Role of the Building Envelope in Preventing Mould and Rot

The building envelope is everything that comes between the inside of a building and the elements: the roof, walls and foundations as well as the windows and doors. Water, dust, or mud should not become trapped within walls, vents, or crevices. Standing water will rot wood and cause mould and damp. As well as being unhealthy and smelling unpleasant, rotted supporting structures such as joists or beams can affect a building’s structural integrity.

To keep the interior temperate and free of damp, the envelope relies on sub-systems like plumbing, ventilation, air conditioning, and heating. Freezing temperatures can damage sodden concrete and brickwork, causing more water to come in. Mould will flourish anywhere warm and damp, but rot does not need heat. In kitchens and bathrooms, human activity, such as drying clothes, may lead to condensation and other problems. Landlords beware: overcrowding can push the capacity of any envelope.

Signs that damage to the envelope has caused rot include:

• Nasty odours coming from mould and fungi and wood rot ‐ sometimes clearly visible.
• Water running down external walls when guttering or downpipes fail
• Peeling paint
• Water stains
• Spongy walls
• Floors that groan and feel too springy

If problem areas are caught early then they are relatively cheap to sort out. However, costs increase dramatically the longer the situation is left unresolved. Replacing roofs and fumigation seem like minor problems if a building is condemned or loses so much value that lenders foreclose a loan.

Planned, regular inspections by someone who is properly qualified, knows the local building code, understands seismic stress and has the right equipment for measurement and sample analysis, are just as important for private homes as they are for large apartment buildings and office blocks. The key is to catch the rot before it causes permanent damage.