Foundations

Question 1

What are the FOUR common forms of foundation?

Answer 1

1. Trench or strip footings
2. Raft
3. Piled
4. Pad

Question 2

What is a trench or strip footing foundation?

Answer 2

• Generally used for residential dwellings, for walls and closely spaced columns.
• Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics.
• Trench is a shallow foundation that avoids bricklaying below ground.
• Deep strip foundations may be necessary where soil with a suitable bearing capacity is deeper.

Question 3

What is a raft foundation?

Answer 3

• Entire basement floor slab acts as the foundation.
• The weight of the building is spread evenly over the entire footprint of the building.
• Generally constructed on a compacted hardcore base.
• A layer of blinding concrete may then be laid to allow formation of the raft with a waterproof membrane above.
• The concrete raft tends to include steel reinforcement to prevent cracking.

Question 4

What is a piled foundation?

Answer 4

• Long and slender reinforced concrete cylinders.
• Deeper in the ground when load-bearing ground conditions are weak (weak compressible strata.
• Driven piles are useful in offshore applications, are stable in soft squeezing soils and can densify loose soil.

Question 5

What is a pad foundation?

Answer 5

• A slab foundation system under individual or groups of columns so that the column load is spread evenly.
• Concrete ‘pads’ support localised single-point loads such as structural columns, groups of columns or framed structures.
• Generally suitable where the bearing capacity of ground is sufficient at relatively low depths.

Question 6

Standard measurement of a brick?

Answer 6

215mm x 102.5mm x 65mm

Question 7

What determines the type of foundations used?

Answer 7

• Age of the building
• Ground conditions
• Size of building and loadings required

Question 8

What are the TWO types of wall construction used?

Answer 8

1. Solid wall construction

2. Cavity wall construction

Question 9

What is a solid wall construction?

Answer 9

Solid brickwork with headers, normally at least one brick thick, with different bricklaying patterns incorporating headers (e.g. Flemish bond) to tie together the layers of brick

Question 10

What is a cavity wall construction?

Answer 10

• Two layers of brickwork are tied together with metal ties, with a cavity that may be filled with insulation.
• No headers used
• Evidence of a cavity tray, air brick or weep holes may be seen

Question 11

What is a stretcher?

Answer 11

Brick laid horizontally, flat with the long side of the brick exposed on the outer face of the wall.

Question 12

What is a header?

Answer 12

Brick laid flat with the short end of the brick exposed on the outer wall.

Question 13

How can you tell if a property has cavity wall insulation?

Answer 13

• No headers used.

- Can see cavity tray or weep holes.

Question 14

What are the various types of defects associated with brickwork construction?

Answer 14

• Efflorescence

- Brick Spalling

Question 15

What is efflorescence?

Answer 15

• White marks caused by hydroscopic salts in the brick work
• Formed when water reacts with the natural salts, by way of a chemical process, contained within the construction material and mortar
• Water dissolves the salts which are then carried out and deposited onto the surface by the natural evaporation that occurs when air meets the surface of the wall

Question 16

What is brick spalling?

Answer 16

Damaged brickwork where the surface of the bricks starts to crumble because of freeze/thaw action, after it has become saturated in the winter months