Plans
Now that we understand the overview of the planning application process, we can take a more in depth look at the different plans and documents that are required for the work to be carried out. Building contractors require a certain level of information within the plans in order to carry out the works to the agreed specification. When a package of drawings has been assembled, with contributions from both an architect and structural engineer, the contractor should possess all of the necessary information to carry out the works. The following is a description of the different types of drawings that are involved with the overall plans, and the information that can be ascertained from them.
Orthographic projection
Orthographic projection is the name given to the drawing techniques and processes involved in displaying three dimensional objects in 2 dimensions. Whilst a 3-dimensional drawing of an object can accurately represent the shape from a specific perspective, much information is left to be desired when viewing it in a 2-dimensional manner. In terms of technical construction drawings, 3-dimensional renderings alone do not provide adequate information about the building. When carrying out construction work, many different styles of drawings from varying perspectives come together to provide the necessary information. The most common types of drawings used to carry out construction operations are created through the process of orthographic projection.
The process of orthographic projection is simple. In basic terms, we imagine ourselves unfolding the net of a 3-dimensional building as if it were a box, into 2 dimensional planes for each face of the building. The diagram shows a regular house that has been unfolded into a flat net of the building, with each plane of the building being represented. This specific method is known as “third angle projection”, though that doesn't matter to us in this application. Each side of the house is displayed with a 2 dimensional “elevation drawing”, with a singular top down “plan” view of the house. These drawings feature no perspective in terms of distance and serve as a good neutral platform for displaying existing and proposed elements, as well as written measurements. We will see shortly how these different perspective drawings can be interpreted within technical drawings.
Scale in drawings
Within the world of design, accurate architectural and structural plans are drawn “to scale”. In order to maintain the accuracy of both the dimensions and proportions of a real-life object when orthographically projected on paper, a scale ratio is used. The scale ratio of a drawing portrays an accurate proportion of the drawing in relation to the full-sized object. Plans are commonly drawn on A2 or A3 paper, and so the scale must be suitable for the drawing to fit on the page.
The scale of a drawing is displayed as a ratio, for example “1:100”. This ratio simply displays the relationship between the drawing and the real object it is portraying. Any measurement displayed or taken from the scale drawing is 1/100 of the true size of the object. Another way of stating this is that “every unit drawn represents 100 of the same units in real life”. On a 1:100 scale drawing, 1 millimetre represents 100 millimetres in real life - The real-life object is 100 times bigger than the drawing.
These same statements are factually correct for any scale, though there are industry standard scales used in the creation of technical drawings. Larger objects will require larger scales in order for the drawing to fit on the page. The same is true in the other direction, with smaller objects being drawn to smaller scales.
The scale of a drawing is displayed in the ratio format beside the drawing, or in the title block of the plan. If the ratio of the printed page is correct, the drawing can be scaled using a scale ruler on the appropriate scale. The accuracy of the drawing in relation to the denoted scale can be checked by using the printed linear scale. Even so, most technical drawings state that they should not be scaled. If the drawings are annotated fully with measurements and dimensions, then a scale is not required. Sometimes there are no measurements present though, and the drawing must be scaled to ascertain the dimensions of the build.
Plan view
As we looked at with the orthographic projection, the plan view refers to the top-down view of the item or building in our case. The plan view displays a birds eye view of the building in various different capacities depending on the type of plan. Plans are the most commonly used drawings in construction to reference the layout and dimensions of a building, as they can accurately display measurements in both horizontal planes simultaneously.
Location plan
Location plans are large scale, plan view drawings that depict the surrounding area of proposed construction works. The scale of these drawings is typically 1:1250 or 1:2500 and displays the streets and properties within the immediate vicinity of the site. The information required for a block plan was traditionally collected via ordnance survey records, though modern satellite imaging has made the process faster and easier. The block plan serves to highlight the location of the site amongst the surrounding area and is too large to provide accurate component measurements or details relating to the site. These drawings are provided by the architect as a part of the design package and are submitted during the planning application phase.
Block plans
Block plans are large, but smaller than location plans, plans that display the site with detail about the surrounding area. The scale is smaller, around 1:500, and displays a smaller area for greater detail.
Site plans
Site plans are medium scale, plan view drawings that display the site where the proposed works are being carried out in relation to the most immediate properties in the vicinity. This includes any neighbouring properties, boundaries, existing structures on the property, proposed and existing utilities, and access. These drawings are typically drawn from around 1:100 up to a 1:500 scale and can display overall dimensions and measurements for the proposed construction. These drawings are provided by the architect as a part of the design package and are submitted during the planning application phase.
Floor plan
Floor plans are medium scale, plan view drawings that display the accurate layout of each floor within a building. Each floor of the building will have its own floor plan to display the layout, typically with an existing floor plan to show what is currently there, and a proposed floor plan to display the proposed works. The scale of these drawings is often around 1:100 in order to display the layout in enough detail. They often feature dimensional measurements and are usually large enough to accurately scale off of. The floor plans display all of the structural and architectural design features of the floor, showing components such as stud and masonry partitions, doors, stairs, external window and door openings etc. These drawings can also commonly be referenced to determine material width, thicknesses, and types, as this information is often displayed here. We will look at how floor plans are drafted and the symbology used later on, as these are the most commonly referenced plans in residential construction.
These drawings are provided by both the architect and the engineer as a part of the design and structural packages. The architect's floor plans are submitted during the planning application stage.
Kitchen plan
Kitchen plans are medium scale plan view drawings that display a kitchen layout within a portion of a floor plan. These plans are commonly provided by the supplier of a fitted kitchen, and serve primarily to inform the kitchen installer, as well as the electrician and plumber about the location of their first fix operations in relation to the finished kitchen. The scale of these drawings is typically around 1:50, and are often accompanied by section, elevation, and rendered drawings of the kitchen as a part of the kitchen plan package.
Assembly drawings
Assembly drawings are small scale drawings that display the intended assembly of a specific component. Whilst sometimes used in construction to explain how a component is intended to be assembled, they are more commonly used in manufacturing and R&D applications. The drawings typically display information about the component at a range of angles, such as a plan, through section, and 3-dimensional rendering. The scale of these drawings is typically around 1:20 or less.
Detail drawing
Detail drawings are the smallest type of drawings that are used for displaying information about very small components. The scale of these drawings is often around 1:10, though small components may be drawn and displayed in 1:1 scale or even scaled up from the size of the actual component to display it larger on the page. As with the assembly drawings, these drawings may display their information in a plan view, section drawing, or isometric rendering.
Elevation drawings
Elevation drawings are drawings that display information about the sides of the box that we can unfold through the process of orthographic projection. Whereas the plan view drawings are drawn from the top looking down, elevation drawings are drawn looking at the vertical faces of the building or component. In terms of construction, these drawings display information about each face of a square building in reference to the access of the building. For example, the front elevation of a building is the front of the building, with the rear elevation and side elevations being named respectively. For irregularly shaped buildings that are not square, or those that feature curves, directional elevations may be required to accurately display the information. North, South, East, and West are all directions that can be used to describe the angle of these irregular elevation drawings, as well as all the subdivisions in between, to allow for a full 360-degree selection of perspectives to render the building from.
Elevation drawings are often drawn to a scale of around 1:100 and display important information about the finish of a building and the materials to be used, as well as providing critical height and width dimensions. Elevation drawings are drafted by both engineers and architects as a part of the design and structural packages. The architect's elevation drawings display the existing and proposed elevations of a property and are submitted during the planning application process. The engineers' elevation drawings display details of any structural components and elements.
Section drawings
Section drawings are elevation style drawings that display the details of a building at a specific line through the building. Imagine cutting the building in half and looking at the new inside elevation that has been created. Section drawings are used to display internal components at their through section, to give more detail and insight about how the building is supposed to be constructed. A typical through section will display components on all floors of the building and how they come together, such as how the joists bear on internal structural walls, and how stud partitions come together. The design-based section drawings are produced by the architect as a part of the design package. When structural components such as steels are present in the build, the engineer will typically produce section drawings as a part of the structural package.
The location at which the section is taken from is displayed on the floor plans with a special symbol. When looking at the floor plan, we can see an actual line drawn across the plan with a lettered triangle at each end. This represents the location of the section “A”. When section “A” is drawn, it is referenced from this point in relation to the floor plan. The scale of section drawings is typically around 1:100.
Whilst mostly drawn in 2 dimensions, the section drawings taken at a specific point can be reproduced accurately as a 3-dimensional rendering to provide additional context.
Isometric perspective
Isometric projection is a method of rendering a 3-dimensional object in 2 dimensions whilst maintaining the 3-dimensional perspective of the item. The drawing is created from a set perspective, with the outside corner of the object being the closest to the viewpoint. All of the vertical lines of the object are drawn vertically, with the connecting horizontal lines being drawn at 30 degrees to the horizontal plane of the drawing. Isometric drawings like this are used to display information about an item or building without having to account for the changes in shape due to distance and perspective. With all of the angles and faces at a set angle apart from each other, we’re left with a drawing that can help us to understand the intended shape of a building. These drawings are commonly used in engineering to represent small components.
Perspective renderings
Perspective renderings are an architectural drawing style that are used to accurately represent the perspective view of an item or building. Whilst not so good at physically displaying measurements and critical elements, they are more of an architectural sketching tool, that provide context and accurate visualisation to the drawn technical plans. There are many styles of perspective drawings, though they all achieve the same desired outcome. The real object is drawn from a specific viewpoint, with the diminish of a building over distance being rendered accurately, so that the drawing looks correct as it would in real life. 2-point perspective is commonly used in residential construction; to display the building as it should look from the street.
Plan view legend
As we’ve looked at, the plan view drawings that are provided by the architect and engineer define the parameters that we work to. Within these drawings are a plethora of architectural symbols that are used to denote and display specific components. Here is a rundown of the most commonly used standardised symbols used in technical construction drawings, and what they mean.