Sapping point

[Seasoned Alcoholic]

Prior to 1.5 patch, i often built them, but used them only if they were deployed in acceptable position. Due to a siege tower bug, I use them more often now, unless I want to watch my soldiers dance around tower entrance.
Fortunately, it happens only at large stone walls!

This bug is seriously annoying, its a good job it only occurs when you build siege towers when attacking Large Stone Walls.

Another irritating feature with sieges is the 'randomness' of saps. Sometimes they are available to build as siege equipment, other times they are greyed-out and not possible (this is against all 3 types of stone walls btw). I've noticed that they may become available to construct if you wait a turn or so (IE maintain siege).

However, if you combine this sap problem and the siege tower bug when facing large stone walls, you are seriously running out of options. In this case, you either have to hope that there are some exisiting holes in the settlement walls (which the AI never repairs) from previous saps, or use onagers to punch a hole through. If your're playing a vanilla version as a Barbarian faction, you won't have onagers and will therefore have to wait until the AI sallies or not.