A draughty gap at the bottom of an exterior door is one of the most common sources of heat loss in New Zealand homes. The good news is that sealing it is a straightforward DIY job that can make a noticeable difference to your comfort and heating bills — and in rental properties, it may also be required under the Healthy Homes Standards.
Why the Door Bottom Matters
Cold air sneaking under an exterior door doesn't just cause discomfort — it forces your heating system to work harder and can introduce moisture, which contributes to condensation and mould. Energywise notes that draught-stopping is one of the simplest and most cost-effective ways to improve home energy efficiency. For landlords, the Tenancy Services Healthy Homes Standards require rental properties to be draught-stopped, so gaps at door bottoms must be addressed.
Choosing the Right Seal
There are several product types suited to different door styles and thresholds. Choosing the right one depends on your door material, how much clearance you have, and whether you have a step or a flat threshold.
| Seal Type | Best For | Notes |
|---|---|---|
| Door sweep | Most hinged doors | Screws to the door face; suits uneven floors |
| Automatic door bottom | Timber or aluminium doors | Drops a seal when door closes; lifts when opening |
| Threshold seal / weather bar | Doors with a step | Fitted to floor; door closes against it |
| Draught excluder brush strip | Slight gaps, internal use | Easy fit; less durable for exterior use |
| Combined threshold + door bottom | High-traffic exterior doors | Best weather performance |
For New Zealand's variable climate — particularly in wetter regions like the West Coast, Northland, or Wellington — look for seals rated for exterior use with UV-resistant and moisture-tolerant materials such as EPDM rubber or aluminium-backed brush seals.
What You'll Need
Step-by-Step: Fitting a Door Sweep
1. Measure the Door Width
Measure the full width of the door at the bottom. Most sweeps come in standard lengths and can be cut down with a hacksaw.
2. Check the Gap
Close the door and slide a piece of paper underneath. If it moves freely, you have a gap worth sealing. Note whether the gap is even across the full width — an uneven gap may mean the door has dropped or the floor is uneven.
3. Trim the Seal to Length
Cut your door sweep to match the door width exactly. Deburr any sharp edges with sandpaper.
4. Position and Mark
Hold the sweep against the interior face of the door, flush with the bottom edge. The rubber or brush fin should just contact the floor when the door is closed — not drag heavily, which causes premature wear. Mark the screw hole positions with a pencil.
5. Drill Pilot Holes and Screw in Place
Drill pilot holes to avoid splitting timber doors, then screw the sweep firmly. Check the door opens and closes smoothly.
6. Test for Draughts
Close the door and check with your hand or a piece of paper. On a windy day you'll notice the difference immediately.
Fitting a Threshold Weather Bar
If your door closes onto a flat surface with no existing threshold, a weather bar screwed to the floor can create a seal the door closes against. Ensure the bar height doesn't create a trip hazard — keep it as low as practical and consider a ramped profile if mobility is a concern.
What If the Door Itself Is the Problem?
Sometimes the gap is caused by a dropped or warped door rather than a missing seal. Signs include:
- The gap is much larger on one side than the other
- The door drags on the floor at one corner
- The door no longer latches properly
A dropped door may need its hinges tightened, shimmed, or the door re-hung. A badly warped door may need replacing. These jobs are best handled by a qualified joiner — you can find local joiners on tradedirectory.co.nz.
Does This Require a Building Consent?
Fitting a door sweep or threshold seal to an existing door is routine maintenance and does not require a building consent. However, if you are replacing the entire door unit or making changes to the door frame or surrounding structure, check with your local council — some work may fall outside the Schedule 1 exemptions under the NZ Building Code. MBIE Building Performance has clear guidance on what requires consent.
When to Call a Professional
Call a qualified joiner or carpenter if:
- The door has dropped significantly and needs re-hanging
- The door frame is rotten or damaged (common in older NZ homes with timber weatherboards)
- You're replacing the entire door unit, which may involve structural or weathertightness considerations under NZ Building Code clause E2 (External Moisture)
- You're unsure whether the work requires a building consent
A Licensed Building Practitioner (LBP) should carry out or supervise any restricted building work. Check credentials at Licensed Building Practitioners.
