HKIA Exam Paper 6 Quiz 46

Special foundation can make use of diaphragm wall way of construction to build cruciform shaped foundation (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.4 – An Outline of Foundation System in Hong Kong – Foundation Types).

A cavity wall is a wall constructed in two leaves with space or cavity between them. The two leaves are constructed of solid bricks or building blocks, each not less than 100mm thick with the intervening cavity not less than 50mm and not more than 75mm wide (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.5 – Brickwork and Block Work – Cavity Wall).

Acrylics have good unprimed adhesion and good weathering characteristics but a strong, obnoxious odor. With a 10 to 15 years life expectancy outdoors, they can accommodate movement up to ±12.5% joint width (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.7 – Roofing, Waterproofing, and Expansion Joints – Sealants).

Boarded strip flooring is of teak or other hardwood with finished thickness as 20mm minimum. Width for solid teak is 75mm and 100mm; that for solid maple is 50mm. Length varies (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Flooring).

Certain impurities in water are permissible. Chlorides must not exceed 50mg per litre. Sulphates shall not exceed 1000mg of sulphur trioxide per litre. Alkali carbonates and bicarbonates shall not exceed 1000mg per litre (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.3 – Concrete Work – Water).

Solid core flush doors are infilled with 25mm vertical battens tightly cramped together or with 50mm horizontal battens (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Doors).

Metal for roofing includes corrugated steel sheet, corrugated aluminium, milled sheet and rolled copper sheet, strip, and foil (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.7 – Roofing, Waterproofing, and Expansion Joints – Metal Roofing).

To ensure stability of the structure and to produce a better outlook, the laying of bricks is done in more recognized pattern or bond such as stretcher bond, English bond, Flemish bond, etc (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.5 – Brickwork and Block Work – Workmanship).

A lower standard of finish is the parquet flooring of hardwood with block size as 120 x 25 x 8mm thick. Fixing is done by dipping the undersides in Ucar latex or equal adhesive and laying on screeded bed coated with similar adhesive. After sanding and filling in, the even surface is ready for wax polishing (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Flooring).

Actual thickness of granite slabs for cladding depends on the type of stone and the size of panels, generally ranging from 30mm to 40mm (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.6 – Masonry and Granite/Marble Works – Stone Cladding).

The waterproofing materials available are also thus categorized
i. Integral waterproofers as addictives to cementitious mixes, e.g., concrete, mortars. These operate as pore fillers combined with water repellent chemicals.
ii. Pre-packed integral waterproofers requiring only addition of water at site which makes site mixing simple. These contain active chemicals reacting with free calcium in the substrate to form insoluble crystals which block the capillaries preventing the ingress of water.
iii. Polymer modified cementitious systems as emulsions when used in cement sand mixes the emulsion breads down to form a fibrous lattice with the mortar structure affording improved adhesion, flexural strength, and reduced permeability.
iv. Emulsions based on bitumen or bitumen/rubber designed to provide either waterproof external coatings or waterproof membranes. These should be covered with a screed protections.
v. External water repellants based on silicone resins or stearate complexes design to repel rain from permeating into vertical surfaces. However, these allow the release of dampness from within the substrate.
(Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.7 – Roofing, Waterproofing, and Expansion Joints – Waterproofing (Besides Roofing)).

The handrail is required to be located at a height between 850mm and 1000mm. The projection onto the staircase for a handrail should not exceed 90mm.
(Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.9 – Staircases, Steps, and Handrails – Handrails).

Nominal size of clay bricks in 225 x 105 x 70mm. Concrete block is constructed of mixes as 1 part Portland cement, 2 parts clean washed sand, 3 parts granite fines plus 5 parts 10mm granite aggregate. Standard block size is 390mm long by 190mm deep with varying thickness to suit wall construction (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.5 – Brickwork and Block Work – Materials).

The maximum permissible moisture content in timbers are:
i. Internal timber for use in air-conditioned space 12%
ii. Internal timber generally 16%
iii. Timbers with one side to the exterior of the building and one side to the interior 20%
iv. External timbers 20%
(Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Materials).

Grillage foundation makes use of a grid system of H-section steel beams to spread out the load. Concrete is then used to cover the steel beams
(Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.4 – An Outline of Foundation System in Hong Kong – Shallow Foundation).

Panalled door is a common way to construct solid hardwood door. Thickness of door is 40mm minimum with 100mm wide styles. top rail and muntins and 200mm wide middle and bottom rails. Panels for glass can be installed (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Doors).

Aluminium sections will have a minimum wall thickness of 1.6mm and dovetail grooved for weatherstrip.
Finishing to aluminium can be clear anodized, colour anodized with average 25mm thick, proprietary hard coat anodic finish with hard-wearing qualities (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.10 – Metal Windows and Doors – Materials).

On a concrete roof, a cement sand screed makes up the base. Then a coat of bitumen primer is brushed on and allowed to dry. The first bitumen felt layer is partially bonded to the base at perimeter and in spots or strips with hot bitumen based bonding compound at the rate of 0.5kg/sq m. Subsequent layers then fully bonded with an even coating of hot bonding compound at the rate of 1.5 kg/sq m. The final surface is dressed with bitumen compound applied at the rate of 3 kg/sq m dressed immediately with stone chippings lightly rolled in at the rate of 15kg/sqm (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.7 – Roofing, Waterproofing, and Expansion Joints – Bitumen Felt Built-Up Roofing).

Formation of glass sheets is by various processes of drawing, floating, or rolling (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.10 – Metal Windows and Doors – Glass).

For infill brickwork or blockwork, a 300mm wide metal lath is installed across the joint between the brick/blockwork and concrete before plaster is applied to prevent future cracks along the joints
Tolerance for blockwork is set at ±10mm for setting out dimensions and vertical plumb in any storey height (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.5 – Brickwork and Block Work – Workmanship).

For schools, treads are not less than 250mm wide and risers are not more than 150mm nor less than 75mm high (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.9 – Staircases, Steps, and Handrails – Requirement for Staircases, Steps).

Flush door is the common method of door construction in Hong Kong. Stiles and rails are generally are 75mm wide (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Doors).

Accessible roofs are required to be protected by parapet or railing not less than 1100mm in height from finished roof level and so constructed at to prevent climbing or passage of objects more than 100mm in their smallest dimension (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.7 – Roofing, Waterproofing, and Expansion Joints – Roofing in General).

Architraves are fixed in one length between angles with mitre joints at the angle (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Doors).

Generally for boundary wall or fence not exceeding 1.8m high, brick or block must not be less than 100mm thick. if exceeding 1.8m high but less than 3m high, wall thickness is not to be less than 225mm thick (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.5 – Brickwork and Block Work – Cavity Wall).

50 x 40mm battens of hardwood pre-treated with wood preservatives are laid at 350mm centers on concrete bed level with 1:3 cement mortar (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Flooring).

Spread footing is a reinforced concrete mass supporting point load from columns and can be classified as rock or soil footing (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.4 – An Outline of Foundation System in Hong Kong – Shallow Foundation).

Oil-extended or oil-based caulks are suitable for temporary structures that undergo little or no movement. Life expectancy is 2 to 10 years. Failure occurs by hardening, shrinkage, and cracking. Movement is up to 5% joint width.

Urethane sealants form another type of high-performance sealants. Most characteristics of urethane sealants lie between polysulfides and silicones. But urethane is more susceptible to problems with dampness with applied surface. Movement allows ±25% but can go up to ±35 for some urethanes (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.7 – Roofing, Waterproofing, and Expansion Joints – Sealants).

Manufactured from soda, lime, silica, and other minor ingredients such as magnesia and alumina, glass is a suitable material for glazing (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.10 – Metal Windows and Doors – Glass).

As a common form of domestic flooring, woodblock is of teak or other hardwood. Block size is 300 x 50mm with 20mm minimum finished thickness (Building Materials and Technology in Hong Kong – Chapter 2 – Trades of Materials and Technology – 2.8 – Carpentry, Joinery, and Ironmongery – Flooring).