For structural works on HDB properties, the Qualified Person (QP) must ensure full compliance of his design according to the current Code of Practice and local regulatory/ statutory requirements.
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Type of Structures
Minimum Concrete Grade
Substructures, superstructures, precast reinforced concrete piles, pile caps, and building precast concrete components
Grease trap, inspection chamber, and screen chamber
Structure and Location
Minimum Concrete Cover (mm)
Top, bottom, and sides
To main reinforcement bars
To vertical bars
Inner face in contact with water
Top and sides
From pile head
Most types of pile foundations (bored piles, steel H-piles, micropiles, jack-in steel pipe piles, jack-in steel H-piles, and precast reinforced concrete piles) are acceptable except for timber piles. All pile foundations have to be designed with a minimum safety factor of 2.5 times the nominal working load.
For the design of footing, the bearing capacity of the soil must be based on borelog results. If no soil information is available, the bearing capacity of the soil must be limited to 50kN/m2 at 1.5m below ground level.
The QP must submit the slope stability and design calculations for proposed slopes greater than 2.5m in height. Slope-protection measures must be in place to stabilise any slopes that fail to satisfy the required factor of safety. A minimum factor of safety of 1.5 is required for slope stability.
For the earth-retaining wall, the following factors of safety have to be considered:
Factor of Safety
Overturning and sliding
Allowable bearing pressures
Overall stability or slip circle failure
In addition to the factor of safety stated, the following requirements must to be adopted:
The new column must be designed as a short column and founded for independent structures.
Columns or walls that are next to driveways must be checked and designed for vehicular impact load. Tie beams must be provided for columns at the ground floor and roof.
No opening can be made through the columns.
The proposed structure must be independently supported. For cases where the soil information is not available, the QP must consider the safe bearing capacity to be limited to 50kPa with a minimum founding depth of 1.5m.
A minimum air gap of 150mm must be provided between the cold/ chiller room and existing structure. The existing floor slab needs to be topped up with approved insulation material. Construction of the cold/ chiller room is only allowed on the first storey.
S275 steel sections must be used for general structural steel members.
Drilling is not allowed if a steel hollow section is used. Only steel plates, angels, or cleats can be used and they must be welded to secure the cladding or metal roofing sheets.
If roofing sheets or claddings are designed by a specialist, the QP must check and ensure that the design complies with current safety, stability, and durability requirements.
The appropriate separator must be used at the contact between 2 different metals to prevent galvanic corrosion.
All grease traps, inspection chambers, and screen chambers must be subjected to a design-imposed load of 5kN/m2. They do not have to be subjected to a vehicular load.
The total operating weight (with full content weight) must be considered in the design.
New walls can be erected as long as the maximum thickness of the brick or hollow blocks does not exceed:
A lightweight awning can be mounted onto the existing structural member as long as it is not a cantilever beam.
Awnings that span more than 2.4m and are supported directly by reinforced concrete columns or peripheral beams must be propped up.
For an Outdoor Refreshment Area adjacent to buildings taller than 4 storeys (high-rise), its structure must be supported on independent foundation. The roofing material has to be non-combustible and be composed of:
If the composition of the proposed sandwiched panel deviates from the reference above or if other (non-combustible) roofing material is to be used, the structural professional engineer must conduct an impact load test with an accredited laboratory and submit the test report to us. The report must justify that the material is able to withstand the impact load of a 6-kg flower pot falling from the height of 45m, assuming that the impact contact time is 0.1 sec.
A precast ferrocement roof must have:
Outdoor Refreshment Area adjacent to buildings that are 4 storeys or shorter require: