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The House Doctor - Dr Thomas Brennan - Damp & Mould

Tuesday, 10 November 2009

Tom will show us the common causes, types and best solutions to mould.

Dr Thomas (Tom) Brennan

Has devoted the greater part of his life to developing and researching methods of non-destructive treatment and protection of historic buildings and family homes. He has pioneered several non intrusive exploratory techniques which has greatly reduced damage and costs normally associated with general inspection methods. He is involved in many European research projects and has lectured in Trinity, UCC, and RICS etc. With a doctorate in conservation, he has won the Conservation Award of Excellence and numerous awards for his work as on the Old County Hospital Portlaoise, Farmleigh House and 25 Eustace Street, Dublin.

What will Tom be doing today?

Tom will be showing us the actual damp and mould (different colours) on the inside of the house in the bathroom and kitchen and around basin.

From the roof, (using a cherry picker) we will see how the most common internal damp/mould is caused by water getting into the house from the roof, blocked gutters, gulleys etc by leaves and debris.

. Defective valleys
. Defective rain water goods gutters
. Defective down pipes take water into the earth
. Gulleys or de-watering gulleys - on ground level
. Chimney and ridge flashings where slates meet the chimney, made of lead, copper or zinc, they are a vulnerable failure area around chimneys

Internally dry rot is caused again by ineffective de-watering, leaks in the plumbing/ sewage system, poor ventilation in bathrooms causing aspirillus or stacciborus - black mould and blue fungus, we'll see that in the kitchen and sink. The floor is destroyed by dry rot - black and brown fungus.

Why are there so many different colours of fungus?

. Can be pink when coming out of red sandstone or brickwork
. Can be white fluffy tinge if limestone
. Takes a lot of energy from the material it's growing out of, self destructive.

Tom will open the wall up in one of the bathroom areas; using a small jigsaw he will cut a section of the wall. We will see the surface and then open up the wall to see what is behind. He will suggest how to dry this out and reseal it. Some modernised areas were dry lined incorrectly, masking off damp, resulting in mould - different types.

Is damp and mould in a house a seasonal problem?

. Well rot is an all year round problem that occurs in many both old and young houses.
. What is more prevalent this time of year is blocked downpipes and gulleys due to leaves.
. Also relative humidity is much higher than in the summer, so this means the air is full of moisture. You get a better result for dehumidifying (by opening windows etc) in the summer. If the outside relative humidity is 95, it will increase the internal Relative General Humidity, so it will increase the relative moisture.

Why do you find black mould etc in corners?

You will find it in corners or behind curtains where the air movement is slower. Or on wardrobes, in your leathers. Warm up the area or increase the ventilation.

What is the best treatment for mould and damp?

The most common treatment is with chemical treatments, but you shouldn't have to live in a toxic environment. There are a lot of alternative measures should be tried first. Get a neutral opinion first from building surveying specialists (engineer/architect).

How can a modern house or apartment get mould or damp?

It could be a leak in the plumbing if a modern house/apartment gets mould. New timber is also more susceptible to mould than dry rot, because it still has some sap in it. Old timber is virgin grown timber, not farm grown. New farm grown timber is not as resilient to fungal growth.

Problems & Solutions

Condensation from high relative humidity in air
Condensation occurs where moist warm air comes into contact with colder dryer air, or a surface which is at a lower temperature.
Condensation is more noticeable on non-absorbent surfaces i.e. windows, mirrors or tiles but it can form on any surface and it may not be noticed until mould growth or rotting of the material occurs.

In Bathrooms - evidence of mould growth?
How long does it take for moisture to disappear off cold surfaces after baths or showers. Is there an extractor fan in use?

. Check that the walls are not suffering from rising damp.
. Ensure that there is an effective damp-proof course, that is not bridged or damaged. A new damp proof course can be installed by removing one brick at a time and inserting a physical DPC
. The damp proof course should be at least 6" above any outside paving to avoid heavy raid from bounding back up and soaking the brickwork.
. Try to increase the rate of change of air in the room - increase ventilation. Add forced ventilation to areas which produce a lot of moisture i.e. kitchen bathroom.

Penetrating damp through the walls.
. In properties with cavities, the installation of cavity wall insulation will keep the house considerably warmer and will also prevent condensation.
. Use External wall insulation.
. Rising damp - usually caused by non-existent or defective damp proof courses.

. Installation of Electro Osmosis damp proofing system.
. Consider lowering the paving around the house where necessary.
. Liner systems. Tanking systems.
. Wet or damp basements or crawl spaces
. Damp walls or floors. Under boxes and carpets. Cracks and holes. Efflorescence (mineral deposit which is a sign of moisture entering the home).

Inadequate ventilation cause condensation and black mould.

Inadequate heating
. After a bath or shower the room should be ventilated to the outside, not to the rest of the house - just opening the window and closing the door will help. Fit an extractor fan.
. Consider changing the fuel you use. Electric is the driest. Paraffin probably the wettest.
. Liner systems.

Water leaks from windows
Leaks from Roof
Leaks from guttering and downspouts
Internal Plumbing

. Not a common problem but could cause drafts.
. The biggest cause of rot in buildings.
. The most common cause of rot
. If left unattended can cause damage to fabric of the building - wood , plaster etc

. Inadequate cleaning and drying after major water leaks or floods
. Use of dehumidifiers after a major flood.
. Leave maximum drying out period before re-decorating a house after a leak or floor.

I think whenever you cover the damp-proofing systems, the de-watering systems, the examples of damp with paper falling off the wall as mentioned earlier today, and the various rots that can be present in our buildings - this will more than cover the first programme and may necessitate a follow up programme.