How to Fix Gap Between Door and Floor (Front + Exterior Threshold)

If you’ve ever caught yourself getting increasingly worried by the size of the gap under your front door or exterior doors- you’re not alone. Neither are you overreacting. The size of the gap between the base of the door and the floor is an important consideration that can help you prevent various problems. In this article, we’ve detailed the correct way to fix or seal gaps between the door and the floor, and why you should even seal these gaps in the first place.

How big should the gap be under a door?

The appropriate gap size under a door depends on whether it’s an exterior or interior door. For exterior doors, you almost want no gap, as this helps to keep external elements like snow, cold air, and rain water from seeping into your house. Meanwhile, for interior doors that are hung above a floor that hasn’t been finished yet, the gap between the bottom of the door and the floor should be no more than 2-inches high.

However, if the floor has been finished, a gap that’s between 0.5- 0.75 inches will suffice. If the floor is not level- though- you may need a threshold height that’s slightly greater than 0.75-inches to prevent the interior door from rubbing against the floor finish as it swings.

The proper gap size under front and exterior doors allows for effective air return, which is crucial in homes with central Heating, Ventilation, and Air Conditioning (HVAC) systems. The gap allows for efficient airflow through the registers/ducts, consequently ensuring proper balance of the HVAC system. Proper airflow also prevents inefficiencies within your heating system, leading to lower energy bills.

How to fix a gap under a door

Improper gap sizes under doors- whether too large or too small- can lead to a variety of problems. With excessive threshold height, you may have to deal with chilly drafts, rainfall leaks, and critters and bugs creeping through the oversized gap and into interior rooms. What’s more, light from other rooms may illuminate too far into the next room if the gap under the door separating them is too large.

On the contrary- if the gap is too small- the door may jam as you try to close or open it. Fortunately, you can weatherstrip your doors or install door threshold plates to fix gap size issues between the doors and the floor, as described below:

Weatherstripping

Weatherstripping, also referred to as weather-sealing, is the process of sealing off gaps around and under doors to keep out the elements and keep internal air in. To effectively weatherstrip the base of the door and the door jambs, we recommend using door sweeps. There are several types available, including bristle-like sweeps, slide-on door sweeps, wrap-around door sweeps, and rubber door sweeps.

To effectively screw on a door sweep, first measure the width of the door and transfer the measurement to your door sweep with a marker pen. Next, using a hacksaw, cut out the sweep at the marked section and align it to the base of the door to close out the gap. Finally, fasten the door sweep to the door by driving screws through the pre-drilled attachment holes on the door.

If you’re a DIYer and prefer something that’s easier to install, consider a slide-on type of door sweep. After cutting the sweep to size, open the door and slide the sweep along the base. For larger gaps, a wrap-around door sweep is recommended. This type of sweep features flexible construction that enables it to curve around the bottom of the door and effectively close down the gap.

Installing a Door Threshold

Door thresholds are designed to be fastened directly to the floor and protrude upwards to effectively seal gaps at the bottom of door frames. This type of gap sealer is the most difficult to install. However, once placed in correctly, they’re the most aesthetically pleasing since they don’t look like add-ons.

To effectively install a door threshold after cutting it to size, place it under the door and fasten it by driving mounting screws through the pre-drilled holes. Finally, seal off the gap between the bottom of the door and the floor by sliding a gasket through the threshold channels.

Importance of sealing front and exterior door gaps

The most important reason why you should consider fixing the gaps on your front and exterior doors is to prevent cold drafts. Also referred to as air leaks, drafts enter the house through spaces on the window- and on the side and bottom of exterior doors. This cold incoming air causes the HVAC system to work more to heat internal air to the appropriate temperatures. This results in significant energy wastage.

Meanwhile, during summer, warm air coming in from outside through leaks at the base of the floor causes the home’s cooling system to spend more energy in cooling the house. According to the US Department of Energy, homeowners stand to save between 5-30% in annual energy expenses by taking the necessary measures to minimize air leaks. One of these measures- of course- is to seal the gaps under front and exterior doorways.

Apart from causing higher energy expenses, cold air from outside causes a drafty feel at the entryways to the house. This makes for an uncomfortable feeling as you enter or leave the house. One way to prevent your front and exterior doors from feeling cold to the touch is by weatherstripping them to seal off the gaps at the bottom of the doors.

The third reason why it’s necessary to seal off gaps at the base of front doors is to keep off dirt, dust, and debris from outside from finding a way through into the house. Dust particles present various problems. For starters, they can cause your flooring to scratch, necessitating costly repairs. A dirty, dusty floor is also breeding ground for disease-causing microbes.  

Finally, a drafty home can also be a breeding ground for bugs that thrive in cold weather. To keep off ants, spiders, cockroaches, and other type of cold-weather bugs from invading your home, consider sealing off gaps at the bottom of the door frames.

What material is best for door thresholds?

The best material for door threshold plates depends on what kind of flooring you have. For instance, if you have a concrete floor, the best type of door threshold would be one that features a rubber gasket, as it sticks well to the cement-based slab and is sturdy. This kind of threshold is not only strong and durable enough to withstand the weight of the door frame, but also heavier stuff like cars. That’s why rubber gasket-type thresholds are recommended for sealing off the bottom of garage entryways.

If you have wood flooring coming all the way up to your front and exterior doors, your best option would be to install wood thresholds. Timber thresholds are great for aesthetic effects, as you can match the grain of the wood on the thresholds to that of your wooden flooring. And that’s not all, this type of gap sealer can also be stained the same color as the wood floor.

Finally, for stone tile flooring- such as marble, granite, and travertine floors- aluminum threshold plates are the best option. This is because it forms an airtight seal when caulked and rubber gaskets can be slid through them to close off the gap between the base of the doors and the stone tile floor.

Take note that while door thresholds can be classified according to construction material, they can also be differentiated by structural design and general purpose/use. In this regard, there are saddle thresholds, heavy-duty thresholds, bumper seal thresholds, thermal break thresholds, and carpet dividers.

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