Fitting a draught excluder to the bottom of an exterior door is one of the most cost-effective DIY jobs a homeowner can tackle. It takes a couple of hours, requires only basic tools, and can make a noticeable difference to warmth and energy bills — especially in New Zealand's cooler southern regions or draughty older homes.
Why Bother with a Door Bottom Seal?
Gaps under exterior doors are a major source of heat loss and cold air infiltration. For rental properties, landlords should be aware that Tenancy Services' Healthy Homes standards require adequate draught stopping, so sealing door gaps isn't just about comfort — it may be a legal obligation. For all homeowners, Energywise notes that draught-proofing is one of the simplest and cheapest ways to improve home energy efficiency.
Types of Draught Excluder
Choosing the right type for your situation makes the job much easier:
| Type | How It Works | Best For |
|---|---|---|
| Automatic door bottom seal | A spring mechanism drops a rubber or brush seal when the door closes | Doors with a threshold or rebate; high-traffic doors |
| Surface-mounted brush strip | A flexible brush seal screwed to the door face or bottom edge | Uneven floors; sliding or French doors |
| Threshold seal / door sweep | A rubber or vinyl wiper fixed to the floor threshold | Doors with a small gap and a flat threshold |
| Foam or rubber self-adhesive strip | Adhesive-backed foam compressed when door closes | Temporary fix; low-traffic internal doors (less durable outside) |
For most NZ exterior doors, a surface-mounted brush strip or an automatic door bottom seal gives the best long-term result. Self-adhesive foam strips tend to deteriorate quickly in outdoor conditions.
You'll find a good range of options at Bunnings or Mitre 10.
Tools and Materials You'll Need
- Tape measure and pencil
- Hacksaw or tin snips (to cut metal-bodied seals to length)
- Cordless drill or screwdriver
- Sharp utility knife
- Sandpaper (80–120 grit)
- The draught excluder of your choice
- Screws (usually supplied with the product)
Step-by-Step: Fitting a Surface-Mounted Brush Strip
1. Measure the Door Width
Measure the full width of the door at the bottom. Most brush strips come in standard lengths (typically 900 mm or 1000 mm) 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 floor is level — an uneven floor may mean you need a flexible brush rather than a rigid rubber wiper.
3. Prepare the Door Surface
Lightly sand the bottom edge of the door where the seal will sit. Remove any old paint flakes, dirt, or remnants of previous seals. Wipe clean with a damp cloth and allow to dry.
4. Cut the Seal to Length
Mark the seal to your measured door width. Cut carefully with a hacksaw, keeping the cut square. Deburr any sharp metal edges with sandpaper or a file.
5. Position and Mark Screw Holes
Hold the seal against the door bottom (on the inside face for most brush strips). The brush or rubber wiper should just touch the floor when the door is closed — not drag heavily, as this causes premature wear. Mark the screw hole positions with a pencil.
6. Drill Pilot Holes
Drill pilot holes at your marks. This prevents the door timber from splitting, especially in older rimu or pine doors common in NZ homes.
7. Screw the Seal in Place
Fix the seal with the supplied screws. Don't overtighten — snug is enough. Check the door opens and closes smoothly.
8. Test the Seal
Close the door and repeat the paper test. You should feel resistance when pulling the paper out. Check along the full width for any remaining gaps.
Fitting an Automatic Door Bottom Seal
Automatic seals are slightly more involved but give an excellent result. The seal body is mortised or surface-mounted into the door edge, and a plunger contacts the door frame or stop when the door closes, pushing the seal down. Follow the manufacturer's template carefully for mortised types. If you're not confident routing a mortise, a surface-mounted automatic seal is easier and still very effective.
Tips for a Good Result
- Check the door frame and threshold too — sealing the bottom is pointless if the sides and top are also leaking. Consider a full draught-sealing kit.
- Paint or prime exposed timber on the door bottom edge before fitting the seal to protect against moisture — important in NZ's wet winters.
- Allow clearance for floor coverings — if you're planning to add a mat or new flooring, account for the extra height.
- For timber doors, BRANZ has useful guidance on maintaining exterior joinery to prevent moisture and draught issues.
When to Call a Professional
Fitting a draught excluder is generally straightforward DIY work and does not require a building consent under Schedule 1 of the Building Act — but always confirm with your local council if you're unsure. However, call a qualified carpenter if:
- The door itself is warped, swollen, or badly fitted — a draught seal won't fix an underlying door alignment problem.
- The door frame or threshold is rotten and needs replacement.
- You need a mortised automatic seal fitted and aren't confident with a router.
- The door is a fire door — modifications to fire doors must comply with the NZ Building Code and should be done by a professional.
You can find experienced local carpenters on tradedirectory.co.nz who can assess your door and recommend the best solution.
