External Walls Flashcards
Concept of a building envelope
the physical barrier or separator between the exterior and interior environments by enclosing a structure
Functional requirements of building envelope (7)
- Strength and structural stability, 2. Exclusion of moisture and weather protection, 3. Thermal and acoustic insulation, 4. Fire resistance, 5. Ventilation, 6. Durability and freedom from maintenance, 7. Adaptability and sustainability
External walls and cladding meaning
The exterior skin or envelope of a building, including all moisture barriers and siding materials used to cover the outside of the structure
How to traditional buildings bear loads?
Through loadbearing walls EG masonry, stone, block. Usually used in domestic building
How do modern commercial buildings distribute loads?
Transmitted through a structural frame, instead of loadbearing walls
What are the three non-loadbearing types of walls?
External cladding, curtain walling, infill walling
Loadbearing walls
Carry their own self-weight together with loads from other building elements. Masonry is most commonly used.
Types of cladding (8)
Terracotta, timber, stone, metal, stick frame, curtain wall, fibre cement, brick
Difference between external cladding and curtain walling?
Curtain walling is not part of the building’s structure. Attached to exterior but is completely self-supporting. Cladding imposes additional loads on the building’s frame structure. Think curtain, light!
Curtain walling
(building glass facades) good aesthetics, poor to moderate thermal performance. Single glazed outer layer allowing thermal gain, double glazed inner layer, air between rises up and out. Fixed to the independent self-supporting framework of the building
Infill walling
provides weather proof enclosure but is non-loadbearing. It leaves the main structural frame of the building expoosed.
Loadbearing walls advantages (3)
- Familiar, 2. Good loadbearing performance, 3. No need for frame
Loadbearing walls disadvantages (3)
- Slow 2. expensive, 3. Height of building limited
External cladding disadvantages (2)
- Maintenance of joints may be required, 2. heavy if concrete used
External cladding advantages (4)
- Cheap if mass produced, 2. fast, 3. Frame is covered, 4. Variety of materials can be used
Curtain walling advantages (4)
- Modern aesthetic, 2. Prefabricated, 3. Self-supported/independent of frame, 4. Upgradable
Curtain walling disadvantages (2)
- Expensive, 2. Non-traditional appearance
Infill walling advantages (3)
- Cheap, 2. familiar technology, 3. supported off structural frame
Infill walling disadvantages (3)
- Potential for cold bridging, 2. old-fashioned appearance, 3. Exposed frame requires maintenance
What does weather protection entail?
The ability to exclude wind, rain, snow and heat/glare
What is EPBD and what is it aimed at in UK Building regulations?
Energy performance of buildings directive. It is concerned with Conservation of fuel and power
what are some methods of sound insulation?
A Baffle wall (wall closer to the road), fast growing conifers, triple glazing on road side, double glazing other side
Resistance to fire characteristics for cladding? (2)
- They need to achieve a certain level of fire resistance EG FR60, 2. Cladding must have properties to protect the structure from collapse, and must not support spread of flame or fire from one part of the building to another
Ventilation requirements for cladding? (1)
Be able to open windows, natural ventilation of fresh air
Durability and freedom from maintenance requirements for external walls/cladding? (3)
- Should be durable for expected lifespan of the building and require little maintenance, 2. Avoid corrosion, the deterioration of materials by chemical interaction with environment. 3. Cover is required to reinforcement in reinforced concrete to protect against environment/give fire resistance (15mm internal, 50mm external
Ground floors main components (3)
- Hardcore, 2. DPM, 3. Concrete bed
Solid ground floors - concrete bed (3)
- made of plain or reinforced concrete, 2. Minimum thickness of 100mm, 3. Floated (smooth) finish to take DPM, insulation and screed
Solid ground floors - functional requirements (6)
- Structural Stability, 2. Thermal insulation, 3. Exclusion of ground water, 4. Durability, 5. Provision of appropriate surface finish 5. Gas resistance (OCCASIONALLY) - building sites on top of landfill where methane and radon might be in the ground require other resistances.
Suspended floors (2)
- Has positions between the beams for ventilation, 2. Made of timber or concrete/steel, typically plywood sheeting on top
Upper floors strength and stability requirements (3)
- Provide lateral rigidity to the frames, 2. Provide lateral restraint to load bearing walls, 3. Transfer wind pressure to columns
Upper floors dimensional stability
Take care for differential movement
Upper floors prevention of the effects of vibration
- Deflection (floors bending a bit) needs to be allowed for to a minimum extent, 2. To minimise cracking to surface finishes, 3. To reassure building occupants
Upper floors thermal properties
Thermal insulation, cold bridges need to be avoided
Upper floors fire resistance
UFs are expected to act as fire resistant barriers between different levels of the building. Finishes to floors need to be non-combustible
Upper floors sound insulation
Important in flats/offices etc. Boarded timber floors acceptable in a house, but inadequate elsewhere
Functional requirements of upper floors (7)
- Dimensional stability, 2. Strength and stability, 3. prevention of vibration, 4. Thermal properties, 5. Moisture, 6. Fire resistance, 7. Sound insulation
Types of upper floors - precast concrete slabs advantages (4)
- High construction speed, 2. No need for formwork, 3. Mostly precast slabs or beams, 4. Dense or aerated concrete
Types of upper floors - precast concrete slabs disadvantages (4)
- Can be pre-stressed, 2. May require drilling to accommodate services, 3. Can be hollow, beam and block or slab sections, 4. Lead in time, lifting on site
Cast in-situ slabs (4)
- Floor slab poured together with beams, 2. Usually used when in-situ concrete is the frame of choice, 3. Used in buildings up to 4 storeys, 4. heavy
Concrete composite floors (4)
(A concrete slab with holes already in it) 1. Lighter than solid concrete floors, 2. Can house services in the holes, flat surface under beams so no need for suspended ceiling, 3.Blocks positioned on the formwork, then poured over with concrete, 4. Combines the benefits of precast and in-situ
Steel decks covered in concrete (5)
- Common method for steel frame buildings, 2. Are easily handled, 3. Galvanised on both sides (corrosion), 4. Act as permanent formwork, 5. Fast construction method
Timber floors (2)
- Used in conjunction with timber frame multi-storey buildings, 2.Sometimes additional steel beams are used to support the floor
Floor finishes (8)
- Plastic, 2. Concrete, 3. Sheet-supplied rolled flooring (EG lino) 4. Boards, 5. Timber flooring, 6. Clay, 7. Composition blocks, 8. Carpets and felts
Functional requirements of roofs (7)
- Strength and stability, 2. Weather resistance, 3. Fire resistance, 4. Thermal/sound insulation, 5. Durability, 6. Aesthetics, 7. Sustainability
Roof decks
A deck is the structural substrate of a flat roof, to support the dynamic and static loads
Roof deck material types (6)
- Timber decking (traditional), 2. Plywood, 3. Oriented Strand Board (OSB) a type of wood panel, 4. Woodwool slab (rigid timber and cement based panels, 5. Concrete (common with flats/commercial), 6. Profiled metal decking -galvanised steel or aluminium
Flat roof covering
Single-ply membranes are manufactured as sheets offering a reliable and durable method of waterproofing
Flat roof coverings - thermoplastic
Tends to soften with increased temperature allowing thermo-welding of the edges of the sheets to create a continuous membrane
Flat roof coverings - elastomeric
Less temperature sensitive than thermoplastic but more elastic
Flat roof covering - asphalt roofing
A homogenous coating, applied in liquid form to create a continuous, jointless coating
Flat roof covering - soft metal covering
Includes lead, zinc and copper. More expensive so infrequently used.
Flat roof covering - green roofs
Vegetation and soil/drainage on top of a waterproof membrane and structural support
Pitched roofs (3)
- A roof is pitched if its slope is greater than 10 degrees. 2. It can be integral to the structural frame (portal frame) or independent of the structural frame