Allowing air to seep through a gap between the floor and the bottom of your front or back door is like throwing money to the wind. Don't waste your money; replace the broken, warped or deteriorated door threshold and seal the gap. Installing a new threshold strip is a cheap and effective solution.
Measure the gap between the floor and the bottom of the door. Then measure the width of the doorway. These numbers will be your reference when buying your new threshold strip.
Buy your new threshold strip. They are available at most home improvement and DIY ships. There are several types of thresholds, so know what you want. Do you want a wood or metal threshold for a door that already has weather stripping? Or an aluminium threshold with a weather strip in the middle? Check the height and length of the threshold strip to make sure it coincides with your door's gap and width measurements.
Remove the old threshold by unscrewing the strip from the floor. If the old threshold has rubber weatherstripping, pry out the rubber to expose the screws that hold the threshold to the floor.
Double-check the width of the doorway. Mark this measurement on the new threshold strip.
Use the appropriate saw to cut the threshold strip to size. Use scissors to cut the weatherstrip if included.
Lay the threshold on the floor to mark where you need to drill pilot holes for screwing the new threshold down. Check if the old threshold strip's screw holes can be used to hold down the new strip.
Install the threshold strip securely, then attach the weather strip if applicable.
Some wood thresholds can be adjusted to fit the gap between the floor and the bottom of the door. You may want to consider this for a door that has built-in weatherstripping.
When removing the old threshold avoid damaging the corners of the door jamb.
Use a foam sealant to fill any small gaps or cracks.
Always wear protective gear when using power tools.