A1 A methodology of CAD drawing on actual relative floor levels in preparation for 3D.

(AutoCAD & AutoCAD LT on the Windows 95/98 operating system)


It is preferable and possible to design in the actual floor plane levels in multi-level buildings. This gives a realistic relationship between elements and makes design presentation work in 3 Dimensions (3D) easier for yourself or a bureau service set up for presentation work. Work in "21/2 D" is undertaken by having those items that only need to be in 2D drawn as such but with an ever increasing availability of 3D pre-drawn manufacturers componentry, these items too can be selectively used within the project at hand to improve speed and presentation.. The designers own work in 3D can be included in this of course.

Having items / objects / components / presentation graphics etc. at their true height in relation to each other also helps to interpret complexities and find potential conflicts early. They can be viewed easily in isometric or perspective views to give that added understanding to the designer and for illustrating to the client various design features. Showing structural, mechanical, civil etc. consultants particular complexities or concerns is more readily done too.

Layer names will normally include the floor level reference for easy selection as a batch with the filter setting dialogue box (within the layer control).

Setting up floor levels (example)

These can be pre-set up as a specific working level in a specifically named UCS (User Coordinate System) for easy access.

This example is for a 3 level plus undercroft building

Using a height of "0" for the ground or entry level and having it as the standard level that AutoCAD opens up with in its "World" coordinate system gives a ready mental reference point.

Description RFL Rel. Floor Level UCS Named as
Level 3 +6000 3_6000
Level 2 +3000 2_3000
Level 1 0 World (as standard)
Undercroft -1 -3000 -1_3000

The named UCS in having both the reference height plus the Level number in its name, is readily identifiable and provides confirmation of the relative working height.


Setting up a named floor level is a simple as typing in the following:

Type in followed by key press action Comments

ucs enter or right mouse button

o enter or right mouse button letter "o" for "origin"

0,0,6000 enter or right mouse button changes z to 6000

ucs enter or right mouse button

s enter or right mouse button save

3_6000 enter or right mouse button saves this UCS' name

ucs enter or right mouse button returns to world ucs

Repeat the process above, to create the UCS level & name for Level 2 and Undercroft 1.

If Level 1 (ground) is not at 0.00 level then it too should be given a name and saved separately.

Designing using named UCS floor levels

To select the floor level, go to the "Named UCS" icon.

In the dialogue box, highlight the level you want to go to, then select the "current" button followed by " OK" button.

Any 2d or 3d objects drawn or blocks inserted will then be drawn onto this selected level.

(Assuming the blocks' insertion point was at a "z" value of zero as is usual).

Verifying a height level of an object or point

Note: when using the "List" or "XYZ point" command to check the level of something ensure you are back in "World" UCS otherwise the "z" height figure may not be as you expect it.

i.e. It will show as a "0" (zero) if its level is the same as the current UCS level


When scaling an object ensure that the position picked for the base point is on the same UCS level as the object being scaled otherwise AutoCAD will apply the scaling factor to the distance between the two UCS levels. The result being your object located on the wrong z level.

Saving floor levels in a template file

If working with a particular set of buildings or for a particular client etc. you may wish to save the level settings in a "Template" file so that they come up pre-set for a project.

More complex buildings / sites

In larger or more complex buildings you may wish to consider additional pre-set layers for:

Ceiling levels

Split levels

Roof soffit level

Plant platform level

Street level

Carpark level etc.

Consultant-specific levels (i.e. Ceiling electrical plans at their correct level)

Site split-levels (for inserting 3D presentation graphics at the right level).

Working with consultant's and site levels

A standard pro-forma document outlining the levels, level heights, UCS named views etc. should form part of any complex project's inter-consultant documentation.

Insert the Floor /Relative Level/UCS chart along with your usual layer linetype, x/ref lists.


Please provide feedback on this system to Allan Johanson, E-mail ajohans@ ozemail.com.au. As a central reference point for future updates.

Copyright Allan E Johanson & Associates 1997

Addendum 1 February 1999
Lost in 3D Space - no more.
If working in 3D and you have various named UCS that represent floor levels
(or other z levels) you could get lost in 3D space. But no more!!
Thanks to AutoCAD Diesel (String Expression Language) is very easy to have a
little reminder placed on the screen to tell you what named UCS you are in.
Command: modemacro (enter)
type: $(getvar,ucsname) (enter)
Assuming you have created and named UCS's prior to this, the current name
will now pop up  at the bottom left of the screen (usually to the left of
the co-ordinates display).
The only one it won't show up is "World", so you have to create a UCSNAME at 0,0,0 with a different name.
Besides setting up floor levels, UCS's that relate to elevational views
could also be used.
To return to previous (default) mode macro setting type in: modemacro
(enter) . (enter)
It helps if the UCS name relates to useful info (see above).