TvZ: how to handle quick zerg transitions?

Yesterday I played Terran against Zerg (that is actually 1-2 leagues better then me). I played pretty well half of the game. It was something like this:

• I scouted Zerg too late (Metalopolis map), my mistake;
• Zerg made quick expo, I did too;
• Few minutes Zerg was leading in drone amount (he had around 45-50 drones, I had - around 35 SCVs), but it was mostly compensated with my MULEs, also I did him hellion drop and killed around 15 drones;
• mutas killed my medivacs in the end of drop.

Middle game:

I made 2nd expansion, zerg did 2 more. I denied his 1 and killed drones on the 2nd exp (so he left on 3 bases with around 40 drones), he denied my 2nd exp (so I left on 2 bases with 40 SCVs too).

The next thing was his mutas+ultralisk+lings+bannelings attack on my natural. I had enough Vikings, marines, medivacs, some banshees, and had time to save all my SCVs. He lost whole army, but I saved 5-6 vikings, few banshees. So it was more or less good for me.

The end.

Still, I had few problems (as I saw from replay):

• I had some minerals/gas left and didn't mine for some time...
• I didn't have enough production facilities (4 barracks, 3 factories, 2 star-ports) to build enough army in time... Actually, that is not so small for 2 bases, right?

Next his push was mainly consisted from bannelings + zerlings... (more then 50 banelings). He destroyed both my CCs...

But if I had enough production facilities, I still could't know what should I build: helions? tanks? thors? banshee or vikings?

If I have map control I can see his army coming in 20-30 seconds, but I won't be able to build enough army to defend for this time...

My own summaries: I needed to scout him earlier and try to deny expansions earlier... probably in this way he would have less larvas/minerals... and I will be able to build enough and proper army in time...

But:

Question 1: how can you know what kind of army expect from Zerg (if he has all 3: ban.nest, roach warren, spire)?

Possible answer: Just to push constantly and keep him under pressure without giving any chance to produce more or less big army?

Question 2: If I am correct, how can you push and still keep your base well defended (against quick mutas/zerlings)?

Possible answer: the best deffence is offence... but still, you need to be able to react on 5-7 mutas mineral line harassment...

Any other thoughts are welcome.

So the quick Zerg transition is a myth (kind of like the Yeti or his North American cousin the Sasquatch); Zerg take just about as long to transition from one build to the next as every other race. Where this misconception comes from is the Zerg's ability to remax, very quickly, with a new army.

Now obviously, I could tell you about how you need to scout better, but as I've mentioned before I don't think that's much better than telling you to "play better," so instead I'm going to tell you what you did wrong in your replay:

You didn't build tanks.

I'm not saying there aren't other viable Terran builds, or that other units aren't good for a Terran, or that you won't need other units too, but against a Zerg its hard to do better than Siege Tanks.

I'm going to quote Day9 on this one (on SotG):

[As Terran] you need that strong Tank back bone.

While going Bio heavy has its merits, against a Zerg player (especially in mid to late game), you need a strong Siege Tank back bone to deal with things like: Roach/Hydra, Ling/Baneling, Ultralisks, Broodlings. Otherwise you're essentially giving up one of your biggest advantages: AoE. The entire reason a lot of Zerg players struggle mid-late game ZvT is because these Siege Tank back bones are unassailable. As a result the Zerg often feels he needs to pull off some sort of clever Nydus or Drop play to break that Siege Tank line (called, catching him out of position).

To augment your Tank line, there are a very large number of things you can build (Marines, Marauders, Hellions, Thors, Banshees, Vikings, etc), and this is where you start to customize yourself to what you're seeing from the Zerg (remember scouting). Against heavy Muta play, I tend to prefer Marines with a few Thors thrown in for range. A lot of Zerg will try to counter this with Ling/Baneling, but if you have that solid Tank line (and they're well spread out), you can usually handle that situation. On the other hand, if I'm seeing more Corruptor/Broodlord play, I want to have Vikings. Vikings are one of the few units you can really keep pace with Zerg production on (especially if he's dumping Corrputors into Broodlords). If I see Ultralisk, or Roach/Hydra. I like to back up my Siege Tanks with Marauders. While Siege do great damage against Ultra, its Marauders who are the real cost effective killers there. If you're starting to see Infestors, you need Ravens and Ghosts, so your Tank line doesn't get slimed.

But remember, you still need that solid Tank back bone before you stand a chance. I'm not saying build tanks first, but if you find yourself in mid game without a dozen or so Tanks, its going to be an uphill battle for you.