MANAGING MOULD

Condensation and mould can occur in any type of home

construction, including weatherboard, brick veneer, solid brick,

masonry veneer and monocrete.

 

 

Mould is a common problem, especially in older houses and units, and can be a legal

nightmare for landlords and property managers

Mould

Mould is a form of fungus and is spread primarily by airborne spores that will develop and

grow on almost any surface providing the following conditions are present:

* A relevant indoor humidity of 80% or higher.

* Moisture, usually from condensation. Mould can develop in the absence of condensation,

but its growth is accelerated by the presence of moisture.

* A nutrient. Research shows that certain ingredients in most paints, household dust,

and cooking fumes all provide excellent food for mould.

* Sooty mould, the most common type, leaves surfaces with a brown or black stain and

usually occurs on the walls and ceilings of bathrooms, bedrooms and in cupboards. Untreated,

this mould will spread to other rooms in the house.

* Green furry mould grows on organic or organic-bearing surfaces, such as shoes or clothes.

 

Mould growth is retarded by the circulation of dry air. It follows that proper ventilation will

prevent most mould growth. To prevent green fluffy mould on clothes and footwear, ensure

that they are thoroughly dry before storage.

The main causes of mould

* water leaks from windows, roof, downspipes, guttering, internal plumbing and flooding;

* penetrating damp through walls; rising damp – usually caused by non-existent or defective

damp proof courses;

* wet or damp basements or crawl spaces;

* condensation from high relative humidity in air;

* too much water vapour or steam being generated through cooking, washing, bathing,

showering and clothes drying which is allowed to travel throughout the house;

* inadequate ventilation;

* inadequate heating; 

* inadequate cleaning and drying after major water leaks and bursts or floods.

 Where does mould typically appear?

In the house:

* on the walls, under the bottom corners of windows;

* on floors around toilets and under dishwashers;

* near damaged or blocked downpipes;

* at the bottoms of exterior walls.

In the crawl space:

* on exposed soil;

* on standing water;

* mould growth on the joists or sub-floor;

* on wood debris on ground.

In the basement:

* on damp walls or floors;

* under boxes or carpets;

* in cracks and holes.

 

 

Removal of mould

Mould cannot exist and grow without moisture. Therefore you must first find and eradicate

the source as described above. Completely remove and dispose of mould-contaminated

materials. Find any mould on porous items that may have absorbed moisture.

In particular, insulation, plaster, carpeting and other floor coverings, ceiling tiles,

wood, clothing and textiles, furniture and furnishings, and paper. If you see evidence of

mould, these items should be bagged in plastic and removed. Non-porous materials can

be saved if they are properly cleaned and dried. It is possible for mould to grow on hard

materials like plastic, concrete, glass, or metal, but this can usually be removed with careful

cleaning. Solid wood items can also be salvaged through cleaning, if they are structurally

sound. Thoroughly scrub all contaminated surfaces. Use a stiff brush, hot water, and a

non-ammonia soap/detergent or commercial cleaner. Collect excess cleaner and cleaning

water using a wet/dry vacuum cleaner, a mop or sponge. Finally, rinse the surface or items

and clean up the whole area with clean water. Collect and fully dispose of the excess rinse

water, and dry everything out as quickly as possible. After you have removed all visible

mould from contaminated surfaces, a disinfectant may be used to kill some of the mould

that may still be present. When mould is disturbed, it can greatly increase the amount of

mould spores present in the air, so follow these precautions when working with mouldy

materials:

* Use rubber gloves.

* Use eye goggles that seal out fine dust.

* Wear disposable overalls.

* Wear a medium to high-efficiency filter dust mask.

* Do not eat, drink or smoke in the contaminated area.

 

People with existing health problems or those sensitive to mould should not do clean-up

work in situations where there is heavy mould growth. If you have any doubts about the

safety or effectiveness of your work, it may be prudent to consider using professionals

to do the clean-up work for you.

What is condensation?

Condensation occurs where moist warm air comes into contact with colder dryer air, or a

surface, which is at a lower temperature. Condensation is generally noticeable where it forms

on non-absorbent surfaces (i.e. windows, window sills, mirrors or tiles) but it can form on

any surface and it may not be noticed until mould growth or rotting of material occurs.

Conditions for condensation

The moisture in the air comes from a number of sources within the house. Water vapour is

produced in relatively large quantities from normal day to day activities such as breathing,

cooking, baths and showers, and washing clothes. Moisture can also be drawn from the

structure of the building into the internal air, from below the floor or through the walls/ceilings.

Problems with the structure of the building can mean that its moisture content is unnecessarily

high. This can either be due to the method of original construction or as a result of structural

failures. Older houses may not have a damp proof course (DPC), which prevents soil moisture

from rising up into the living areas. Solid floors can also lack a DPC. Any room that is

underground, or partly underground, is prone to condensation and mould. Basement walls

and floors, unless they are tanked and thoroughly insulated, present cold surfaces to moving

warmer air which invariably results in condensation. DPCs can become damaged or bridged,

either externally through soil build-up, or internally through mortar debris in the cavity.

This allows moisture to soak into the masonry and rise into the living areas. Buildings may

lack or have insufficient air vents to allow adequate under floor ventilation, which is vital

to prevent mould growth and timber rot problems. Structural failures or design faults can

range from missing or bridged DPCs, damaged gutters, downpipes and sumps, porous

pointing or brickwork, and lack of cavity trays on adjoining extensions, to leaking roofs.

Keeping the moist air in the house through effective draft proofing aggravates the effect

of moisture generation. It is theoretically possible to avoid condensation altogether by

adequately venting moist air from the room in which it is generated. In certain areas of a

house (such as bathrooms and kitchens) the warm air contains a lot of moisture; if that air

then spreads to cooler parts of the house it condenses on any colder surface. Condensation

is encouraged by poor air circulation where stagnant air pockets form (behind furniture and

in cupboards) and the first evidence is often the appearance of mould growth and a musty

smell on clothes in wardrobes. The warm moist air rises to the highest points in the building,

forming condensation in those areas, which are often coldest, including bedrooms, wardrobes

and upstairs bathrooms and toilets etc. The modern lifestyle, and particularly that of tenants,

means that many houses remain unoccupied and unheated throughout the greater part

of the day, allowing the fabric of the building to cool right down. The moisture-producing

activities are then concentrated into a relatively short time period, producing large amounts

of steam when the building structure is still relatively cold. The true cause of condensation-

based mould growth is often complex and a combination of things. It is sometimes caused

by inadequacies in the building but very often the main cause of mould growth is the

lifestyle of the occupants. Once the mould growth has been allowed to take hold at some

point in the history of the property – say with a tenant who lived with inadequate heating

and ventilation, and produced excessive amounts of moisture (steam) through cooking,

washing, internal drying etc – it can reoccur again and again. Even years later, once the

conditions are allowed to deteriorate again, without the property having undergone

thorough eradication treatment, the mould can quickly re-appear. In other words, the

mould spores can lay dormant when the conditions are against them, but will be re-invigorated

once cold, damp moisture laden conditions are allowed to re-appear. Older properties,

especially those with solid walls (no cavity and no cavity wall insulation) are more prone

to condensation problems.

Minimise your liability

Mould and condensation is a particular worry to landlords and property managers because

of potential legal claims. It may be difficult to defend a claim for damage caused by mould

in the Consumer, Trader and Tenancy Tribunal. However, landlords and property managers can

minimise their risk and liability by setting and following strict procedures for preventing and

treating mould, including:

* keeping accurate repairs records;

* investigating further when mould indicators such as damp and musty smells are brought to your attention;

* taking prompt action to eliminate mould when it appears; 

* carrying out preventative maintenance when building defects are identified

 
What can a landlord or property manager do?

 

Check the structure of the building first for obvious defects:

* Check that the walls are not suffering from rising damp.

* Ensure that there is an effective damp-proof course, that it is not bridged or damaged.

* Check that any wall cavities are clear of rubble and debris.

* Check that all air vents are clear and consider fitting additional air vents to ventilate

under suspended floors.

* Check the roof to make sure that it is sound and directing rain into the guttering, not

into the structure of the building.

* Check the guttering and down pipes, make sure that they are carrying the water away

and that there are no damaged/blocked gutters or drainpipes causing the external wall

to become soaking wet. Consider whether sumps may be required to prevent guttering

overflow during heavy rains.

* Check solid floors to ensure that they are dry and free from

condensation. If not they may need a damp proof membrane and insulation below –

potentially a big job.

* Check that there are no leaking water tanks or pipes within the house.

* Ensure that garden beds are below dampcourses and brick weepholes.

Once you are happy with the structure of the building, look to the occupation lifestyle.

Educate the tenants

Prudent property managers should educate tenants about how to avoid condensation.

It would be a good idea to provide this in writing, for example, with an information

sheet that includes that following points:

After a bath or shower, the room should be ventilated to the outside, not to the rest of the

house – just opening a window (and closing the door) will help. Fit an extractor fan. 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. Dryers should have external air extraction. When people

come in with wet coats, they should be hung outside to dry (such as on the porch)  

 

Methods to prevent condensation and mould

Reduce indoor humidity by good ventilation and through regular airing of the dwelling.

Keep ventilators and exhaust fans clear of fluff. Do not block air vents in winter to keep

out the cold – they are necessary for good ventilation of the property. Dry indoor air with

space heaters and wipe dry any surface on which condensation appears. Avoid the use of

kerosene room heaters. Unflued gas heaters may also cause problems. Dry clothes and

footwear thoroughly prior to storage. Allow sunlight into the home whenever possible by

opening the blinds during the day. Remove any sign of mould growth on walls ceilings

and furniture using diluted household bleach or suitable household cleaner. Furniture should

not be pushed up against walls. This creates dark airless areas and allows mould spores to grow.

 

via REINSW Journal Nov 2009