How do I properly seal an exterior door?

Question

I've recently discovered that rain is getting in around my exterior (front) door and forming a little pool in the frame under the door. I'm assuming I can fix this by adding a seal around the door (which would also help with insulation too). Is this assumption correct, and if so what products would people recommend for the seal?

EDIT: Sorry, I realise my question was ambiguous, or even completely ill-phrased. The gap in question is actually the gap between the door itself and the door frame within which it's hung. So there has to be some gap there, but it appears that the gap I have is too large or something and that is allowing rain in a bit (when it comes at a particular angle). I'll add some photos once it's light outside ;)

Answer 1

Depending on your siding material, it is possible that the door isn't properly flashed, or the existing flashing needs replacement/repair. If this is the case, I would recommend two things

1) using some expanding foam, fill (but dont over fill!) the void between the door frame and the surrounding studs.

2) Properly flash around the door to make sure water can't get behind the door frame. Depending on the flashing material used, this may involve some caulk to seal the flashing (though peel and stick flashing won't require any caulk, and is quite easy to work with).

I am going to leave the info about the flashing, as it might be helpful to others, but in regards to your re-worded question-

Depending on where the water is coming in, you might need to either replace the rubber gasket/seal that fits to the outside of the door stop (if water is coming in on the sides/top of the door) or you may need to replace the door sweep (the rubber or bristle bit that hangs down from the bottom of the door itself, and seals everything shut when the door closes).

Answer 2

You need either, a new frame seal, door realignment or a weather/rain bar fitted to the bottom of the door. A rain bar diverts any water, that runs down the face of your door, away from the gap between the door and frame and onto the floor outside. If its getting in the sides of the door and running down then its probably a new seal or realignment.