Starcraft 2 Zerg Strategy - An alternate Spanishiwa Build

Despite what it says on the Team Liquid Wiki, Spanishiwa has altered his build on occasion to the following (you can see it in some of his replays):

This Zerg build order is good in ZvT match-ups.

• 9 Overlord
• 13 Hatch
• 15 Spawning Pool
• 16 Overlord
• Double Queen when Spawning Pool finishes
• 2 Zerglings for scouting
• Use both Queens for Creep Tumors first
• Spinecrawler at Expansion
• Once at 40 supply, take all 4 gas
• Double Evo Chamber
• Lair with first 100 gas
• Roach Warren
• +1 Range / +1 Carapace Upgrades
• Roach Speed
• Lots of Roaches, big Roach push to deny expansions
• Infestation Pit
• Spire ---> Greater Spire for Broodlords

This list isn't a complete step-by-step for this build - it obviously starts changing depending on what your opponent is doing.