How to Stop Drafts Under Doors: Weatherproofing Guide

Quick summary: Drafts under doors happen because of worn seals, warped frames, or gaps left by builders who assumed carpet would fill the space. Fixing it usually takes under an hour and costs less than $40. This guide covers measuring the gap, fitting a door sweep or threshold seal, using door snakes for quick relief, and knowing when the problem is actually a hinge or frame issue that needs a professional.

Why Drafts Form Under Doors

Most Australian homes lose a surprising amount of heat through gaps most people never think about. Under-door gaps are one of the biggest culprits, especially in older weatherboard or brick-veneer homes where doors were hung decades ago with different flooring underneath.

A gap as small as 10mm under an external door is roughly equivalent to leaving a window cracked open all winter. That's not an exaggeration — building researchers have compared it to a small open window in terms of airflow.

Common Causes of Door Gaps

A few things usually cause the gap:

• Flooring changes — if you've swapped carpet for floating floorboards or tiles, the door now sits higher above the floor than it used to.
• Worn or missing door sweeps — the original rubber or brush strip has perished or fallen off.
• House settling — frames shift slightly over years, especially on timber-framed homes.
• Warped doors — timber doors exposed to sun and moisture can bow, creating gaps along the sides too.
• Cheap builder-grade doors — project home doors are often hung with generous clearances to avoid sticking, which looks fine but lets air through.

Once you know which of these applies to your door, the fix is usually straightforward.

Tools and Materials You'll Need

You don't need a tradie's toolbox for this job. Here's what covers almost every scenario:

• Tape measure
• Pencil
• Hacksaw or hobby saw (to trim sweeps and seals to width)
• Screwdriver (if fitting a screw-on sweep)
• Scissors or a sharp utility knife
• Door sweep, threshold seal, or door snake
• Self-adhesive weatherstripping foam or V-strip

Budget roughly $15–$45 depending on which product you choose. A basic adhesive door sweep starts around $12, while a proper aluminium threshold seal with a rubber insert can run $35–$60 for a standard 820mm door.

Shopping at Bunnings for Weatherproofing Supplies

Bunnings is the easiest one-stop option for this job. Look in the hardware aisle under "weatherstripping" or "door seals," not with the door hardware itself — they're often shelved separately.

Good options to check out in-store or online:

• The Raven RP55 door seal is a well-known Australian brand sold widely and works for both timber and aluminium doors.
• A self-adhesive door draft stopper strip is the cheapest fix if you're renting and can't drill into the door.
• For a long-term fix, the aluminium threshold door seal with rubber insert handles high-traffic doors like front entries well.

Total Tools and Mitre 10 carry similar ranges, but Bunnings generally has the widest in-stock selection and you can usually find a staff member in the hardware aisle who's fitted a few of these themselves.

How to Measure the Gap Under Your Door

How do I measure the gap under my door for a draft stopper?

Close the door fully and use a tape measure or a folded piece of paper to check the gap at three points — left, centre, and right. Doors aren't always perfectly level, so the gap often varies across the width.

Take the largest measurement as your guide. If the gap is:

• Under 6mm — a basic adhesive foam strip or brush seal is enough.
• 6–15mm — a standard door sweep (brush or rubber blade style) is ideal.
• 15mm or more — go for a threshold seal with a drop-down or compression seal, as a standard sweep won't bridge the gap properly.

Also measure the full width of the door (most standard Australian internal doors are 820mm; external doors are often 820mm or 2040mm height). Buy slightly oversized and trim to fit rather than guessing short.

Step-by-Step: Installing a Door Sweep

This is the most common fix and works for the majority of homes.

1. Close the door and mark the gap height on the inside face, about 10mm above the floor.
2. Measure the door width and transfer that measurement to your sweep.
3. Trim the sweep to size using a hacksaw for aluminium-backed sweeps, or scissors for flexible vinyl ones.
4. Peel and stick, or screw in place — adhesive sweeps are faster, but screw-fit versions last longer under heavy use.
5. Open and close the door a few times to check it doesn't drag on carpet or floorboards.
6. Adjust the height if needed — most quality sweeps have slotted screw holes for fine-tuning.

How do I stop cold air coming under my front door specifically?

Front doors cop more wear than internal doors, so pair a door sweep with a threshold seal for the best result — the sweep handles the door-side gap, the threshold seal handles the floor-side gap. Together they seal both halves of the join.

Using Door Snakes for Quick Fixes

Do door snakes actually work to stop drafts?

Yes, for a cheap and temporary fix, door snakes genuinely help. They're the fabric tubes filled with sand, rice, or polystyrene beads that sit against the base of the door.

They won't fix the problem permanently and need to be manually placed and removed every time you use the door, but they're ideal for:

• Rental properties where you can't drill or stick anything to the door
• Rooms you don't walk through often (spare bedrooms, studies)
• A same-day fix while you wait for proper sweeps to arrive

You can buy one for around $15–$25, or make one yourself with a sock, dried rice, and a needle and thread — genuinely a 10-minute job.

Fitting Threshold Seals for Long-Term Sealing

What is the best way to seal a gap under a door?

For external doors, a threshold seal is the most effective long-term solution. These are screwed to the floor directly under the door and have a raised rubber or silicone strip that the door closes against.

To fit one:

1. Remove any old threshold strip first, including old screws and adhesive residue.
2. Measure the door width and cut the new seal to size with a hacksaw.
3. Position it so the door closes snugly against the rubber insert without dragging.
4. Pre-drill pilot holes if you're fixing into tile or concrete.
5. Screw down firmly, then test the door swing several times.

This combination — sweep plus threshold seal — is what most energy auditors recommend for external doors, and it typically cuts noticeable draft within a single afternoon's work.

Sealing Side and Top Gaps with Weatherstripping

Don't stop at the bottom. Gaps along the sides and top of the door frame let just as much air through, especially on older doors.

Self-adhesive foam strips or V-strip weatherstripping press into the gap between the door and frame. Clean the frame surface with methylated spirits first so the adhesive actually sticks, then run a continuous strip along the frame where the door meets it when closed.

When to Call a Professional for Door Adjustments

When should I call a professional to fix a drafty door?

Most draft problems are DIY-friendly, but call a carpenter or handyman if:

• The door is visibly warped or bowed and won't sit flush in the frame
• The frame itself has shifted and the door no longer closes squarely
• Hinges are worn or sagging, causing uneven gaps top to bottom
• You've fitted a sweep and seal but the door still doesn't close properly or drags badly

A tradie visit for a door adjustment typically costs $80–$150 depending on your area and how much planing or rehanging is needed. It's worth it if a $20 sweep keeps failing because the underlying door problem hasn't been fixed.

Maintaining Your Door Seals Over Time

Rubber and foam seals degrade with sun exposure and daily use. Check them every six months, especially before winter:

• Press the seal — if it feels flat or cracked instead of springy, it's time to replace it
• Reapply adhesive strips if edges start lifting
• Lubricate threshold seal hinges or drop-seal mechanisms with a silicone spray
• Repaint or reseal exposed timber doors annually to prevent warping

A $15 sweep replaced every couple of years is far cheaper than the heating bills lost to a gap you've stopped noticing.

Bottom Line

Stopping drafts under doors is one of the cheapest, highest-return weatherproofing jobs you can do in a weekend. Measure your gap, match it to the right product, and fit a sweep or threshold seal properly rather than relying on a draft snake forever. For most homes, a $40 trip to Bunnings and an hour with a screwdriver is all it takes to notice a real difference in comfort — and on your next power bill.