How Do You Stop Water from Coming in Under Door (Threshold)

Two of the most common problems homeowners often deal with in relation to exterior/front doors are water leaks and cold drafts. The first of these two issues is rather concerning, as it can trigger a host of structural and health issues. Here’s an in-depth guide on how you can put an end to water leaks through the bottom part of your exterior doorways.

Why is water coming in under door threshold?

The consequences of water leaking through the bottom of exterior doorways can be quite costly. For starters, you may have to pay a lot to refinish your interior floor. This usually happens as water leaks through the doorway during storms and pools up on the floor surface. And if the exterior door happens to be on an upper floor (such as a balcony door), it can cause structural damage to the ceiling beneath it.

So, just why would water be leaking under your door? Well- the problem lies with the threshold. If the threshold plate lies too low, or is poorly bedded, water is more likely to seep under the door and into the house.

Sometimes, you may still have water leaks even when the threshold plate is installed to the appropriate height. That’s probably because the fastener holes on the threshold plate aren’t properly sealed.

Additionally, it’s not practicable to install a threshold that totally seals the gap beneath the door. A tiny gap is still needed to allow for opening and closing of the door without the frame getting stuck on the threshold.

By finding fixes for all the above causes, you can effectively stop water from seeping into your house through the front/exterior door.

How to Stop Water from Coming in Under the Door

Replace your Door Threshold

One of the most common solutions that professionals often recommend is the replacement of the door threshold plate. While you can choose to re-anchor a door threshold that wasn’t properly bedded the first time it was installed, replacing it with a new one that’s properly measured out might be a better solution. To replace your door threshold, follow the steps detailed below:

Gather the Tools Needed

One thing most DIY-ers often disregard but’s very important is to gather all the equipment and supplies needed for door threshold installation projects in one place before starting out. This saves you time as you don’t have to move back and forth fetching stuff as you try to work. For this project, you’ll need the following:

  1. A drill and drill bits.
  2. Caulk and a caulk gun.
  3. Screw fasteners.
  4. Paper towels.
  5. A wet mop/ vacuum cleaner.
  6. Sealant.

Prep the Area

Before removing the current threshold and installing a new one, undertake some prep work. You probably have water and debris from recent storms still lying on the inner side of the exterior doorway. Removing built-up dirt around the door area ensures that the sealant sticks better to the threshold plate. You’ll, therefore, want to mop up all of this dirt, standstill water, and grime from the door threshold and the door sill.

Remove the Old Threshold

Now, take out the existing threshold by unscrewing it open. Once the threshold plate is out, clean out the area below it too using a vacuum cleaner.

Create Pilot Holes

After prepping the area and removing the old door threshold, proceed to drill pilot holes through the new threshold plate using a drill and a suitable drill bit. Pilot holes allow the threshold to firmly attach to the flooring or door sill underneath it. Professionals recommend drilling the holes at least six inches apart.

After drilling the pilot holes through the threshold, drill some more through the door sill or floor area on which the door threshold will sit. Ensure to match the placement/spacing of this second set of pilot holes to that of the first set that you’d drilled on the threshold plate. This will allow for a perfect fit.

The type of drill bit you should use depends on the type of material you’re drilling through. For instance, a standard drill bit will work just fine on wooden thresholds and wooden door sills/floors. Meanwhile, for metallic thresholds, a titanium drill bit is the most effective. Finally, concrete/stone floors and door sills call for a masonry drill bit.

Apply Sealant/Caulking

To stop water leaks through the bottom of your door threshold, apply caulking to the area. For about $10, you can easily purchase a transparent caulk sealant online. Not only will it effectively make the lower part of the threshold watertight, but also preserve your doorway’s aesthetics as it won’t yellow after curing.

Install the threshold Plate

Next, replace the door threshold to the floor or door sill below it. To do this, use a screw gun to drive screw fasteners through the pilot holes that you’d drilled earlier. You’ll want to ensure that you’re driving in the screws in as vertical a position as possible. Angled fasteners tend to leave gaps that allow for water leaks through the exterior door during downpours.

As the screws firmly fasten the threshold to the surface below it, excess caulking that you’d earlier applied to the area may seep through the edges. Wipe this off using a piece of old clothing or a paper towel.

It’s also important to note that if the new threshold sits too low to effectively close up the gap, you can install shims in the space between the floor/door sill before installing the threshold. This will allow the threshold to sit higher and properly shrink out the gap below the door.

Apply Final Coats of Sealant

After properly replacing the threshold, finish off the job by applying a liquid rubber sealer. Ensure to spray the sealer along the inner edge of the threshold and along the edge where you’d applied caulking as well. When purchasing sealant, consider the curing times. Sealers that dry faster are preferable as it allows you can apply additional coats faster after the first coat cures. This ensures that you can complete your doorway threshold project sooner.

Install Weatherstripping

Another effective way to stop water from leaking indoors through the bottom of the door is by installing weatherstripping underneath it. One of the easiest and fastest ways to gasket under your door is by installing a door sweep. Typical American doorways usually have a 1/8-inch gab between the top of the threshold plate and the bottom of the door frame. Mounting a door sweep under the door will effectively close this gap.

To effectively weatherproof the bottom of an exterior door using sweeps, we recommend the steps below:

  1. Before buying a door sweep, measure out the size of the gap between the bottom of the door frame and the bevel of the threshold. This ensures that you’ll purchase a sweep that fits.
  2. After finding the accurate gap size, it’s time to buy a door sweep. You can either go for a U-shaped sweep or a metal sweep. The former slides under doorways to seal the gap, while a metal strips can be fastened to the bottom of the door frame by stapling, screwing, or nailing it down.
  3. Next, install your door sweep. Mounting a U-shaped door sweep is easy, as all you have to do is slide it into place. Installing a metal strip door sweep, on the other hand, can be quite tricky. First, you have to take the door off its hinges for easier access to the bottom of the frame. Then, you need to drill matching pilot holes through both the metal sweep and the bottom of the door. Finish off by driving screws through the pilot holes to fasten the metal strip to the door.
  4. Finally, test your door sweep to ensure that it doesn’t cause your door to get stuck as you open and close the door. If you went for DIY installation and are experiencing this problem, you may have to call in a professional.

An even better alternative to a door sweep is an automatic door bottom. This type of weatherstripping is adjustable. Thus, when you close your exterior door, it automatically drops to seal the gap. It then retracts as you open the door, preventing the door from binding to the threshold bevel.

Can you waterproof a door bottom?

To make the bottom of your exterior door or patio door watertight, install reinforced weatherstripping that features waterproof foam construction. Felt weatherstripping or open-cell foam weatherstripping is not recommended, as they don’t offer enough protection against the elements.

Does sealing an exterior threshold prevent storm water?

Remember, a door threshold and bottom door weatherstripping work to shrink the space beneath the door as much as possible. This helps keep out critters, dirt and dust. They don’t- however- make the lower part of the door 100% waterproof.

You can, therefore improve the door’s capability to keep off storm water by sealing around the edges of the threshold and weatherstripping. And it’s not just storm water that you’ll be keeping out. A strong seal around your exterior threshold will also help keep out cold drafts during winter.


Take note that for commercial structures, some building codes restrict the installation of threshold plates that are above a certain height. This is to allow for better building accessibility by disabled persons. If you’re a property owner, you’re probably looking for a way around the water leak issue without going against the building code. We recommend installing weatherstripping, canopies, overhangs, or awnings to minimize the water leak problems.



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