Cold air across the floor. A puddle after every storm. A gap under the door you can see daylight through. Nine times out of ten the culprit is not the door, the weatherstripping, or the lock. It is the threshold: the metal or wood sill the door closes down onto. In Toronto and across the GTA it takes the worst of the freeze-thaw cycle, road salt, and standing water, and it is the single most overlooked part of an exterior door.

This guide covers how to tell whether your threshold needs adjustment or full replacement, what the job actually involves on residential and commercial doors, what drives the price, and when it is worth calling a technician instead of buying a big-box kit.

What a door threshold actually does

The threshold is the horizontal piece that runs along the bottom of the door frame. On a modern exterior door it is usually an aluminum extrusion with a wood or composite core and an adjustable cap, paired with a rubber or vinyl door sweep on the door itself. Together they form the seal that keeps out air, water, dust, and pests.

An adjustable threshold has screws under the cap that raise or lower it. Over a few winters those screws seize, the cap sinks, and the sweep no longer makes contact. That is when the drafts start.

Signs your threshold needs attention

You can see daylight under the closed door

The simplest test there is. Close the door, turn off the lights in the room, and look along the bottom. Any visible light is a gap, and a gap that lets light through lets air and water through too.

Water pools inside after rain or snowmelt

This is the one that turns into an expensive problem. Water that gets past the threshold soaks the subfloor and the bottom of the jambs. Left alone it becomes frame rot, which is a much bigger repair than a sill swap.

The door drags or scrapes when it closes

A threshold cap that has been cranked too high, or a sill that has heaved with the frost, will catch the bottom of the door. If you are also fighting a door that sticks or jams, the two problems are often the same problem.

The metal is pitted, split, or lifting at the ends

Road salt eats aluminum. Once the cap is pitted or the ends are curling up, adjustment will not save it. That threshold is done.

Heating bills climb every winter

A quarter-inch gap along a 36-inch door is roughly the same as leaving a fist-sized hole open in the wall all season. It shows up on the bill, and it is one of the classic Toronto winter door problems.

Adjust, repair, or replace? How we decide

Adjustment

If the threshold is structurally sound and only the cap has dropped, backing the adjustment screws out a few turns can restore the seal in minutes. Do it in small increments and test the door after each turn. Raise it too far and the door binds.

Sweep or seal replacement

Often the threshold is fine and the door sweep has gone hard and cracked. Swapping the sweep and refreshing the perimeter seals is the cheaper fix, and it pairs naturally with weatherstripping replacement.

Full threshold replacement

Replacement is the right call when the sill is rotted through, the aluminum is corroded or split, the substrate underneath has gone soft, or the threshold was the wrong size for the opening in the first place. On steel doors and wood doors alike, a bad sill will keep damaging the bottom rail until it is dealt with.

What the job involves

1. Assess the opening. Check the sill for rot, measure the width and depth, and confirm whether the jambs are sitting on the threshold or beside it.
2. Remove the door if needed. On most residential doors we can work with the door in place. On commercial units with heavy closers it usually comes off.
3. Cut and lift out the old threshold. The old unit is often caulked and screwed to the subfloor, and on older homes it may be nailed into a rotted sill plate.
4. Repair the substrate. This is the step DIY jobs skip. If the wood under the threshold is soft, the new one will fail the same way. Rot gets cut out and replaced before anything new goes down.
5. Set and seal the new threshold. Bedded in sealant, fastened, and caulked at the ends where water usually finds its way in.
6. Adjust and test. Cap height set so the sweep seals with the door closing smoothly, then a water and light test.

Residential versus commercial thresholds

On homes the priority is the seal: stopping drafts and water at the front, side, and back entries. That work sits under residential door repair, and often comes up alongside exterior frame repair.

On commercial entrances the priorities shift. Thresholds at storefronts and service entrances take constant traffic, carts, and salt. They need to be low-profile and firmly anchored, and on many properties they need to stay flush enough for accessible entry. If the threshold sits at a storefront entry or a fire exit door, a lifting or damaged sill is also a trip hazard and an inspection item. Commercial work runs through commercial door repair, and the 2026 commercial cost guide covers how these jobs get quoted.

Why Toronto is hard on thresholds

Three things do the damage here. Freeze-thaw cycling lifts and settles the sill plate under the threshold repeatedly through the winter. Road salt tracked in on boots sits on the aluminum and corrodes it. And spring melt puts standing water right at the doorway for weeks. That combination is why thresholds in the GTA fail faster than the manufacturer’s expected life, and why an annual look at the bottom of every exterior door is worth the five minutes.

What drives the price

Threshold work is quoted per opening, not off a flat rate, because two doors that look identical can be very different jobs once the old sill comes up. These are the factors that move the number:

Factor	Why it matters
Adjustment vs replacement	Resetting an adjustable cap is a short service call. A full swap is a half-day job.
Condition of the substrate	Sound wood underneath keeps it simple. Rot means carpentry before the new sill goes in.
Threshold type	Standard residential aluminum, heavy commercial saddle, or a low-profile accessible unit.
Door size and weight	Double doors and heavy commercial slabs take longer to remove and rehang.
Related repairs	Sweeps, weatherstripping, and jamb bottoms are frequently replaced at the same time.
Timing	Scheduled work costs less than an emergency call-out.

For a sense of how door work is priced across the board, see the residential door repair cost guide for 2026. For your specific opening, a photo and a two-minute call gets you a real number.

Can you do it yourself?

Adjusting an existing threshold is a reasonable DIY task. Two screws, a screwdriver, ten minutes. If that solves it, you are done.

Full replacement is a different story. The failure point in DIY threshold jobs is almost always the same: the old unit comes out, the substrate underneath turns out to be soft, and the new threshold gets fastened down onto rotten wood. Six months later it is loose and leaking again. If you pull the old one and find dark, spongy wood, stop and call. That is a frame repair, not a sill swap.

Frequently asked questions

How long does threshold replacement take?

A straightforward residential replacement is usually two to four hours. Add time if the sill plate needs rebuilding or the door has to come off and be rehung.

Can you replace the threshold without removing the door?

Often yes on residential doors. On commercial units with closers, panic hardware, or heavy slabs, taking the door off is faster and safer.

My door leaks only in heavy rain. Is that still the threshold?

Sometimes. Water in heavy rain can also be coming from a failed head seal, a damaged jamb, or missing flashing above the door. We check the whole opening rather than assuming.

Should I replace the threshold or the whole door?

If the door slab and frame are sound, replacing the threshold is far cheaper and solves the problem. When the frame itself is compromised, the calculation changes. Our breakdown of repair versus replacement on steel doors walks through how to decide.

Do you work on commercial buildings after hours?

Yes. We schedule commercial threshold and entrance work outside business hours so your entrance stays open during the day.

What about the gap at the sides, not the bottom?

That is the weatherstripping and often the strike alignment rather than the threshold. It is covered in our roundup of common door problems across the GTA.

Areas we cover

Ontario Door Repair services Toronto and the surrounding region, including Etobicoke, North York, Scarborough, Vaughan, Markham, Richmond Hill, Mississauga, Oakville and Hamilton.