Air gets past an exterior door in four places: under the slab at the threshold, around the latch and hinge stiles where the seals have flattened, at the head, and behind the casing where the gap between the jamb and the rough framing was never insulated. Which one it is decides the repair. A door that is out of level with uneven gaps round the frame cannot be sealed by any amount of new weatherstripping until the door and frame are corrected first.
How to find where the draft is really coming from
Homeowners call about a cold front door. What we actually find divides into things that are the door and things that only look like the door:
- Under the slab, at the threshold
- The bottom strip has worn flat. It is the part that takes every footstep, and a worn door bottom strip is one of the most common single items on our repair lists.
- A gap that is wider at one end than the other
- The slab is out of level in the frame. We have taken on door units whose slabs sat out of level with uneven gaps all the way round — that is not a seal problem, and new weatherstripping fitted to a crooked opening simply gets crushed at one end and misses at the other.
- Around the latch and hinge stiles
- Compression seals go hard and stop springing back. When the door has also dropped, the seal is doing two jobs it was never designed for.
- Behind the casing, not around the door
- The gap between the jamb and the rough framing. On every unit we set, that cavity is packed with fiberglass insulation or expanding foam before the trim goes back. Where it was skipped originally, the air comes in behind the trim and no seal on the door will stop it.
- A storm door that no longer closes
- We see failed closers and storm doors worn past the point of adjusting. A storm door that stands ajar gives the main door no help at all.
- Somewhere that is not a door
- Open soffit gaps, unsealed crawl space walls, and basement walls below window level with no vapor barrier all move more air than a tired door seal does.
Door sweeps, thresholds and bottom seals
The bottom of an exterior door is the hardest joint in the house to keep closed. It has to seal against a threshold that people walk on, water runs over and the sun bakes.
- Door bottom strips and sweeps are replaced as a matter of course when they have gone flat. They are cheap to put right and they are usually the largest single gap.
- Adjustable thresholds can be raised or lowered to meet a sweep that no longer touches. Raising a threshold too far makes the door drag, so it is set against the door, not by eye.
- The sill itself gets checked at the same time. A threshold that has lifted, cupped or separated from the framing is a water problem as much as an air one.
- Where a door bottom cannot reach the threshold because the slab has dropped, the door and frame are corrected first. Otherwise the sweep is being asked to close a gap that will only widen.
Jamb and head weatherstripping on an exterior door
The seals around the sides and top of a door work by compression: the slab squeezes them shut when the latch pulls it home. Two things break that.
The first is the seal itself going hard. The second is anything that stops the door pulling fully home — and that is more often hardware than weatherstripping. On one property we found worn weatherstripping and a failed door closer together, and the closer was why the door had never been seating properly. Replacing seals on a door that does not close all the way is money spent on symptoms.
So the sequence on a door that whistles is: check that the door closes and latches fully, correct the hardware and the frame if it does not, then fit new seals to a door that now shuts square. Locksets and deadbolts are standard items on our door work, and a lock that has to be pulled or lifted to engage is telling you the slab is not where it should be.
Why a door that will not close properly cannot seal
This is the single most useful thing on this page. A large share of draft complaints are alignment complaints. On one call the reported fault was simply that a door would not close properly; what we found was hinges, locksets and the frame all out of alignment with each other. The work was:
- Remove and reinstall the hinges and locksets, securing them to the frame at the proper spacing.
- Level the door so it opens and closes properly.
- Adjust the frame so the slab meets the stop evenly along its whole length.
- Only then fit or renew the seals, against a door that now shuts square.
Done in that order, the seal works and stays working. Done in the other order, the new weatherstripping fails in a season. Where the frame or jamb has moved because the wood beneath has gone soft, see door repair for how a jamb is corrected.
Threshold flashing: sealing a door sill against water
Air sealing and water sealing are not the same job, and at the bottom of a door they meet. Every exterior door unit we set gets new threshold flashing, installed before the door goes in and sealed with polyurethane caulk specifically to prevent decay of the jamb and house framing. Where water has been getting in at the head rather than the sill, top-rail flashing goes in too.
The reason is what we find when old units come out. Damaged wood on both sides of a front door frame, rotted up to around six inches from the bottom, is a pattern we have seen more than once — the base of a door frame is where water sits and where rot starts. Caulk alone over that is cosmetic. The flashing is what actually carries water away.
Where rot has already taken hold in the trim or framing, rotted wood and trim repair covers that work. Exterior trim goes back as rot-resistant composite brick molding or PVC board rather than plain pine, because the next twenty years look like the last twenty.
Window weatherstripping and sash seals
Windows leak air the same way doors do, and the repair is often smaller than people fear. On one job the weatherstripping had failed on six bedroom windows; the work was to repair it and secure all of the weatherstripping back to the window panel itself — not to replace six windows.
- Seals coming away from the sash are refastened to the panel so they compress properly again.
- Gaps around the window frame are treated like the gaps around a door frame: foam insulation into the cavity around the unit, which we also do where soffit gaps sit next to windows.
- Sashes that will not close fully are an operating fault first. A window that does not shut cannot seal, and that is repaired before anything is fitted to it.
For sashes, balances, glazing and rotted sills, see window repair and replacement.
Air sealing the gaps no door seal will fix
When a house is cold despite good doors, the air is coming from somewhere structural. The conditions we find and correct:
- Open crawl space walls. We have found crawl spaces with open cracks and gaps in the walls and vents standing open to rodents. All openings and cracks get sealed, R-21 kraft-faced high-density fiberglass insulation goes in, a new vapor barrier is laid, and vents are fitted with screen covers.
- Soffit gaps. Foam insulation into the gaps and a plastic vapor barrier in the soffit area, usually alongside trim repairs that exposed them in the first place.
- Basement walls below window level. On one house these had to be opened so the cavities could be re-insulated and sealed with a moisture and vapor barrier — the walls were damp as well as cold.
- Under-insulated ceilings and walls. Where we re-insulate whole houses the specification runs to R-48 in the ceiling, R-15 in walls and R-19 at the soffit, with soffit baffles fitted so the new insulation does not block the ventilation path.
That is a different scope from a door seal, and it is covered under insulation and air sealing.
When weatherstripping is not enough and the door is replaced
There is a point past which sealing an old door is throwing good money after bad. We call it when:
- The slab and frame can no longer be brought into alignment. If leveling the door and adjusting the frame will not close the gaps evenly, the unit is worn out.
- The frame is rotted at the base. Soft wood will not hold a seal, a strike plate or a screw.
- The storm door has failed as well. A worn storm door and a failing main door together is usually one job, not two.
- The door is no longer wanted at all. We have permanently converted unused exterior doors into fixed panels — framed, insulated and finished properly rather than screwed shut and caulked over.
New units go in on new threshold flashing, with framing gaps packed with fiberglass insulation or expanding foam so the opening is sealed against drafts from the day it is fitted. See front door repair and replacement and storm door repair and installation.
What door weatherstripping and draft sealing costs
We do not publish prices or give them by phone. A worn sweep on a square door and a front door that has dropped, rotted at the base and lost its flashing are the same complaint from the homeowner and completely different jobs on site.
An estimator comes out, works out where the air is actually coming from, and gives you a written price before anything begins. Sam and Sons Services has worked in Northern Virginia since 1999 and provides handyman carpentry in Washington DC as well. Virginia DPOR license 2705070610; the number is (703) 256-8080.
