Here is a list of Skaven units and the buildings you need to make them.

 

Burrows-

• Skavensalves

Lair-

• Skavenslave Spears

Nest-Lar-

• Skavenslave Slingers

Clan Mors Headquarters or Clan Pit-

• Clanrats

Clan Pit – 

• Clanrat Spears
• Clanrats

Clan Barracks-

• Clanrat Separs (Shields)
• Clanrats (Shields)

Clan Armory + Construction Cavern-

• Stormvermin (Halberd)

Clan Armory + Warpforge- 

• Stromvermin (sword & Shield)

Hidden Lair-

• Night Runners
• Night Runners (slings)

Assassins Hideout-

• Gutter Runner Slingers
• Gutter Runners
• Assassins

Den of Secrets-

• Gutter Runner Slingers (Poison)
• Gutter Runners (Poison)

Den of Secrets + Pestilent Nave-

• Death Runners

Weapon Burrow-

• Poison Wind Globadiers

Weapon Burrow + Warp Turbine Plant-

• Death Globe Bombardiers

Weapon Burrow + Warp Forge-

• WarpFire Thrower

Construction Cavern-

• Plagueclaw Catapult

Warp-Forge-

• Warp Lightning Cannon
• Warlock Engineer

Warp- Turbine Plant-

• DoomWheel

Pox Cauldron-

• Plague Monks

Pestilent Nave-

• Plague Priest

lague Abbey-

• Plague Monk Censer Bearers

Growth Vats-

• Rat Ogre’s

Laboratory-

• Hell Pit Abomination