Dampness in Building

Why some timber can float on water for some time before it sinks?

• Voids are not fully saturated

• Solid mass of timber is quite low

• Voids are readily filled with water

• Solid density of timber is quite high

How can the dampness find its way to the floor through the substructure?

• Action of rain

• Condensation

• Exposed tops of walls

• Raising moisture from ground

Which of the following is NOT an effect of moisture on building materials?

• Expansion

• Contraction

• Efflorescence

• Timber damage

Which of the following is NOT a method of water entering during construction?

• Poor site control of storage of materials

• Residual water used in nearby settlements

• Inadequate protection of partially built structures

• Water used for mixing of mortar, concrete and plaster

What is formed when water and glass are in contact?

• Meniscus

• Hydration

• Pores and voids

• Cohesion forces

Which of following is NOT a measure to prevent rotting of windows and doors?

• Use of thicker glass

• Use of anti-capillary grooves

• Inward opening of external doors

• Use of sealant around frame edges

Which is NOT a measure to prevent water from penetrating roofs?

• Spaces are made bigger between tiles

• Adequate ventilation of the roof space

• Tiles are curved to reduce capillarity between them

• A minimum pitch, usually 35°, to reduce water absorption

What causes the drawing up of water through a narrow tube or channel in capillarity or capillary action?

• Gravitational forces of the water molecules

• Shear forces between the glass and water molecules

• Adhesive forces between the glass and the water molecules

• Compressive forces between the glass and the water molecules

Which of the following is a porous material?

• Iron

• Glass

• Plastic

• Concrete

Which of the following is NOT a porous material?

• Glass

• Mortar

• Timber

• Sandstone