When is Pre-Baking Pie Crust necessary

Here is the rule of thumb I use for pre or par-baking pie crusts: pie crust usually takes about an hour to bake through. If your filling will not bake that long, you’ll want to bake it first.

For fruit pies I do not blind bake but berries, especially, can throw off a lot of liquid - oftentimes more than whatever thickener you've added can handle.

I therefore always sprinkle into the bottom crust, before adding the filling, a good layer of crushed amaretti or Italian "savoiardi" ladyfingers, or other dryish cookies, such as plain biscotti. The French grandmother of a dear friend uses bits of day-old baguette, which I've been known to do when no cookies can be found. Both work well!

Also, I always chill the crust in the freezer for 20 - 30 minutes before filling and baking. ;o)

Generally with fruit pies I don’t par or pre bake the crust, I do for custard pies and tarts because they tend to get more soggy. You can also put a cookie sheet or pizza stone in the oven and set your pie on that, it’ll help set the bottom.