The 4 mm crack and the 10-day exchange

I would not classify the rear crack as cosmetic. A 4 mm diagonal crack that runs into a lintel bearing, combined with a sticking window, is a potential structural symptom, not simply decoration. Possible causes include lintel failure, roof spread, thermal or moisture movement, or subsidence; the 2019 reference to 'settlement' without monitoring does not resolve the cause. The correct output is a clear observation, a reasoned differential diagnosis and a recommendation for specialist investigation, not a definitive diagnosis.

Before exchange I would recommend: (1) a structural engineer's inspection, including opening up the lintel bearing and checking the roof structure; (2) a request for the 2019 survey and any engineer's report; (3) monitoring with tell-tales or a crack gauge for a period, although the 10-day timetable makes this difficult; (4) inspection of drainage and external levels; and (5) a roof inspection by safe access. The report should record the limitation on roof and loft access and state that the cause has not been established. I would advise the buyer in writing that exchange should not proceed until the structural advice is available, and that if they proceed without it they do so against advice.

The client is asking for an assurance that the evidence does not support. I must remain objective and not be influenced by the timetable, the agent's undocumented comment or the desire to complete. A surveyor cannot delegate judgement to an unavailable verbal report; if an engineer has looked at the crack, I should ask for the written report and confirm the scope and date of that inspection.

I would explain to the client why the wording matters: a false reassurance could expose them to repair costs and could expose me to a negligence or professional conduct complaint. I would record the instruction, my advice and the client's response. If the client insisted on a report that omitted the crack or described it as cosmetic, I would decline to do that and, if necessary, decline the instruction. Any suspected misrepresentation by the agent should be documented factually rather than argued in the report. The report should be written for the client's benefit, use plain language, distinguish fact from opinion and make the limitations and recommendations prominent.

The summary should say that a 4 mm diagonal crack is present above the rear window and extends into the lintel bearing; that the window is stiff in operation; that the cause is not confirmed; that the crack is not considered cosmetic; and that structural engineer's advice should be obtained before exchange. The recommendations should include opening up the lintel bearing, checking roof structure and drainage, obtaining the 2019 report, and monitoring if appropriate. I would include the access limitations, the fact that the loft was not inspected and that no ladder access to the roof was available.

I would not state a definitive cause such as 'subsidence' or 'lintel failure' without investigation. I would not describe the crack as cosmetic. I would not say the property is 'structurally sound' or 'free from movement'. I would not rely on the agent's verbal statement as evidence. I would avoid meaningless hedging such as 'may or may not be significant' without explaining what should be done next. The report should be useful to a first-time buyer under time pressure without overstating certainty.