Building Wrap And moisture control By Angus Robertson

Building wrap allows water vapour ( invisible steam) to pass through but does not allow water to pass through. This prevents the build-up of moisture inside the house that can cause mould and health problems for the occupants. Moisture is created inside the house by people breathing and cooking as well as clothes drying or gas cooking and heating appliances.

What is Building wrap? It is a building paper, synthetic wrap or sheathing used as part of the wall cladding system to control the movement of moisture by ensuring that moisture that occasionally penetrates the building is directed back to the outside of the building. Another name for building wrap is wall underlay. The product may be synthetic ( this is the type we use on the Unitec house) paper or rigid such as plywood or fibre cement.

Polythene will not allow moisture vapour tor escape from the building.

Building wrap will allow moisture vapour tor escape from the building.

Household Activity Average moisture added to the indoor air Cooking 3.0 litres day Clothes washing 500 ml per day Showers and baths 1.5 litres per day per person Dishes 1.0 litre per day Clothes drying (unvented) 5.0 litres per load Gas heater (unflued) 1.0 litre per hour Breathing 200ml per hour per person Pot plants As much as you give them

The manufacturer tells us how to use their product and we must follow their advice if we want them to honour any guarantees that are made with the product. For Example- The building wrap must be run horizontally. Horizontal laps must be at least 75mm wide. End laps must be 150mm wide. Holes in the wrap must be repaired by lapping the damaged area by 150mm or by taping or both.

Mould and damage to paint and wallboard caused by high moisture content in room

Mould also causes health risks

Flexible Flashing Systems

Flexible flashing systems are designed to prevent air leakage and water penetration around window and door openings at framing junctions.

This is the area that the Flexible Flashing tape will prevent rot in.

The manufacturer tells us how to use their product and we must follow their advice if we want them to honour any guarantees that are made with the product. For Example- The Aluband flexible flashing system must not be installed at temperatures of less than 10° If the Aluband is exposed to weather or UV light for more than 90 days it must be replaced. Any laps must be at least 100mm/

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