A property survey is one of the more valuable few hundred pounds you'll spend when buying a home. It's also frequently misunderstood, and the misunderstanding causes real problems afterwards.
The core issue: a survey is a visual inspection of what's accessible on the day. That's a much narrower thing than most buyers assume.
What "visual" excludes
A surveyor generally does not lift carpets, move furniture, open up walls, or dismantle anything. They look at what can be seen.
Which means: nothing under floor coverings, nothing behind fitted furniture, nothing inside a wall cavity, nothing in an inaccessible roof space, nothing under insulation.
A house with wall-to-wall carpet, full furnishings and a boarded loft can be inspected quite thoroughly and still leave large areas genuinely unseen.
This is stated clearly in every report, usually in a section about limitations that buyers skim past on the way to the summary.
What's usually not tested at all
Several systems are excluded from a standard survey and require separate specialist inspection.
Electrics. A surveyor will note obvious problems — an old consumer unit, visible damage — and will not test the installation. A proper electrical condition report is a separate job by a qualified electrician.
Heating and plumbing. Similarly, visual observation only. Whether a boiler is functioning correctly, whether pipework is sound, whether a system has been maintained — a separate inspection.
Drainage. Almost never inspected as standard. Drain surveys use cameras and are a separate specialism. Drainage problems are expensive and common in older properties, and they're one of the most frequent post-purchase surprises.
Structural analysis. A surveyor may identify signs of movement and recommend a structural engineer. They generally will not determine the cause or the remedy, and the referral is where the real cost usually appears.
Asbestos, damp cause, timber decay extent. All typically flagged for specialist investigation rather than resolved.
The levels of survey
Terminology varies by country but the general structure is similar: a basic valuation-oriented report, a mid-level condition report, and a full building survey.
The most common mistake is treating a lender's valuation as a survey. It isn't. A valuation exists to tell the lender whether the property is adequate security for the loan. It is not an assessment of condition for your benefit and it will not tell you about defects.
For anything old, unusual, extended or visibly imperfect, the full building survey is the appropriate level. It costs more and it examines more.
The weather and season problem
Rarely mentioned and genuinely significant. Some defects are only visible in certain conditions.
Damp problems are far more apparent in winter. Roof leaks show themselves in heavy rain. Drainage issues appear when the ground is saturated. Movement in clay soils is seasonal.
A survey conducted during a dry spell in summer may genuinely find nothing wrong with a property that leaks every November. The surveyor hasn't failed; the conditions weren't there.
If you can, visit the property yourself in bad weather before completing. It's free and it reveals things a report can't.
How to read the report
Reports typically use a rating system flagging items by urgency. The temptation is to look at the ratings and stop.
Better approach: read the limitations section first, so you know what wasn't examined. Then read every recommendation for further investigation, because those are the surveyor telling you there might be a significant problem they couldn't assess. Those referrals are where the expensive discoveries live.
A report full of "further investigation recommended" is not a clean bill of health. It's a list of unresolved questions.
Using it in negotiation
A survey identifying significant work is a legitimate basis for renegotiating, and it's normal.
What works better than a general demand is obtaining actual quotes for the specific work and negotiating against those figures. A seller presented with a builder's estimate is in a different position from one presented with a surveyor's note.
Be realistic about proportion. Every property of any age will have a list. Minor items on a hundred-year-old house are expected and attempting to renegotiate over them tends to sour a transaction to no benefit.
The thing nobody tells you
Talk to the surveyor. Most will take a phone call after issuing the report, and what they'll say verbally is frequently more direct than what they'll write.
Written reports are drafted with professional liability in mind, which produces careful, hedged language. On the phone you can ask what actually concerned them, and the answer is often considerably more useful than the document.
It costs nothing, almost nobody does it, and it's the single best return on a survey fee available.
What the neighbours know
A source of information that costs nothing and is almost never used: talk to people who live on the street.
Neighbours know things no survey captures. Whether the road floods. Whether there is a long-running dispute about a boundary or a right of way. Whether the previous owners had persistent problems with damp, drains or subsidence. Whether a large development has been proposed nearby.
People are generally happy to talk, particularly if approached politely and without a clipboard. Ten minutes on a doorstep has saved buyers from purchases that every professional report cleared, and it is the cheapest due diligence available.