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Residential Homes

Scale Drawings:
A Basic Introduction

Architectural drawings that are drawn to scale are used to construct or remodel buildings.

Plan Drawings

Plan drawings are scale views looking straight down. Examples include floor plans, roof plans, site plans, etc.

Consider the following two-story house:

Figure 1:  Two-story house.

Here are the floor plans for that two-story house:

Figure 2:  Floor plans for the house of Figure 1. The top drawing is for the upstairs, and the drawing below that is for the downstairs.

Features of these floor plans including:

  • North is up in these plans, because the direction of North is not specified.
  • The two floor plans are lined up: in this case, the main West and East walls of the building line up.
  • The main entry is marked with a pointer, in this example a triangle pointing to the front door on the North side of the first floor.
  • Unless otherwise specified, an arrow along stair treads points in the upward direction, as in this example.

Note also that the roof overhangs and ridgeline are marked with dashed lines on the upstairs floor plan.


Consider another house, this one build in 1907:

Figure 3:  Rangemoor house, Brisbane, Australia.

Here is a floor plan of that house, drawn in the 1970s to assist in remodelling:

Figure 4:  Rangemoor house floor plan.

For this drawing, North is down, as specified in the plan. And the scale is 1:200, which means that a ruler with 1/200 markings can be placed on the original drawing to determine room dimensions.

A scale of 1:200 means that 1 mm on the drawing equals 200 mm at the building, 1 cm on the drawing equals 200 cm at the building, etc.

These kinds of drawings are kept at the job site, along with scale rulers to determine measurements from the drawings.


Scale Ruler

A scale ruler (also called architect’s scale) is a multi-sided ruler that can be flipped around until the desired scale is in position to take measurments on a scale drawing.

Figure 5:  Scale ruler positioned to take measurements at a scale of 1:200 on the left side of the ruler in this photograph. [TiiaMonto]

Figure 6:  Scale ruler placed on site plans. [AlBordeau]

Elevation Drawings

An elevation drawing shows a vertical wall or building side, viewed from a horizontal direction. This type of drawing can be in line with other drawings.

Figure 7:  Front elevation (“principal facade”) of multi-family housing (quad-plex), above and in line with floor plan of the building. France, 1921. [Guimard]

Figure 8:  Elevation lined up with plan drawing, Florida Southern College campus design drawings, 1950s.
(1 MB)

High resolution JP2 files can be viewed in Image Glass o


Section Drawings

A section drawing is a cut-away view of a wall, or of a building elevation, or of other vertical objects.

Figure 9:  Side elevation (“lateral facade”) on the left, in line with a section drawing of the elevation on the right. Section drawings have a title under the section drawing, in this example “Section CD” (or “Coupe CD” which translates as “Cut CD”) because it is a section drawing at the cut lines C and D in the elevation drawing. [Guimard]

In the section drawing of this figure, the roof on the right of the section drawing, is the lower of the two roofs in the elevation drawing. And the roof at the top of the section drawing, is the upper roof in the elevation.


Detail Drawings

A detail drawing is a drawing of a specific part, such as a light fixture, trim detail, etc.  Detail drawings could be section drawings or portions thereof; the terms section and detail may be used interchangably.

We consider section and detail drawings in the plans that were used to construct the E. T. Roux Library.

Figure 10:  E. T. Roux Library at Florida Southern College in Lakeland, Florida. The round reading room (left) has clerestory windows to help provide daytime illumination inside.
(113 k)

Figure 11:  Reading room mezzanine, E. T. Roux Library. Small desk lamps (not shown) provide additional lighting.
(760 K)

A section drawing of a wall is generally perpendicular to an elevation drawing of the wall: instead of showing the face of the wall, it shows a cross-section view of what the wall is made of, and its dimensions in that direction. Exemplary cut lines on plan or elevation drawings show the position of the section drawing, usually labelled with letters, like AA, BB, etc.

Consider the following plan drawing that was used to construct the E. T. Roux Library:

Figure 12:  Sheet No. 1: Foundation and Lower Floor Plan.
(1.5 MB)

Note: High resolution JP2 files can be viewed in Image Glass o. Use the Plus and Minus keys to zoom in and out.

Zoom in to the lower right portion of the drawing, as shown here:

Figure 13:  Lower right portion of Sheet 1.

That section drawing, in the lower right portion of Sheet 1, has its title (Section AA) below the section drawing, along with the scale of the section drawing, since the scale is different than the scale of the plan drawing.

In the plan drawing, to the left of the lower part of that section drawing, zoom in and notice, below where Axis X-X intersects the curved wall, are two arrows each labelled A, to illustrate how Section AA cuts that wall:

Figure 14:  Sheet 1 cut AA.

The foundation footing projecting inward beyond the cut (above cut AA in the floor plan), illustrated with dashed lined rectangle on the floor plan (where Axis X-X meets the perimeter wall in Figure 14), is shown in the background of Section AA:

Figure 15:  Foundation footing, 11 inches high, projecting 2 feet (24 inches) inward (toward center of wall radius, which in this section is toward the left). These drawings used Imperial units (feet and inches).

The projecting footings are positioned along the downhill side of the building, at chord lengths of 22 feet-10 inches (274 inches):

Figure 16:  Chord distances between projecting footings.

Returning to Section AA, zoom in to the main floor level (datum zero) on Section AA to see the floor vent detail.

Figure 17:  Section AA, floor vent detail (“ventilator”) at this section of the building perimeter. Vent grating is at floor level.

From the position of Section AA cut on the plan, we have already followed the exterior wall (round building perimeter) to the lower part of the drawing that shows the chord lengths. Now keep going along the curved wall, further to the left in the plan.

Where the last chord line ends, a note outside the building perimeter says the dashed line that follows outside the building perimeter is the “Line of footing, see Section AA”.

Referring back to Section AA (zoom in to the lower-right portion of the drawing shown in Figure 13), we see that footing (which wraps around the outside of the building and extends to the right in the section) was specified in the drawing to be 14 inches high, with the bottom of the footing at least 24 inches below ground level.

Continuing on, the wall is interrupted (horizontal contact offset) at the outside of the flower box (left side of Figure 16 above), to reduce thermal expansion ballooning of the building.

Moving further along the round wall, past the inner side of the flower box, is the last projecting footing of the round portion of the building (which again references Section AA), after which begins the polygonal (non-round) portion of the building.

Follow along the straight exterior walls of the building, around an obtuse corner, and find the cut lines for Section BB.

Section BB is drawn above Section AA (on the right side of the sheet) without specifying scale because it uses the same scale as Section AA below it.


Sheet 2

Figure 18:  Sheet 2: Main Floor Plan.
(1.6 MB)

Sheet 2 shows the two entrances where the reading room meets the polygonal portion of the building (along a secant), at datum zero of the plan, which is the main floor level that extends throughout the polygonal portion of the building and along the inside perimeter of the round reading room.

The reading room has multiple coencentric floor levels, beginning with the outer floor at main floor level of the building (“datum zero”), with each floor level inward 9 inches lower (negative datum).

There is a step inset between desks or shelves that arc along edges of floor levels, to form two 4.5 inch high steps between each floor level.

Figure 19:  Reading room floor levels are 9 inches apart, with the lower level 27 inches below the main floor level. Multi-radix conversions had to be pencilled in (top of this figure) because of using Imperial units. Multi-radix conversions like that are only required for Imperial units (not used in SI units, which eliminate that potential for error).

Sheet 3

Figure 20:  Sheet 3: Roof lighting.
(1.4 MB)

Figure 21:  Sheet 3 detail of in-roof light fixture, with its own scale.

SI Units

Architectural scale drawings that are used to construct a building are called working drawings.

Working drawings list lengths (dimensions) as meters (m) and millimeters (mm), not centimeters (cm).

If a dimension has a radix point, the dimension is meters. The radix point could be a period or a comma, and is referred to as a “decimal point” because SI units only use base-10 (decimal radix).

If a dimension does not have a radix point (if it is an integer), then it is millimeters.

For example, one-and-a-half meters can be specified as follows:

1.5
1,5
1500

All three of those are valid and specify the same distance. Using that convention, the suffixes m or mm are not used, and reading the distances becomes easier and less error-prone.

Figure 22:  Working drawings using meters and millimeters.

Figure 23:  Dimensions in meters.

Figure 24:  Dimensions in millimeters.

Publicity Drawings

Publicity drawings may use centimeters, because the public uses centimeters. For example, when a consumer shops for furniture, the sizes of furniture are given in centimeters.

To convert millimeters to centimeters, simply remove the least significant digit from millimeters (conveniently possible because SI units use a decimal radix).

Figure 25:  Promotional banner hanging on a passivhaus apartment building in Austria, to advertise housing units on the top floor. The building was formerly a factory. [Moser]

Figure 26:  Portion of preceding figure showing a floor plan using centimeters. Floor areas are still listed as square meters (m2).

This figure shows a floor plan of Apartment B15. The apartment has 46.87 square meters (m2) of floor area, listed in the table to the right of the plan. Entrance to the apartment is shown in upper portion of the plan, in a hallway next to entrance of another apartment that is not shown but is denoted as having more square meters.

The lower portion of floor plan shows a 7.04 x 2.03 balcony with two lounge chairs (in addition to the 46.87 m2 of the apartment). The balcony is actually a roof terrace (dachterrase) — it sits on top of (is the roof of) an apartment below.

Not having cantilever balconies as building add-ons reduces thermal bridging o and structural weathering. It is better to hold up small balconies with vertical posts from the ground instead of horizontal cantilever from the building, to reduce structural building membrane penetration. That was done for the second floor of this building. Even better is to use roof terraces, as specified for the top (third) floor in these plans.


References

Rangemoor house

Florida Southern College:
Photos | Drawings


“One of the Ecole’s former students, Jean Victor Poncelet, was taken prisoner in 1812 in Napoleon’s retreat from Moscow. He kept his spirits up during a terrible winter by reviewing what his old teacher, Monge, had taught him about descriptive geometry. This is a system of projections of a solid onto a plane – or rather two projections, one vertically and one horizontally (giving what are called to this day the plan and elevation of the solid).”
— 
Brannan, Esplen, and Gray, Geometry: Second Edition

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2021–Sep–22  19:58  UTC