I believe you cannot build 1 building behind it, you might need a lot of buildings lol or there will be gaps.
@Demise
Building a rax would be good strategy provided that the lings cannot kill it faster, of course if they 6 pooled, you can do anything and still be ahead assuming you do not die XD. But what I mean is 11/11 Rax type of quick 2 raxes, it is almost a pre-emptive measure which is not good if they do not cheese >< unless you want to cheese.
@Aristole
If I can do it....but sometimes the zerg is good at preventing that. You see they have all their attention on my base, so technically they should be able to prevent me from getting the marine to the bunker or stop it from getting up.
The other solution would be super early scout. But this can put you behind because early game each SCV is important. I guess if you scout as you make supply depot you can easily defend 6 pool. If you defend it....hehe 6 rax time all the way! Need your own cheese to rub it in their face.