Slabs & Footings

Question 1

What are the 3 main foundation systems

Answer 1

Strip Footing
Waffle Slab
Raft Slab

Question 2

What is a strip footing?

Answer 2

Rectangular cross section poured in a continuous horizontal reinforced strip for placement underneath a wall

Question 3

What is a stiffened raft slab?

Answer 3

Concrete slab on ground with external and internal stiffening beams

Question 4

What is a waffle pod slab?

Answer 4

Stiffened slab constructed on ground

Question 5

Foundation movement for slabs & footings are measured as how much chance of happening over what period?

Answer 5

Less than 5% chance of being exceeded over 50 years.

Question 6

Site Classifications

Answer 6

A, S, M, H1, H2, E, P

Question 7

Site Classification, what does A stand for?

Answer 7

Sand and rock sites - Little or no movement

Question 8

Site Classification, what does S stand for?

Answer 8

Slight movement - Clay sites

Question 9

Site Classification, what does M stand for?

Answer 9

Moderately reactive clay site

Question 10

Site Classification, what does H1 stand for?

Answer 10

Highly reactive clay site with high ground movement from moisture change

Question 11

Site Classification, what does H2 stand for?

Answer 11

Highly reactive clay site with very high ground movement from moisture changes

Question 12

Site Classification, what does E stand for?

Answer 12

Extremely reactive site with extreme ground movement from moisture changes.

Question 13

Site Classification, what does P stand for?

Answer 13

Problem - Soft or unstable foundations, reactive site subject to abnormal moisture conditions

Question 14

Maximum length of slab before control joint required?

Answer 14

AS 2870 - 30m
NCC - 18m

Question 15

What are vapour barrier requirements?

Answer 15

-.2mm thick
-Medium impact resistant vapour barrier
-Damp-proofing membrane - High impact resistant
-200mm overlap
-Taped penetrations

Question 16

Minimum bearing pressure required for an edge beam & Strip footing kPa

Answer 16

Edge Beam 100kPa
Strip Footing 50kPa

Question 17

What are the MPA, aggregate size and nominal slump requirements for a slab

Answer 17

NCC 4.2.10 (a) (i) Strength @ 28 days not less than 20MPA
(ii) 20mm max aggregate
(iii) Nominal 100mm slump

Question 17

Trench Mesh and Slab Mesh overlap requirements?

Answer 17

Trench Mesh - 500mm (full width across section)

Slab Mesh - 2 outermost transverse wires must overlap the same other sheet

Question 17

Minimum edge rebate depth?

Answer 17

20mm

Question 18

What is required at the internal corners of a slab?

Answer 18

Re-entrant or internal corner reinforcing 2000mm long on a 45degree angle

Question 19

If an edge beam requires deeper excavation this becomes?

Answer 19

Deepened edge rebate

Question 20

How many strips of reinforcement need to be placed in a strip footing?

Answer 20

2 - Top and Bottom

Question 21

Df meaning?

Answer 21

Depth of footing

Question 22

What is the maximum spacing of an internal beam from an external corner?

Answer 22

4 meters

Question 23

Where 1 side of a re-entrant corner is less than 600mm, what is the minimum length of the continuity beam?

Answer 23

2 X D minimum.

Question 24

What is the maximum offset for a LBW?

Answer 24

1000mm

Question 25

Concrete Cover to Unprotected Ground

Answer 25

40mm

Question 26

Concrete cover to a membrane in contact with the ground?

Answer 26

30mm

Question 27

Concrete cover to an internal surface?

Answer 27

20mm

Question 28

Concrete cover to external exposure?

Answer 28

40mm

Question 29

Bar chair spacings centeres?

Answer 29

800mm

Question 30

Minimum splice for reinforcing bars Up to 12mm 12mm - 16mm

Answer 30

Up to 12mm - 500mm minimum 12mm - 16mm - 700mm minimum

Question 31

For design purposes, the life of a structure is said to be how long?

Answer 31

50 years

Question 32

On a stiffened raft slab how thick must a slab be where slab thickening supports a load bearing wall?

Answer 32

150mm

Question 33

On a stiffened raft slab how wide must the slab thickening be where it supports a LBW?

Answer 33

500mm

Question 34

In a stiffened raft slab up to 18m long what size mesh is used?

Answer 34

SL72

Question 35

In a stiffened raft slab between 18m and 25m long what size mesh is used?

Answer 35

SL82

Question 36

In a stiffened raft slab greater than 25m long what size mesh is used?

Answer 36

SL92

Question 37

In a waffle raft slab what is the allowable thickness of a garage slab?

Answer 37

85mm

Question 38

List the requirements for fireplace footings on a Class A and S site Single storey pad thickness? Double storey pad thickness? Pad footings to be reinforced with what size mesh and extending how far past the edges of masonry?

Answer 38

Single storey - 150mm Double storey - 200mm Mesh size SL72 Extended 300mm past masonry edge

Question 39

Where can service penetrations sit in edge and stiffening beams?

Answer 39

Middle 3rd

Question 40

What is the minimum depth of concrete below the edge rebate?

Answer 40

150mm

Question 41

Where the edge rebate is greater than 400mm, what is the minimum stem width?

Answer 41

200mm

Question 42

What are the 3 re-entrant reinforcement options?

Answer 42

2 Strips of 3-L8TM 1 Strip of 3-L11TM or 3 x N12 Bar

Question 43

At external corners what is the MAXIMUM distance from external beam to 1st internal beam?

Answer 43

4m centre

Question 44

If a beam cannot be placed in a straight line what is the maximum deviation ratio allowed?

Answer 44

1 in 3

Question 45

Slab beam layout

Question 46

What are the angle of repose degrees for sand and clay?

Answer 46

Sand 30 Degrees Clay 45 Degrees