Cutting down on air infiltration in old houses without changing their character can be a challenge. For example, an aluminum threshold with a vinyl seal would certainly cut down on the air leaking under a front door. And it would be just as certain to look out of place.
The drawing shows a technique that we use to keep the wood thresholds in old houses while still cutting down on air leaks. First, we trim the bottom of the door to leave a 3/8-in. gap between the door and the threshold. Next, we cut a 1/2-in. by 1/2-in. groove in the bottom of the door. Then we secure a strip of EPDM rubber roof membrane in the groove. The strip is held in place by 2-in. screws run through a length of 12-ga. Romex wire. With screws about 4 in. apart, the Romex acts as a clamp, spreading out the holding power of the screws.
We trim the two protruding rubber strips so that they are each 1/2 in. long. They make an effective, inconspicuous (and easily replaceable) seal for the door that is also in keeping with the character of the house.
Don Mathis, Macomb, IN