Essay: Low-rise residential building construction

Section one

In this section I will be giving a detailed description and explaining the terminology of the main elements that comprise a low-rise residential building.

In the construction of a low-rise building it is formed in two parts, the substructure and superstructure. From this it is further broken down; the substructure, which is an underlying or supporting structure, made up of the foundations, the walls below ground and ground floor.

And the superstructure which is the upward extension of the pre-existing substructure, which is composed of the external walls, the upper floors (and stairways), the internal walls and partitions, the roof structure and coverings, the windows and external doors and finally the internal finishes.

Starting with the substructure, the foundations which are arguably the most important element as it is what the building is formed and dependent upon. The function is to support the combined loads forced on the building and transfer them to the ground safely, avoiding any deformation to the building, or effect on the ground that may impact the stability of other surrounding buildings.

For a low-rise residential building the most common foundation used would traditionally be a strip foundation, which is shown below.

 

A strip foundation would be most appropriate for a low-rise residential building as they are intended for use where building loads are relatively modest and distributed evenly which is the case of the low-rise residential building.

The walls below ground provides an imperative link between the substructure and superstructure. The main functional requirements of the walls below ground are to provide structural stability, to be durable and to exclude moisture. The aesthetics of the sub-ground walls are not of much importance as they are unlikely to be seen.

To conclude the substructure, the ground floor which for a low-rise residential is usually a ground supported concrete floor, its function is to be able to provide a dependable base for the utilities required by the user and to be able to withstand and endure daily use, with the main functions to provide structural stability, thermal insulation, durability, exclusion of ground water and to be finished appropriately.

Moving on to the superstructure in the construction of a low-rise residential building.

The external walls are made of 8 main functional requirements which are:

1. Strength and stability

2. Resistance to weather and ground moisture

3. Durability

4. Fire safety

5. Thermal Insulation

6. Acoustic Insulation

7. Security

8. Aesthetics

In most low-rise residential buildings masonry walls are the most common to be used for the external walls. To be successful the walls must measure up to the required levels of structural stability for it to be able to withstand the loads inflicted upon it during its life span. In modern construction and in many older buildings it is found that external walls are doubled up to be loadbearing walls, and to hold their own weight as well as the weight of other elements such as the roof. The building loads are transferred from the external wall to the foundations in the substructure. This ensures that the buildings structural integrity is maintained.

The upper floors which primary function is to be able to withstand the range of usual home activities to go about in a safe, and comfortable manner. To do so, the upper floor must support the loads imposed upon it by, amongst other things, like people and furniture.

To do this it must be strong and structurally stable, be durable and provide restraint for the external walls, be fire resistant to delay the spread of fire and smoke as well as providing adequate sound and heat insulation. It is very common for low-rise residential buildings to have upper floors which are supported by timber joists and strutting (usually Herringbone). Where traditionally timber joists would have been built into the load bearing walls it was discovered that it posed the threat of exposing the joists to damp, causing risk for decay. It is now common practice to use joist hangers to prevent damp causing damage to the timber.

The low-rise residential building must predominately include stairs to allow occupants to get from ground floor to first floor. However, on occasion staircases are made an aesthetic statement piece and can be an impressive element of architectural quality.

Home statistics show that trips and falls on stairways make up a significant number of the accidents in the home. Although many are accidental, some could be caused due to poorly designed finishes, stairways and handrails.

Internal walls and partitions primary function is to divide up the space between the external walls to create separate rooms within the building. The solid internal walls which may be constructed from bricks can also double as load bearing wall and separate two rooms.

Whereas lightweight walls usually made up of timber frames and plasterboard are for the sole purpose to dividing up the space.

 

The roof structure for low-rise residential buildings are usually pitched roofs which are constructed using engineered timber trussed rafters. From this the roof covering is then placed over the rafters to make the property water tight. Most commonly slates are used and nailed to battens at their head, with malleable non-ferrous rivet fixing at their tail to prevent wind uplift to construct the roof cover.

Section two

In this section, there will be recognition of different construction materials and a detailed description of how they are combined and commonly used in traditionally constructed low-rise buildings, and the way in which they are incorporated into the structure, fabric, components and finishes.

Starting with one the most common construction materials; concrete, which is used through-out the construction of a building, particularly in the foundations, ground-floors and walls.

Concrete is readily available and is made up of several different components including aggregates, coarse and fine, ordinary Portland cement and water. However, it must be noted that when constructing in sites where levels of soluble sulphates are high in the soil, ordinary Portland cement should not be used. This is because there is a possibility that the concrete could be weakened if the sulphates were to react with it. In these cases, sulphate resisting Portland cement should be substituted in instead.

When mixing the concrete, it’s important to add the correct amount of water, this is because if too much water is added, the excess will evaporate whilst curing and leave small voids within the concrete which can significantly reduce its strength.

Concrete is a perfect material to be used in construction as when it’s first mixed, it is fluid and plastic, meaning that it can be easily transported to site and be poured into foundation trenches and manipulated into the desired position with minimal difficulty. As well, it can be made in to blocks, bricks or slabs of almost any dimension to fit the criteria it is needed for. Once concrete is cured, it is strong and durable and is resistant to attack from ground water and moisture.

Another main construction material is steel, which is an alloyed mixture of iron and approximately 0.2 % carbon which is its most common alloying material, but other elements such as manganese or chromium can also be added and act as hardening agents. By controlling the amount of alloying elements added, can indirectly effect the hardness, ductility and the tensile strength of the steel produced. Steel is a versatile material because the composition and internal structure to tailor its properties can be adjusted by us. This allows the material to be used for a large variety of things in the industry from large structural steel beams and columns, to wall ties and timber joists.

 

Timber is used most commonly and traditionally in the roof and upper floor constructions as it has several benefits that make it excellent for use in a variety of construction projects. One of which is its thermal properties, this gives it an advantage in terms of its resistance to high temperatures. Where steel may expand or even collapse in high heat, wood dries out and becomes stronger. Furthermore, wood conducts heat relatively poorly in comparison to other materials such as aluminium or steel. This gives wood an advantage in terms of being used in the likes of wall coverings and ceilings as it is a better thermal insulator which would be wanted within a residential property to prevent heat escaping, whether it be through the roof or the walls.

Another important characteristic of wood is its tensile strength, which gives it its ability to bend under pressure without fracturing or failing. Wood has a relatively high strength to weight ratio. Its tensile strength is also one of the main reasons for choosing timber as a building material; its remarkably strong qualities make it the perfect choice for heavy-duty building materials such as structural beams.

Wood stands out from other materials as it is a truly versatile product. With its many qualities such as aesthetic appeal, tensile strength, insulation properties, and ease of fabrication enable it to remain a favourite choice for use in an extensive array of construction applications.

However, it must be made sure that any timber beams or frames used must be properly insulated from water and moisture as exposure to this could cause issues of decay and/or rot to the timber that could cause structural issues in the future.

There are several materials on the market used for insulation. Mineral wool is one of these materials and refers to numerous different types of insulation which are all environmentally friendly. It can refer to glass wool which is manufactured from recycled glass to produce fibreglass. It can refer to rock wool which is made from basalt. Or it can refer to slag wool which is produced from the slag from steel mills.

Mineral wool can be purchased in rolls or as a loose material. Most mineral wool does not have additives to make it fire resistant, making it poor for use in situation where extreme heat is present. However, it is not combustible. When used in conjunction with other, more fire-resistant forms of insulation, mineral wool can be an effective way of insulating large areas.

 

Section 3

In this section by using references to historic, and contemporary models it will be shown, by illustration and description, how the construction of low-rise residential buildings has evolved over the years through performance requirements of building elements and emerging technologies how technical innovation and development of new materials has delivered the current code compliant and low/zero carbon aspirational dwellings of today.

Early developments of the box frame construction was a revolutionary way of how houses were built back in the 16th century. This allowed buildings to be multi-storeyed and became the main way in how commercial and prestigious buildings and town houses were constructed. By the late 17th century, some timber-framed buildings had become highly decorative but the demise of timber-frame came about from changes in fashion, shortages in timber, as well as the ever-present risk of fire and the cheaper brick housing. In more rural and traditional areas the timber-framed housing remained popular until the late 18th century. However, with changes in fashion many of these timber-framed housing had been disguised with new facades and claddings.

Many of the 16th, 17th and 18th century stone buildings copied the shape of the timber-framed buildings until fashion once again influenced change.

In the early 1700s, construction of middle-class housing was largely made of brick due to the rise in brick production. A lot of these middle-class homes had influences from Queen Anne housing and as well as some Dutch inspiration and classism behind the designs. Their main characteristics were their sash windows which dominated the façade of the building, their stone quoins and triangular pediments.

Some Baroque style buildings were still be in constructed, which began in Italy in the 17th century which ignored convention to produce architecture of striking affect, however this form of housing was on its way out with the rise of the Georgian architecture becoming more popular amongst the patriotic citizens supporting British styled architecture. The early Georgians adapted the Italian architect Palladio’s architectural ideals to form their own unique which incorporated symmetry, proportion, harmony and restraint.

Regency housing moved away from the regularity of Georgian housing, with their characteristics being windows which were tall and thin with very small glazing bars separating the panes of glass. The balconies featuring extremely fine ironwork, made from delicate curves which were often a prominent feature. The proportions were kept simple, having a minimalist approach rather than decorative, for effect.

In the early 1800s, the housing, initially was in the rural areas being located close to where the origins of materials were. Housing was designed to serve the basic needs of the workers, it was functional and low cost which gave the reflected the view of what it was, poverty stricken and hard living. However, as the industrial revolution evolved more people moved into the inner-cities to work. Factory owner built houses to accommodate their workers. The demand for this housing then lead to back to back terraces. This meant there was only one exterior wall exposed, meaning it was the only one able to provide sunlight and air into the property, making these houses the unhealthiest to live in due to inadequate amount of ventilation being allowed through the building.

The garden city concept, had the ideal of a planned residential community. It was thought up by Ebenezer Howard an English town planner. It was his plan that garden cities would be an improvement in the quality of urban life, which over the years become overcrowded and congested due to the increased population density in urban areas due to the Industrial Revolution.

Post-war, to accommodate the high demand of housing due to the damages caused by enemy bombing, the systematic building technique was to build higher. By the 1960s, 20% of local council authorities housing, was buildings of 5 stories or more. The high-rise revolution helped to decrease the amount of urban sprawl, and several systems, such as concrete were developed to help speed up construction. But due to these systems not being tested properly, caused problems later. With some of the high-rise buildings partially collapsing, causing several fatalities.

Where some of the buildings constructed had no faults and are still standing today, some had so many structural issues the only solution was to demolish them.

More recently, after coming into the new millennium, the 21st century had new concerns surrounding construction. With the reality of climate change hitting, and the realisation that old habits must change, instead of constructing new homes with aesthetics in mind, environmental aspects have become more important.

With zero and low carbon home being at the vocal point of government environmental strategies, this is where construction has had a turning point to follow guidelines such as the code for sustainable homes to meet said government targets.

Section 4

In this section, it will be discussed how the Building Regulations are the principal legislation for the construction of low-rise residential buildings in England. By using Approved Document 7 there will be a description of how the adequacy of materials and workmanship can be established with confidence by specifiers. And a hypothesise on the way in which current legislation influences development of new environmental technologies.

Specifiers and constructors can be confident that the materials for building work will be compliant with current Building Regulations as in section 1 of Approved Document 7 shows eight different ways of establishing the fitness of materials.

1. CE marking under the Construction Products Regulation

2. CE marking under other EU directives and regulations

This can help to assure specifiers and constructors as “The CE mark is a claim that a particular construction product can be legally placed on the market of member states of the European Economic Area (EEA) and indicates that the product is consistent with the data provided in the relevant Declaration of Performance as issued by the manufacturer”

3. British Standards

This can give piece of mind as “it indicates that the product has been independently tested by BSI to confirm that it complies with relevant British Standards, and that BSI have licensed the product manufacturer to use the Kitemark.” This shows that the material has been vigorously tested and should be of a high quality.

4. Other national and international technical specifications

5. Independent certification schemes

6. Tests and calculations

7. Past experiences

8. Sampling

These 8 ways should give specifiers and constructors confidence as it shows them exactly what credentials they should be looking for when deciding on what materials to use in construction. Therefore, they should be able to pick out materials which are suitable and reliable for what construction work they are intended for.

Specifiers and constructors can be confident that the workmanship for building work will be compliant with current Building Regulations as in section 2 of Approved Document 7 shows six different ways of establishing the fitness of workmanship.

1. CE marking

2. Standards

Much like the materials workmanship can be held to standards within different codes of conduct which is determined by bodies such as the MTS where it states that “Workmanship Standards present the requirements for quality and consistency of our product in the clearest practical manner. This includes criteria of acceptability and/or reject-ability to which products are designed, manufactured, inspected, tested and installed”

3. Independent certificate schemes

These schemes can vary throughout the industry dependent on the sector in question. Throughout the industry there are opportunities for certificates and recognition to be gained where it is deserved for those who are particularly well trained in their trade. These sorts of certificates can give constructors more confidence in the job to be carried out.

4. Management systems

5. Past experiences

This can be gained from recommendations or reviews from previous employers or contractors. By doing thorough research and checking references can give specifiers and constructors confidence.

6. Tests

With current legislation introducing schemes such as the CRC Energy Efficiency Scheme which goal is

“The Carbon Reduction Commitment (CRC) Energy Efficiency Scheme is a mandatory carbon trading system designed as both a ‘carrot and stick’ to incentivise large public and private sector organisations, which are responsible for around 10% of total UK greenhouse gas emissions, to reduce their environmental impact. It rewards businesses that adopt energy efficiency measures, and punishes those that remain passive by forcing them to buy carbon credits.”

The scheme therefore encourages both individuals and organisations in both the public and private sector to cut down on carbon footprint by developing better energy management techniques by having an improved knowledge and understanding of their energy usage. With use of emerging renewable technologies can help to continue the success of schemes like this in both businesses and residential properties.