Windows, doors and glazing
What does it mean if you can see daylight under an external door, along the threshold?
It means there is a gap at the bottom large enough to see light through, which is a draught and a route for driven rain. That is a threshold gap, not the wider finding that the door no longer meets its frame at the sides and the head, and the door can still latch while showing light underneath. A home survey records the gap if it was seen, does not test the locks, and daylight is not a reading of the damp-proof course.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Look along the threshold from inside on a bright day. A bright line means the door, the threshold bar or the weatherboard is not closing that edge. The stiles can still fit the jambs. A survey that says the door does not meet its frame is talking about the leaf not sitting in the opening. This question is only the undercut. Both can be true, and they should not be copied into one sentence if only the bottom was open.
A bar, a new weatherboard or a planed adjustment may close the gap. A decayed threshold is a bigger repair, and only if the timber was soft. There is no standard price. Do not buy a new door because you can see light, unless the leaf is also failing. Do not call the gap a failed damp-proof course. If the outside paving is higher than the floor, that is yet another sentence about levels. The survey should keep the light, the fit and the paving apart.
What should you ask your surveyor?
- Where could you see daylight: under the door, at the sides, or both?
- Is the threshold soft, or only gappy?
- Did you test the lock, or only look at the gap?
What are the typical next steps?
- Show a joiner the light under the door before you price a new leaf.
- Do not draft-proof over rotten timber if the survey found softness.
- Keep paving levels and lock tests as separate questions.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a visible gap at the head the same?
It is a different edge. Daylight over the door is not the threshold. Ask which edge was open.
Does a brush seal cure it?
A brush can block a draught. It does not prove the threshold is sound, and the survey has not tested the seal in rain.