Construction Technology & Environmental Services

What is substructure?

All elements of work that are undertaken below the damp proof course, and provides a basis for the superstructure to be constructed upon

What is the external envelope?

• The materials and components that form the external shell of the building

• These may be load or non-load bearing

What are the Building Regulations?

• Set out the minimum performance standards for the design and construction of buildings

• Supported by the Approved Documents and other codes of practice

What are the approved documents?

A - Structure

B - Fire safety

C - Site preparation and damp proofing

D - Toxic substances

E - Sound proofing

F - Ventilation

G - Hygiene

H - Drainage and water disposal

I - Not in use

J - Heating appliances

K - Protection from falling, collision and impact

L - Conservation of fuel and power

M - Disabled access and facilities

N - Glazing

O - Not in use

P - Electrical safety

What are British Standards?

• Publications by the British Standards Institution - BS

• They give recommended minimum standards for materials, components, design and construction practices

What are international standards?

• Publications issued by the International Organisation for Standardisation - ISO

• Compatible with and complement the British Standards

What is superstructure?

• All internal and external works above the damp proof course

• Includes: external walls, stairs, roof, structural walls, suspended ceilings, raised floors

What are the typical components of site investigations?

Objective is to collect and record data to help with the design and construction process.

Should include matters in relation to the site that may impact the development such as:

• Boundary hedges and fencing

• Existing trees

• Size, depth and location of existing services

• Existing buildings

• Ground water conditions

• Soil investigation

• Trial pit information

What is the purpose of soil investigations?

• To determine the suitability of the site for the proposed works and determine type and costings for foundation design

• Should determine the potential difficulties associated with the ground conditions

What are the main site considerations?

• Access considerations

• Storage considerations

• Accommodation

• Temporary services

• Plant

• Fencing & hoarding

• Health and safety risks

What is a retained facade?

• Facade of the building is to be retained whilst everything behind the front wall is demolished

• Allowances need to be made for a temporary support structure, cleaning and restoration

• Often required as a result of listed building requirements

What are temporary works?

• Do not normally appear on the construction drawings but may be required depending upon the construction methodology

• Temp works may be required as a result of health and safety requirements to ensure a safe method of construction

What is a tower crane and what are some considerations during its erection and operation?

• A tall crane used for lifting objects into high places

• Boom allows a longer reach with 360 degree access

• Longer boom reduces the payload capability

• Use a smaller crane to erect a tower crane

• Weather conditions could prevent it from working (strong winds)

What is a scaffold?

• Temporary working platform erected around the perimeter or structure of a building

• Provides a safe working place at a convenient height

• Usually required for work 1.5 above ground level

What is shoring?

• Form of temporary support given to existing buildings

• Provide a precaution against damage or injury due to collapse of the structure

What are the main components of concrete?

• Cement

• Aggregate (natural rock, crushed stone, gravel)

• Water

What is a borehole?

• Can be used for soil investigation or for geothermal heating solutions

• Most suitable method of soil investigation when foundations are over 3m deep

• Geothermal boreholes are permanent boreholes that use the Earth’s natural heat to raise the temperature of circulated water

• This is a closed system and can be used to heat the building above (adopted as sustainable technology)

What are piles?

• Series of columns constructed or inserted into the ground to transmit the load of a structure to a lower level of subsoil

• Used where no suitable foundations conditions are present near ground level or if there is a high water table

What are the different types of piles?

• Sheet piles: deep trench excavated and concrete pored act as retaining walls or basement

• Secant piles: interlocking piles are bored to provide a combination of foundation and basement walls

• Bored piles: an auger is used to excavate and the concrete is poured in

• Pre-cast piles: hammered into the ground, not favoured due to the noise and lack of diversity in depth

What are the different ways that the piles transfer their load to the surrounding ground?

• End bearing piles - through load bearing capacity soil to a strong stratum such as rock

• Friction piles - frictional resistance between their outer surface and soil in contact

• Settlement reducing piles - incorporated beneath the central part of a raft foundation in order to reduce differential settlement

• Tension piles - resist uplifting forces that might otherwise cause the structure to be extracted from the ground (movement)

What are the difference between bored vs pre-cast piles?

• Bored piles removing spoil carried out by a boring technique

• Bored piles are used in formation of friction piles and where noise and vibration needs to be limited

• Precast piles driven using a drop or single action hammer

• Issues can arise from pre-cast piles due to the noise levels associated with the installation

What are the problems to the PQS regarding cost control with piling and who owns the risk?

• The end depth of the piles are never certain

• The procurement route used determines who takes the risk

• Traditional or D&B the main contractor would usually take the risk

What is a raft foundation?

• Spread the load of the superstructure over a large base and reduce the load per m2 of the area

• Useful in low bearing capacity soils

• Can be a solid raft slab or beam and slab raft such as a ground beam system and suspended PC concrete ground flood

Under what conditions would you expect a raft foundation to be used for a substructure?

• A raft can be used for lightly loaded buildings on sites with poor soils

• Heavy loads to the rafts have the potential to cause the raft to move sideways as a result of raft foundations not being very deep

What is a strip foundation?

• Formed by creating a shallow continuous excavation to support the perimeter and internal walls

• Also referred to as strip footings

• Suitable for most subsoils and a light structural design

What are pad foundations?

• Provide a based for reinforced concrete or steel columns

• Usually formed by making an isolated excavation in the shape of a square or rectangle

• Often have reinforcement mesh as part of the construction and spread the load to a layer of bearing soil or rock below

What are retaining walls?

• Act as an earth retaining structure for the whole or part of their heights

• Used to support and retain soils laterally so it can be retained at different levels on the 2 sides

What are the main types of excavation for forming basements?

• Open excavations - battered sides cut back to a safe angle

• Perimeter trench excavations - earthwork support at perimeter

• Complete excavation - centre excavated and sides supported by struts

What is a basement?

A storey constructed below ground level

What are the 3 different types of basement construction?

• Retaining wall and raft foundations

• Box and cellular raft, where internal walls are used to transmit loads over the raft and divides the basement into cells

• Piled solution, loads carried by columns and transmitted to the ground via pile caps and bearing piles

What are the 3 main methods of waterproofing a basement?

• Dense monolithic - using high quality reinforced concrete

• Tanking - materials using asphalt, polythene sheeting, bitumen, epoxy resins applied internally and externally

• Drained cavity - allows small amount of water infiltration which is collected, drained and pumped out

What is scabbing?

• Uses piston driven carbide tipped heads which impact surface material rapidly

• Pulverises concrete or brittle coatings

• Effective to remove coating where shot blasting does not work

• Can remove the level inconsistencies in concrete floors

What are the technical disadvantages of steel frames?

• Require fire protection

• Fixings may require replacement

• Price of steel often fluctuates

• Installation requires experienced builders, difficult to resource

What are the technical advantages of concrete frames?

• Fire protection included inherently

• Reduced cash flow expenditure as slower build time

• Low maintenance requirements

• Provide good sound and heat insulation properties

What are the technical advantages of steel frames?

• Quicker to assemble

• 100% recyclable

• Highest strength to weight ratio

• Not vulnerable to termites

• Do not expand or contract with moisture & temperature

• Non-combustible

• Lighter than concrete frames

What are the technical disadvantages of concrete frames?

• Time consuming to install

• Cannot be completed in cold weather conditions

• Would require steel reinforcement with fluctuations in price

• Often heavier and require larger foundations

Describe a typical Cold Flat Roof Construction

• Void or roof slab is insulated from heat loss from room below and therefore is at a colder temperature during cold weather

• Insulation is located above the ceiling level

• Ceiling joists run horizontal and are fixed to wall plates

• Insulation is inserted between the joists with an air gap for ventilation to reduce risk of condensation

• Plywood is secured onto the joists and finished with the roof covering

Describe a typical Warm Flat Roof Construction

• Insulation is placed on top of the roof deck but beneath the waterproof membrane

• Vapour control layer is placed under the insulation to reduce risk of condensation

Describe a typical Inverted Flat Roof Construction

• Where insulation is placed on top of the waterproof membrane

• No vapour control is needed

• Roof void and deck are maintained at a similar temperature to the room

• Insulation protects the membrane from damage but must be anchored down

Describe a typical parapet wall - roof abutment detail

• The parapet wall or dwarf wall is built along the perimeter edge of the roof

• The wall height extends above roof level

• Flashing / waterproofing detail required where wall intersects with roof

• DPC closer to be placed above the flashing and at the head of the wall under the coping detail

Describe a pitched roof detail

• Typically made up of rafters

• Rafters span from the apex of the roof and are fixed to the top of the external wall by a wall plate

• At the apex of the roof are the ridge tiles which are supported by the ridge board

• Roof covering is typically fixed to roof battens

• Supporting the rafters and roof coverings are the struts, purlins and roof beams

• A soffit and eaves board may be fixed to the end of the rafters along with guttering

• Vent tiles may be used to provide ventilation to the roof space

Describe a cladding rainscreen detail

• Provides a screening function rather than an enclosure in its own right

• Used to shield a wall

• Designed to permit some controlled leakage with the main functions of resistance to air and water being provided by the shielded wall behind

Describe a cladding stick system

• The curtain wall frame (mullions) and glass are installed and connected together piece by piece

• Versatile and allow for the integration of other systems such as windows.

• Tend to be less specialised

• Require multiple steps to erect and seal the wall, more time spent on site

Described a unitised cladding system

• Narrow width, storey-height units of aluminium framework containing glazed insulated panels

• Pre-assembled under factory-controlled settings

• Usually craned into position, with pre-positioned brackets attached to the floor slab or structural frame

Describe a Panellised system

• Constructed in the factory to improve speed and quality control

• Large prefabricated panels of bay width and storey height, connected to columns or floor slabs

• Panels are usually steel framed or precast concrete and are cladded with a variety of materials

• Good quality control and rapid insulation but tend to be more expensive than other systems

What are the common components you would expect to see within a steel frame construction?

• Beams

• Columns

• Purlins

• Rafters

• Eaves

• Eaves haunch

• Base plate

• Apex haunch

• Cladding rails

• Cross bracings

• Fixings

What are the common components you would expect to see within an external wall / foundation detail?

• Strip foundation

• Concrete block foundation wall

• Rebar reinforcement

• Damp proof course

• Air bricks

• Suspended floor slab or ground floor slab

• Backfilling

• Drainage

What are the different parts of a steel beam?

• Flange - top and bottom of the vertical steel

• Web - vertical part of the steel

• Root - where the flange and web join

What is powder coating?

• Durable factory applied coating on metals

• Sprayed on and is followed by heat curing to give a film thickness of 50 to 100 microns

• Any holes and cutting should be carried out before the coating is applied

What is a RHS vs SHS?

RHS - Rectangular Hollow Section

SHS - Square Hollow Section

What is intumescent paint?

• Fire resistant paint that is sprayed on in the factory and touched up on site

• Works by stopping oxygen from meeting the surface of the material it is protecting

What is an upstand?

A vertical strip or skirting

What is post tensioned concrete?

• Usually employed where stressing is to be carried out on site after casting an in-situ component or where a series of pre-cast concrete units are to be joined together to form the required member

• Concrete is cast around ducts or sheathing in which the tendons are to be housed

• Stressing is carried out after the concrete has cured by means of hydraulic jacks opening for one of both ends of the member

What is formwork?

• Anything that holds fresh in-situ concrete in place until it hardens

• Falsework holds the formwork in place and includes items such as wedges and clips to make stripping away easily

What is slip forming?

• A method for constructing a repetitive structure such as a core, lift shaft or stairwell

• The formwork is constantly moving upwards during the installation

• The concrete that becomes exposed must be cured enough to support the structure above

What is jump forming?

• Where a significant height of concrete is cast and left to cure

• The whole formwork module is moved up and repeated

• It works similar to slip forming, but is slower and cheaper in process terms

In a brick block cavity wall, how are window openings dealt with in terms of preventing water penetration and structurally?

Preventing water penetration

• Cavity trays cross the cavity to form a gutter that leads to a weephole

• DPC (damp proof course) strip of impervious material to stop moisture rising

Structurally

• Lintels installed over a window or door head which carry the wall load above

What is the size of a brick?

Standard bricks are 215mm x 102.5mm x 65mm

What is the frog and which side does it go on?

• An indentation in one of the bed faced of a brick, usually the top

• Bricks with 2 frogs are known as double frogged

• Should be laid frog facing up with mortar filling the frog

• This gives a stronger wall and superior sound installation

How many bricks are in a m2?

There are about 60 bricks per m2

What are the different types of brick bond?

• Stretcher - commonly used with walls half a brick wide

• English - alternating courses of headers and stretchers

What other elements will be affected by the type of cladding systems used?

• Frame

• Roof

• M&E

What is an air brick?

A perforated air brick to allow for ventilation into a room or an underfloor space

What are the factors that might affect the choice materials for internal partitions?

• Fire rating requirements

• Restriction for noise

• Visuals

• Fixed or movable

• Strength requirements

What are the different types of screed?

• Bonded - laid onto ready prepared rough, cleaned concrete base

• Unbonded - laid onto a sound clean bitumen damp proof membrane

• Floating - laid with steel reinforcements onto the insulating board

• Resin bonded - laid onto a clean, rough pre-pared concrete base acts as a damp proof membrane

What is the purpose of a threshold strip?

• Lightly rounded metal strip over the joint between floor finishes or coverings that meet under the door

• Prevent fraying and provide an aesthetic finish

What are the main components of a hipped end pitched timber roof structure?

• Principle rafters - support to roof covering run from eaves to ridge

• Jack rafters - shorter rafters that run from hip to eaves, or ridge to valley

• Ridge boards

• Wall plates

• Hip rafters - 2 roof surfaces meet to form an external angle

• Valley rafter - 2 roof surfaces meet to form an internal angle

• Purlins - horizontal to support rafters

• Battens - to where the roof covering is affixed

• Covering

What are the elements of a flat roof?

• Joists - fixed to wall plates to act as main support

• Firrings - fixed to top of joists to provide required gradient of incline

• Particle board - fixed to firrings to provide flat surface

• Felt - made up of 3 layers bonded with bitumen to provide waterproof covering

• Stone chippings - protection to the felt and reflect sunlight

What are the pro’s and con’s of a single layer membrane flat roof covering?

• 1 layer of felt with a base sheet of fibre glass or polyester integrated with hot bitumen

• Both sides coated with waterproof bitumen compound and dusted with sand on one layer, with a thin layer of polythene on the other

• After cooled, cut in strips ready to use

• Single layer membranes are thin and easily punctured

• Commercially the cheapest option

What are the pro’s and con’s of a built-up membrane system flat roof covering?

• Constructed using 3 layers of felt

• The first is laid at right angles to the fall commencing at the eaves

• The second layer is laid parallel to the fall

• The final layer is laid at right angles

• It is then covered with stone chippings

• More common than single layer but can be easily punctured if proper care is not taken

What are the pro’s and con’s of a asphalt flat roof covering?

• Consists of an aggregate with a bituminous binder cast into a block ready to be reheated on site

• Heated to 200 degrees Celsius and transported in liquid to form the roof, 2 layers required

• Reduce the risk of transportation related defects

• Cools quickly so needs to be heated close to the roof

• Dangerous working conditions working with hot materials

• Hardwearing

• Some companies offer 60-year guarantee due to their durability

What items would you expect to find on a timber or part glazed door that was required to have a half-hour fire rating?

• 3 hinges

• Intumescent strip on door or edge of frame

• A self-closing device

• If a glazing panel is present must be 6mm thick, wired glass to a max of 1.2 m2 with 13mmx13mm wood beads encased with non-combustible materials

What is an MF ceiling?

Mineral Fibre plasterboard suspended ceiling

What is a metal grid ceiling and what are the benefits?

• Suspended ceiling system formed by a square grid

• Normally quicker to install than alternative options

• Allow for service runs through the void above, therefore allowing greater floor to ceiling height

• Offer easy access for service repairs

• Damaged tiles can be replaced rather than needed to repair or replaster the entire ceiling

What is the difference between rolled and tiled carpets and why do we use each type?

• Rolled - better quality, more expensive, common within dwellings

• Tiles - harder wearing, cheaper, individual tiles can be replaced, used in offices and hospitals

What is top down construction?

• Used to speed up the construction process of a building with basement levels

• Ground floor slab is cast with an access hatch

• The ground below is excavated and another slab is formed

• Piles are usually used as foundations and act as retaining walls

• Allows for the building to be constructed at the same time as the basement

What is bottom up construction?

Traditional construction build. Forms the basement and then works upwards.

What is a three phase electrical supply?

• 3x AC voltages 120 degrees out of phase with each other

• Cheaper and easier to transmit electricity than single phase

Explain how power is distributed to floor boxes in a raised floor?

• Incoming power connects to a LV switchboard

• Then connects to a distribution switchboard

• Dist. switchboard will have an underfloor busbar

• The busbar will have a number of sockets to which the floor box plugs into

• The floor box has sockets which the appliances can plug into

What is Cat II lighting?

Light fittings suitable for the use with VDU screens, designed to limit the amount of glare from computer screens and the like

What is a symphonic drainage system?

• Alternative to gravity drainage system

• Water is sucked from the guttering via a vacuum

• Advantage that narrower down pipes can be used

Describe the different types of lift available?

• Passenger lifts - tend to be in offices / hospitals

• Residential lifts - tend to be in smaller shops

• Platform lifts - move a wheelchair 2m or less

• Freight lifts - similar to passenger lifts but designed to carry goods

• Dumbwaiter - a small freight lift, usually used in 2 storey kitchens to move dishes

What fire safety provisions would you expect to find in an office block?

• Max. occupancy listings

• Fire exits with above signage visible in event of power failure

• Easily accessible fire extinguishers and alarms

• Restricted use of flammable materials

• Installation of fire alarm control panels

What are automatic fire sprinklers?

• Individually heat-activated

• Tied into a network of piping with water under pressure

• When a fire raises the temperature, a solder link will melt or liquid-filled glass bulb shatter to open that single sprinkler and release the water

What are the main types of air-conditioning system available?

• Refrigeration cycle

• Evaporative coolers

• Absorptive chillers

Describe a VAV (Variable Air Volume) AC system?

• Vary the airflow at a constant temperature

• Utilise a supply duct that distributes cooled air

• Temp is kept constant and air flow varies to meet the falling and rising heat gains

• System is made up of supply and return ductwork

• A VAV box is also referred to as a VAV terminal unit

Describe a VRF (Variable Refrigerant Flow) AC system?

• Can be made up of a heat pump system or heat recovery system

• Heat pump is connected to multiple independent indoor units

• The energy recovered from one unit to be used to heat another unit

• This system takes up much less space than traditional ductwork

How are fire barriers formed in suspended ceilings and what happens when services pass through the barriers?

• If a suspended ceiling is not fire resistant, fire barriers would be required within the ceiling void

• Barriers would be installed between the soffit of the floor above and the suspended ceiling

• Smoke stops will sometimes be required

• Services in the ceiling must be sealed to prevent the fire spreading

What is a UPS and why does a building require one?

• Uninterruptible power supply

• Maintains a continuous supply of electric power to electrical equipment that must not be shut down unexpectedly

Why do we install generators in buildings?

• Act as a backup power supply

• Becoming less common as technological advances are made in the UPS

What is busbar trunking?

Bare copper or aluminium conductors fixed inside trunking that distribute heavy-duty electrical power to tap-off units

What do the abbreviations FCU, AHU and VAV stand for?

• Fan Coil Unit (FCU)

• Air Handling Unit (AHU)

• Variable Air Volume System (VAV)

What types of bridge construction are there?

• Beam bridge with simple beam or cantilever

• Arch bridge

• Suspension bridge or cable stayed bridge

• Movable bridge - swing bridge, draw bridge, lift bridge

How does a cable stayed bridge work?

The load exerted from the bridge deck and all live loads are transferred through the wires to towers and into ground anchorages

What is the difference between a tower and a pier?

• The towers protrude through the deck vertically to provide a connection point for the cable stays which transfer the load

• Piers support the bridge deck

What type of building work is covered by the Building regulations?

• The erection or extension of a building

• Installation or extension of a service that is controlled by the regulations

• Alteration projects which will temporarily or permanently affect the building in terms of structure, fire and access

• Insertion of insulation into cavity walls

• Underpinning of building foundations

What are the specific areas covered by the Building Regulations?

A - Structure

B - Fire safety

C - Site preparation and resistance to moisture

D - Toxic substances

E - Resistance to the passage of sounds

F - Ventilation

G - Hygiene

H - Drainage

J - Heat producing appliances

K - Protection from falling, collision and impact

L - Conservation of fuel and power

M - Access and facilities for disabled people

N - Glazing

P - Electrical safety

What are the Building Regulations Approved Documents?

• Provide general guidance on performance of materials expected in order to comply with functional requirements of the building regulations

• The only provide guidance & therefore there is no obligation to adopt specific solutions if it is possible to meet requirements via a different means

Who ensures the building regulations are complied with?

Building control services such as the Local Authority or Approved Inspectors

What would be a typical programme for a new build structure?

• Site clearance

• Enabling works

• Site setup

• Haul and access roads

• Setting out

• Excavate to reduced levels

• Excavate foundations

• Cast foundations

• Frame erection

• Cladding

• Roof

• Floors

• Services

• FF&E

• Testing

• Commissioning

• Landscaping

• Snagging