Understanding building structures

Besides familiarising yourself with the plan form of the space, you should try to make yourself aware of the methods used in the construction of the building. Understanding construction is not simply an academic exercise; knowing how a building is put together is a lesson in possibilities. Once you have a good idea of the structure you will find it easier to make decisions relating to the implementation and practicality of your design work, especially when looked at it in conjunction with the constraints incumbent upon the project, be they time, budget, legal or technical.

A study of building construction will oft en change the way you look at buildings that you use on a daily basis, and an enquiring eye is a very useful skill to develop. The knowledge that you gain by looking at structures will add greatly to your projects and, just as importantly, being able to speak with a degree of confidence about structure will give you credibility with contractors and clients alike. Unfortunately, details of the building structure are oft en hidden away underneath surface finishes and detailing. In the absence of definite information regarding its construction, experience will help you make some reasonable assumptions or deductions about the building.

Building construction principles

As previously described, all buildings are subject to various forces that must be resisted if the building is not to collapse. Although the first structures in history were built through intuition rather than any theoretical understanding, they used many of the same principles that underpin building construction today.


Essentially, the structure of almost every building can be described in one of two ways; they are either frame or load-bearing. These two terms describe how the loads that the building experiences are transmitted to the foundations.

Framed structures

Framed structures are essentially a collection of horizontal beams (forming each floor level) that transmit forces to vertical columns. These columns in turn provide a pathway through which the forces can travel downwards to the foundations and from there into the ground. The vertical columns may form the walls at the perimeter of the building, or they may be distributed throughout the space. Where they are part of a wall structure, they will be covered with suitable materials to create the finished walls. When positioned within the space, two or more columns may be joined to create internal divisions, or they may be left as discrete columns. The great benefit of this multi-level framework is that, because the columns are transmitting the loads vertically, solid-wall structures are not needed to support the floors above, and can therefore be omitted (creating large open-plan spaces punctuated by the supporting columns), or walls can be created using nonstructural materials such as glass. Framed structures allow us to build high-rise buildings that are oft en characterised by facades apparently composed entirely of glass, though the materials used for these curtain walls (that are mechanically suspended off the frame) can be practically anything. Radical architects of the Bauhaus movement in Germany in the 1920s first conceived the use of glass in this innovative way. Because of the strength of frames, buildings can be made very tall. It was the development of framed structures in the latter part of the nineteenth century that lead to the first high-rise buildings.

If the internal divisions are not carrying any load (other than their own weight), they can be moved or altered without the need for any significant interventions to the surrounding structure in order to maintain its integrity. For the designer, therefore, framed structures can give a lot of freedom in planning spaces.

Framed structures do not need to be large scale. The principle can just as easily be applied to houses as it can to skyscrapers. Lightweight timber frames are a common method of construction in many regions of the world, though the frame is usually invisible under a skin or veneer of other materials such as timber weatherboarding or brick. Frames of this type will usually be braced to prevent twisting by the addition of a plywood skin to the outside of the frame. Timber framing of residential developments allows fast and accurate construction by a relatively low-skilled workforce, as it is an easy material to work with. Sections of the frame are oft en pre-fabricated off site under good working conditions, then brought to the site for rapid assembly.

Timber frames are also an environmentally acceptable construction method, assuming that the timber used is from a sustainable source. Highly energy-efficient buildings can be made by inserting insulation between the vertical and horizontal timbers, creating buildings that perform extremely well in some of the most extreme climates, such as the northern hemisphere winters of Canada and Scandinavia. Light frames can also be made from thin section steel, galvanised to prevent corrosion. The internal face of the frame can be very easily covered in plasterboard or other materials to provide a surface suitable to receive decorative finishes.

The framed structure of The Farnsworth House by Mies van der Rohe in Plano, USA, is clearly evident and is a major visual feature of this iconic design. It is considered by many to be one of the most beautiful buildings ever designed.

Load-bearing structures

In a load-bearing structure, it is the masonry construction of the walls themselves that takes the weight of the floors and other walls above. The walls therefore provide the pathways through which forces travel down the structure to the foundations. There is no separate constructional element of the building to do this, as with the frame in a framed structure. The implication of this is that care must be taken when adapting existing load-bearing elements of a structure, if the integrity is not to be compromised. If changes are made to the structure without adequate precautions being made, then the structure will at best be weakened, and at worst collapse.

If it is desired to move door or window positions, or make new openings in a wall for whatever reason, then the loads that are being supported by the wall must be diverted to the sides of the opening to prevent collapse. This is usually achieved by the insertion of a beam or lintel at the top of the opening. This lintel will carry the loads travelling through the wall into the structure at the side of the opening, from where they will travel downwards and so maintain the integrity of the structure. The beam or lintel itself will need to be adequately supported at both ends within the remaining structure. A lintel is a single, monolithic, component and can be manufactured from any suitable material; timber, stone, concrete (either reinforced or pre-stressed) or steel are the most common. Pre-stressed concrete lintels can span considerable distances, as can rolled steel joists (RSJs), which are oft en used in renovation work to allow the removal of internal walls by supporting of the structure above.
If greater distances need to be spanned, it may be more appropriate to construct an arch rather than use a lintel, and this was certainly true before new technologies allowed the use of steel and concrete. Because of their superior mechanical properties, arches can generally support greater loads than lintels. An arch is considered as a single unit, but unlike a lintel it can be composed of a number of shaped components (usually stone or brick, called voussoirs), though it too can be monolithic, like a lintel. Once the individual elements of the arch are in place, the compressive forces (weight) of the building materials above hold them together. The simplest shape of arch is the round or semicircular arch, but there are many variations of form, even fl at arches (sometimes called jack arches). Arch construction is a very practical engineering solution to the problem of spanning openings that are oft en treated as decorative elements of a building’s facade.

Renovation of this load-bearing structure (a traditional Victorian terraced house in London) required the introduction of supporting rolled steel joints (RSJs) in order to allow the removal of internal load-bearing walls. Here the steel beams are being brought into the house through the front window.

Variations

Although the principles outlined above are relatively simple, experience will soon show that there are many variations on these themes that are used throughout construction. Manufacturers develop new methods and interpretations of existing solutions and the desire of architects to challenge existing ideas of what a building is mean that these techniques soon become feasible. Changes to building regulations and codes for reasons of fire safety, tougher acoustic performance, reduced environmental impact and so on, all mean that there is a need for new building practice. Details change but the principles remain the same. With experience, it becomes easier to discern the theory behind the construction, but it is worth bearing these complexities in mind when looking at building structure.

In the same London house, the RSJ (painted red) can be seen during its installation into the floor space. This has necessitated the trimming and re-attachment of several floor joists. A structurally simpler, but aesthetically less pure, solution would have involved fitting the RSJ below the existing floor joists.

Thinking point: Manual or digital?

Are there any designers who still sit at their drawing boards to draw by hand? Can’t drawings all be made by using drafting soft ware on any good computer? And what about model making – why would anyone want to work with glue, scissors, sticky tape, craft knife, card and paper to make a model when they could use that very same piece of drafting soft ware to produce a digital model of the space that can be rendered and lit an infinite number of ways? Isn’t it sensible to tap into the power and freedom that computers give us for all our design work?

The answer is both yes and no.

There is no question that computers allow us to work smarter, more efficiently and with more freedom than is oft en the case when using manual techniques, but this argument misses a vital point about the relationship between old and new methods that can more than compensate for the efficiency that computers bring. Manual drafting and model-making is a craft that gives you a real connection with the project. There is a wonderful link that allows ideas to flow through you and your pencil on to the paper which means you to engage more fully with the project. All the decisions about placement of lines and so on belong to you, and not a computer, and you are forced to think carefully about what you are drawing. There is no doubt that working manually leads to a better understanding of drawings, what they represent and how they work. The manual process allows for a more expressive and spontaneous approach that computer-based design oft en lacks; a sweep of the hand across a sheet of paper which leaves a unique and eloquent pencil line is not something that can easily be reproduced by a computer, for example.

On the other hand, computers give us the opportunity to copy and edit work quickly and easily. Simple functions such as ‘Copy / Paste’ are incredibly liberating – no more laborious hand drawing of 30 tables and 120 chairs on a restaurant plan, for example. Instead after just a few keystrokes, the designer is free to concentrate on the design, rather than the act of drawing itself. Drawing with the computer also means that ideas can be exchanged quickly and easily by email or other means of file transfer. So, computers give us freedom and versatility throughout the design process, which is very appealing. But you should remember that the CAD (computer-aided design) soft ware is essentially only a pencil, a tool to aid the drafting process. It has functions that enable some of the tedious aspects of working on drawings to be automated, and it can put lines on to a virtual sheet of paper where you tell it to, but CAD soft ware cannot create a drawing by itself, nor is it able in most instances to decide if what is being drawn is sensible or logical in construction or space-planning terms. It is, therefore, important that the operator understands what it is that is being drawn and how it should be represented on the page. The computer cannot add creativity to a project: that is the sole responsibility of you, the designer.

The section

The section works in the vertical plane as does the elevation, but with one important difference. A section can be placed at any distance away from the wall that is the subject of the drawing, thus including or excluding features at will. In fact, the cut does not even need to be a single planar cut through the space; it can jump from plane to plane, varying in distance from the subject wall, but remaining parallel to it. Like the elevation, there should be no perspective, but unlike the elevation, the structure enclosing the space is shown at the point where the section cut dissects it, so wall thicknesses and so on are indicated.

Shown here is a quick section sketch by Emily Pitt for the design of a house in Notting Hill, England. Colour has been used to show use: green for guest areas and blue for occupant areas.

The elevation

Where plans show horizontal surfaces, elevations show vertical ones. In other respects they are very similar; they represent a record of height and width, and are drawn to scale. As with other technical drawings, they do not represent the space as we see it in real life, but they are an ideal way to assess the proportions of elements such as walls, windows, doors, fireplaces. They give a good understanding of spaces when used together with plans. The conventions employed when drawing elevations are similar to those used for plans. The vertical cut is taken one meter in front of the wall to be depicted, and all furniture and objects that sit closer to the wall than this line are shown in the elevation.

Once again, the furniture is not shown as if it has been cut in two; the complete piece is shown even when parts of the piece extend further from the wall than the one-meter cut line. As with the plan, there is some flexibility in what is shown and how it is depicted. Clarity is the key. Unlike the plan, an elevation does not show walls, floors and ceiling structures. Instead, the elevation ends at the face of the boundary building element. There must be a total absence of linear perspective in the elevation. This is relatively easy to understand when looking at a completed elevation, but oft en difficult to master when drawing one. Many people experience the temptation to add illicit glimpses of perspective to their elevations, many more so than feel the need to do the same to their plans. It is not clear why this should be so, but it may have to do with the fact that we naturally feel disconnected from the plan (it is only very occasionally going to be a view that we come close to seeing in real life), but we have a natural affinity with the elevation (a view we think we see almost all the time).

The plan

Plans are simply maps, a vertical bird’s-eye view of a space. As described earlier, they are drawn to scale and therefore show a proportionally accurate representation of the space and associated walls without the linear perspective that we usually experience when viewing an object. Plans generally try to show no more than the extent of one floor or level within a building, and may only show a single room. Separate plans will show other floors or levels. They show detail within the room that can be easily drawn at scale, and many details are coded into symbols that should be easily recognisable to anyone with a little experience of reading plans. The convention is to show on plan all detail that would be visible if the space was cut horizontally at one meter above the floor level, with the top section removed. All structure and objects that are wholly or partially below this level are shown on the plan drawing in their entirety. For example, a two-meter-high cabinet that sits on the floor is drawn as if viewed whole from above, and not as if it has been cut in half horizontally by the one-meter cut. Objects that are wholly above one-meter level may be shown on the plan, but will be delineated in a different style of line to objects below the one-meter level to aid the legibility of the drawing (usually a broken or ‘dashed’ line).

The one-meter cut is not, however, absolute; common sense should prevail when deciding what is and what is not shown in the plan. For example, it would be unreasonable and misleading to omit windows from a plan just because the windowsill was at a height of 1100 mm (1.1 m) above floor level. It would be just as inappropriate, though, to include clerestory-style windows that were, for example, 600 mm (0.6 m) tall, and which were positioned directly below ceiling level. You should take care to show everything that you think appropriate; however, you shouldn’t expect that the plan by itself can tell the whole story. When two-dimensional drawings are used to describe three-dimensional space, a combination of plan (representing the horizontal plane) and elevations and/or sections (representing the vertical plane) will be used to portray all the features of that space, and they must always be read concurrently.

Drafting (the process of drawing) can employ different conventions of line weight and style to try and convey information; wider lines can be used to delineate structure, and lines can be softened by freehand drawing to represent upholstered furniture, for example. Annotations can also be added to drawings to highlight features that would not otherwise be entirely clear. North points are shown to aid orientation and drawings are carefully titled (for example, plan or east elevation) to instantly identify them. These small points are important; carefully crafted and easily legible drawings promote confidence and convey a sense of professionalism to your colleagues and clients.

Plans have an important role to play in architecture and interior design in that they are usually the first tool used during space planning. However, in the same way that plans should not be read in isolation, the planning process must work in the vertical as well as the horizontal. A study of plans that show furniture layouts and structural elements will soon show that plans in themselves can be drawn entirely correctly but can still be misleading in their representation of space. The process of space planning must consider the impact of the vertical almost as soon as work on the horizontal plan is begun, and for that it is necessary to draw elevations and / or sections.

This survey drawing for a flat in London shows a floor plan and an elevation of one of the walls. Note the title block, showing all the relevant information such as scale and date of drafting.

This elevation drawing shows part of the bar area of a hotel in Bangalore, India. The rendering shows material finishes and proposed lighting effects, and figures have been added to animate the drawing of what should in real life be a bustling and lively space.

A typology of technical drawing

Before discussing some of the most common forms of technical drawing in interior design, it is worth emphasising that technical drawing is used throughout the design process. It is simply because this is the first point in the design process at which technical drawing is encountered that the following exposition of drawing is placed here. It could equally well have come at other points of this book, and indeed drawing is referenced in Chapter 8, when presentation drawings are examined in more detail.

The three most basic technical drawings that we might use are plans, elevations and sections. All three are scale drawings, and are therefore accurate representations of the proportions of spaces in either the horizontal or the vertical plane.

Only occasionally do we draw the subject of a technical drawing at its full size. For interior designers this might be feasible when showing details of part of a scheme (for example, how two different materials are treated at their junction), but clearly it will never be possible to show a complete interior at full size. Most drawings, therefore, represent their subject at some fraction of their true size. The ‘scale’ of the drawing indicates the ratio between a single unit of length on the drawing and the equivalent ‘real-life’ measurement. It is most usually expressed on the drawing as that ratio – for example, 1 : 25, where one centimeter on the drawing represents 25 cm in the actual space. Less commonly it might be expressed as a fraction – 1/ 25, where each unit of measurement on the drawing is shown at one twenty-fifth of its actual size (though essentially these are two different ways of saying the same thing). Scale is sometimes represented graphically on the drawing as a ‘scale bar’. Because it is so easy to casually photocopy drawings and either reduce or enlarge them in size at the same time (and therefore change the scale), the scale bar can be very useful as there is always a visual representation of the scale on the paper.

Scale rules are used to facilitate accurate plotting and measuring at scale. The rule comes ready marked with a linear representation of distance at various scales, so no calculations need to be made to change real-life size to paper size, or vice versa.

Rules can be marked in metric units (millimetres or metres, as appropriate), or in feet and inches. In this latter case the scale ratio will be expressed as ‘x inches to the foot’ (for example ½” = 1’ 0”, which is a ratio of 1 : 24).

There is no right or wrong scale to use for a drawing. The aim is to show the maximum amount of detail possible in the space, and therefore the most appropriate scale will usually be the one that neatly fills the space available on the drawing paper that is being used. A quick comparison of the overall dimensions of the space at typical scales will show which scale is the most appropriate for a particular drawing. When drawing manually, the scale needs to be decided before drafting begins. When drafting with CAD, the drawing scale can usually be changed prior to printing the finished drawing on to paper. Whatever scale is ultimately chosen, it should be clearly stated on the drawing, and because of the possibility of uncontrolled enlargements or reductions being made outside of the drawing office, it is good practice to state paper size in addition to the scale, for example 1 : 25 at A3.

This list shows some metric and inch / foot scales used for interior design drawings. It is clear that common inch / foot scales are similar to, but not precisely the same as, common metric scales.

The largest scale shown (1 : 10 ) might be used for showing construction details or similar. The other scales could all be used for drawing plans, elevations and sections to describe spaces from small rooms to entire floors of large buildings.

When it is necessary to show construction details for bespoke work, it might be appropriate to draw at full size, or a scale of 1 : 1. In some instances, details might be enlarged to show clearly how they are to be constructed. A scale of twice full size would be written as 2 : 1.

Understanding through models

Models are a three-dimensional method of visualising a three-dimensional space. The word ‘model’ implies a carefully constructed scale representation of a space. Some models do fit this description but others can be very simple ‘sketch’ models constructed from thick paper or other craft materials and adhesive tape in a matter of minutes. It doesn’t matter how well finished the model is, it ’s more important that it captures the essence and spirit of a space and helps you to visualise the three-dimensional reality that you are trying to understand. Models can be made to a very high standard, but this is generally only for presentation purposes.

Like drawings, models can be amended over time to represent changes to the design, and the process of constructing a model, however rough it may be, will help you to understand how the space works, and how the different planes and surfaces meet and interact. Sketch models are almost infinitely adaptable. Openings can very quickly be cut that represent new windows, doors or staircases. Pieces of paper can be taped in place to suggest new ways of dividing paces. The sketch model should be treated like a sketchbook; it is a physical way to get ideas out of your head and into some sort of reality where they can be more readily assessed, compared and shared. This is a very important technique, and one that designers should make use of as much as possible. As with sketching, you do not need to be embarrassed about your abilities with paper, scissors, craft knife and tape; it is much more important that you simply use the technique. The use of basic materials and fixing methods such as drafting tape or pins adds to the spontaneity of the process, and helps in the ready appreciation of structural changes and interventions. The process of manufacture tells you as much about the space as subsequent study of the model.

Sketch models can be made very simply to help our understanding of the space and its possibilities. They can easily be viewed from any angle, and can be photographed to simulate specific views. They do not need to have realistic finishes in order to be useful.

This is another model that does not attempt to realistically portray the decorative finishes. Instead, the uniform appearance of the card from which it has been made focuses attention on the space. This in itself can be a very useful feature of a model

Case study : Construction drawings in action

These drawings show a bathroom created by Studio DAR. They are construction drawings, showing information that will allow the contractors to implement the design.

This drawing includes a plan, a‘reflected ceiling plan’ showing light fittings and ceiling detail, construction drawings for a stone bench within the shower enclosure, and a section through the bespoke basin.

Here, elevations for each of the four walls are shown. They expand on information shown in the plan. Also included for the contractor’s reference are manufacturer ’s drawings of the taps and shower fittings.

A perspective sketch has been produced that the designer intends to be used alongside the plans and elevations to help visualise the space. This is useful for the designer and contractor alike.

The installed bathroom. Details of the bespoke cabinetry and the lighting detail in the ceiling can be related to the perspective sketch, the elevations and the plan.

Understanding through technical drawings

The drawings that designers most often use to help them understand a space are technical drawings, rather than illustrative ones. That is, they are drawings that form a meticulous and accurate record of the relationships between widths, depths and heights. As a result, they clearly indicate the proportions of the elements of an interior space, but they are not drawings that show spaces as we are used to seeing them. Because of this they can appear cold, unnatural and somewhat daunting to the uninitiated, but through practice most people will become comfortable with reading them and will appreciate them for the information that they contain and communicate. Variations in the presentation of technical drawings do occur, but they also share certain standard conventions that allow anyone familiar with them to read drawings created by others.

Drawings will be amended and added to over time to reflect the development of a design, but initially they will be used to give a feeling for the space. It is important to realise that although reading a drawing which already exists will go a long way to informing you about the space, the most immersive experience comes when the drawing is actually created by you, the designer. And the experience will be stronger still if you have undertaken the measured survey that precedes the act of drawing. It is only this hands-on approach that gives us the most complete knowledge of the space. The process of drawing, where each measurement and the placement of each line is carefully considered, intensifies the relationship that the designer has with the space, and gives an even more intimate understanding of a building. The act of drawing also gives time for reflection, which leads to an understanding of the possibilities that the building possesses, too.

Accurate technical drawings are based on careful measured surveys. All relevant dimensions are taken in situ and noted in sketch form. These survey notes are then used in studio to create the scale drawings. Ultimately, the detail shown in the drawings will be partly dictated by the scale at which they are drawn, but the survey should account for every possible dimension that might be needed to produce the drawings. Photographic references of details are very helpful. Undertaking a survey also gives a great insight into the intricacies of a space. Although it is oft en a task that designers contract out, performing the survey and drawing up the first set of survey drawings is a worthwhile task to undertake.