Here is how you can achieve a great and long lasting weatherstripping.
Stop and think!
Weatherstripping is 95% design and 5% actual installation. Resist the urge of picking up a random gasket next time you visit a hardware store. Avoid glueing, nailing or screwing anything before you have assessed the situation and proven that there is no other solution.
The best way to figure out which weatherstripping product will best seal is to inspect the opening for built-in weatherstripping holders. Most doors manufactured in the last 30 years have been designed with weatherstripping in mind and most of them have a gasket holder. Hardware store (physical and internet stores) sell a large selection of gaskets designed for most popular doors. Use them because they’ll give the best seal, hold well and last long.
In my case, the built-in mecanism is a long opening designed to receive a vinyl clad gasket. If the previous owner looked at the dor jamb for 15 seconds, he would have noticed it and installed the right gasket. The left picture below is not from the same door but has a very similar kerf for gasket. The right picture shows the section of the adequate vinyl clad which will fit in the opening and seal the door appropriately.
The white part is made out of rigid pastic and goes in the kerf while the v-shapped black part get compressed when the door closes and seals the gap.
If there is no obvious holder for weatherstripping and there is already a weatherstripping solution, remove the old weatherstripping. The holder may hide behind existing weatherstripping. Sometimes, holders may hide behind several coats of paint. If you can’t find any holder, try to find the name of the manufacturer and look up online for the best gasket type. It is easier than it sounds.
If you really cannot identify the right type of gasket or if the door is not designed to receive a gasket (possible in very old houses), visit weatherstripping manufacturers’ web sites (for instance M-D) and look at your options. Prefer a screwed / nailed solution (more sturdy) than a glue on solution.
In my case, it was longer to remove the glue left by the inadequate weatherstripping than it was to install the new gasket. Here are a few views of the result:
The top corners are butted. The kerf on the jamb goes all the way up to the jamb while the kerf on the top stops 1/4 inch so I butted the gasket to follow this pattern (see right picture).
Sometimes, finding and installing the adequate gasket is not enough. In my case, the lock’s striker plate was installed too far away for the door to compress the gasket appropriately. The bad weatherstripping was interfering with the operation of the door and instead of fixing the real problem, the previous owner compensated for it by moving the striker plates. Once the plates were moved, the door closed fully and compressed the gasket adequately to form a tight seal.