Question: What is the best type of weather strip product to use on the bottom edge of an overhead garage door? The door is for a two car garage. The concrete floor is split down the middle (expansion joint), and that small space allows lots of air to enter the garage. The original weather stripping is a bit old and worn as well. Appreciate your help!
Answer: The standard these days is a thick soft rubber "garage door bottom seal" or weather strip made just for this application, as shown in Figure 1. You can find it at a big box home improvement stores labeled in very similar terms. It has a cross section sort of like a "L" whose angle is more oblique than 90--The long part of the L rests flat against the door bottom and gives you a wide nailing or screw strip, and the shorter part of the "L" contacts the ground and has enough cushion to seal against variations in the concrete. Ice, mud and/or sand will shorten its lifespan.
It will be rolled up in a bag and available in 16 foot lengths, don't pull it too tight as you fasten and trim the overall length to fit, to give you a continuous seal along your door bottom.
If there is more than 3/8" variation (for instance it has no crack on one end, and a large gap on the other) in the crack under your door, your door may need some adjustment.
If that gap at your expansion joint is very large, you might consider tapping a small piece of cedar shim or some other relatively soft material down between the slabs to partially fill the gap. The idea would be to leave it flush with the surface of the concrete to give the weather strip a contact area and to make sure it won't be disturbed by tire and foot traffic.