Home Building Manual: Part 1 Section 2 Tables 1 - 7
Home Building Manual: Part 1 Section 2, Table 1
Residential site class designations
| TYPICAL FOUNDATION MATERIAL | CHARACTER OF FOUNDING MATERIAL | EXPECTED RANGE OF TOTAL SOIL MOVEMENTS (mm) | ASSUMED DIFFERENTIAL MOVEMENT (% OF TOTAL) | SITE CLASS |
| Rock (excluding mud rocks which may exhibit swelling to some depth) | STABLE | NEGLIGIBLE | - | R |
| Fine grained soils with moderate to very high plasticity (clays, silty clays, clayey silts and sandy clays) | EXPANSIVE SOILS | <7,5 7,5-15 15-30 >30 |
50% 50% 50% 50% |
H H1 H2 H3 |
| Silty Sands, sands, sandy and gravely soils | COMPRESSIBLE AND POTENTIALLY COLLAPSABLE SOILS | <5 5-10 >10 |
75% 75% 75% |
C C1 C2 |
| Fine Grained Soils (clayey silts and clayey sands of low plasticity), sands, sandy and gravely soils | COMPRESSIBLE SOILS | <10 10-20 >20 |
50% 50% 50% |
S S1 S2 |
| Contaminated soils, Controlled fill, Dolomitic areas, Landslip, Landfill, Marshy areas, Mine waist fill, mining subsidence, Reclaimed areas, Uncontrolled fill, Very soft silts/silty clays | VARIABLE | VARIABLE | P |
Home Building Manual: Part 1, Section 2, Table 2
Classification of damage with reference to masonry walls in single storey units
| DESCRIPTION OF DAMAGE IN TERMS OF EASE OF REPAIR AND TYPICAL EFFECTS | APPROXIMATE MAXIMUM CRACK WIDTH IN WALLS (mm) | CATEGORY AND DEGREE OF EXPECTED DAMAGE |
| MINOR DAMAGE - CATEGORIES 0 TO 2 | ||
| Hairline cracks less than about 0,25 mm width are classed as negligible. | <0,25 | 0 Negligible |
| Fine internal cracks, which can easily be treated during normal decoration. Cracks rarely visible in external masonry. | < 1 (Isolated; localized) | 1 Very slight |
| Internal cracks easily filled. Redecoration probably required. Recurrent cracks can be masked by suitable linings. Cracks not necessarily visible externally. Doors and windows may stick slightly. | <5 | 2 Slight |
| SIGNIFICANT DAMAGE - CATEGORIES 3 TO 5 | ||
| Cracks can be repaired and possibly a small amount of masonry may have to be replaced. Articulation joints may have to be cut into some of the walls. Doors and windows sticking. Rigid service pipes may fracture. Weather tightness often impaired. Up to 10 mm gap between ceiling cornices and walls. | 5 to 1 5 (or a number of cracks (3 to 5) in one group) | 3 Moderate |
| Extensive repair work which includes breaking out and replacing sections of walls, especially over doors and windows, cutting of articulation joints in walls and the construction of moisture trenches and apron slabs around the building, or the jacking of foundations depending on the type of soil movement. Window and door frames distorted, floor sloping noticeably. Walls leaning or bulging noticeably, some loss of bearing in beams. Service pipes probably disrupted. Up to 20 mm gap between ceiling cornices and walls. | 15 to 25 (depending also on number of cracks in a group) | 4 Severe |
| Major repair work required, involving partial rebuilding and the above mentioned repair techniques. Beams loose bearing, walls tilt badly and require shoring. Windows broken and distorted. Danger of instability. | Usually greater than 25 (depending also on number of cracks in a group) | 5 Very severe |
NOTE:
1. Crack width is only one factor in assessing damage and should not be used on its own as a direct measure of damage. In assessing the degree of severity of damage, account must be taken of the location in the building where it occurs, and also of the function of the building.
2. This classification is based on the ease of repair which may be considered under three headings representing a progression in difficulty of repair, viz. redecoration due to wear and tear, remedial work to reinstate functional efficiency and structural repair. former two categories relate to minor damage (categories 0 to 2).
3. In most instances, minor damage (categories 0 to 2) represent aesthetic damage as opposed to serviceability damage (Categories 3 and 4) and stability damage (category 5).
4. Where cracks less than 1 mm are widespread throughout the building, the damage may be regarded as being Category 2.
5. The descriptions contained in the first column relate to single storey construction. In multi-storey construction, these descriptions will require modification for a particular category of expected damage.
Home Building Manual: Part 1, Section 2, Table 3
Classification of damage with reference to concrete floors
| DESCRIPTION OF TYPICAL DAMAGE | APPROXIMATE MAXIMUM CRACK WIDTH IN FLOOR (mm) | MAXIMUM DEVIATION OF ANY JOINT FROM A 3 m STRAIGHT EDGE (mm) | CATEGORY AND DEGREE OF EXPECTED DAMAGE |
| MINOR DAMAGE - CATEGORIES 0 TO 2 | |||
| Hairline cracks, insignificant tilt of floor or change in level. | <0,3 | <5 | 0 Negligible |
| Fine but noticeable cracks. Floor reasonably level. | <1,0 | <1,0 | 1 Very slight |
| Distinct cracks. Floor noticeably curved or changed in level. | <2,0 | <10 | 2 Slight |
| SIGNIFICANT DAMAGE - CATEGORIES 3 TO 5 | |||
| Wide cracks. Obvious curvature or change in level - local deviation of slope from the horizontal may exceed 1 :100 | 2 to 4 | 10 to 20 | 3 Moderate |
| Gaps in floor. Disturbing curvature or change in level. | >20 | 4 to 5 Severe to very severe |
|
NOTE: Local deviation of slope, from the horizontal or vertical, of more than 1/100 will normally be clearly visible. Overall deviations in excess of 1/250 are undesirable.
Home Building Manual: Part 1, Section 2, Table 4
Classification of damage caused by ground floor slab settlement
| DESCRIPTION OF TYPICAL DAMAGE | APPROXIMATE CRACK WIDTH IN FLOOR (mm) | APPROXIMATE GAP (mm) | CATEGORY OF DEGREE OF EXPECTED DAMAGE |
| MINOR DAMAGE - CATEGORIES 0 TO 2 | |||
| Hairline cracks between floor and skirtings. | Up to 1 | 0 Negligible | |
| Settlement of the floor slab, either at a comer or along a short wall, or possibly uniformly, such that a gap opens up below skirting boards but which can be masked by resetting skirting boards. No cracks in floor slabs, although there may be negligible cracks in floor screed and finish. Slab reasonably level. | Up to 5 | 1 Very slight |
|
| Larger gaps below skirting boards; some obvious but limited local settlement leading to slight slope of floor slab; gaps can be masked by resetting skirting boards and some local re-screeding may be necessary. Fine cracks appear in internal walls which may require some redecoration; slight distortion in door frames which may result in sticking of doors. No cracks in floor slab although there may be very slight cracks in floor screed and finish. Slab reasonably level. | Up to 1 | Up to 15 | 2 Slight |
| SIGNIFICANT DAMAGE - CATEGORIES 3 TO 5 | |||
| Significant gaps below skirting boards with some areas of floor, especially at corners or ends, where local settlements may have caused slight cracking of floor slab. Sloping of floor In these areas is clearly visible. (Slope approximately 1 in 150). Some disruption to drain, plumbing or heating pipes may occur. Damage to internal walls is more widespread with some crack filling or re-plastering of partitions being necessary. Doors may have to be refitted. Inspection reveals some voids below slab with poor or voids below slab with voids below slab with poor or loosely compacted fill. | Up to 5 | Up to 20 | 3 Moderate |
| Large, localized gaps below skirting boards; possibly some cracks in floor slab with sharp fall to edge of slab; (slope approximately 1 in 100 or more). Inspection reveals voids exceeding 50 mm below slab and/or poor or loose fill likely to settle further. Local breaking-out, part refilling and relaying of floor slab or grouting of fill may be necessary; damage to internal partitions may require replacement of some portions of masonry walling. | 5 to 15 | Up to 25 | 4 Severe |
| Either very large, overall floor settlement with large movement of walls and damage at junctions extending up into 1st floor area, with possible damage to exterior walls, or large differential settlements across floor slab. Voids exceeding 75 mm below slab; and/or very poor or very loose fill likely to settle Risk of instability. Most or all of floor slab requires breaking out and relaying or grouting of fill; internal partitions need replacement. | Usually greater than 15 but depends on the number of cracks | Greater than 25 | 5 Very severe |
NOTE: "Gap" refers to the space, usually between the skirting and finished floor, caused by settlement after making appropriate allowance for discrepancy in building, shrinkage, normal bedding down and the like.
Home Building Manual: Part 1, Section 2, Table 5
Foundation design, building procedures and precautionary measures for single storey residential structures founded on expansive soil horizons.
| SITE CLASS | ESTIMATED TOTAL HEAVE (mm) | CONSTRUCTION TYPE | FOUNDATION DESIGN AND BUILDING PROCEDURES
(Expected damage limited to Category 1) |
| H | <7,5 |
Normal | * Normal construction (strip footing or slab-on-the-ground) foundation.
* Site drainage and service/plumbing precautions recommended |
| H1 | 7,5-15 | Modified normal | * Lightly reinforced strip footings. * Articulation joints at all internal/external doors and openings. * Light reinforcement in masonry. * Site drainage and plumbing/service precautions. |
| H1 | 7,5-15 | Soil raft |
* Remove all or necessary parts of expansive horizon to 1,0 m beyond the perimeter of the building and replace with inert backfill compacted to 93% MOD AASHTO density at -1 % to + 2% of optimum moisture content. |
| H2 | 15-30 | Stiffened or cellular raft |
* Stiffened or cellular raft of articulated lightly reinforced masonry. * Site drainage and plumbing/service precautions. |
| H2 | 15-30 | Piled construction |
* Piled foundations with suspended floor slabs with or without ground beams. * Site drainage and plumbing/service precautions. |
| H2 |
15-30 | Split |
* Combination of reinforced masonry and full movement joints. |
| H2 | 15-30 | Soil raft | * As for H1. |
| H3 | >30 | Stiffened or cellular raft |
* As for H2. |
| H3 | >30 | Piled Construction |
* As for H2. |
| H3 | >30 | Soil raft | * As FOR H1. |
NOTE:
1) Differential heave equals 50% of total heave.
2) The relaxation of some of these requirements, e.g. the reduction or omission of reinforcement or articulation joints, may result in a Category 2 level of expected damage.
Home Building Manual: Part 1, Section 2, Table 6
Foundation design, building procedures and precautionary measures for single storey residential structures founded on soil horizons subject to both consolidation and collapse settlement
| SITE CLASS | ESTIMATED TOTAL SETTLEMENT (mm) | CONSTRUCTION TYPE | FOUNDATION DESIGN AND BUILDING PROCEDURES
(Expected damage limited to Category 1) |
| C | <5 |
Normal | * Normal construction (strip footing or slab-on-the-ground) foundations * Good site drainage |
C1 |
5-10 | Modified normal | * Reinforced strip footings. * Articulation joints at some internal and all external doors * Light reinforcement in masonry. * Site drainage and service/plumbing precautions * Foundation pressure not to exceed 50 kPa |
| C1 | 5-10 | Compaction of insitu soils below individual footings |
* Remove insitu material below foundations to a depth and width of 1 ,5 times the foundation width or to a competent horizon and replace with material compacted to 93% MOD AASHTO density at -1 % to + 2% of optimum moisture content. |
| C1 | 5-10 | Deep strip foundations | * Nomal construction with drainage precautions. * Founding on a competent horizon below the problem horizon. |
| C1 | 5-10 | Soil raft |
* Remove insitu material to 1 ,0 m beyond perimeter of the building to a depth of 1 ,5 times the widest foundation or to a competent horizon and replace with material compacted to to 93% MOD AASHTO density at 1% to - 2% of optimum moisture content. * Normal construction with lightly reinforced strip footings and lightly reinforcement in masonry. |
C2 |
>10 | Stiffened strip footings, stiffened or cellular raft |
* Stiffened strip footings or stiffened or cellular raft with lightly reinforced or articulated masonary. |
C2 |
>10 | Deep strip foundations | * As for C1 but with fabric reinforcement in floor slabs. |
| C2 | >10 | Compaction of insitu soils below individual footings | * As for C1 |
C2 |
>10 |
Piled or pier foundations | * Reinforced concrete ground beams or solid slabs on piled or pier foundations. * Ground slabs with fabric reinforcement * Good site drainage. |
C2 |
>10 |
Soil raft | * As for C1. |
NOTE:
1) Differential settlement equals 75% of total settlement.
2) The relaxation of some of these requirements, e.g. the reduction or omission of reinforcement or articulation joints, may result in a Category 2 level of expected damage.
Home Building Manual: Part 1, Section 2, Table 7
Foundation design, building procedures and precautionary measures for single storey residential structures founded on soil horizons subject to consolidation settlement.
| SITE CLASS | ESTIMATED TOTAL SETTLEMENT (mm) | CONSTRUCTION TYPE | FOUNDATION DESIGN AND BUILDING PROCEDURES
(Expected damage limited to Category 1) |
| S | <10 |
Normal | * Normal construction (strip footing or slab-on-the ground) foundation. * Foundation bearing pressure not to exceed 50 kPa * Good site drainage. |
S1 |
10-20 | Modified normal | * Remove insitu material below foundations to a depth and width of 1,5 times the foundation width or to a competent horizon and replace with material compacted to 93% MOD AASHTO density at -1 % to + 2% of optimum moisture content. * Normal construction with lightly reinforced strip foundations and light reinforcement in masonry. |
| S1 | 10-20 | Compaction of insitu soils below individual footings |
* Remove insitu material below foundations to a depth and width of 1 ,5 times the foundation width or to a competent horizon and replace with material compacted to 93% MOD AASHTO density at -1 % to + 2% of optimum moisture content. |
| S1 | 10-20 | Deep strip foundations | * Normal construction with drainage precautions. * Founding on a competent horizon below the problem horizon. |
| S1 | 10-20 | Soil raft |
* Remove insitu material to 1,0 m beyond perimeter of building to a depth of 1,5 times the widest foundation or to a competent horizon and replace with material compacted to 93% MOD AASHTO density at -1 % to + 2% of optimum moisture content. * Normal construction with lightly reinforced strip footings and light reinforcement in masonry. |
S2 |
>20 | Stiffened strip footings, stiffened or cellular raft |
* Stiffened strip footings or stiffened or cellular raft with lightly reinforced or articulated masonry. |
S2 |
>20 | Deep strip foundations | * As for S1 but with mesh reinforcement in floor slabs. |
| S2 | >20 | Compaction of insitu soils below individual footings | * As for S1. |
| S2 | >20 | Piled or pier foundations | * Reinforced concrete ground beams or solid slabs on piled or pier foundations. * Ground slabs with fabric reinforcement. * Good site drainage. |
S2 |
>10 |
Soil raft | * As for S1. |
NOTE:
1) Differential settleSment equals 50% of total settlement.
2) The relaxation of some of these requirements, e.g. the reduction or omission of reinforcement or articulation joints, may result in a Category 2 level of expected damage.
3) Account must be taken of sloping sites where differential fill heights may lead to greater differential settlements.
4) Settlements induced by loads imposed by deep filling beneath surface beds may necessitate the adoption of a construction type appropriate to a more severe site class.
Home Building Manual: Part 1, Section 2, Table 8
| DOLOMITIC AREA CLASS | DESCRIPTION | TYPICAL FOUNDATION SOLUTIONS
|
| D1 | No precautionary measures are required to permit the
construction of housing units due to an adequate overburden
thickness.
Sites can be classified in accordance with Part 1, Section 2, Table 1 on the basis of the characteristics of the near surface soil horizons. |
Foundations in accordance with Part 1, Section 2, Tables 5 to 7. |
D2 |
The risk of sinkhole and doline formation is adjudged to be such
that only general precautionary measures, which are intended
to prevent the concentrated ingress of water into the ground, are
required to permit the construction of housing units.
Sites can be classified in accordance with Part 1, Section 2, Table 1 on the basis of the characteristics of the near surface soil horizons. |
Foundations in accordance with Part 1, Section 2, Tables 5 to 7. |
| D3 | The risk of sinkhole and doline formation is adjudged to be such
that precautionary measures, in addition to those pertaining to
the prevention of concentrated ingress of water into the ground,
are required to permit the construction of housing units. |
Possible solutions include the use of either shallow reinforced strip footings or reinforced concrete slab-on-the-ground foundation which in turn are founded on engineered fill mattresses comprising chert gravel or other granular fill; concrete raft foundations spanning between near surface pinnacles or other appropriate solutions
|
| D4 | The risk of sinkhole and doline formation is such that precautionary measures cannot adequately reduce such risks to acceptable limits so as to permit the construction of housing units or the precautionary measures which are required are impracticable to implement. |
NOTE:
The method of scenario supposition (Buttrich and Van Schalkwyk 1995) should be used to arrive at dolomitic zone designations (See Addendum to Code of Practice for foundations and superstructures for single storey residential buildings of masonry construction, May 1998).