Using It! - Working in Brick Dimensions

This piece covers a couple of techniques for working with brick dimensions.

The first method relies upon the ability of the wall tool in AECOsim Building Designer (ABD) to place walls by offset, the second uses MicroStation's units settings file to add the dimensions of a brick as usable units.

AECOsim Building Designer

In the model(s) that are to be used for setting out brickwork (assuming strict observance of the brick module!) change the Grid Settings to match the coordinating size of the brick being used (ensure the Grid Display Attribute is On!). In the UK the standard brick coordinating length is 225mm, the coordinating width 112.5mm. I have set the Grid Master size (that is the spacing of the grid points (the dots) to 112.5mm to allow placement by half brick dimensions. The Grid Reference, the square grid that gives scale, has been set to 8 (i.e. 8 x 112.5mm = 900mm).

Turn on Grid Lock.

Start the ABD Place Wall tool, pick a brick wall type, set the Side Offset value to 5mm. Setting this offset will allow you to place the wall locked to the coordinating grid but with the correct brickwork dimensions.

Gris Lock can be toggled Off when not required to control placement. Applying a rotated ACS will rotate the grid for the same degree of control in other orientations.

MicroStation Unit Settings

The Master and Sub units in MicroStation V8i/CONNECT applications are file specific display attributes so can be changed when necessary to suit the current working operations without affecting the actual size of any modelled elements. Note: operationally it is a good idea to stick to the same working units in all project files just to avoid potential confusion/error when switching files.

MicroStation's units are defined in the settings file: units.def.

The location of this file will vary slightly depending which application you are using, for example:

C:\ProgramData\Bentley\MicroStation V8i (SELECTseries)\WorkSpace\System\data\units.def

C:\Program Files\Bentley\MicroStation CONNECT Edition Update 1\MicroStation\Default\Data\units.def

C:\ProgramData\Bentley\AECOsimBuildingDesigner V8i Ss6\WorkSpace\System\data\units.def

Most standard imperial and metric units are included in the file (with the less commonly used units, e.g. Angstroms, commented out). If we do not provide units that you require they can be added to the settings file.

Setting out of masonry building by brick size (horizontally and vertically) is obviously common practice, suitable units can be added to units.def to add brick to the available units.

If you would like to try this out the steps are:

Copy units.def to your site standards folder, e.g. W:\SS6\Standards\data and rename to Company_Units.def.

Insert the red text into the file (around line 77):

# MicroStation Standard Unit Examples
#Label,Label,...; Name(singular); Name(plural);              Numerator;           Denominator; Base; System

# Brick Dimensioning Units
BL;               Brick Length;   Bricks Length;            4.65116279;                   1.0;    1;      0
BH;               Brick Height;   Bricks Height;           15.38461538;                   1.0;    1;      0
BJ;               Brick Joint;    Bricks Joint;                  100.0;                   1.0;    1;      0

#  SI (metric) units

Note, these lines are put at the head of the list so they are obvious when editing the file in future.

In this case, in the UK a standard brick joint is 10mm, i.e. 1cm. The entry for cm has the same Numerator value which stops the parsing of the list, units listed after cm are then not available in the UI. To get around this comment out the cm line. Note I tried moving the cm line to the end of the file but that resulted in the unit label being cm, which is not helpful. Understandably this part of the software did not anticipate duplicate values.

The brick sizes used are standard UK metric bricks 215 x 102.5 x 65mm. For other brick sizes just change these values or add further entries.

The reason that the values used are actual brick unit dimensions, not coordinating dimensions is that we can enter MU:SU dimensions with number of bricks (MU) plus number of joints (SU) but not number of bricks (MU) minus a joint (SU).

The Numerator value is the number of units that fit into 1m, so for the brick length 1000/215 = 4.65116279

Add the variable MS_CUSTOMUNITDEF to your site configuration set to point to Company_Units.def.

Once these changes are made start MicroStation (or ABD).

From the Settings menu pick Drawing Scale. Dock the Drawing Scale dialog (this is worth always having open and docked in any case), you should see Brick Length, Height and Joint available:

  • To work on plan, select MU = Bricks length, SU= Bricks Joint.
  • For elevation MU = Bricks Height, SU= Bricks Joint.

As mentioned above, these are just changing the display of units not the actual size of anything.

Place elements by keying in in the format MU:SU as shown, the semi-colon key will work as well as the colon if you have a UK keyboard:

You need to enter the number of bricks and the number of joints. Consider the following examples:

run of 10 bricks, external corners at each end (UK CO-) = 10 bricks (MU) plus 9 Joint(SU), enter 10:9 into AccuDraw.

run of 10 bricks, external corners to one internal corner (UK CO) = 10 bricks (MU) plus 10 Joint(SU), enter 10:10 into AccuDraw.

run of 10 bricks, internal corners at each end (UK CO+) = 10 bricks (MU) plus 11 Joint(SU), enter 10:11 into AccuDraw.


I think the best way to use this might be to have brick dims setting out files with these units set, using these files to draw controlling setting out shapes that are then used as underlays to the primary design files. This is instead of swapping between units in the active file.

In this example, brickDims_SettingOutPlan.dgn, set with brick units, is referenced into brickDims_DesignModel.dgn, set with mm, and activated. Note that as brickDims_SettingOutPlan.dgn is activated the working units change to brick units.

Adding Dimensions

Entirely optionally (this may or may not be useful!) dimensions can also be set up to show the brick dims, if at any time the units are not round numbers you immediately know that they are not whole bricks:

In this example (which works fine for whole bricks, read on...) I have copied an existing dimension style for use when dimensioning plans (the dimension tool doesn't know the difference between plan and elevation graphics) added secondary units to the Dimension Style:

  • Master Units: Bricks Length with the label b
  • Sub Units: Bricks Joint with the label j

(the labels are a single character to they don't take up too much space)

A similar style can be created for vertical dimensioning setting Master Units: Bricks Height with the label h.

Note the way I have set this up is with Brick height = 65mm plus a brick joint of 10mm. There could also be a unit of 75mm for brick courses. I'd be interested to hear what anyone think of that.

Dimension Limitations:

However there is a limitation to this secondary dimensioning (and I've 'shown my working' above as I think it is helpful to understand how these things work), it is designed for units such as feet and inches and cannot cope so well with situations like half-bricks, after all you never have a half foot, just whole feet plus inches!

As can be seen in this example where I have drawn (from left to right) the first three lines in 1 1/2 bricks, with the Secondary dimension set to 'MU label SU label' the half bricks are expressed as a number of brick joints, albeit with consistent numbers. This is still pretty confusing.

So setting the dimension style to show only Master Units with 2 decimal places...

...we get more comprehensible information:

the first line on the left is 1 1/2 bricks so contains 1 joint, the middle line has two internal corners so is 1 1/2 bricks plus three joints.

These are really just useful indicators for checking during design. A set of BDA brick dimension tables is still going to be an essential reference!