

Passyfier Ventilation units were invented and developed in the UK as one answer to the problem of condensation. Airflow through the unit is controlled automatically by an intervening mineral wool slabs which subsequently stops undue draughts. It is mainly used in habitable rooms where it operates continuously without noise and over a 24 hour period can extract up to 2.5 litres of water vapour.

The passyfier contains no moving parts and works on basic principles accepted in building physics. When a combination of internal room temperatures and humidity is higher than it is externally, the vapour pressure difference causes the moist air to ventilate outwards.

No Running Costs No Noise Reduces Draughty Airflow and Heat Loss Works at Peak Condensation times Works Passively 24 hours a day Extracts up to 2.5 litres of Water Vapour per day

Party Walls

Party walls are the walls you share with your neighbours.

Semi-detached and terraced house share walls with their neighbours they separate buildings belonging to different owners.

If you want to develop, repair or alter a party wall you must serve notice on your neighbour and obtain your neighbour's agreement before you can start works such as:

• Injection damp proofing works
• Extensions
• Some internal refurbishment
• Structural alterations

The Party Wall etc Act 1996 came into force in 1997 and property owners throughout England and Wales must follow the procedure when building work affects a party wall or party fence wall or excavations are near neighbours' walls.

The Act is meant to reduce disputes by ensuring property owners use a chartered surveyor to determine how and when work is carried out.

For most of these works you must give written notice to your neighbours two months before starting any party wall works. Your neighbour must give written agreement within 14 days of your notice or it will have been deemed they have declined.

If the building next door is let, you will need to ask the landlord, as well as the person living in the property, that you will be carrying out building work to the party wall. Where there are several owners of the property or more than one adjoining property you must let them know as well. Written notice to owners above or below may also be necessary.

Plastering is considered to be a minor works and is considered too trivial to come under the act therefore an alternative to an injection damp proof course would be to apply a ‘tanking’ membrane to the wall and plastering accordingly.

Salting Data

Damp patches on or around chimney breasts - sometimes showing yellow or brown stains in wallpaper or paint – indicates you may have 'hygroscopic' chimney salts that are attracting moisture from the air, which may include tars and other chemicals from burning wood or coal.

These 'salts' are very difficult to hold back in the wall, even with the re plastering carried out to perfection.

At this stage remedial action will be required to make the salts contained within the building fabric insoluble to subsequently stop them transferring through to the plaster and decoration.

Removal of plaster is required prior to the remedial works and it is recommended to leave the brickwork open for as long as possible to allow initial drying of the wall.