Top Viewing Tips from a Building Surveyor For Property Investors
Guest Blog Series from a RICS Chartered Building Surveyor
(7-8 Min Read)
Most people approach a property viewing looking for reasons to buy.
For an investor, that instinct shows up differently. You're not picturing where the sofa goes, you're picturing the layout as five HMO bedrooms, or the derelict shell as a finished flip, or the tired buy-to-let with a new kitchen and a higher rent.
It's still an emotional pull, just dressed up as numbers on a spreadsheet.
The problem is that once a deal "feels right," it's easy to let enthusiasm outrun due diligence. The issues that cost investors the most are rarely the ones spotted on a first walkthrough. They're the hidden risks, the signs that are easy to dismiss, and the questions that were never asked before an offer went in.
After years of carrying out surveys as a Building Surveyor including plenty for investors buying HMO conversions, derelict buildings, and tired buy-to-lets, I've learned that the best investors aren't the ones who find a perfect property.
They're the ones who understand exactly what they're buying, and exactly what it will take to turn it into the asset they've modelled.
Here are the things I'd suggest looking for when viewing an investment property, and why they matter. This list isn't exhaustive, but these are some of the key points that get missed most often.
1 / Stop Looking for Reasons to Buy, Start Looking for Risks to Understand
The biggest shift is changing the way you approach a viewing.
Most buyers walk in trying to confirm the deal stacks up. A surveyor walks in trying to understand what could become a problem, what it might cost to resolve, and whether that changes the numbers.
That doesn't mean being negative as every property has defects, and a derelict building or tired buy-to-let is expected to need work. The aim is to replace assumptions with information before you commit capital. The difference between a good deal and an expensive mistake is usually understanding the risks before you exchange, not after.
2 / Boundaries and Shared Liabilities are Easy to Ignore Until They Become a Problem
Investors often focus entirely on the building and forget they're also buying the responsibilities that come with the land and surrounding areas.
Walk the boundaries and look at fences, walls, hedges, and access routes. Consider whether there are shared driveways, private roads, communal areas, retaining walls, or drainage systems that involve shared maintenance responsibilities.
Ask who is responsible for repairs, whether any agreements are in place, and how costs are divided. A boundary wall, private road, or drainage system may seem insignificant during a viewing but could become a costly obligation, or a licensing issue, further down the line.
Compare what you see on site with the information provided by the seller and your solicitor. Your solicitor will investigate the legal position, but they won't physically visit the property, they'll rely on you flagging anything that needs further investigation.
Boundary disputes and shared liabilities are much easier to understand and resolve before purchase than after completion, and far easier to price into your offer than to negotiate after you own the problem.
3 / Know How the Property Was Built
Not every property is constructed in the same way, and construction type has a direct bearing on your refurbishment budget and your options.
Many buyers assume traditional brick construction, but some properties particularly certain post-war stock often picked up cheaply for conversion use non-traditional methods such as steel frames, timber systems, or precast reinforced concrete.
Some non-traditional properties perform well, but certain construction types have known issues, require specialist repair methods, or are harder to mortgage and refinance which is a serious consideration if your strategy relies on a refinance to pull capital back out. Construction type can also affect insurance, and in some cases eligibility for certain finance products entirely.
Understanding how a property was built is just as important as understanding how it looks and should shape your refurbishment costings before you offer.
4 / Fresh Decoration Can Hide Previous Problems
A tidied-up property is designed to impress, and on tired buy-to-lets and quick flips, that's exactly what sellers do.
Pay attention to fresh paint, isolated repairs, recently decorated areas, or rooms that feel unusually different from the rest of the property. Look around chimney breasts, corners, ceilings, and external walls, where moisture problems often appear.
Not every repair is a concern, but every unexplained repair is worth asking about and worth pricing a contingency against.
5 / The Roof Is Often Forgotten
The roof is one of the most expensive elements to get wrong, yet it's often the least examined during a viewing.
From outside, look for slipped or missing tiles, damaged chimney stacks, uneven roof lines, or obvious repairs. Inside, check ceilings for staining and, where possible, look in the loft for signs of leaks, poor insulation, or damaged timbers.
On derelict or long-vacant properties, roof condition is often the single biggest driver of your refurbishment budget as a full recover or replacement can run into tens of thousands, and won't always be visible from a quick walkthrough.
Spray foam insulation is also worth investigating, particularly on stock that's been prepared for a quick sale. When correctly specified and installed it can improve thermal performance, but some installations conceal defects, trap moisture, or make roof timbers difficult to inspect and can complicate both your survey and any future buyer's mortgage. If it's present, ask when it was installed and whether documentation is available.
6 / Signs of Structural Movement — Cracks Need Context
Many buyers become concerned when they see cracks, but not all cracking means the same thing.
Some cracks simply relate to normal movement or ageing materials. Others indicate more significant issues and on derelict or long-neglected buildings, movement is more likely to be live and ongoing rather than historic.
The important questions are: Where is the crack? How wide is it? Is it getting worse? Does it continue through the building?
A surveyor looks at the pattern and context, not just the presence of a crack and on a heavy-refurbishment project, structural risk needs pricing in before you commit, not discovered once you've started stripping out.
7 / Damp, Condensation and Ventilation — The Issues That Hide in Plain Sight
Damp and condensation are among the most misunderstood issues investors encounter, and among the most consequential for HMO conversions specifically, where Building Regulations set clear ventilation standards per room.
A musty smell, mould growth, peeling paint, or staining around windows and ceilings can all signal moisture, but the cause isn't always obvious. It could be poor ventilation, condensation, plumbing leaks, penetrating damp, or issues with the building fabric.
Look carefully in corners, behind furniture, around window openings, inside cupboards, and in bathrooms, where moisture problems often appear first. Check whether extractor fans are installed and working, and consider whether the layout you're planning more bedrooms, more bathrooms, more occupants will they need additional ventilation to comply.
With homes becoming increasingly airtight and HMOs housing more occupants per square metre, good ventilation matters more than ever. Getting this wrong doesn't just cost money to fix, it can hold up your HMO licence application.
8 / Don't Ignore the Services
Some of the most expensive problems in a property are hidden behind walls, under floors, or inside cupboards and services are often the item most underestimated in an investor's refurbishment budget.
Ask about the age of the boiler, electrical installation, consumer unit, and plumbing system. For an HMO conversion, expect the electrical installation to need a full rewire in most cases, along with a new consumer unit, additional circuits, and hard-wired interlinked smoke and heat detection, this is rarely optional and should be priced in from the outset.
A property can look immaculate while still requiring significant investment in its essential systems, so check whatever is visually accessible to get a gauge. With permission, turn on taps, run showers, and flush toilets. Low pressure, slow drainage, unusual smells, or gurgling sounds may indicate issues with plumbing, drainage, or older systems and on a property that's been empty or under-maintained, these checks matter even more.
9 / Older Properties and Asbestos
If a property was built before 2000, there's a possibility that asbestos containing materials may be present and this is especially relevant if your strategy involves stripping out, reconfiguring layouts, or converting to an HMO.
This isn't unusual, asbestos was widely used in construction because of its durability and fire-resistant properties. The important point is understanding where it may be found and whether your plans involve disturbing it.
If you're planning refurbishment, removing ceilings, altering layouts, or carrying out major works, identifying potential asbestos before you start can prevent unexpected delays, costs, and safety issues once contractors are on site.
10 / Look Beyond the Building — Check for Invasive Species
The condition of the property is only part of the picture. The garden, boundaries, and surrounding land can also introduce risks and on derelict or long-neglected sites, this is a genuine and common issue.
Japanese knotweed is the most well-known invasive plant, but it's not the only species that can cause concern. Others, such as giant hogweed, Himalayan balsam, and certain types of bamboo, can also spread aggressively and create management issues.
During a viewing, look carefully at garden areas, boundary lines, embankments, and neglected parts of the plot. Japanese knotweed is most commonly identified by its tall bamboo-like stems, large leaves, and rapid growth, although identification should always be confirmed by someone with the appropriate expertise.
The presence of invasive species doesn't automatically mean a property should be avoided, but it can affect your development timeline, mortgage or bridging finance, and remediation costs. If you have concerns, seek professional advice before committing to purchase.
Leave Every Viewing With Information, Not Just Impressions
After several viewings, properties start to blur together.
You remember the one with the good bones, the one with the big garden, and the feeling you had walking round but you may forget the details that actually determine whether the deal works.
Take notes. Ask questions. Photograph areas you need to remember. Use the same checks every time, on every property, regardless of how good the deal looks on paper.
The best investment decisions aren't made by finding the property with no problems. They're made by understanding the problems, knowing what they cost, and deciding whether they fit your strategy and your numbers.
A viewing tells you whether a property looks like an opportunity. A survey tells you whether it actually is one.