It's easy to focus on the house itself when viewing a property, especially at this time of year, when a garden can look muddy or unremarkable. But overlooking the garden when buying a house can be a costly mistake.
A nicely laid out patio might catch your eye on a viewing, but it can just as easily be masking problems underneath. From drainage issues to root damage, to trees that pose a risk to the foundations, gardens hide plenty of red flags that don't always announce themselves on a quick walk around.
To avoid any expensive headaches down the line, we asked a range of garden and property experts what they'd look out for, and what's worth flagging before you commit to a purchase.
Trees and roots
A mature tree can be a garden's biggest selling point, but it can also be one of its biggest liabilities, so it's worth paying close attention to trees when viewing a house. Ashleigh Bradshaw, lawn expert at Hayter, says a leafless tree in winter can be deceptive: "The leafless tree that looks harmless in January is often the one blocking every scrap of afternoon light by June, so think about its trunk size and how close it sits to the house." After all, what you're judging on a viewing day may look very different from what you'll be living with once summer arrives.
But the potential problems go well beyond light and shade. A tree's root system, if left unchecked, can affect the very foundations a buyer is relying on.
Andrew Pemberton, senior manager of surveying at The Professional Snagging Company, says the level of risk depends on the species, soil and foundation design: "Willow, poplar, oak, elm and eucalyptus are classed by NHBC (National House Building Council) as high water-demand trees," with a much greater influence on moisture on shrinkable clay soils.
And it's not just mature trees that buyers need to consider. Even a young tree, "might look harmless," he adds, "but the risk can increase substantially as they establish over the next five or ten years." That's a particularly easy trap to fall into with newer plantings, where there's little visually to suggest that a small tree today could become a structural problem tomorrow.
Top tip: For anyone planning an extension or new home near existing trees, the potential risks are worth understanding before work begins. Buyers should familiarise themselves with the risks of building by trees, as well as how subsidence develops in the first place.
Ashleigh Bradshaw is Marketing Associate for lawn and garden machinery brand Hayter, part of Toro UK, which has held the Royal Warrant for supplying horticultural equipment since 1960. She regularly comments on lawn care and garden maintenance in the press.
Andrew Pemberton is Senior Manager of Surveying at The Professional Snagging Company. A Chartered Building Engineer with 25 years in residential property, he's a member of CIOB, RICS and RPSA, and specialises in new-build defects, damp and structural waterproofing.
Drainage and standing water
Water is one of the most deceptive red flags a garden can hide because it depends entirely on when you happen to be looking. A garden that looks perfect on a dry day can tell a very different story after a wet week, and viewings rarely line up with the exact moment a problem chooses to materialise.
For Michael Wheat, founder of Ponds by Michael Wheat, the first clue usually comes from topography rather than the weather on the day. He looks at the level of the garden relative to the house first: "If the ground falls towards the property, or the garden sits lower than neighbouring land, I'd ask questions straight away because the water has to go somewhere."
Rushes, heavy moss or damp-loving plants are also a giveaway, but the key test is recovery time: "If one part of the garden stays saturated when everywhere else has dried out... I'd want to understand why." It's a distinction that's worth holding onto – a garden that's simply wet after rain is perfectly normal, but one that stays wet long after its neighbours have dried out is telling you something.
Ultimately, the gap between what a viewing shows and what actually happens across the seasons is what tends to trip buyers up. According to Peter Thum-Bonanno, co-founder of GetAgent, drainage is one of the two issues that most commonly surface at survey stage: "Buyers visit in dry weather and the garden looks fine, then a surveyor flags waterlogging or historic flooding."
His advice is simple: check the Environment Agency's flood risk tool before booking a viewing, "not after you fall in love with the property." It's a step that costs nothing and takes minutes, yet consistently gets skipped in the excitement of finding the right house.
Top tip: If a viewing does turn up standing water, it's worth understanding where drainage should go in a garden and whether a soakaway could help.
Michael Wheat is Founder of Ponds by Michael Wheat, the UK's leading specialist in natural, chemical-free swimming ponds. He's designed and built ponds and gardens across the UK since 2010, with drainage and root-damage remediation a core part of his work.
Peter Thum-Bonanno is Co-Founder and CTO of GetAgent, the UK's largest estate agent comparison platform. A Cambridge engineering graduate, he previously founded Find Properly, and has overseen data from millions of property sales across GetAgent's 7,500+ agent network.
Invasive plants: knotweed, bamboo and ivy
Few plants strike fear into a buyer's heart quite like Japanese knotweed, and for good reason. What makes it particularly dangerous is how easily it disguises itself at exactly the time of year most viewings take place.
Some of the most expensive problems are easiest to miss once a plant has died back for winter. "Japanese knotweed is the major plant to be wary of," says Ashleigh Bradshaw. "It's severe enough to hold up a mortgage and easy to walk straight past in winter, because the plant dies back to a clump of hollow brown canes that look a bit like dead bamboo." In fact invasive bamboo poses a similar risk, since it "travels under fences and patios and removing it properly is a serious job." Either way, it's worth knowing what to look for, as both plants are far easier to spot once you recognise their winter disguise.
Even seasoned property professionals aren't immune, and it's a lesson Jonathan Rolande, founder of The National Association of Property Buyers learned the hard way. He speaks from experience, having bought a property in Wales with an undetected knotweed problem: "A mistake on my part – I trusted the surveyor too much! It took five years and thousands of pounds to remedy."
Top tip: If you already suspect you have it, read our guide to how to kill Japanese knotweed to understand your options.
Jonathan Rolande is a property expert with over 30 years' experience and 1,000+ transactions. Director of House Buy Fast and founder of The National Association of Property Buyers, he regularly comments on the UK housing market for national press, TV and radio.
Structural issues disguised as "cosmetic"
It's easy to write off a slightly wonky flower bed or a patchy patio as purely cosmetic, but some of the most costly red flags in a garden hide in plain sight, disguised as little more than an eyesore. Take Andrew Pemberton's example of a flowerbed sitting too high against the property: "It may look neat during a viewing, but if external ground levels compromise the damp protection built into the wall, water can splash or sit against areas that were designed to remain clear."
Andrew has seen this catch out buyers of new-builds in particular, where a fresh lawn can create a false sense of security: "This is particularly frustrating on a new home because it can be created simply by poor final landscaping. Buyers shouldn't assume a newly laid garden means the levels and drainage have been finished correctly." Anyone who suspects ground levels are the culprit should read our guide to damp proof courses, which explains exactly what to look for.
Patios and paths get much the same free pass, according to Andrew, because buyers are often drawn to how they look rather than how they're built: "These are frequently overlooked as buyers focus on their aesthetic, not their construction." His team checks whether paving falls away from the house, whether ground levels have been built up too high against walls, and whether drainage has been provided where water is likely to collect.
Retaining walls deserve the same scrutiny, since cracking, bulging or leaning indicates a lot more than a cosmetic defect. It's also worth checking who actually owns a retaining wall before factoring in repair costs. None of this is cheap to put right either, according to Andrew getting the sub-base and patio drainage wrong, "could cost between £3,000-£5,000," to fix.
Overgrown planting hides its own surprises too, and not always the kind a survey will catch. Jonathan Rolande has learned to treat dense, unkempt borders with suspicion: "Drainage is easy to hide in dry weather. Thick planting covers broken fences, and dumped rubbish."
His most striking discovery is a reminder that neglect can conceal something genuinely hazardous: "More than once I have discovered concealed debris from a long-removed shed or guttering that is made of asbestos and very expensive to clear."
A quick garden checklist
With so much to keep track of, it helps to have a simple sequence to work through rather than trying to remember every garden red flag at once. For a fuller walkthrough of what to check both inside and outside a property, see our house viewing checklist. For the garden specifically, here's where to start:
- Start at the house. Ground levels should sit below the damp-proof course, air bricks clear, with no moss, staining or marks on the walls
- Test the lawn. Push a heel in: spongy and sinking means thatch, barely giving means compaction
- Walk to the end of the garden, not just to the kitchen doors
- Look up as well as down. Trees, boundary and retaining walls, and anything that's shifted, and check behind sheds and into dense planting
- Check access, so you're not carrying a lawn mower through the kitchen
What to do if you spot a red flag
Finding an issue doesn't necessarily mean walking away from the purchase, but it should change your approach. Jonathan Rolande's advice is to raise concerns before exchange, and get the insurer to confirm in writing what's covered, "since insurers rarely pay for a fault that already existed, or one you could reasonably have spotted before you bought."
Michael Wheat agrees, adding that undoing someone else's mistakes rarely comes cheap: "You're not just paying to solve the problem, you're also paying to remove and reinstate what's already there."
As the experts make clear, a specialist report is often the difference between an educated guess and genuine negotiating power. For more on this, see these three survey findings that should make you think twice about a purchase and our guide to choosing the right home survey.
If boundaries are on your mind, it's worth knowing the fence rules and who's responsible for what. And if drainage is more of a concern, our guide to what a French drain is and whether you need one is a good next stop. Whatever you find, it's rarely worth skipping the professional check altogether, and here's why buying a house without a survey isn't a good idea.
