Stand by your front door on a windy January day and you can often trace the draft with your hand — along the latch side, under the sill, through the corner. Every one of those leaks has a specific cause, and many have genuinely cheap fixes. Others are the door's way of telling you it's finished.
Here's the same diagnostic sequence we use, from easiest fix to full replacement.
Find the leaks first
On a cold or windy day, run your hand slowly around the door perimeter and note where you feel air. A lit incense stick works too — the smoke visibly bends at leaks. Common entry points: the latch-side edge (worn weatherstripping), under the door (sweep or threshold), the hinge-side corners (sagging door), and around the frame trim (missing insulation behind the casing).
Weatherstripping: the highest-value fix
Most modern doors seal with compression weatherstripping set in a groove (kerf) around the frame. It compresses millions of times, hardens with age and UV, and eventually stops springing back. Replacement kerf-style weatherstrip is inexpensive, and swapping it takes minutes per side once you have the right profile. If your existing strip is flattened, cracked, or paints-over-stiff, this is your first move.
Door sweeps and threshold adjustments
Light showing under the door means the sweep is worn or the threshold has dropped. Screw-on and slide-in sweeps are simple replacements. Many thresholds are adjustable — four or five screws raise or lower the sill cap so it just kisses the sweep. Aim for gentle contact: a threshold cranked too high wears the sweep out and makes the door drag.
When the door itself is the problem
If new weatherstripping still won't seal, the door or frame is likely warped, sagging, or out of square. Telltales: uneven reveal gaps around the door, a deadbolt that fights you, daylight at one corner but not the other. Hinge shimming and strike adjustments can recover small misalignments, but a warped slab or racked frame will defeat every gasket you throw at it.
Old doors also leak through the panel itself — an uninsulated wood or hollow door conducts cold straight through, no gap required.
The replacement threshold
Our honest rule: if the door is warped, rotted, uninsulated, or over 25 years old and you've already replaced the weatherstripping once, stop patching. A modern insulated prehung entry door seals as a complete engineered system and pays you back in comfort every single day of a Minnesota winter.
JMB Builders installs entry doors across the Twin Cities metro — and we'll tell you plainly if a $40 weatherstrip kit is all you actually need. Free estimates: 763-204-2099.
