Since space is at a premium on my Lenovo Windows 10 x86 tablet I tend to periodically check for space wasters. During one of my recent checks I have noticed that Avast takes up 938MB on my tiny SSD.
When looking through the folder structure I did not immediately notice caches or other folders that would be candidates for deletion. Is there a way to reduce the space taken up by Avast?
Only way to reduce the space that avast is using, is to remove components that you don’t need/want.
You have to do a userdefined install!
=Snake=
I think you mean Custom Install. 
http://screencast-o-matic.com/screenshots/u/Lh/1467121600851-98260.png
Just out of interest I took a look at my Windows XP install, it’s a minimal install just the file + web shield.
It’s using 1GB. The biggest culprits are
C:\Program Files\AVAST Software\Avast\defs < 430MB
C:\Program Files\AVAST Software\Avast\setup < 420MB
You also need to check out the C:\Documents and Settings\All Users\Application Data\AVAST Software folder as depending on what avast version and elements installed could be large.
Mine on a minimal installation (all shields, software updater and Browser protection is just under 50MB. Add that to my C:\Program Files\AVAST Software folder of 569MB (size on disk) so just under 620MB.