13-11-2012, 10:58 AM
Water Penetration In Buildings
Water Penetration.pptx (Size: 662.23 KB / Downloads: 100)
Defective rainwater goods
Replace cracked or damaged cast iron gutter and downpipe sections. Use the identical section and material as the original.
Dismantle gutters and downpipes where joints have failed and reassemble with a red lead joint.
Repair cast iron hopper heads and all lead rainwater goods if defective, do not replace them. Splits in lead downpipes should be patched not soldered.
Remove all vegetable growth and debris from the discharge point of downpipes at gulleys.
Realign gutters if necessary to falls.
Defective external wall
Repoint open joints in brickwork in a mortar to match the original pointing where the mortar is absent or extremely loose.
Specialist advice should be sought where joints have opened due to movement in the wall.
Hairline cracks in render should be widened sufficiently to repair. Render for the repair should be of a similar mix to the original.
Why does condensation occur?
Moisture is present in the atmosphere
in the form of water vapour. Warm air
can hold more than cool air.
When the air is cooled the vapour will
revert to liquid at a certain temperature
called dew-point.
If any surface inside a building is below
dew-point temperature it will cool
the adjacent air causing condensation
on that surface.
The temperature at which dew-point
occurs varies depending on the
amount of moisture in the air.
Cool porous surfaces
Moulds, normally black in colour will occur on the surface of paint or wallpaper. Rising damp however may cause similar growth.
Moisture readings will be uniformly high, unlike those for rising damp which decrease with height.
Cool impervious surfaces
Condensation appears as tiny droplets of water on cool non-porous surfaces.
In extreme cases it forms vertical streamlets.
It can occur for instance on oil paint, metal surfaces and wall tiles.
Reducing water vapour
Maintain high levels of ventilation to the building, especially in kitchens, bathrooms, stores and roof voids.
Treat damp in external walls and solid floors caused by rising damp or rainwater penetration.
Reduce human activities which raise the moisture content of air eg clothes drying, cooking etc.
Ground levels and finishes
Lower the ground level around the building to 150mm below the internal floor level.
Remove impervious surfaces from around the building. Leave at least a 50mm gap to aid evaporation.
Create a fall away from the building to the surrounding ground to prevent ponding.