Without a photo of your finished loaf, it is difficult for me to zero in on how to fix your problem.  Here are some possibilities:

1. It's sounds as if you could proof a bit longer -- maybe by 10 or 15 minutes -- so that the loaf can grow a bit more before the final oven kick.
2. If letting it proof a bit longer means your crown gets too big before baking, then you might want to consider using less of this particular dough in your pan.
3. It's also possible that the heat from your oven is a bit too intense to allow the crown time to grow properly.  If you back off of the baking temperature by 10-20 degrees, you MIGHT see that the loaf has a minute or two longer to grow before the crown begins to crust over.
4. Using steam would be a last, desperate resort.  It helps to insulate the loaves very briefly from a very hot oven, but it also encourages gelatinization of the starches at the crown's surface.  That might cause premature browning before the loaf has finished baking inside, and it also might make the top crust a bit hard eventually.

Whether you choose one of these possibilities or come up with a fix of your own, the thing you need to aim for is a way to prevent the crown of the loaf from crusting over before the dough inside has finished growing.  You might not get an optimal fix in just one try, so don't be disappointed if you need three or four attempts to get it all right.

--Dan DiMuzio

Or use larger pans.  I rather like the look of loaves split along the sides.