Exterior Door threshold sealant or sill: HOW to install it

A door threshold sealant is in essence a piece of metal, wood or plastic that closes the gap between the floor and your door.

A door seal can wear out over time. The seal can get compressed, bent, or ripped. You would want to put new weather seals ASAP. Otherwise, the chilly wind or hot air from outside can flow into the room. Or if you have an AC, the air of the cool room will flow out, leaving you feeling hot.


Sealing a door threshold is not a very difficult job. You have to measure the door to cut the sealant to size. Once this is done, you can use a screwdriver to hold this part in place. To fill in the gaps that your door has, you have to use an expanding foam sealant or silicone.

This article aims to give you all the knowledge you must have to seal a door threshold. 

Why seal a door threshold?

You don’t necessarily have to seal a door threshold, but it is always better to do so, especially for an exterior door. Putting a sealant over the door threshold will reduce the airflow from outside or between rooms. Your AC will not need to work harder to maintain a comfortable room temperature. It is best to opt for a metal weatherproof sealant as they are more durable. These are more expensive though. 

Additionally, an exterior door threshold sealant stops water to come inside your home. This also saves the floor from getting damaged. Therefore, a sealant also protects the interior of the home.

How to seal an exterior door threshold properly?

It is wise to seal your exterior door threshold after you have installed it. It will stop air, water, and moisture to seep in and cause any damage inside your home. While adding a door threshold sealant, you must do it properly to create a strong seal. Follow the given steps:

Measure the gap

First, you have to measure the length and width of the threshold area. And of course, you have to measure the gap between your door and the floor. Take precise measurements. If you measure inaccurately, the door threshold strip will come off sooner or later. The seal should fill in even the tiniest gap, or the threshold will be useless. 

Get a threshold strip

Second, purchase a new threshold. The measurements that you took will help you in buying a new strip. Home improvement stores sell thresholds in the standard sizes. You can also go to a lumberyard to get it cut according to the required size. Purchase a metal or wood threshold. If you need a little help with your decision-making, we would suggest you go for a metal threshold. It will be more weather-resistant, whereas water can damage a wooden threshold. 

Some thresholds can be installed on the door itself if you have a wooden door. This can make it easier to install everything but damages your door and is less durable.

Remove the old threshold

Third, you have to remove the old threshold from the door. Remove the screws which were used to set the old strip. Remove the entire threshold strip with the help of a pry bar. Be careful that you don’t damage the door or floor though. If your door has a rubber weather-stripping installed, you should remove that too. 

You can use a mop and towel to remove the dirt and dust. You can also use a degreaser and scaper to remove the old glue.

For an exterior door, you can check if the metal sill pan is still looking good or has to be replaced as well.

Start floor/placement marking

After you have removed the old seal, you have to make marks on the floor where you will put the new threshold. You can cut the strip with a pair of scissors or a hacksaw. Then you have to place the new threshold on the marks and make pilot holes with a drill.

Affixing the weather strip

You have to firmly attach the weather strip right in the middle of the threshold.

We have already mentioned expanding foam as an option. But you should first consider using urethane or silicone for the indoor threshold.

If you are looking for a suitable sealant for your exterior door threshold, you can also use a silicone caulk. More importantly, whatever you use as a sealant, it should ideally be a good-quality weatherproof material.  And along with the sealant, you can also put a weatherproof strip along the threshold. 

For a garage, you can use a rubber strip. These are quite heavy but can last a long time. In most instances an adhesive is used to keep them in place.

Do not test the door before you have given the caulk enough time to dry up. Otherwise, the caulk will be dislodged. Hence, you will break the seal even though you may not be able to understand it immediately. 

Test the door

After you have let the caulk have plenty of time to cure, you should test the door. Check whether the door is opening and closing without any dragging. You will most likely not be facing this problem if you have taken accurate measurements. 


So there, you now know everything about how to put a door threshold sealant. You can start getting ready to seal your door threshold. Additionally, you must keep two things in mind before you start the project. The first is to see the weather prediction and work on a day when there will be no chance of any rainfall. You should get started on a sunny day. This is when you will be sealing an exterior door threshold. 

And if you will apply the door sealant at a place that has a considerable footfall, you need to plan ahead. Think of a time when the footfall will be at its minimum. Any sealing adhesive will take anywhere between half an hour to an hour to dry. And if you are using a rubber seal adhesive, you have to give it a day or two to set.