10 Red Flags to Spot When Viewing a House (That Most Buyers Miss)

Introduction: Don’t Fall in Love Before You Look Closely

Viewing a house can be exciting—but beneath fresh paint and clever staging some properties hide serious (and costly) issues . As a first-time buyer or even an experienced mover it’s easy to miss the signs.

This guide reveals the top 10 red flags to look for when viewing a home in the UK —plus explains common but critical property defects like damp subsidence and Japanese knotweed .

We’ll also cover:

• How to spot early warning signs

• What questions to ask the seller or estate agent

• When to walk away—and when to renegotiate

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House Viewing Checklist UK: 10 Red Flags Buyers Miss

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Hairline Cracks in Walls or Ceilings

Cracks aren’t always a dealbreaker—but some indicate structural movement or subsidence .

What to check:

• Wide diagonal cracks (>5mm)

• Cracks near doors/windows

• Cracks in exterior walls or bricks

Multiple or worsening cracks could suggest foundation problems. You’ll need a structural survey.

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Signs of Damp or Mould

Damp is one of the most common (and sneakiest) issues in UK homes. It can damage plaster rot timber and even cause health issues.

Look for:

• Musty smells (especially in cupboards or basements)

• Peeling paint or wallpaper

• Dark patches on walls or ceilings

• Condensation on windows

Use your hand to feel for cold or damp walls. Don’t ignore newly painted walls—could be covering stains.

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Sloping Floors or Uneven Ground

Not all sloped floors are charming Victorian quirks. Significant sloping may indicate:

• Subsidence

• Poor renovation work

• Damaged joists or foundations

Use a marble or small ball on the floor—if it rolls quickly investigate further.

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Windows and Doors That Stick

This might be more than bad carpentry.

It can signal:

• Structural movement

• Warped frames due to moisture

• Foundation shift

Test multiple doors and windows—especially in corners or extensions.

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Fresh Paint or New Plaster in Isolated Areas

While redecorating is normal patchy repainting can be a cover-up tactic.

Ask: “When was this redecorated?” and “Has there ever been a leak or damp in this area?”

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External Wall and Roof Issues

Outside look for:

• Loose or missing roof tiles

• Moss buildup (could signal poor drainage)

• Cracked rendering or brickwork

• Damp patches on external walls

Poor external upkeep often reflects deeper issues or deferred maintenance.

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Location of Drains and Gutters

Blocked broken or missing gutters can lead to damp and foundation damage.

Look for:

• Overflow stains

• Pooling water at the base of walls

• Signs of inadequate drainage

Use house viewings to walk the full perimeter of the property.

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Nearby Trees or Plants That Could Be a Threat

Large trees near foundations or aggressive plants like Japanese knotweed can cause major legal and structural headaches.

Knotweed is invasive and can devalue or restrict mortgages .

More on that below.

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Extensions Without Proper Paperwork

Ask to see:

• Planning permission documents

• Building regulations approval

• Completion certificates

Without them you could inherit liabilities—and struggle to sell later.

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Noisy Location or Strange Smells

Traffic noise sewage odours or factory fumes might not appear in the listing—but they’ll affect resale value and your enjoyment.

Do this:

• Visit at different times (evenings weekends)

• Walk around the neighbourhood

• Chat with neighbours if possible

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UK Property Problems Explained: Damp, Subsidence, Knotweed

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What Is Damp in Houses?

Damp is excess moisture in a home’s structure often caused by:

• Leaking pipes

• Poor ventilation

• Rising damp from ground level

• Defective roofs or gutters

Types of damp:

A damp survey or homebuyer report can confirm the cause.

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Subsidence UK Explained

Subsidence occurs when the ground under a property shifts or sinks often due to:

• Clay soil shrinking in heat

• Tree roots absorbing too much moisture

• Leaks weakening the foundation

Key warning signs:

• Cracks wider than 5mm

• Doors/windows sticking

• Floors sloping

You may need a structural engineer and a full building survey if suspected.

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Japanese Knotweed in UK Properties

Japanese knotweed is an invasive plant that grows rapidly and can damage foundations walls and drains.

How to identify it:

• Bamboo-like stems

• Shovel-shaped green leaves

• Grows aggressively in summer

• Often found near fences walls or rivers

Lenders may decline your mortgage if knotweed is present without a treatment plan in place.

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Summary: What to Look for When Buying a House

Final Thoughts: Don’t Let Red Flags Catch You Out

Even dream homes have flaws—what matters is whether those issues are manageable negotiable or a dealbreaker .

With the right questions a good survey and a careful eye you can avoid the biggest traps and buy with confidence.

Want help understanding survey results or red flags?
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