Drawing Number System

The drawing number system identifies both the computer files containing the drawings and each sheet of the printed drawings.

Number structure

Computer file numbers have the format BFR where B is the building number, F is the file digit, and R is the revision digit. The number of each sheet of a drawing is BFR-SL, where BFR is the same as the file number, SL is the dash number, S is the sheets digit, and L is the layer digit.

Building number

The building number has four digits. The first digit is 1 for a one-story building, 2 for a two-story house or two-story rowhouse (townhouse) apartment building, 3 for a three-story building, and 4 for a two-story building with four flats (up-and-down fourplex).

Building number first digits 0, 5, 6, 7, 8, and 9 are not used. They are reserved for other types of buildings, files, or documents. The first digit 3 is not used either, because there are no three-story buildings.

The second digit tells the number of bedrooms, bedrooms and bathrooms, or habitable rooms.

not used
1 bedroom
2 bedrooms and 1 bathroom
2 bedrooms and 2 bathrooms
2 bedrooms and 2.5 or 3 bathrooms
5 rooms -- 3 bedrooms
6 rooms -- 4 bedrooms
7 rooms
8 rooms
9 or more rooms

The third digit identifies a particular model. There can be ten different models for each combination of the first two digits of the building number. The models can be related, such as models with different garage arrangements, or be completely different.

The fourth digit tells the number of dwelling units in the building. A house has one unit, a duplex has two units, and an apartment building has three or more units.

File digit

Each building has more than one computer file. The file digit F identifies a particular file for that building:

not used
first story floor plan group
second story floor plan group
elevations
foundation plan
roof plan
not used
not used
not used
not used

For small two story buildings, the first story and second story floor plan groups are combined into file digit 1. If the building has a basement (only the hillside designs do), it is shown in the first story floor plan group.

Revision digit

The revision digit R starts at 0. When a building is extensively revised, the revision digits for all of the building's files are incremented.

Dash number

Drawing numbers have a dash number SL added to the computer file number to identify each sheet of the printed drawings. The dash number allows one to four single-sheet drawings in a file, or a single drawing with one to four sheets. The files can also contain mirror images of the drawings.

The sheets digit S tells the number of sheets in a drawing. If the sheets digit is 0, the file contains only single-sheet drawings. If the sheets digit is not 0, the file contains one drawing with the number of sheets equal to the sheets digit.

The layer digit L tells which layer of the file is combined with layer 0 or 5, the title layers, to make up the drawing. The layer colors are:

black
red
blue
dark green
dark magenta
dark gray
dark red
dark blue
dark yellow
dark cyan

The page color is white. Locked layers are dark gray.

For floor plan groups, the sheets digit is 0 and the layer digits are:

title layer for layers 1-4
floor plan
schematic plan
room plan
ceiling plan
title layer for layers 6-9
mirror image of floor plan
mirror image of schematic plan
mirror image of room plan
mirror image of ceiling plan

For all other files, the sheets digit is not zero and the layer digits are:

title layer for layers 1-4
sheet 1
sheet 2
sheet 3
sheet 4
title layer for layers 6-9
mirror image of sheet 1
mirror image of sheet 2
mirror image of sheet 3
mirror image of sheet 4

Duplexes, fourplexes, and sixplexes are symmetrical, so the mirror image layers are not used because they would be the same as the non-mirror layers. Also, no mirror image plan is needed for a rectangular roof.