Having a draft or cold air come through under your door can be annoying and uncomfortable. There are a few potential causes for this draft that are worth exploring.
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Gaps Around Door Frame
One of the most common reasons you may feel a draft coming under your door is gaps around the door frame. As a house settles over time, it can cause the door frame to shift and create small gaps between the frame and the wall. There may also be gaps between the threshold (the piece along the bottom of the door frame) and the floor. These gaps allow cold air to seep in from outside or from other rooms.
Gaps around the door frame are most noticeable around exterior doors, but can also happen around interior doors between rooms. The gaps tend to be larger at the top and bottom of the frame but can occur along the sides as well.
Checking for Gaps
You can check for gaps around the door frame by running your fingers along each side of the frame, feeling for any light coming through. You can also hold a piece of paper up to the edges and see if it moves from air passing through.
Gaps are easiest to detect with the door closed and then looking at the edges all the way around the frame. Be sure to check along both sides, the top, and the threshold at the bottom.
Fixing Gaps
If you find noticeable gaps in the door frame, there are a few options for fixing them:
- Apply weatherstripping – Self-adhesive foam or rubber weatherstripping can be applied along the door edges to seal gaps.
- Caulk around frame – Caulking gaps with acrylic latex caulk will seal out drafts.
- Adjust door in frame – For larger gaps, you may need to tighten hinge screws or re-hang door in frame.
- Replace threshold – Badly fitting thresholds can be replaced with a new, well-fitted one.
Sealing gaps around the frame is usually the most effective solution for eliminating drafts coming under the door.
Poor Door Fit
In addition to gaps around the frame, a poorly fitted door itself can also allow air to pass underneath. If a door fits loosely in the frame, it will have larger gaps when closed. Interior doors can develop a poor fit over time as their alignment gets thrown off through use and the house shifting slightly.
Checking Door Fit
You can check how well your door fits in the frame when closed by looking at the gaps around all sides. Close the door and look at each vertical edge, holding a piece of paper up to the gap. If the paper moves easily from air passing through, the fit is too loose.
Also check the gap at the bottom of the door under the threshold. Hold a piece of paper just above the floor and see if there is a substantial gap under the door.
Fixing a Poor-Fitting Door
If the door fits too loosely, there are some DIY ways to improve the fit:
- Sand top & bottom – Lightly sanding the top and bottom edges can help improve clearance.
- Plane door edges – Using a hand plane to take down high spots along the edges.
- Adjust hinge screws – Tightening or loosening door hinge screws can shift the alignment.
- Add shims – Adding thin wood shims under hinge screws can minimize gaps.
In some cases, the door itself may be warped or damaged and need replacement for the best fit. Installing a new interior door is a reasonably easy DIY project in most homes.
Lacking Door Sweeps
Another factor that can lead to a draft under doors is the lack of proper sweeps along the bottom edges. Door sweeps are vinyl, brush, or felt strips that seal the gap between the bottom of the door and the threshold or floor.
If you don’t have sweeps or old ones have fallen off, it provides an unobstructed path for air to flow under the door. This is especially an issue on exterior doors that lack proper sealing along the bottom edges.
Types of Door Sweeps
There are a few types of door sweeps that can be added to block drafts:
- Vinyl seals – Adhesive vinyl strips that stick into place to seal gap under door.
- Brush seals – Dense brush bristles sweep the floor under the door.
- Felt seals – Adhesive felt weatherstripping to seal small gaps.
Sweeps come in standard sizes for most interior and exterior doors. Make sure to measure the width of your door to get the right size sweep.
Installing Door Sweeps
Installing door sweeps is a very easy DIY project. To attach a new sweep:
- Clean bottom of door and threshold where sweep will be applied.
- Cut sweep to length of door width.
- Peel adhesive backing on sweep and firmly press to bottom of door.
- Ensure sweep makes solid contact with threshold when door is closed.
Adding door sweeps is an affordable and easy solution if you notice the draft seems to be coming from directly under the door itself.
Air Pressure Differences
Pressure differences between rooms or between indoors and outdoors is another common reason you may feel cold air coming in under a door. Even if the door has a tight seal all the way around, air pressure differentials can cause drafts.
Examples of Pressure Differences
Some examples where pressure differences commonly cause drafts include:
- Between a heated room and unheated attic or basement – Stack effect causes air to rise up in the house.
- Between a room with an exhaust fan and rest of house – Negative pressure sucks air under door.
- Between indoors and outdoors on windy days – Outdoor wind pushes air indoors.
- Between rooms with large air leaks – Air pushed from leaky to tighter room.
Even if there are no gaps around a door’s seal, this pressure differential can push or pull air under the door.
Minimizing Pressure Differences
To deal with drafts caused by different air pressure, you need to equalize the pressure on both sides of the door. This can be done by:
- Sealing other air leaks between the rooms.
- Adjusting ventilation systems to balance air flow.
- Installing make-up air systems.
- Adding a door sweep or gasket to provide tighter seal.
Achieving perfect air balance is difficult, but sealing major leaks can help minimize pressure differences and related drafts under doors.
Heating and Cooling Issues
Problems with your heating and cooling systems can also sometimes lead to noticeable drafts under doors. Issues like closed vents, imbalanced ductwork, and malfunctioning units can create temperature differences between rooms.
How Heating Issues Cause Drafts
Some examples of how heating and cooling problems lead to drafts include:
- One room not getting enough conditioned air from vents being closed.
- Ductwork leaks causing uneven air distribution between rooms.
- A/C issues making one room much cooler than others.
- Heater malfunctioning and not keeping one room warm enough.
These temperature imbalances then lead to air moving underneath doors from warmer to cooler areas.
Fixing Heating and Cooling Issues
To address drafts caused by HVAC problems:
- Make sure all vents are fully open.
- Have ductwork inspected for leaks.
- Change A/C filters regularly.
- Have heater serviced to ensure proper operation.
- Insulate doors to cooler rooms.
Ensuring your HVAC system is running optimally helps equalize temperatures and minimize drafts under doors throughout the home.
Conclusion
There are a variety of issues that can lead to feeling cold drafts coming from under doors, but the problem typically comes down to either air gaps or pressure differences. Carefully inspecting your doors and frames for leakage points, adding proper weatherstripping and sweeps, and addressing whole-house ventilation issues are the best ways to stop annoying drafts under doors.
With some diligent troubleshooting and DIY door sealing, you can successfully eliminate those chilly drafts and keep the heat where you want it this winter.