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Age and type of house

What should you ask if a bay window seems to sit under a timber lintel?

Ask whether the surveyor could see the timber, or only a crack and a dip at the window head. Older bays often have timber lintels that rot if they stay wet. A home survey does not open the plaster to prove the timber, and it should not call a rotten lintel “subsidence” without saying why. Approved Document A is not a certificate for this opening.

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?

The clues are a dropped head, a crack from the corner, and soft timber if it is exposed in the reveal. A replacement window can hide the lintel behind plastic trim. RICS inspections do not remove finishes as standard. If the bay roof is also leaking, the water and the lintel are related but not the same quote. There is no RICS price for a new lintel.

A builder who props and replaces a lintel is doing structural work. Papers and temporary support matter. Do not knock the plaster off on a viewing to settle a bet. If the survey is unsure, the next step is to see the timber, not to underpin the house.

What should you ask your surveyor?

  • Could you see timber, or are you inferring it?
  • Is the movement at the window head only?
  • Are you separating this from foundation movement?

What are the typical next steps?

  1. Do not order underpinning for a bay lintel.
  2. Ask a builder what they would need to expose before they quote a replacement.
  3. Fix the bay roof leak if that is what is wetting the timber. Do not only replace the window.

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 concrete boot lintel the same?

No. It is a later concrete lintel. Rust staining and cracks are the clues. Timber rot is a different material.

Does a steel beam over a bay always exist?

Not in an original timber bay. The survey should not invent a steel it did not see.

Sources