A glossy kitchen and a well-staged sofa can make almost any property feel like The One. But the top warning signs before buying are rarely found in the estate agent’s photographs. They tend to be quieter: a slightly springy floor, a fresh patch of paint in one suspicious corner, or a crack that seems to have been asked to keep a low profile.
Buying a home is not about finding a fault-free building. Especially in South London, where Victorian terraces, converted flats and post-war homes sit side by side, every property has a story and a maintenance list. The aim is to understand which issues are routine, which may cost serious money, and which deserve a proper investigation before you commit.
Top warning signs before buying a property
Cracks that do more than decorate the wall
Hairline cracks in plaster are common. Buildings move a little with changing temperatures, drying materials and ordinary settlement, and cosmetic cracking is often just that – cosmetic. The concern rises when cracks are wide, diagonal, stepped through brickwork, or noticeably larger outside than inside.
Pay attention to doors and windows too. If they stick, frames are distorted, or floors slope markedly towards one side of the room, there may be movement beneath the surface. This does not automatically mean subsidence. It could relate to historic movement, altered openings, poor drainage or local ground conditions. The point is not to diagnose it from a viewing, but to avoid waving it away because the wallpaper is nice.
A RICS survey can assess visible evidence, explain the likely significance and advise where further investigation is sensible. That distinction matters: an old, stable crack and active movement call for very different decisions.
Damp, mould and the faint scent of trouble
A musty smell is not a period-home feature. Nor is mould around windows something to dismiss as simply a tenant’s failure to open a vent. Condensation is common in homes with limited ventilation, cold external walls or busy family life, but it can still point to an environment that needs improvement.
Look for peeling paint, bubbling plaster, tide marks, dark patches at low level and unusually fresh decoration concentrated in one area. Check behind furniture where possible and take note of bathrooms without effective extraction. In basement flats and older solid-wall houses, moisture management needs particular care.
Damp can arise from a straightforward gutter repair, leaking pipework, defective pointing, bridging at ground level or inadequate ventilation. Those are not equivalent problems, either in cause or cost. A surveyor will look at the pattern of moisture and the building’s construction rather than reaching for a one-size-fits-all verdict. The presence of damp does not always mean walk away, but the cause should be understood before your budget gets dampened too.
A roof that has been quietly auditioning for retirement
Roofs are easy to overlook at a viewing because most people understandably spend their time imagining where the dining table will go. Yet roof repairs can be disruptive and expensive, especially where access is awkward or the property forms part of a converted building.
From ground level, look for slipped or uneven tiles, sagging roof lines, damaged chimneys, loose flashing and gutters overflowing onto walls. Inside, inspect ceilings in top-floor rooms and loft spaces for staining, daylight where it should not be, or signs of old leaks. A roof may have been repaired previously and be perfectly serviceable, so evidence of patching is not itself a red flag. What matters is its condition now and whether the repair appears appropriate.
For flats, establish who is responsible for the roof and whether major works are anticipated. A charming top-floor flat can become less charming when a large service-charge demand arrives wearing a hard hat.
Electrics, heating and plumbing that cannot be judged by appearance
A smart thermostat and a shiny boiler cupboard do not confirm that the systems are safe or correctly installed. During a viewing, note old fuse boxes, exposed wiring, loose sockets, poor water pressure, radiator cold spots and any boiler that looks as though it remembers Britpop first time round.
Ask about the age and servicing of the boiler, the last electrical inspection, and whether there are certificates for recent work. A survey is not a full electrical, gas or drainage test, and a sensible report will say so clearly. Where visible signs suggest a concern, arranging specialist checks before exchange can give you a clearer view of likely expenditure and safety issues.
This is a useful place to be practical rather than perfectionist. An older consumer unit may warrant an electrician’s advice, but it does not necessarily make the property unbuyable. A lack of documentation, recurring faults or unsafe visible work deserves more urgency.
Drainage, trees and the bits below ground
Drainage is a classic out-of-sight, out-of-mind issue until a blocked drain makes itself very much everybody’s business. Lift inspection chamber covers only if it is safe and appropriate to do so, and look out for slow-draining sinks, unpleasant smells, damp ground or overly lush patches of planting near the house.
Large trees close to a property are worth noting too. They are not villains by default – mature trees add character, shade and value – but their relationship with foundations depends on soil type, distance, species and building history. In areas with clay soil, the issue can require more care, particularly if there is evidence of movement.
A drainage survey or specialist opinion may be worthwhile where concerns are identified. It is usually easier to investigate before you own the problem, rather than after a Sunday afternoon backs up into the utility room.
Warning signs in the paperwork matter too
Not every costly surprise is visible in a wall or roof. Before buying, read the property information forms and leasehold documents with the same attention you would give a survey report. If something seems vague, inconsistent or missing, ask early.
For leasehold flats, consider the remaining lease term, service-charge history, ground rent provisions, reserve funds, planned major works and restrictions on alterations or letting. A low monthly service charge may sound attractive, but it can also mean little money has been set aside for future repairs. The right answer depends on the building, its management and the work anticipated.
For houses, check boundaries, rights of way, shared access, previous alterations and whether planning or building regulations approval appears to have been obtained where needed. A loft conversion, rear extension or removed chimney breast can be a genuine asset – provided the work has been properly designed, approved and documented.
How to use a viewing without becoming a building detective
You do not need to arrive with a clipboard, torch and an alarming amount of technical vocabulary. You do need to slow down. Visit at a different time of day if you can, listen for traffic and neighbour noise, open and close windows, check cupboards for staining, and look up as well as around.
Ask direct questions: How long has the property been on the market? Has there been any history of flooding, leaks or insurance claims? When was the roof last repaired? Are there guarantees for damp treatment or glazing? Answers are useful, but documents and professional inspection carry more weight than reassurance delivered beside a designer lamp.
If your offer is accepted, choose the level of survey that matches the building and your appetite for risk. A RICS Level 2 Home Survey often suits a conventional property in reasonable condition. A RICS Level 3 Building Survey is usually more appropriate for older, altered, larger or visibly tired homes, or where you are planning significant works. The right choice is not about buying the most detailed report for the sake of it; it is about getting enough evidence to make a confident decision.
When a warning sign should change your offer
A survey finding does not have to produce an immediate yes-or-no verdict. Many buyers use clear evidence of repair needs to renegotiate, plan works or request further specialist advice. The key is to separate manageable maintenance from uncertainty that could materially affect cost, safety or future saleability.
Be wary of making decisions based on estimates plucked from thin air. Obtain quotations where possible, allow a contingency for older buildings, and think about timing. Replacing a boiler next year is different from addressing active water ingress before winter. If several issues are connected – failed gutters, damp walls and decayed joinery, for example – the overall cost can be greater than the sum of each individual repair.
A good survey should leave you better informed, not unnecessarily spooked. South Surveyors’ role is to turn visible defects and local property knowledge into clear, usable guidance, so you can decide with your eyes open. The best home purchase is rarely the one with no imperfections; it is the one whose imperfections you understand, can afford, and are genuinely happy to take on.
