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Medium-Rise Buildings

Typically range from four to ten stories.
Found in urban and suburban areas, often in commercial or residential zones.
Offer a mix of residential, commercial, and office spaces.
Construction materials may include a combination of concrete, steel, and glass.
Provide a higher density of occupancy while still maintaining a sense of community.
Often equipped with elevators for efficient vertical transportation.
Can offer a variety of amenities such as gyms, parking lots, or shared spaces.

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High-Rise Buildings

Generally, have more than ten stories, reaching significant heights
Predominantly located in densely populated urban areas
Primarily used for commercial purposes, such as offices, hotels, or condominiums
Designed to maximise floor space in areas with limited land availability
Constructed using advanced engineering techniques and materials like reinforced concrete and steel
Require vertical transportation systems, including multiple elevators
Offer panoramic views, prestige, and potential for iconic architectural designs

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Forms of Low-rise Construction

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- A variety of construction methods are available for low-rise dwellings and structures.�- Method selection influences cost, speed, durability, and sustainability of the project.

Forms of Low-rise Construction

Table 1. The three main construction methods for low-rise structures

Framed Structures	Traditional Construction	Modular Construction
Incorporate a skeletal framework, typically using steel, timber, or reinforced concrete	Utilises load-bearing walls, masonry, and in-situ methods	Relies on prefabricated components manufactured off-site
Allow larger, open interior spaces and flexibility in layout	Valued for robustness, thermal mass, and brick or block aesthetics	Enables rapid assembly, reduced site waste, and greater quality control

Each construction method presents distinct advantages and considerations in project design
Choice of method can impact energy efficiency, maintenance needs, and adaptability of the building.

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Framed Structures - Introduction

A framed structure is a network of beams and columns forming the skeletal framework of the building.
It transfers the weight of the structure to the foundation, while limiting excessive deformation, thus minimising reliance on load-bearing walls.
The types include:

Structural steel framing

Cast-in-place concrete framing

Timber/wood framing system

Hybrid systems

For commercial and industrial building, considerations have to be given to:

Heavy traffic and large design loads.
Larger open spaces.
Easy maintenance.

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Steel Framing Structure

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Framed Structures– Steel Skeleton Frame

Structure Description: Consists of upright and horizontal members.
Components: Uprights (columns) and horizontals (beams).
Orientation: Set at right angles to support floors, walls, and roof.
It starts with pad foundations (we’ll learn about this later).

Enhanced Stability: Achieved through lift shafts, staircases, and external cladding.

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Framed Structures– Steel Skeleton Frame

Structural members are fabricated off site.
Members are delivered to the site.
Members are erected per the design.

Figure 1. Steel framing arrangement (Alexander, 2016)

https://youtu.be/rwvmru5JmXk?si=SigHsKlQebebQNGf

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Portal Frame

Portal frames use rigid connections between vertical columns and horizontal (or pitched) beams for structural stability.
Offer clear internal spans with minimal need for internal supports, ideal for large open spaces.
Typically made from steel, concrete, or engineered timber such as glulam.
Common for single-storey and low-rise buildings, especially warehouses and industrial units (SteelConstruction.info, 2000)

Cross-section showing a portal frame and its restraints (SteelConstruction.info, 2000)

Principal components of a portal framed building (SteelConstruction.info, 2000)

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Advantages of Portal Frame Structures

Structural Efficiency: Wide spans achieved with less material compared to conventional frames
Cost-Effective Construction: Fewer materials and rapid installation reduce cost and time
Design Flexibility: Suitable for various roof shapes (pitched, mono-pitch, curved) and scalable to site needs
Low Maintenance: Durable materials ensure longevity and reduced upkeep requirements
Fast Construction: Prefabricated components allow for quick on-site assembly (Bromsgrove Steel, 2025; SteelConstruction.info, 2000)

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Concrete Framing Structure

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Framing Structures: Cast-in-Place Concrete

Forms are built;
Reinforcing is placed;
Concrete is poured and finished in place.

Figure 2. Cast-in-place concrete framing arrangement (Alexander, 2016).

https://www.youtube.com/watch?v=GB92JyubAJA

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Framing Structures: Precast Concrete Structure

Advantages

• Increased efficiency and quality control with plant casting.

Durable, reusable steel forms reduce formwork costs compared to site-cast concrete..

Plant-Cast Precast Concrete Structure

• Reinforced concrete elements, cast and cured in a manufacturing plant, then transported to the construction site.

• Use of high early strength cement and steam curing allow concrete members to be cast and cured in as little as 24 hours.

• Controlled casting conditions and high-quality forms for precise surface finishes.

https://www.youtube.com/watch?v=HO7ECuUtswc

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Framing Structures: Precast Concrete Structure

Plant-Cast Precast Concrete Structure

• Structural Reinforcement:

Elements reinforced with tightly stretched pretensioned steel strands for increased efficiency.
Conventional steel reinforcing added for resistance to thermal and secondary stresses.
Construction Site Assembly:
Precast concrete elements lifted into place and assembled into structural assemblies.
Faster erection compared to in-situ concrete, less affected by adverse weather conditions.

https://www.youtube.com/watch?v=HO7ECuUtswc

A vacuum lifting device is used to lift and place precast concrete pranks

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Precast Concrete Structure

Precast Concrete Slabs

• Used for floor and roof decks.

• Deeper elements (toward the right below) span further than those that are shallower (toward the left).

Precast Concrete Beams and Girders

• Provide support for slabs.

• The projecting reinforcing bars will bond with concrete cast on site.

• Right: Inverted tee beams supported by precast columns.

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Concrete Framing - Benefits

Durability: Concrete has excellent durability and can withstand various environmental conditions, including weathering and exposure to harsh elements. Robust, weather-resistant,
Structural Strength: Cast-in-place concrete provides exceptional structural strength, making it suitable for high-rise buildings and structures that require robust support. It supports heavy cladding finishes (brick, stone etc.)
Mass and Damping Qualities: Offers good sound insulation through inherent mass and damping qualities

In fire, concrete performs well – it has the highest fire resistance classification (class A1: does not contribute to fire at any stage, including a fully developed fire) under EN 13501-1:2007- A1:2009. In most cases, concrete does not require any additional fire-protection because it is a non-combustible material.
Minimal Maintenance: Once constructed, cast-in-place concrete requires minimal maintenance over its lifespan, reducing long-term operational costs.

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Precast Concrete Framing – Technical Considerations

Concrete Mix Design: The concrete mix used in the framing system must comply with BS EN 206-1:2013, which specifies requirements and guidance for concrete composition, production, and conformity
Concrete Curing: Essential for achieving the desired strength and durability. It is generally between 4 - 6 days, depending on the cement type and surrounding conditions (The Concrete Society, no date). The curing process should comply with standards such as BS EN 13670.
Thermal Conductivity: Concrete is thermally conductive and often requires external insulation. Thought is needed to avoid cold bridges.
Quality Control: Quality control measures, including testing of concrete strength, reinforcement placement, and overall construction quality, should be in line with relevant standards to ensure the integrity of the framing system.
Concrete (cast-in-situ or precast) is not readily altered, so particular consideration of future adaptations and flexibility is needed. Typically, knock-out panels and soft spots are incorporated where changes can be anticipated.
Embodied Energy: Potentially high, requiring project-specific investigation for cement content and associated emissions.
Requires careful design and construction of panel joints described in BS 8297:2017.

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Group-assessment Task

Incorporate at least TWO photographs of well-known or locally relevant buildings in Wales, UK to illustrate each building concept.
Present each image alongside a brief description about the distinguishing features of each building type and/or structural approach.

Select imagery depicting:
Low-rise building
Medium-rise building
High-rise building
Steel frame structure
Concrete frame structure

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Timber Framing Structure

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Framed Structures - Timber Framing System

Description: Panelised structural walls and floors using small timber studs.
Cladding: Panels clad with board products.
Load Transmission: Timber frame transmits vertical and horizontal loads to foundations.
Ascent: The 87 meter, 25-story high-rise is the world's tallest mass timber structure, edging out Norway's Mjøstårnet: https://www.youtube.com/watch?v=xxnUmyOVQ7Q
Advancements: Despite technological progress like engineered timber, hesitation remains for high-rise timber buildings.

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