does any body know the ratio for the units in radiant to real world,
ex: 1 meter= X units

Im pretty sure 1unit = 1 inch

You'll have to do the imperial-metric conversion....

1 unit = 1 inch

Doorways = 56 units wide/96 units high

For high traffic areas it is sometime best to make it a double door.

Double door = 128 units wide/96 units high

Window Height = 32 units from floor to the bottom of the window frame.

Window Frame = minimum of 46 units wide 72 units high. (Inside diameter)
Stairways

Interior = 8 high / 10 deep 64 unit min. width
Hallways

Hallways = 128 units wide
Walls

Building wall/One story high = 128 units high

Wall thickness = 8 units

Columns = 32-48 units wide

A 32 unit wide column is barely enough to still offer valid cover for the player. And after the column_cover node animations have been added 32-48 units will also provide valid cover and firing angles from both sides of the column for AI as well.
Streets

Large - Four car width = 512 units

Small - Two Tank width = 320 units

Alleyway – small street = 192 units wide
Sidewalk

Small = 128 units wide

Medium = 192 units wide

Large = 256 units wide (this is more for Singleplayer levels)
Cover

Standing cover height = 48 units high

Crouching = 32 units

Prone cover height = 16 units high

Prone crawling height clearance = 32 units high

Damn, Rasta. Bookmarking this when I get home, lol

Or I'll just steal the information and repost it on my forums...that okay with you? lol

thx a lotall that really helped