Building technology

Question 1

What are the main building ages?

Answer 1

Georgian - 1720-1820
Victorian - 1920-1901
Edwardian -1901 - 1920
Post war
etc

Question 2

What are the defining characteristics of Victorian buildings (1837-1901)?

Answer 2

• Solid brick walls.
• Decorative features.
• Domestic buildings tend to be formed in terraces.
• Timber sliding sash windows.
• Bay windows.
• Slate roof coverings.
• Timber roof structure.
• Timber suspended floors.
• Slate DPCs (in later Victorian properties after compulsory DPCs in 1875).
• Air bricks (in late Victorian properties).

Question 3

What are the defining characteristics of a Georgian building (1714-1837)?

Answer 3

• Symmetrical architecture.
• Classic features.
• Lack of detailed ornamentation.
• Solid brick walls usually formed of two skins of stretchers and snapped headers butted together.
• Brickwork faced with stucco render.
• Parapet walls and gutters.
• Absence of physical DPC.
• 6 over 6 timber sash windows.

Question 4

What kind of loadings would a structural engineer take into account when carrying out a loading assessment?

Answer 4

• Dead load: load imposed by the structure itself.
• Live load: load imposed by occupants and objects in a structure.
• Environmental load: load imposed by rainfall, snow and wind.

Question 5

What considerations would you need to make when installing photovoltaic panels to property?

Answer 5

• Whether the existing power and infrastructure is sufficient.
• whether the structure of the building can take the new imposed load of the panels.

Question 6

What is the typical payback period for solar PV panels? What is serviceable life of a solar PV installation?

Answer 6

• 6 to 10 years depending on energy costs, weather and size of system installed.
• Fill this card out more!
• 20 - 25 years with good maintenance.

Question 7

How do solar PV systems work?

Answer 7

• The PV cell consists of one or two layers of a semi conducting material, usually silicon. When light shines on the cell it creates an
  electric field across the layers causing electricity to flow.
• The solar panels generate DC electricity from sunlight which is fed through an inverter to convert it into AC electricity.
• The inverter is connected to a consumer unit (fuse board) so the electricity can be used in your home.
• Any solar generated electricity which is not used in the home immediately will usually feedback to the grid (export).

Question 8

What would be the build up of a party wall installed to the former openings?

Answer 8

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Question 9

What is BS 8214?

Answer 9

British Standard for timber fire door assemblies.

Question 10

What should a fire door with a half-hour fire rating have? What part of the building regulations would you use to confirm?

Answer 10

• Three hinges.
• Intumescent strip on door or edge of frame.
• Self closing devise.
• If glazing panel present, it must be 6mm thick, wired glass to a max of 1.2m2 with 13mm x 13mm wood beads encased with non-combustible materials.
• Approved Document B - Fire Safety

Question 11

What is a syphonic drainage system?

Answer 11

• Drainage system is an alternative to the gravity drainage system. In
  syphonic drainage, water is sucked from the guttering in to the drain pipe so there is
  no need to have pipes set at a gradient and to rely on gravity to pull the water to the
  drain (a vacuum is created to achieve this).
• Syphonic drainage has the advantage that narrower down pipes can be used.

Question 12

What other installations would you recommend to a client to improve the EPC of a property?

Answer 12

• Lighting – install LED light fixtures.
• Improve thermal efficiency:
   Install insulation backed plasterboard to the walls (British gypsum Gyproc wall lining board with expanded polystyrene
  backing).
   Replace single glazed windows for double glazed units.
   Increase thermal insulation to the roof void (rolled insulation / rigid insulation boards) or suspended floor.
• Install means of renewable energy sources:
   Photovoltaic system (PV) to roof).
   Ground source heat pumps – extract heat from ground and uses it for internal heating.
• Utilise more energy efficient service installations / reduce energy expenditure:
   Remove gas installations and replace with electric, e.g remove gas central heating and install electric panel heaters.
   Install PIR sensors and daylight dimming to light installations.
   Low flow sanitary fixtures.
   Dual flush cisterns – can use smaller flush.

Question 13

Out of all of the EPC improvements, which ones would you recommend to a client and why?

Question 14

What is composite cladding?

Answer 14

• Composite cladding is formed of a sandwich construction which comprises 2 outer layers of steel or aluminium sheet enclose an inner core of adhesive-bonded lightweight insulation.
• Insulation can comprise of the following:

1. Rigid polyurethane (PUR)
2. Polyisocyanurate (PIR)
3. Extruded polystyrene (EPS)
4. Phenolic foam
5. Mineral fibre

Question 15

What did you pre-purchase advise did you give to your client with regards to composite cladding?

Answer 15

• Advised the client that they should have the vendor confirm the specification of the cladding, including the material that makes up the insulation core and whether the panels are Loss Prevention Certification Board (LPCB) approved.
• Advised that the vendor may have access to this information is they are in possession of the H&S file for the property.
• Approached one of the main manufacturer’s (Kingspan) to see if they had record of the cladding purchased for the property.
• Advised that insurers consider that any risk containing non-LPS compliant panels represents a higher potential for fire spread, they will either restrict cover or offer cover on higher rates, perhaps with higher excesses. If panels of unknown origin are contained within an existing building an assumption may be made as to the type of insulant in order to set the premium accordingly. On this basis, insurance requirements could dictate the replacement of panels, the fitting of fire suppression systems, improved compartmentation and routine fire risk management procedures.

Question 16

Why should you be careful when specifying composite panels?

Answer 16

• Selecting composite cladding materials that comply in all respects with Building Regulations does not mean that building insurers will automatically accept a risk, nor does it mean that they will not inflate premiums. Building Regulations are aimed at ensuring the health of users and neighbours of the building (and of course visitors and emergency services), whereas insurers may seek higher standards of protection, fire suppression and or more reliance upon non-combustible materials.
• Insurer’s will likely want to see that the cladding is LPS Certified.

Question 17

What is the test that is conducted to certify composite cladding materials?

Answer 17

• LPS 1181 (fire growth) and LPS 1208 (fire resistance).
• LPS = Loss Prevention Standards
• LPS 1181 - Is a suite of robust large scale tests designed to determine the fire growth performance of cladding products. Has two parts; Part 1 (external wall and roofs) and Part 2 (internal wall and ceilings).
• LPS certification as tests are carried out are large scale and therefore mimic performance of panels once installed on a building - others will test performance of single panels etc.
• The standards were developed in consultation with a wide range of key stakeholders including the Associated of British Insurers and trade association representatives of the panel manufacturers.
• LPS standards can be downloaded via the REDBOOK LIVE website.
• There are two main LPS product grades:
• Grade EXT-A: Product that satisfies requirements of both fire resistance (LPS1208) and fire growth (LPS 1181 Part 1).
• Grade EXT-B: Product that satisfies fire growth (LPS 1181 Part 1) only.

Question 18

What is the difference between PIR and PUR isolation?

Answer 18

• The most significant difference between PIR foam and PUR foam is its resistance to high temperatures and fire. Whereas PUR foams start to degrade at temperatures of around 230-250°C, some PIR foams will only begin to degrade as temperatures rise towards 400°C.

Question 19

How would you identify a composite panel?

Answer 19

• Flat or micro-ribbed panels, usually 900-1200mm width, often (but not exclusively) laid horizontally.
• Top hat type vertical joint covers on side sheeting.
• Interlocking edges with concealed fixings.
• Shallow profiles with wide troughs and thinly ribbed liner panels.
• Spacer type primary fastenings. (These have a thread just below the head washer together with a separate thread to the main
  shank. The top thread supports the outer metal sheet and prevents crushing of the insulation.) It will be necessary to remove a
  primary faster for examination.

Question 20

What is the size of a standard brick? What is the standard size of a block?

Answer 20

Standard brick = 215mm x 102.5mm x 65mm

Standard block = 440mm x 215mm x 100mm

Question 21

What are the main types of foundation that you know?

Answer 21

• Traditional strip foundation.
• Trench fill foundation.
• Pad foundation.
• Raft foundation.
• Pile foundations.

Question 22

What is the typical width of a cavity in a cavity wall?

Answer 22

• Traditional cavity would be 50mm
• Modern cavities are 100mm but can be greater for better thermal efficiency.

Question 23

What is a movement joint and why are they used?

Answer 23

An expansion joint or movement joint is an assembly designed to safely absorb the heat induced expansion and contraction of construction materials. Allows some movement from settlement or differential settlement.

Question 24

What are strip foundations ?

Answer 24

• A continuous strip of concrete supporting load-bearing walls. For a single storey building strip foundations will typically be 450mm wide and at least 200mm deep, and for two storey building 600mm wide and 200mm deep. Strip foundations are used to support a line of loads, either due to a load-bearing wall, or if a line of columns need supporting where column positions are so close that individual pad foundations would be inappropriate.
• Suitable where good load-bearing strata near the surface.
• Two types:
• Traditional strip:
  + Mass concrete foundation poured into excavation (minimum 450mm deep - to avoid frost action), blockwork is then used to build up wall to ground level. Width of trench depends on total of loading and the bearing capacity of the soil.
• Trench fill:
  + Mass concrete fills the majority of the excavated trench, then blockwork to ground level.
  + More economical than traditional as it is quicker and labour costs have increased.

Question 25

What is a raft foundation?

Answer 25

• A reinforced concrete raft.
• Rafts come in 3 main forms:

1. Simple raft: Uniform, reinforced raft that thickens at the edges where there will be a concentration of loading from walls, columns etc. Thickening also aids to protect the soil at the edge of the raft to prevent erosion.
2. Rafts with downstands: as above but with downstands throughout the raft to accommodate increased loads from walls or supporting columns.
3. Hollow / buyant raft: hollow structures between downstands reduce the overall imposed load on very weak strata.
   - Raft foundations used on soil with poor loadbearing capacity - load is spread over a wide area preventing differential settlement.

Question 26

What is a pad foundation?

Answer 26

• Formed of reinforced mass concrete and tend to be used to support point loads from structural columns, usually for steel framed
  buildings.
• Their shape is usually square / rectangular but can widen at one end to reduce the loads on strata close to adjacent buildings and structures.
• Can be used in conjunction with concrete ground beams that span between the pads which can distribute the loads of the superstructure (e.g low level brickwork on warehouses) to the foundations - quicker and cheaper than excavating traditional excavations between columns.
• The steel reinforcement increases the tensile strength of the concrete allowing the load to be spread across the foundation.
• Cheap to produce due to small surface area.
• Require good load-bearing strata near the surface.

Question 27

What is a piled foundation?

Answer 27

• Pile foundations are deep foundations. They are formed of column shaped elements typically made from steel or reinforced concrete
• Pile foundations are principally used to transfer the loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth, increasing the effective size of a foundation and resisting horizontal loads. They are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement.

Two main types:

1. Displacement piles
   - Solid pile or hollow casing is forced into the ground using a jack or driving rig. If hollow pile used then pile is driven in, steel reinforcement installed to the void then concrete poured into the casing, the casing is then slowly withdrawn.
2. Replacement piles
   - Soil is excavated using a weighted grab (repeatedly dropped and raised to remove soil) or by a rotating auger.
   - Sides of the excavation are supported using a shell / casing usually made from steel.
   - Concrete poured and steel reinforcement installed.
3. Continuous flight auger piles:
   - Auger excavates ground and a concrete pump fills void with concrete immediately. No need to provide support and pile is formed quickly.

• Piles are either friction piles of end bearing piles:

Friction pile = supported by friction of soil along shaft.
End bearing pile = load directly imposed on end of pile and strata immediately below.

• Ground beams usually transfer loads from superstructure to groundbeams with span between the piles. Multiple piles may need to be installed in very weak strata which are then consolidated using a pile cap.

Question 28

Describe the typical build-up of a concrete floor slab.

Answer 28

• Subgrade / formation level: The earth that the slab is built upon – this is compacted to provide a uniform finish.
• Subbase: Hardcore which provides a working platform for construction. Could use MOT Type 1 / 2.
• Blinding layer: Closes off rough spots in the subbase.
• DPM: Stops moisture ingress, protects against sulphate attack. Polythene sheeting used (required as part of building regs).
• Concrete slab: Usually strengthened with steel rebar mesh - increases tensile strength.
• Wearing surface: Concrete screed / epoxy floor finish.

Question 29

What are the main types of framed structure you have come across?

Answer 29

• Skeleton frame: Series of rectangular frames at right angles with roof and floor spanning between beams.
• Steel frame - most prevalent in UK is the portal frame.

Question 30

What are the main types of portal frame structure?

Answer 30

Question 31

Draw a portal frame

Answer 31

Question 32

What is a composite, in-situ cast concrete floor?

Answer 32

Question 33

What are the main floor construction types you would find in commercial properties

Answer 33

ADD ALL NOTES FROM PAGE 303- Industrial and commerical buildings

Question 34

What is a hollow clay pot floor?

Answer 34

• Common during post war years from the 50s to early 80s.
• Originally used to construct fireproof floors in multi-storey buildings. Also found to form inner leaf of masonry cavity walls in 60s high rise buildings.
• Floor is composed of hollow clay pots that span the floor with spacer tiles that set the width of the concrete ribs. The hollow clay pots form permanent formwork as concrete is then poured over the spacer tiles to form the concrete ribs in situ. A structural topping is then poured on top of the entire hollow clay pot floor surface.
• There are two types of clay pot floor:

1. Ribbed slabs whereby the concrete topping contributes to the structural strength of the floor.
2. Ribbed slabs whereby the concrete topping does not contribute to the structural strength of the floor, simply a screed with reduced strength compared to concrete cast for structural ribs.

Question 35

Review the reverse - hollow clay pot floor

Answer 35

Question 36

Sketch a typical warm roof detail

Answer 36

Question 37

Draw a sketch of a cold roof detail

Answer 37

Question 38

Draw an inverted roof

Answer 38

Question 39

What are the advantages of an inverted roof?

Answer 39

• Waterproofing membrane is protected from UV damage, thermal stress and impact damage.
• Can be walked on safely – allows access to plant room on office buildings / useable space on residential terraces.

Question 40

What are the advantages and disadvantages of pre-cast concrete framed buildings?

Answer 40

Advantages:

• pre-cast = cast in factory and ready made components e.g. beams, columns
• advantages:
o Since precast is manufactured in a controlled casting environment it is easier to control the mix, placement, and curing
o Quality can be controlled and monitored much more easily
o Since a precaster can buy materials for multiple projects, quantity discounts can lower costs
o Weather is eliminated as a factor-you can cast in any weather and get the same results, which allows you to perfect mixes and methods
o Less labor is required and that labor can be less skilled
o On site, precast can be installed immediately, there is no waiting for it to gain strength and the modularity of precast products makes installation go quickly
o Repeatability-it’s easy to make many copies of the same precast product; by maximizing repetition, you can get plenty of value from a mold and a set-up

Disadvantages:

o Limited design flexibility
o Connections can be difficult
o Cranes are required
o Transportation problematic

Question 41

What are the advantages / disadvantages of in-situ cast concrete framed buildings?

Answer 41

• insitu = pouring concrete on site over formwork or in reinforcement
• Advantages:
o High level of strength means suitable for foundations and floors
o High degree of insulation – no gaps
o Versatile – can be moulded to suit
• Disadvantages
o Labour
o Weather a factor
o Quality control more variable

Question 42

What factors would you consider when selecting a frame for a building?

Answer 42

• Ease of getting material to site (steel lighter and easier to transport than concrete).
• Spans required (steel can typically achieve greater spans)
• Fire performance (additional trade for steel – e.g. coating in intumescent paint but concrete frame inherently fire protected by nature)
• Sustainability – consider advantages of selecting material for BREEAM assessment. E.g. timber can be sustainably locally sourced. Steel considered more environmentally friendly by BRE.
• Loadbearing capabilities – concrete better under compression. If long span tension forces being applied steel may be better.

Question 43

Tell me about timber frames. What are the types and advantages and disadvantages?

Answer 43

• Most common in residential construction.
• Less weight than traditional masonry methods.
• Increases speed of production.
• Lighter construction = smaller foundations.
• BRE (find out which) recommends maximum of 6 storeys for timber frame.
• Two main types:
  
  • Balloon frames: Walls constructed as complete entities (span all floors), floors are suspended from panels.
  • Platform lift: Walls constructed as a storey height element, better suited for pre-fabrications.
• Advantages: Sustainable, cheap and quick to construct.
• Disadvantages: Excess moisture can lead to structural degradation, risk of insect / fungal attack, risk of fire spread, differential movement between brick skin and timber frame.

Question 44

What is a wall system?

Answer 44

• Non-structural cladding systems for external walls of buildings comprised of a lightweight aluminium frame onto which glazed or opaque infill panels are fixed.

Question 45

What are the main types of curtain wall systems?

Answer 45

• Stick system – Installed piece by piece on site, with glazing inserted into the frame from the inside or outside depending on access conditions.
• Unitised systems – Prefabricated system comprised of prefabricated panels of framework with glazing panels already installed. Panels are craned into position on site and fixed to pre-positioned brackets attached to the concrete floor slab and structural frame.

Question 46

What are the main advantages and disadvantages of stick and panellised curtain wall systems?

Answer 46

Stick curtain wall:

• Can be assembled without large lifting equipment.
• More versatile and can allow integration of other systems such as sliding doors.
• More time spent installing on site – increased labour costs.

Unitised curtain wall system:

• Reduced time installing on site – less disruption to the programme.
• Modern systems can be craned in reduces need for scaffolding.
• Higher direct costs.
• Built in controlled condition – quality control.

Question 47

How are cladding panels attached to a warehouse portal frame?

Answer 47

• Aluminium side rails span between the portal frame columns and are fixed in place by bolts or rivets.
• Cladding panels are then bolted / riveted into the side rails.

Question 48

What are the advantages and disadvantages of steel framed buildings?

Answer 48

Advantages of steel:
o Quicker than concrete
o Recyclable
o Highest strength to weight ratio
o Dimensionally stable (doesn’t move with heat)
o Lighter
• Disadvantages:
o Needs fire protection
o Price is variable
o Needs experienced builders
o Fail and collapse in heat

Question 49

What are the advantages and disadvantages of concrete framed buildings?

Answer 49

• Advantages:
o Inherently fire protected
o Maintenance is low
o Cladding can be fixed easily
o Good sound and heat performance
• Disadvantages:
o Time
o Sustainability
o Needs steel reinforcement
o Heavier
o Doesn’t perform as well in tension

Question 50

Tell me about pre and post tensioned concrete

Answer 50

Pre-tension = steel first tensioned in a frame and concrete cast around
o Advantages = speed, done in factory, avoid expensive falseworks
• Post-tensioning = concrete cast around tendons in sleeve and then tightens as concrete develops sufficient hardening
o less concrete needed, faster, beams are bonded in grout and less likely to corrode

Question 51

What are the main brick bond?

Answer 51

• English bond – alternating courses of stretchers and headers, used for walls one brick thick. Very strong but requires more facing bricks than any other bond (expensive).
• Stretcher bond – used for walls half a brick thick, used for internal walls or external leaf of a cavity wall.
• Flemish bond – alternating headers and stretchers in each course, weaker than English bond and requires skill to align all mortar joints.

Question 52

What is a syphonic drainage system?

Answer 52

In syphonic drainage, water is sucked from the guttering in to the drain pipe so there is
no need to have pipes set at a gradient and to rely on gravity to pull the water to the
drain (a vacuum is created to achieve this).
Syphonic drainage has the advantage that narrower down pipes can be used.

Question 53

Draw a built up roof detail

Question 54

What remedial options did you recommend for the asbestos warehouse roof in Bermondsey?

Answer 54

• Cleaning of the existing roof - closed box system.
• Removal and replacement.
• Oversheeting.

Question 55

What are the issues with composite cladding?

Answer 55

• Difficult to extinguish a fire as the combustible cores can catch fire and then are protected by the external panel skin. This means that fire fighters or sprinkler systems have little effect.
• This internal spread of fire means that the cladding can breach the buildings compartmentalisation such as concrete floors and spread to successive floors in the building.
• Lack of fire resistance of panel fixings can lead to sudden collapse or delamination of the panels, exposing the combustible insultation directly to the fire.
• When the plastic core burns this leads to toxic, dense black smoke.

Question 56

What certification would you look for to confirm that a composite panel did not pose a risk to a property? What other certification / technical details would you look for with regards to combustibility?

Answer 56

• In the UK building systems should be LPCB approved: the relevant standard is LPS 1181 Part 1 & 2 and LPS 1208.
• Complying with the criteria set out in the approved document B paragraphs 12.5 to 12.9.
• Ensuring the cladding system as a whole (rather than individual components) meets the criteria set out in BS 8414 Fire performance of external cladding systems, and satisfying the performance requirements set out in BR 135 Fire Performance of external thermal insulation for walls of multi-storey buildings.

Question 57

What is ACM cladding? Why is it notorious with regards to fire safety in buildings? What statutory instrument governs its’ use?

Answer 57

• Aluminium composite cladding.
• Aluminium composite cladding with a polyethylene core (Reynobond PE ACM) was though to be in part responsible for the Grenfell Tower Fire on 14 June 2017.
• Approved Document B - ‘The external envelope of a building should not contribute to undue fire spread from one part of a building to another part. This intention can be met by constructing external walls so that both of the following are satisfied. a. The risk of ignition by an external source to the outside surface of the building and spread of fire over the outside surface is restricted. b. The materials used to construct external walls, and attachments to them, and how they are assembled do not contribute to the rate of fire spread up the outside of the building.’