Damp and Decay


Dealing with condensation dampness in the Forest of Dean

Condensation dampness is probably the most widespread form of dampnessin houses in the Forest of Dean. It is also often mistaken for other defects such as penetrating and rising dampness and often inappropriate damp-proofing works are carried out. Condensation in houses can be considered as an environmental process. For example, when air in a building becomes heavily laden with moisture from cooking or bathing and then comes into contact with surfaces that are colder such as glass or external walls, condensation will form. In buildings,it is more usual to be affected by condensation between the months of October through to March when it is colder and we are already getting extra calls about condensation dampness and mould growth.

Air naturally increases and decreases in its moisture content minute by minute throughout the day, although warm air will hold more water than cold air.The moisture content of air can be measured by a specialist using an instrument called a hygrometer which displays relative humidity (RH) as a percentage from 0 to 100%. As an example, a level of 90% is much more humid than a level 10%. As an overview, the process of condensation occurs when warm moist air cools down quickly by touching a cold surface such as a window or wall, water droplets then form as the air reaches a stage known as its dew point (when the air can no longer hold the water vapour), at this juncture we refer to this physical change from a gas to a liquid as condensation. An easier way to understand this effect is to remember the last time you were sitting in the beer garden of your local pub on a warm day having a cold pint of lager or cider and seeing droplets of water running down the outside of your glass, this is because the surface of the glass is cold ( lower than the dew point) and when warm air comes into contact with the glass then condensation occurs.

Condensation dampness is most commonly found in buildings usually after cooking or bathing has taken place, although people and pets also produce water vapour which is not readily seen. This also adds to the overall balance of moisture in the air. It is also made worse by poor ventilation or a lack of extraction of moist air.Where there are surfaces that are impervious to water, such as a plastic or metal window frames, the condensate can easily be seen. Whereas, on permeable surfaces such as plaster or wall paper, this condensate is not so easy to readily observe.When trying to identify condensation, the most common aid to diagnosis is to look for mould spores on the surface of walls, behind furniture, on window cills and openings as an example and condensation dampness is often most commonly associated with black spot mould (Aspergillus Niger). There are however, some types of mould which are said to be toxic (Stachybotrys) but there is no scientific evidence to prove this

Together with the mould growth, an observation of the average internal temperature, the level of heating and the ventilation in the property will aid in the diagnosis of condensation. A good indication of condensation however is when the mould appears in the colder months, particularly where it has not been previously. One of the easiest ways of combating condensation dampness is to turn the heating up slightly and improve ventilation.

It is worth pointing out that condensation may be a problem for one occupier where it was not for the previous one and vice versa. This is because a persons or families lifestyles can have a dramatically differing effect on the levels of moisture in a property. The effects on health by condensation can be severe and lead to conditions such as bronchitis, pneumonia, asthma and other related conditions such as Aspergillosis.

When condensation becomes a problem in your home, this can manifest itself in any number of locations, as an example, it is not uncommon to find water condensate droplets in roof spaces where it can form on the underside of bituminous roofing felts.

The water droplets can then affect the localised timbers which can then form rot. By retro fitting adequate ventilation and thermal insulation in the roof void, this will greatly reduce the risk of this occurring. Surface damage from mould to wall paper, curtains, clothes and other surfaces is also very common, although mould can sometimes be easily removed with a good fungicidal cleaner.

In simple terms, condensation occurs naturally. The initial way to alleviate the effects of condensation is to provide adequate heating, ventilation and reduce the level of relative humidity in kitchens and bathrooms. Increasing the heating in a property should ideally be done through either electric forms of heating such as night storage heaters or gas central heating, as other forms of heating such as gas fires will actually introduce more moisture into the atmosphere.

Ideally, airflow could be provided through background ventilation i.e. air bricks and trickle vents in windows or the installation of passive dehumidifiers.It may however be necessary to set the windows on the security catches in the semi open position, assuming that this will not pose a security risk. If this is still not effective, the regular opening and closing of windows will be required. To reduce more larger and difficult amounts of humidity will most likely require a greater degree of effort as modern living tends to produce vast amounts of excess moisture that becomes absorbed into the fabric of the building.

This is not so easy to dissipate as most houses in the Forest of Dean are now well insulated and moist air cannot escape so condenses on walls leading to mould growth. In the first instance, it is sensible to close bathroom and kitchen doors when cooking or bathing. However, if this is not practical, but it is permissible to do so, then an excellent way of reducing this moisture is to fit humidistat fans. These types of fans monitor the relative humidity in an area. At such a point as the air begins to become too moist, the fans turn themselves on until the humidity returns to an acceptable level,at which point the fans then shut off and continue to monitor the background atmosphere.

If a whole house is affected by condensation dampness then it is often more cost effective to install a Positive Input Ventilation (PIV) in the loft . We usually fit the Drimaster Heat PIV, but this can also be fitted by a competent builder/electrician ,which draws air from the loft and pumps it into the house after going through a heater. This drier, warm air mixes with the moist air in the house and reduces the relative humidity so that condensation does not occur. The cost to supply one of these units is around 550.00, running costs with the heater on are around 6p per hour (so if it was on for 8 hours per day would work out at less than 50 pence a day). To install a Drimaster Heat PIV unit costs 750.00.pound

We also supply and fit passive dehumidifiers which remove around three litres of water vapour a day. Cost to supply and install is around 350.00 pounds and supply only is 50.00 pounds.

PIV units will also improve indoor air quality and reduce radon count to safe levels.

Forest Dampbusters have thirty years experience in diagnosing condensation dampness and other related problems and we can advise house-owners in the Forest of Dean & Wye Valley on the best course of action to alleviate damp and toxic black mould growth caused by condensation dampness and all other forms of dampness.

If your house is suffering from condensation dampness and toxic black mould growth then please call Forest Dampbusters on 01594 837300 or 07595 611585 for a FREE damp survey

Posted on: 21/06/2015 09:11:04


Sensible advice on the diagnosis and treatment of dampness in the Forest of Dean

The majority of reported problems with buildings have dampness as either a cause or a symptom. It is also the problem that most people have trouble living with.

In order to deal with a dampness problem, we have to understand where the water is coming from. Very broadly, there are four sources:

1-Rainwater, penetrating through the parts of the building above the ground; walls, roofs and exposed floor soffits

2-Groundwater, penetrating through the parts of the building below the ground. This includes damp basements and sub-floors, and rising damp

3-Plumbing leaks and overflows: water pipes, tanks,gutters etc.

4-Water from the atmosphere. Condensation dampness in its various manifestations such as steamy windows and black mould growths.

Once the source of the dampness has been identified and dealt with, it is important to allow the building; particularly timber parts to dry out before reinstating plaster, paintwork and other finishes which can take weeks, and possibly months

. RAINWATER PENETRATION

Unless the building has had problems from the start, rainwater penetration will usually be associated with damage or poor maintenance. The most common reasons are missing or broken tiles or slates, worn or missing pointing, torn or slipped flashings, holes in flat roof coverings, or rotted unpainted timber. Look carefully at the outside of the building, starting at the place where the damp stain appears internally, but remember that water can fall vertically through a void or track horizontally on a flat surface such as the top of a beam. The necessary repair is often obvious once the defect is identified.

Cavity walls work by having an air gap to isolate the inside of the house from the outer skin of brickwork. The cavity face, outer brickwork leaf, will be wet during heavy rain and this is quite normal. Any water running down inside the cavity should be able to get out at the bottom of the wall, or directed outward by a cavity tray above window openings etc.

Dampness can occur if the cavity is bridged by debris or some types of insulation. The remedy is to open up and carefully clear out the cavity.

Dampness can also occur when building a single storey extension, such as a conservatory, and part of the external wall becomes an internal surface. A new cavity tray should be built-in about 150mm above the new roof.

Solid walls in older buildings work by absorbing water,which then evaporates away in dry weather (a bit like wearing a heavy overcoat rather than a raincoat). It is important to let these walls ?breathe.? Take advice from a experienced building professional with experience of older buildings before considering the use of impervious coatings such as hard rendering or special paints, which can cause more problems than they solve.

The solid walls of many older houses were dry-lined with lath and plaster on timber battens to give an air gap similar to a cavity wall. If this is removed and the wall plastered directly, some dampness can get through. One remedy is to fix a modern form of drylining, using plasterboard, to do the same job as the old lining.

GROUNDWATER

Modern buildings have damp-proof membranes (DPMs) to prevent groundwater penetrating through basement walls or up through solid floors, and damp-proof courses (DPCs) to prevent rising damp in walls.

A newly-occurring focussed damp patch at low level may indicate localised damage to the DPM or DPC,but is more likely to be a plumbing leak.

For expert advice on any aspect of dampness please phone Forest Dampbusters on 01594 837300

Posted on: 21/06/2015 09:01:32


Alleviating condensation dampness in the Forest of Dean

Condensation dampness is the most common form of dampness that affects house in the Forest of Dean and is particularly common in houses which are poorly heated and insulated i.e. have more cold surfaces and usually gets worse in winter. Most of the calls that Forest Dampbusters get during the winter months are related to condensation , black mould etc.

What is condensation?

All air contains a certain amount of water vapour which usually does not become a problem. The higher the temperature of the air the more water vapour it can hold. Condensation frequently occurs when air carrying vapour comes into contact with a cool surface. At this reduced temperature less water can be held and it is deposited. It is for this reason that the bathroom mirror steams up after a shower or a window when you breathe on it.

Where does condensation dampness occur?

The most vulnerable areas will either be rooms where a large amount of moisture is produced, i.e. bathrooms and kitchens but some of this warm, moisture laden air can travel through the house and come into contact with cold surfaces in other rooms . The effects of this process may be visible, for example droplets of water on gloss painted windowsill?s, but often the water droplets will soak into the wall and a problem will not be diagnosed until black mould patches start to appear.

The following areas are particularly prone to condensation:

Cold surfaces such as mirrors, single glazed windows (above) and metal window frames.
K Kitchens and bathrooms.
Walls of unheated rooms.
Cold corners of rooms.
Wardrobes/cupboards and behind furniture against an outside wall.
How to tackle condensation dampness

Condensation is often a lifestyle issue.The major difference between condensation and you may be able to control it and reduce or solve the problem just through changing behaviour in the home. Try following these steps:

Reduce the moisture: Normal activities such as bathing, washing and cooking all produce moisture which cannot be avoided. Simple changes however can prove effective in tackling condensation dampness. Steps to consider are:

Keep lids on saucepans while cooking.
Tumble driers should be vented to the outside.
Avoid the use of bottled gas and paraffin heaters as these produce high levels of vapour.
Dry washing outside when possible.
However, the most effective course of action you can take is:
When creating steam in the kitchen/bathroom open windows and close doors to these rooms. This will let moisture escape and prevent it from spreading through the house.

Increase ventilation: This is required so that 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. It is for this reason many houses have built in ventilation measures such as trickle ventilators and extractor fans.
Kitchen and bathrooms with severe condensation problems should not be draught proofed.
Heating: Condensation is most likely to be a problem in homes which are under heated. Try to keep temperatures in all rooms above 15 degrees celcius (60 farenheit) as this will reduce condensation forming on external walls.

Insulation: Following these steps should significantly reduce any condensation dampness problems you may have. If a problem still exists, insulating your home will have a three fold value in tackling the problem through:

Warming the surface temperature of wall, ceilings and windows.
Generally increase the temperature of the home
. Reducing heating costs thus allowing the home to be heated to a higher standard more affordably.

If you need any further advice on how to tackle condensation dampness then please call Forest Dampbusters on 01594 837300, where we can offer you free, impartial advice on all matters relating to condensation dampness and toxic black mould

Posted on: 20/06/2015 15:21:45


Treating Rising Damp in the Forest of Dean & Wye Valley

Among the many kinds of dampness problems that houses in the Forest of Dean & Wye Valley may have, rising damp appears to be the most mysterious and difficult to cure for most house-owners. Unlike rainwater dripping from a gutter or washing down a slope toward a foundation, rising dampness is noticed only through its symptoms. And since it occurs at the ground floor and lower portions of external and interior partition walls, it is not something that is often noticed.

The suction of ground water into porous building materials is always a likelihood in structures built on ground that is damp and this suction, or capillarity, occurs both vertically and horizontally. The system is like a wick: the more moisture, the higher the rise of damp ;and when there is more evaporation from exposed wall surfaces, the lower the rise of any dampness.

Slight cosmetic blemishes from dampness, such as dissolving plaster and peeling paint, can often be tolerated and remedied with periodic cleaning or repainting. But mouldy walls and rotting wood (such as wet rot in skirting boards and floor boards) are unsightly and often correlates with a damp environment. When moisture reaches an impermeable layer, it may condense and lead to rot, or migrate to a spot where it can escape and evaporate.

Often `rising dampness` in walls can be prevented by allowing walls to breathe. We had a case like this recently in Whitecroft in a old stone built cottage. The owner noted that there was some bubbling of wallpaper and was convinced that this was rising damp and had a free damp survey carried out by a Gloucester based damp-proofing firm who confirmed that the property was affected by rising damp and needed damp-proofing throughout at a cost of 4,000 pounds. We found that the damp was caused by the wall not being allowed to breathe properly and recommended that wallpaper be stripped internally and external render removed from the base of the outside wall.This would allow moisture to evaporate internally and externally faster than the uptake of water from the ground and would therefore alleviate any risng damp and there was no need for any chemical damp-proofing.

Knee jerk reactions to rising damp such as the installation of a chemical damp-proof course should not be considered and persistent moisture problems should be investigated by an independent damp surveyor who has no vested interest in selling popular damp-proofing systems such as chemical damp-proof courses or tube type ventilation inserts (such as Holland/Schrijver). Neither of these systems has been proven to be a reliable or effective form of damp-proofing for old properties in the Forest of Dean & Wye Valley and usually there is amore cost effective method of controlling rising damp.

The overall perimeter drainage system, surrounding grade, soil type, and conditions of the exterior and interior walls should all be examined. Rising dampness is often confused or combined with accumulating rain penetration at the base of solid external walls and this rising dampness from rainwater alone is largely confined to the base of external walls and is most severe on the most exposed elevations, with no dampness showing up on interior partition walls where there is no ready source of moisture.

Causes of dampness can be difficult to isolate. Possible culprits include clay-like, water-retaining soil; a perimeter ground level that is substantially higher than the internal floor level allowing lateral damp penetration, and a hard perimeter surface which prevent water draining leading to water ingress at the base of walls which will in turn lead to rising dampness internally. Dampness can be also be trapped by impermeable finishes or sealers; nylon carpets with foam, latex, or plastic backing or padding; or linoleum or vinyl flooring.

Rain and condensation problems should be treated before addressing damage from ground water, as reducing excess moisture from above may lessen the problem from below. To lower the risk of condensation dampness and the tendency for unsightly black mould and fungal growth on walls ventilation should be increased wherever possible and furnishings should be moved away from walls.

The two most basic approaches for eliminating rising dampness are firstly preventing it from entering the foundation wall or alternatively placing a barrier across the path followed by the moisture. The preferable approach is to prevent water from entering externally by improving perimeter drainage to surface rainwater to drain away from a building before it can enter the wall externally.

A last resort is to install either a physical or chemical horizontal damp-proof course. This may involve cutting the wall and inserting impermeable materials. Many chemically injected damp-proof course systems have been developed for almost any type of wall but they are particularly unsuitable in stone walls in the forest of Dean and Wye Valley as the fluid can just run away in the rubble infill. Avoid ineffective and potentially detrimental techniques, such as Knapen siphons and newer similar systems such as Holland/Schrijver (intended to speed evaporation from a wall), or passive electro-osmotic systems.We have seen a few examples of the Holland/Schrijver damp-proofing systems in Coleford recently on Bowens Hill and Newland Street and also in Littedean and they are always around 300mm off the ground which may prevent dampness from affecting the wall above this height but will leave the wall and timbers still subject to rising damp from the ground which may lead to dampness in plaster and also wet rot in skirting boards

For more information and advice about the effective treatment of rising damp in the Forest of Dean & Wye Valley please call Forest Dampbusters on 01594 837300 or 07595 611585.

Posted on: 21/07/2014 09:04:22


Understanding dampness and timber decay in the Forest of Dean

Houses in the Forest of Dean are built primarily from three materials wood, brick and stone. Some houses are also rendered. Each of these materials deteriorates in a certain way and this determines how well a house is able to stand up to natural weathering. No two houses are the same, but knowing where to look and what to look for will help you spot potential problems before they develop into something more serious.

The fundamental cause of decay is the effect of weather and the associated effect of biological attack by organisms on a building. If the house is poorly constructed or inappropriately repaired or just badly maintained and neglected then the process of decay can cause serious problems.

Lack of maintenance is one of the main contributory factors for decay in older houses. This could be overflowing gutters which can cause moisture ingress and dampness internally, blocked ventilation causing decay to floor timbers or inadequate ventilation resulting in mould growth from condensation.

When materials become saturated frost and the changes in temperature can cause the surface of old bricks to laminate and decay. A high moisture content in materials can also result in damage by salts which will disrupt plaster and paint surfaces.

If materials such as wood are damp and have no chance to dry out then this can lead to infestation by wood-boring insects or wood rotting fungi such as wet rot or dry rot. Often these problems can be solved by eliminating moisture and increasing natural ventilation without resorting to the use of potentially toxic timber preservatives.

Often ill considered or inappropriate alterations can cause decay. A very common problem with older houses is the level of the outside ground level in relation to the structure of the building. External levels can build up over many years so the damp proof course, if there is one, is bridged resulting in rising damp. High external levels can also cause timber suspended floors to become constantly damp resulting in timber decay. Other common inappropriate repairs include the use of cement mortars and renders which do not allow for sufficient evaporation of moisture which can lead to decay.

Some problems are more difficult to diagnose. These can be problems that arise from materials which are incompatible when used next to each other, for example rainwater washing over copper roof flashings can corrode lead lined gutters below. There are also problems when rainwater is very acidic, often caused by pollution, this can dissolve limestone and corrode metal fastenings.

Serious problems can also be due to tree roots which can damage the shallow foundations of old houses particularly in areas of clay soils. Equally removing fully-grown trees in clay soil areas can also cause damage through `ground heave`.

Problems of damp and the need for old buildings in the Forest of Dean to breathe

Damp is high up on a list of concerns for owners of older buildings in the Forest of Deab, but damp is frequently misdiagnosed by those with little understanding of old buildings.

Often a `free survey` is offered by some damp proofing and timber treatment contractors in Gloucester and the Forest of Dean with an interest in showing there is work to be done much of which may be unnecessary and inappropriate. Dampness is one of the most damaging problems for historic buildings and correct diagnosis is vital.

Before the Public Health Act of 1875 it was not compulsory to provide the walls of a building with a damp proof course. Consequently most buildings constructed before this time coped without effective damp proof courses. When water rose from the ground up the walls by capillary action it was able to evaporate higher up because breathable materials were used that allowed this process to happen without damaging occurring.

Problems start to happen in old buildings when people expect them to behave like modern buildings. Floors are sealed with damp proof membranes, lime mortars are replaced with cement rich mortars and walls are coated with impervious paints and renders. These all have the effect of trapping moisture within the fabric of the building which can drive damp further up the wall. Rising damp usually contains salts which are carried up from the soil or from the walling material. These salts can absorb moisture and prolong the problem.

Is a damp proof course necessary?

Often damp proof courses are added in old buildings when the damp problem is not fully understood. Before going down this route think carefully what may be the cause of the problem. Is the problem caused by leaking rainwater pipes or damaged drainage gullies? Is the problem largely one of condensation? Has a damp proof membrane been added to a solid ground floor which has directed damp into the walls?

There are many types of works outside the building which can alleviate damp and make the insertion of a damp proof course unnecessary. Often this can simply mean removing vegetation adjacent to the walls. Lowering external ground levels can have a significant impact on reducing dampness within a wall. Providing the house`s foundations are not too shallow and the ground is permeable the addition of a drainage trench can significantly help the problem.

CONDITION SURVEY CHECKLIST
Roofs, gutters and rainwater pipes
Check your roof regularly
Debris on the ground from broken slates or tiles indicates that there may be a problem. Have dislodged and missing slates and tiles reinstated before damage occurs to roof timbers or plaster ceilings. Avoid bitumen coatings and spray-on foam. They hinder proper inspection, prevent the re-use of slates or tiles and by reducing ventilation, increase the risk of timber decay.
Inspect lead flashings and mortar fillets at chimneys for signs of decay
Parapet walls should be inspected for decay to masonry and mortar joints and the junction between the parapet and an adjacent gutter should also be checked
Clear gutters and rainwater hoppers regularly particularly if your house is surrounded by trees. Signs of blockages or leaks to gutters and rainwater pipes are most obvious during heavy rain. Stains on walls and plant growth provide clues of a problem
Parapet and valley gutters deserve particular attention

Roof space
If your loft has safe access see whether there is evidence of leaks or damage to the roof covering. Where daylight can be seen from inside, through gaps in the roof covering, moisture may well be able to enter.
Make sure that loft insulation is not restricting ventilation at the eaves. If there is an insufficient gap, condensation can cause timber decay.

Walls
Make sure ground levels around the building are not too high. Ideally external ground levels should be at least 150mm below internal floor levels. Clean air bricks which usually ventilate voids under timber floors
Deeply eroded mortar joints in walls should be re-pointed. It is important to use a lime sand mix for most buildings predating about 1900. Localised pointing is usually all that is required
Cleaning unless there is heavy soiling that is causing damage to masonry is not usually necessary

External joinery
Look at windows, doors, fascias and barge boards regularly checking for cracked or rotten wood. It is rarely whole components need replacing if you find decay. A competent carpenter should be able to carry out effective repairs
Painted external joinery can deteriorate rapidly if finishes are not maintained. Expect to redecorate joinery every 3-5 years

Timber defects
Check annually for signs of rot (for instance understairs etc.) Dampness and poor ventilation promote fungal and insect attack. It is important to establish the underlying cause and not to rely solely on chemical timber treatment

Dampness
As with rot always aim to treat the cause rather than the symptoms. Be aware that damp proof courses, water-repellent solutions and plastic type wall coatings do more harm than good when inappropriately applied to buildings.
Where assistance is required consult an independent professional such as an independent consultant or Property Care Association member rather than a damp proofing remedial company with a vested interest in their own recommendations.

Underground Drainage
Monitor underground drainage. Gullies beneath rainwater pipes should be cleaned out and drains should be rodded if they overflow during wet weather.

For any further information on the prevention of dampness and timber decay please call Forest Dampbusters on 01594 837300

Posted on: 22/04/2012 16:31:41


WHY HARD PORTLAND CEMENT RENDERS AND PEBBLEDASH SHOULD NOT BE USED ON TRADITIONAL STONE BUILDINGS

Although technologies for the making of cements and mortars have been used for over two thousand years, the sort of Portland Cement generally used to-day is a recent product. It has only come into common use since the First World War as a means of covering the surfaces of cheap concrete block buildings. Prior to that time, much softer mortars were used, made from lime, ash and grit and sometimes natural fibres. These lime based mortars were specifically formulated for the building of stone walls. They had the ability to `breathe`, thereby allowing internal moisture to quickly evaporate from the surface of walls. They also were able to yield to the micro movements of the stone work due to daily changes in temperature and humidity. The hard mortars made using Portland cement do not have these qualities. They do not breathe and make an impervious barrier to water and any natural internal dampness. Being of a highly structural tensile nature they do not yield to the fine movements of stone work and will crack.

It is therefore amazing that builders in Wales (especially public bodies) continue to use hard Portland cement renders as a means of `enveloping` traditional buildings. A very great deal of information is available to architects and planning authorities describing the folly of this practice. Cadw and the Welsh Office have repeatedly issued circulars and information sheets on the correct way of making compatible lime based mortars for repointing and also for rendering of previously rendered or coated buildings, and their conservation architects are in contact with all local councils. I refer in particular to the technical information sheet 001. `The Use of Lime Mortars` issued by Cadw, and information sheet No.4 `The Need for Old Buildings To Breathe` by Philip Hughes, produced by the Society for the Protection of Ancient Buildings. The Royal Institute of British Architects, The Ecological Design Association, The Ancient Monuments Society and The Institute of Building Biology, have all produced a great deal of technical information about the damage done by the use of hard cements in old buildings and also details of how to make and use lime mortars.

The inappropriate use of hard cement mortars (especially with additional water proofers or plasticisers) over lime based mortars will not prevent internal dampness, indeed it is more than likely to become the cause of it. Placing an impervious layer over a breathing wall will prevent the naturally occurring moisture within the wall space from escaping by evaporation from the exposed surfaces. Any moisture is therefore retained within the structure and will only escape by penetrating the internal gypsum plasters and causing condensation, dampness and mould. This situation is often made worse because renovated properties are fitted with new modern windows with minimal ventilation. Excessive draught proofing and central heating create a harsh over dry atmosphere. But as soon as the heat is reduced the moisture laden air condenses on any conducting surface. Warm, damp, poorly ventilated rooms are a breeding place for germs, and the cause of much ill health.

Because all natural stones expand and contract very slightly due to daily changes in humidity and temperature, the bedding mortars need to be able to take up a small amount of movement. Lime mortars are designed to allow this, but hard cements are not able to yield without eventually cracking. The examination of any cement render will show that it is in fact covered by a network of very fine cracks. These are most easily seen whilst the surface of an exterior wall dries out after a shower. It will be seen that water remains around each little crack. This is because water loves nothing more than a crack to hide in. When the wall begins to dry out by surface evaporation, so the water still within the cracks serves as a small reservoir. In cold conditions this water remaining within the cement cracks will freeze, and cause even larger cracks. Eventually the whole surface deteriorates, or falls away from the stonework. No amount of cement additives will ever prevent the powerful forces of nature. Very soon the weather proof `envelope` becomes instead a sponge for rain water. The dampness seeps into the wall for it cannot escape as effectively as it would from a breathing wall. Eventually the whole wall becomes damp and the render falls away from the structure.

These are the technical reasons why hard Portland cement renders and mortars are not suitable for traditional stone buildings. The use of pebbledash as a quick means to cover a building is also harmful to the architectural quality of our whole built environment. The drab, non descript, blank appearance of rendered buildings is now becoming too common in all of our towns and villages. This whole area of North Wales is renowned for the quality of the traditional stone work. No other region can boast such fine example of the stone builders craft. The mixing of large cut quoins with slate cills and lintels is a sight to witness, especially in wet weather when the natural colours and textures are emphasised. Why are we covering up this heritage that testifies the skill and creativity of our forefathers?

Pebbledash is renowned for its poor weathering qualities. In no time it stains from atmospheric pollutants contained in rain water and the atmosphere. Pebbledash discolours both in places where water runs and also in places where water does not run like under eaves. There is no easy way to clean pebbledash. Often the only solution is to hack it off and replace it. Whilst this sequence of events creates plenty of work for the building trade, it wastes an enormous amount of energy, useful natural materials and money.

Along with pebbledash goes all the stylish details that spoil our heritage of vernacular decoration. Window reveals are squared up with sharp edges, raised decorative window surrounds and architraves which are a common feature are removed, and door and window reveals are given ugly hoods that serve no purpose at all except to highlight the effects of atmospheric pollution. Contrary to the view of planners, pebbledash deserves no place in any vernacular. It is a modern process entirely dependant upon commercially manufactured graded materials. The soft lime based renders used traditionally did not have spa stones thrown upon them, but did sometimes have river grit as a matrix. This was then exposed by washing. However, most traditional rendered buildings were painted or lime washed.

Cement renders are not just damaging to the health of buildings and those who live in them, they are also a waste of materials and a waste of money. Portland cement mixed with building sand and the over addition of water proofers, plasticisers and extenders is very expensive. The thickness used is often 4 or 5 times the thickness necessary if lime based mortars are used. If walls are simply repointed with lime mortar then very little material needs to be used. Most Welsh walls use bold galetting stones as wedges in the joints. The actual manufacture of Portland cement requires a great deal of energy. The production of lime mortars requires very much lower temperatures.

Unlike hard cement that sets within a few hours of mixing, lime mortars can be kept in a tub or bucket for a long time, ready for use as needed. Lime cements set by the absorption of Carbon Dioxide, whereas cements set by a non reversible chemical reaction. Once a cement is set it cannot be recycled other than by being broken up as rubble. Lime mortars could in fact be recycled over and over again. Pre mixed lime mortars can now be obtained ready to use in plastic tubs, but it is a simple material to make from hydrated lime, ash and lime sand. In this part of Wales there is a plentiful supply of lime sand and lime dust. This must be the cheapest building material available. there can be no argument that Portland cement renders must be used on grounds of cost. Lime based renders and repointing mortars are easier to apply, they are effective, and the materials are cheaper by far.

Originally prepared as an article for RURAL WALES, the magazine of CPRW.
Written by John Nicholson, Tanrallt, Rhostryfan, Caernarfon, Gwynedd, LL54 7NT.
Even though this article was written in relation to properties in Wales most of the information still applies to stone built houses in the Forest of Dean and gives valuable advice to householders in the Forest about how to combat dampness in traditional methods

Posted on: 09/04/2012 13:10:36


Damp in Stone walled houses in the Forest of Dean

Stone cottages in the Forest of Dean were built without damp-proof courses or physical protection against dampness and yet for years this was not a problem as they were intended to be semi-permeable, allowing some degree of moisture ingress into stone walls and letting water vapour to enter the building only for it later evaporate and dry out without any harmful effect to the building or its occupants.

Provided a building can breathe it can allow water entry and drying to occur naturally and it is only when moisture is trapped within walls by impervious materials such as waterproof renders that damage and decay can occur.

Stone walls were built without a damp-proof course and are therefore subject to rising dampness from the ground and dampness could often appear internally on walls but this would soon dry due to better ventilation in older properties through fireplaces and chimney flues.

The current installation of a chemical damp-proof courses into stone walls is often futile as when the damp-proofing fluid is pumped in under pressure it simply runs away within the rubble infill of the wall and most damp-proofing firms operating in the Forest of Dean are well aware of this and this is why they will always insist on replacing plaster internally with a waterproof sand/cement render. This dense render often makes the problem worse as it does not allow the wall to breathe and the dampness within the wall is often pushed up higher than the damp-proof render (usually taken up to approximately 1.2m) and will lead to dampness occurring further up the wall.

A better option is to reduce the amount of water available in the ground, which leads to rising damp, by either reducing ground levels or installing a French Drain at the base of external walls. This will allow rainwater to run-off more efficiently and there will be therefore less water available to be drawn into walls, resulting in less rising damp. Internally , instead of applying a waterproof render the walls should be coated with a lime-plaster which will let the walls breathe and therefore allow moisture to evaporate form the wall, reducing the damaging effect of dampness.

Condensation dampness is also a problem in some lots of properties in the Forest of Dean because the amount of washing, bathing, showering and cooking in modern households produces a lot of moisture and water vapour which can condense when it hits a cold surface, such as a windows or cold unventilated wall surfaces.

The best cheapest way to remove excess water vapour is by keeping rooms well-ventilated and increase heating slightly so that wall surfaces just warm enough ( i.e. just above the dew point temperature) to prevent water vapour from condensing on walls.

When most old Forest of Dean houses were built they would have open coal burning fires fires which would draw moisture up the chimney stack when the fire was burning and even when the fire wasn\'t on the chimney would still act as a passive stack ventilation system and allow moisture laden air to trickle out.

Central heating and double glazing has now been installed in lots of Forest of Dean houses and this leads to the build up of water vapour which leads to warm, moisture laden air coming into contact with cold walls and windows resulting in condensation dampness.

Posted on: 19/02/2012 18:50:03


Condensation dampness in the Forest of Dean and Wye Valley

Forest Dampbusters receive several enquiries throughout the winter months regarding condensation dampness, mould growth etc and we have therefore produced this simple guide to explain the causes of condensation and how to cure it

WHAT IS CONDENSATION?
Condensation in a building usually occurs when warm air comes into contact with a cold surface. The air is cooled below its saturation point causing its excess water vapour to change into liquid water. The condensed water usually appears as water droplets or water film on non-absorbent surfaces such as windows or tiles. This form of condensation is described as surface condensation.

CONDITIONS FOR CONDENSATION
Condensation in dwelling houses is mainly a winter problem particularly where warm moist air is generated in living areas and then penetrated to colder parts of the building. Water vapour is produced in relatively large quantities from a large number of activities. Condensation will also occur under suspended timber floors where the temperature of humid air in the floor space is lowered by cold air moving in through ventilators and water is then condensed on the underside of the timber floor, this will often induce timber decay of the wooden floor.

THE CAUSES OF CONDENSATION
In dwelling houses condensation is related to modern living standards, economic pressure and changing building design. The main cause of condensation is naturally the generation of moist warm air by domestic activities. Moist air can come from cooking, bathing, washing and drying clothes as well as paraffin heaters and flueless gas heaters - up to 17 litres of water can be produced daily in some homes! In certain areas such as bathrooms and kitchens the moist, warm air can spread to cooler parts of the house to condense on cold surfaces.

The effect of moisture generation is further aggravated by the way houses are ventilated - it is theoretically possible to avoid condensation by adequate ventilation. Up to about the late 1960s there was natural ventilation in many homes because of the lack of double-glazing, poorly fitting windows and doors, open fireplaces. Present attitudes have eliminated natural ventilation by the use of double-glazing, draught excluders, fitted carpets (preventing air movement up through suspended wooden floor boards) and the removal of open fireplaces with the introduction of central heating systems. To put it simply buildings have being effectively sealed and provided ideal conditions for condensation to occur.

Many houses remain unoccupied and un heated throughout the greater part of the day allowing the fabric of the building to cool down, The moisture producing activities are then concentrated into a relatively short period. This sudden increase in warm air can produce condensation as the air comes into contact with the relatively cold structure which is still warming up. Economic pressure - dramatic increase in fuel prices force many occupiers to under use heating systems not heat unused rooms and seal all draughts and reduce ventilation as described previously.

MOULD GROWTH
Mould growth will appear on any damp surfaces such as plaster, wall-paper and timber and is associated with condensation problems in many buildings. It is unacceptable because of appearance (unsightly growths of various colours - greens, yellows, pinks, black, grey or white).

The main requirement for the development and growth of moulds is a source of moisture although food, oxygen and a suitable temperature are also important. It is available water which is critical to mould development. Moulds can be regarded as high hydrophilic fungi (tolerating high water availability) although individual species have their own optimum requirements for moisture. In most situations where surface condensation occurs and the relative humidity of the internal atmosphere exceed 70% mould growth will be established. There have been approximately 100 species of fungi detected in dwelling houses. The species most commonly encountered were penicillium, cladosporium, rhizopus, and mucor.

CONCLUSION
Condensation is an increasingly serious problem in dwelling houses and offices. It affects over 50% of buildings in the UK. Accompanying condensation there is an increase in the presence of mould growth and many of the household pollutants. Positive Pressure ventilation units along with our Passive Ventilation Units are a cost effective way (guaranteed) to control condensation and black spot mould problems. WHAT IS CONDENSATION?
Condensation in a building usually occurs when warm air comes into contact with a cold surface. The air is cooled below its saturation point causing its excess water vapour to change into liquid water. The condensed water usually appears as water droplets or water film on non-absorbent surfaces such as windows or tiles. This form of condensation is described as surface condensation.

CONDITIONS FOR CONDENSATION
Condensation in dwelling houses is mainly a winter problem particularly where warm moist air is generated in living areas and then penetrated to colder parts of the building. Water vapour is produced in relatively large quantities from a large number of activities. Condensation will also occur under suspended timber floors where the temperature of humid air in the floor space is lowered by cold air moving in through ventilators and water is then condensed on the underside of the timber floor, this will often induce timber decay of the wooden floor.

THE CAUSES OF CONDENSATION
In dwelling houses condensation is related to modern living standards, economic pressure and changing building design. The main cause of condensation is naturally the generation of moist warm air by domestic activities. Moist air can come from cooking, bathing, washing and drying clothes as well as paraffin heaters and flueless gas heaters - up to 17 litres of water can be produced daily in some homes! In certain areas such as bathrooms and kitchens the moist, warm air can spread to cooler parts of the house to condense on cold surfaces.

The effect of moisture generation is further aggravated by the way houses are ventilated - it is theoretically possible to avoid condensation by adequate ventilation. Up to about the late 1960s there was natural ventilation in many homes because of the lack of double-glazing, poorly fitting windows and doors, open fireplaces. Present attitudes have eliminated natural ventilation by the use of double-glazing, draught excluders, fitted carpets (preventing air movement up through suspended wooden floor boards) and the removal of open fireplaces with the introduction of central heating systems. To put it simply buildings have being effectively sealed and provided ideal conditions for condensation to occur.

Many houses remain unoccupied and un heated throughout the greater part of the day allowing the fabric of the building to cool down, The moisture producing activities are then concentrated into a relatively short period. This sudden increase in warm air can produce condensation as the air comes into contact with the relatively cold structure which is still warming up. Economic pressure - dramatic increase in fuel prices force many occupiers to under use heating systems not heat unused rooms and seal all draughts and reduce ventilation as described previously.

MOULD GROWTH
Mould growth will appear on any damp surfaces such as plaster, wall-paper and timber and is associated with condensation problems in many buildings. It is unacceptable because of appearance (unsightly growths of various colours - greens, yellows, pinks, black, grey or white).

The main requirement for the development and growth of moulds is a source of moisture although food, oxygen and a suitable temperature are also important. It is available water which is critical to mould development. Moulds can be regarded as high hydrophilic fungi (tolerating high water availability) although individual species have their own optimum requirements for moisture. In most situations where surface condensation occurs and the relative humidity of the internal atmosphere exceed 70% mould growth will be established. There have been approximately 100 species of fungi detected in dwelling houses. The species most commonly encountered were penicillium, cladosporium, rhizopus, and mucor.

CONCLUSION
Condensation is an increasingly serious problem in dwelling houses and offices. It affects over 50% of buildings in the UK. Accompanying condensation there is an increase in the presence of mould growth and many of the household pollutants. Positive Pressure ventilation units along with our Passive Ventilation Units are a cost effective way (guaranteed) to control condensation and black spot mould problems.

Posted on: 09/01/2012 08:18:50


Damp-proofing old stone cottages in the Forest of Dean and Wye Valley

Most damp-proofing firms in the Forest of Dean and Wye Valley usually carry out damp-proofing by pressure injection of a d.p.c. fluid. This is intended to form a continuous impervious barrier to damp across the entire cross-section of the wall this rarely occurs as most of the damp-proofing fluid is lost within the rubble infill of stone walls when the damp-proofing fluid is pumped it an around 8-9bar.

To cover up the fact that the injected damp-proof course is likely to be ineffective most companies undertaking damp-proofing in the Forest of Dean will insist that internal plaster is removed up to a height of around 1.5m and as long as they re-instate the plaster with a waterproof render they can offer a 20 year guarantee against the recurrence of rising damp.

Replastering is usually required as where there is rising damp in a wall it will have drawn up a salts such as nitrate, chlorides and sulphates which contaminate plaster and can attract moisture from the air even when the walls have been treated against damp. These salts are hygroscopic and will become damp when humidity levels in rooms are sufficiently high and this will lead to walls treated against rising damp still appearing to be damp.

The new plaster will be a sand/cement render containing a salt inhibitor which will prevent the passage of salts from the wall into the new render. The render is usually a dense mix and will also prevent moisture from migrating into the plaster and the walls will appear dry and then damp-proof companies can then claim that their treatment has been successful in preventing rising damp.

As well as preventing moisture to affect the internal surfaces the dense render also has the adverse affect of pushing moisture ever higher due to capillary action and dampness will eventually appear at the top of the waterproof render causing further spoiling to the plaster and extra remedial work will often be required.

Forest Dampbusters offer a much more effective form of damp-proofing stone walls which has been proven to prevent rising damp for up to 30 years. This system still involves the usual drilling of stone walls inside and out at the levels required for the installation of a chemical damp-proof course, but instead of injecting a damp-proofing fluid which is wasted in the rubble infill we insert frozen damp-proof sticks which will gradually thaw and diffuse into the stone and form an impermeable barrier to rising dampness right across the whole thickness of the wall. This system ,patented by Freezteq, is the effective form of damp-proofing in stone walls over 600mm thick and is guaranteed for 30 years.

Plastering to prevent salt damage internally is still required but this is not an integral part of the system and can be undertaken by builders or householders and Forest Dampbusters will still provide a guarantee against the recurrence of rising damp even if we do not carry out the replastering works.

Instead of relying on a waterproof render it is better to apply a breathable lime based render or renovating plaster as these will allow the walls to breathe and the moisture in the wall will evaporate gradually both internally and externally.

Another alternative is to dry-line the walls with thermal plasterboard such as Larfarge which will have dual function of preventing dampness from affecting internal surfaces and also preventing heat loss through the walls and comply with Part L of Building Regulations by reducing u-values of external walls to around 0.3.To prevent residua dampness from affecting the insulated plasterboard we usually fit the plasterboard on tannalised battens which provide an air gap between the damp wall and plasterboard and this cavity allows dampness in the wall to evaporate gradually into the air gap. This moisture can be vented either internally or externally by the provision of discreet vents at the top of the wall.

The Freezteq Damp-Proofing system is backed by an insured guarantee provided by Construction Guarantee Services which is only available to members of the BWPDA/Property Care Association .As far as we are aware Forest Dampbusters are the only damp-proofing and timber treatment company based in the Forest of Dean who are members of the BWPDA/Property Care Association.

For more information on our frozen damp-proofing system then please call Forest Dampbusters on 01594 837300 or 07595 611585. Alternatively e-mail us at enquiries@forest-dampbusters.co.uk

Posted on: 08/01/2012 12:04:59