Nested Familes and File Size Test

A few weeks ago, a colleague of mine (David Lidbury) and I were having a discussion regarding nested families and their effect of the size of a project. We both had initially heard that nesting families wasn’t the best thing to do as it increased the file size, but neither one of us actually have run across that problem. We both have utilized nested families with customers and didn’t have any trouble. So, David did some testing to see what would happen to a file’s size if he built a door that was made of nested components versus a door that wasn’t. The results were a little surprising….

The set up

240kb Door without nested parts
HM door frame with the same parameters as listed below but with all the needed parts (Panel, Plan & Elevation swing) in the same family file.

316kb Door with nested parts
HM door frame with parameters to allow for full flexibility (Separate Fame Head and Jam parameters, etc.). This file is the base for the full family file. Nested families included; Door Panel, 2D Plan swing, Elevation plan swing

Conclusion #1 – The family size with nested parts is 76kb larger


Test - 1
I created a 22,000sf building then saved it as two separate files. I then added 36 doors of each type in there respective files.

1,208kb 36 doors without nested parts
1,308kb 36 doors with nested parts

Conclusion #2 – The file size with nested parts is 100kb larger


Test – 2
I added 99 additional levels and copied the first level up 99 times. This resulted in a door count of 3,564.

14,972kb 3,564 doors without nested parts
14,884kb 3,564 doors with nested parts

Conclusion #3 – The file size with nested parts is 88kb Smaller. This is obviously a surprise (and I did double check which file was which). The file size actually gets smaller as more nested families are added.


Of course this was a very simple project with mainly walls and doors. But, even with taking the project further and adding all the other components a building would have, the family built from nested components really doesn’t have an effect on the file size.