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November 2, 2018
This week’s article is about Plans Reading, how to understand what the designer/architect has specified.
Here’s the evaluation form, so you can rate yourself on your existing understanding. The rating is from 0 (I know nothing about this topic) to 4 (I’m an expert in this topic and can handle complex tasks on the daily). You don’t have to share this with anyone else, so rate yourself honestly!
If you find Plans Reading a challenge, read on. There are links to lots of free exercises and workbooks in this article.
If you’ve got this part of the competency down, tune in next week for the first part of High Performance Housing.
Blueprints, A Story
In 1842, a clever fellow named John Herschel who worked in the shipbuilding industry invented blueprinting. Through a chemical photographic process, everything on the drawing sheet that was black came up white against a blue background. White on blue background was used up until the 1950s when copy machines came into use, and blue or black lines on a white background became more common. Today, the term 'blueprint' refers to any detailed construction document, regardless of how they are printed.
A set of construction drawings (‘plans’) can have several types of drawings in it. We say a ‘set of plans’, but a plan is just one type of drawing that is needed to build a house (or anything, for that matter. If you think of a box, there are six sides: top, bottom, front, back, left, right. The PLAN drawing is one that relates to the bottom of the box, showing the details of how it is cut, folded, or otherwise constructed. The ELEVATIONS are the four sides (front, back, left, right). Another PLAN shows the top of the box. In a set of drawings that show a house, there is a PLAN for each floor level, including the foundation, usually drawn as if you are looking at the plan from about 4 feet off the floor. There is also typically a PLAN for the roof, showing ridges, hips, and slope direction. Together, these PLAN and ELEVATION drawings make up the orthographic projection, and are known as multiview drawings.
A single view drawing simultaneously communicates more than one side of an object in the same view, as in a 3-d view. A single view drawing can be perspective or axonometric. It is an accurate representation of a 3 dimensional object on 2 dimensional plan.
Here’s a blog post from a blog called Drafting Teacher that unpacks orthographic views (keep scrolling, there’s a lot of good info and some exercises, but it’s in a large font size, so not much info on the screen at the same time).
Here’s an excellent tutorial on perspective drawing - you don’t have to do the tutorial, but scroll through to see what’s involved. Some great examples!
There are links at the bottom of this article to videos and another blog post that will help you understand how to read plans.
The Importance of Communication
It used to be just blueprints, but now there are a whole range of documentation for communicating what the project is supposed to be.
There are blueprints, shop drawings, contracts, specification bid sheets, and when they all don't come together, that's where the problems start. Blueprints are the language of construction, providing information on building codes for life and safety, spatial room sizes, volumes, heights of ceilings door and window sizes, floor breaks, materials used in the structure, details and (hopefully) methods used to construct the home.
Phases of a set of construction drawings:
Conceptual, back of a napkin, based on units or modules
Schematic (30% of the information): not many details or dimensions, adding structural materials and sizing of space to conceptual ideas
Design Development (60% of the information): adding more details and dimensions to materials and sizing of spaces
Working Drawings (85% of information): appropriate for bidding with correct dimensions and relationships of parts, but often change
Construction drawings (95% of the information): appropriate for bidding and building the project, often include specification, code compliance, and addenda information.
What do construction drawings tell you about?
Substructure: foundation systems
Superstructure: the building itself, the structural systems, materials, and all the building services
To keep track of various parts of bigger buildings, there are categories. Typical series of sheet numbers in drawings:
A series: Architectural
S series: Structural
C series: Civil
L series: Landscape
P series: Plumbing
M series: Mechanical
E series: Electrical
Many residential projects do not provide as much detail or numbered series as commercial or large projects. Often, a set of construction drawings will only have the ‘A’ series.
How does this look on the drawings?
Here’s an example: A1.2 is the sheet number 1.2 within the ‘A’ series, the architectural drawings. It could be that 1.1 is the first floor plan 1.2 is the floor plan for the second floor and A 1.3 is the floor plan for the third floor.
In addition to the graphic representation of the plans, elevations, sections, and details, there are also written notes on drawings. So we have categories of notes, too.
General Conditions: information that is common to either the sheet, the division of work, or to the project as a whole
Demolition Notes: for removal of trees, vegetation existing structures, and working up against existing structures
Construction or Plan Notes: 'call out' materials, methods of assembly, quality, or design intent
Detail Notes: very detailed and specific to the detail drawing
Landscape Notes: vegetation, plantings, etc.
Revisions/Addendums: 'clouded' notes that show new information from the original version of the drawings. Revision notes can also be made in a revision block. They should be numbered and dated.
How to Navigate a Set of Drawings
All the crucial information about the set of drawings should be on it, the list of drawings, a perspective drawing, information about the site. The name or model of the project and code information. Sometimes also calculations (sq ft) of the size of conditioned space, that area that is inside the building envelope and controlled by the heating and cooling system. Unconditioned space, such as garage does not have heating or air conditioning. What’s on a cover sheet:
Separate sheet or a portion of a sheet
Vicinity or location map with project site
Project name and number, phase of work
Full address of jobsite
Names of design professionals and consultants
Name of owner
Registration seal of design professional
Addendums and their dates
Date of latest version/project
Index of drawings
Possibly a rendering
Nothing is ever all on one page, there’s just too much information to show. So drawings are also broken out into categories that show more or less detail. On the primary drawings, the plans and elevations, you will see symbols that are called ‘designations’. Designations showing where to find sections and details. They act like roadsigns, referring you to a specific page to see a specific section or a detail of that particular part of the house. This allows you to move through the drawings easily.
A set of house plans will include foundation and floor plans, elevations and building sections. Remeber, the plan is sliced horizontally looking at something straight down. The elevation is looking at something straight on. The section is taking object and slicing it vertically and opening it up and seeing what's inside.
The drawing scale is a way to accurately represent a full size building on a small sheet of paper. The scale is shown on the first page, or on all pages, and you need to check it, because not every page is the same scale. When you are doing a take-off of the drawing, or determining what length or width and object is, use the dimensions shown on the drawing. In addition to scale issues, not every page gets printed on the proper size paper, so don’t rely on your ruler to be accurate about taking measurements off the printed sheet.
The floor plan shows all parts of each level of the house. In PLAN view, you are looking down at the building, and the view is of a horizontal slice through the building. Typically, it is sliced at 3-4 feet above the floor level. This means you have objects above and below the view plane.
There are four orientations: Front, left, back, right. All orientations start with the front of the building at the bottom of the page.
Where is the front door? It's not necessarily at the bottom of the page.
Find the front door to orient yourself on the drawing, and then walk through the building mentally.
On any set of drawings, the outermost dimension line is the overall size, length or measure of that side of the structure. When you're looking at dimensions, as you work your way in, towards the building, the measurements get tighter and tighter. Everything on the plan has a purpose, including line weights. Heavy solid lines designate walls. Doors and windows are represented as solid heavy lines that are not as heavy as the wall lines. This is to allow you to see the structure of the building more clearly. Lighter lines are used to show dimensions. Note whether the dimensions are from the inside surface of the wall, the outside surface of the wall, or to the middle of the framing members inside the wall. If for example you have a six inch thick wall, and the dimensions are shown from the inside surface of the wall to the inside surface of the wall, you will be missing a whole foot from the overall length or width of the outside of the structure. The single hashmark is the end point of the dimension.
Wood and masonry walls are shown with different hatches or patterns in them.
Designations tell you the wall type, they can be listed in different ways. The walls (and windows and doors) are listed on a shedule. Being able to break down the components of the drawing takes the mystery out of reading them.
Floor breaks, where the finished floor material changes, are shown with a lighter solid lines. PRO TIP: use highlighter markers to key your drawing so you can pull out all the notes that are relative to your task or job. WIC walk in closet. R&S = rod and shelf (optional)
"The floor plan is a horizontal slice at the 3 to 4 ft height so we have effectively lifted off the top of the building, and that means that there will be objects above and below the view plane of the slice. Anything above the horizontal slice, such as upper cabinets in a kitchen or bathroom, or an arch or header at an opening, will be shown as a light weight short dashed line.
Anything below the line of our slice, say a lower cabinet, is shown as a light dashed line. On a foundation plan, the footing is shown as a longer dashed line. You can't see it.
A section designation another roadsign, takes you to another page. A section view is a vertical cut through an assembly. The arrow head on the designation symbol points in the direction from which you are looking at the vertical slice drawing number on page or sheet.
Doors and windows are usually shown as a symbol on the plan, with the number or letter of the symbol corresponding to a table or chart called a schedule. The schedule is where you find the size, material, type of door or window and other characteristics.
Light dashed line shows door swings, and sometimes opening directions for casement windows
A site plan shows the building's location in regards to the rest of the site, the boundaries of the site, and the major features of the site. Floor Plans include Layouts of rooms and closets, fixtures that are part of the house, like bathrooms. often has inside dimensions of rooms.
If you're having troubles reading a floorplan, here is a great link.
Symbols and Abbreviations
Here is a comprehensive list of symbols and abbreviations commonly found in construction drawings for houses.
Designations are different than typical symbols. They act as road signs that tell you where to go on other sheets to find more information on a part of the drawing. For example, on a plan drawing, doors are identified with a number inside a circle, while windows are identified with a number inside a hexagon or a square. The number inside the shape is found on the window and door schedule.
Schedules are tables that give you key information about the windows, doors, finishes, or other component, like material, type and finish.
Key Features in Plan View include:
Fixtures (electrical, plumbing)
The elevations are the side views of the house from front, left, rear, and right. Floor to floor or ceiling heights will always be shown on the elevations. Cladding finishes, trim, shutters and other notes about exterior finishes are shown on the elevations. Other elevation notes include roof pitch and overhangs.
Checklist of Elevations:
Call out critical vertical dimensions
Best view for locating items outside the building
Exterior: front/side/rear (or cardinal compass points NSEW)
Interior: often combines section information
A section is a vertical slice through the building. The section shows floor, stairs, and ceiling geometry and other critical information that is easily understood in a visual way and can show human scale within the building.
On the plan, a section symbol is a line that shows the extent of the section cut (which could be through a wall assembly or through the whole house). A circle topped with an arrowhead shows which direction (or orientation) the section is pointing towards. The circle contains the information you need to know about the section: the name or number of the section itself and the page number of the drawing sheet on which the section drawing can be found. On the section page, the drawing of the section will be labelled with the section name or number.
A vertical cut through the building and looking in one direction
Best view for locating items between the floors of the building (stairs, etc.)
Indicate major structural features
Cross-section: cut along the short dimension of the building
Longitudinal section: cut across the long dimension dimension of the building
Types of sections:
For a wall cross-section, the drawing clearly describes how the wall is constructed. It depicts the wall area only, and is referenced with the same kinds of section designation as a building section. A wall cross-section shows more detail than a building section drawing.
The view is projected within the wall from the bottom of the footing to the top of the roof, but portions of the wall height are often deleted with squiggly 'break lines'. The wall section allows for further description with additional notes and specifications.
These drawings need a different scale than the floor plan or elevation drawings, as more details are needed.
Typical scales: 1 1/2", 1, 3/4" or 1” to 1'0"
Details are additional information about how assemblies go together. They give a closer look at how to build the different parts of the home. Often the detail is shown in plan and in section. More details are being drawn in 3-d due to Computer Assisted Drafting (CAD).
Some examples of details: Dormer, tub platform, shower seat, kitchen island raised countertop
Detailed wall sections are not always from footing through to the top of roof. A squiggly break line allows the drawing to show details without showing the whole extent of the wall or other assembly.
The number of details varies with complexity of construction.
Notes in detail drawings often direct the work to be done, for example, "provide masonry ties @ 24" on centre (o.c.)”.
Typical scales: 1 1/2", 1, 3/4" or 1” to 1'0"