You’ve just moved into a brand new house. Everything is pristine and perfect. Then, within a few months, you notice cracks appearing in the walls. This is incredibly common and usually nothing to panic about. But it can feel alarming when your home is supposed to be “new”.
This guide explains what’s happening and when you should actually be concerned.
The Short Answer
New build homes develop cracks because building materials go through natural settling, drying, and adjustment processes during the first few years. Most cracks in new builds are cosmetic and expected. However, not all cracks are harmless, so it’s important to know the difference.
Why New Builds Crack More Than Older Homes
There are specific reasons why newly built homes are prone to cracking.
Material Settling and Drying
When a house is built, all the materials are brand new and haven’t been in place before. As they sit in your home environment, they begin to:
- Dry out completely (fresh plaster and concrete retain moisture from construction)
- Settle into their final form
- Adjust to temperature and humidity variations
- Stabilise after the stress of building and handling
This is a completely natural process. Concrete, plaster, timber, and brickwork all go through this adjustment phase.
Foundation Settlement
The most common reason new builds crack is foundation settlement. This doesn’t mean the foundation is failing. It means:
- The ground beneath the building compresses slightly under the weight of the new structure
- The building drops a few millimetres to a centimetre as everything settles
- Materials adjust as the structure finds its permanent resting position
This happens in the first 1-3 years after construction. Most settlement happens in the first 6-12 months.
Timber Shrinkage
If your home has timber components (which most UK homes do):
- Fresh timber contains moisture from the mill
- In your heated home, this moisture is released gradually
- Timber shrinks slightly as it dries
- This shrinkage causes stress in the structure and can create cracks
This is completely normal. Timber has been drying in buildings for centuries.
Thermal Adjustment
Your new home experiences temperature cycles:
- Summer heat causes materials to expand
- Winter cold causes them to contract
- Fresh materials haven’t been through these cycles yet
- The stress from repeated expansion and contraction can cause cracks to appear
Once materials have been through a few cycles, they adjust and further cracking usually stabilises.
Construction Defects (Sometimes)
While most new build cracks are harmless, occasionally they indicate a genuine construction issue:
- Poor workmanship in plastering or rendering
- Inadequate curing time before decoration
- Movement of fresh concrete before it’s fully set
- Structural issues during building
- Use of inappropriate materials
These are less common in major developments but do occur.
Common Crack Patterns in New Builds
Different crack patterns tell different stories and have different implications.
| Crack Pattern | Typical Cause | Concern Level | Likely Timeline |
|---|---|---|---|
| Fine hairline cracks scattered randomly | Plaster drying, normal settling | Low | Weeks to months |
| Vertical cracks 2-5mm, isolated | Foundation settlement, timber shrinkage | Low to Medium | Months 1-12 |
| Cracks above windows and doors | Stress from structure loading | Low to Medium | Months 3-18 |
| Horizontal cracks forming pattern | Structural movement or deflection | Medium to High | Varies |
| Stair-step cracks in brickwork | Structural movement | Medium to High | Indicates ongoing issue |
| Multiple cracks spreading rapidly | Can indicate structural defect | High | Should prompt investigation |
| Cracks with displacement | Structural movement | High | Requires professional assessment |
Timeline: What to Expect
Understanding the typical timeline helps you know what’s normal and what’s unusual.
Months 1-3
What’s happening:
- Fresh plaster is drying out
- Timber is adjusting to humidity levels
- Initial foundation settlement is beginning
Expected cracks:
- Fine, scattered hairline cracks in plaster
- Occasional small vertical cracks (under 3mm)
- Cracks around fresh paintwork or plaster patches
Normal or concerning:
- A few hairline cracks: normal
- Multiple wide cracks: contact builder
Months 3-12
What’s happening:
- Foundation settlement continues
- Timber shrinkage is in progress
- Materials continue thermal adjustment
- Most settlement occurs in this period
Expected cracks:
- Vertical cracks 2-5mm becoming more apparent
- Cracks above windows and doors appearing
- Some existing cracks widening slightly
Normal or concerning:
- Vertical cracks under 5mm: normal
- Horizontal or diagonal cracks: worth monitoring
- Rapid changes: contact builder
Year 1-3
What’s happening:
- Settlement is mostly complete
- Materials have stabilised
- Cracking should be slowing down
- Thermal cycles are having less impact
Expected cracks:
- Most new cracks should be rare by now
- Existing cracks stabilising
- Cracks should stop growing if they’re due to normal settling
Normal or concerning:
- No new cracks or stable existing cracks: normal
- Continued widening of existing cracks: investigate
- New cracks still appearing: investigate
Red Flags: When to Worry
Most new build cracks are harmless, but watch for these warning signs that something might be more serious.
Growth Patterns That Concern
- Rapid growth: A crack that widens visibly over weeks rather than months
- Spreading pattern: Multiple cracks appearing in quick succession or forming patterns
- Continuing after year 1: If cracks are still appearing or growing significantly after 12 months, normal settling doesn’t explain it
- Accelerating growth: A crack that was stable now suddenly starting to grow again
Accompanying Signs
- Doors or windows sticking or not closing properly
- Visible displacement along a crack (one side higher than the other)
- Cracking in multiple rooms suggesting structural patterns
- Crumbling mortar or brickwork
- Damp or moisture near cracks
- Cracks appearing simultaneously inside and outside the building
Building Defect Indicators
Several signs together might indicate a construction defect rather than normal settling:
- Multiple structural cracks forming patterns
- Cracks in structural materials (brickwork, concrete) rather than just plaster
- Horizontal or diagonal cracking (rather than vertical)
- Displacement or bulging in walls
- Cracks continuing to grow significantly after 18 months
- Sticking doors and windows that are worsening
- Visible bowing or leaning of walls
Your Warranty Rights
This is important to understand. Most new build homes come with warranties covering defects.
NHBC Warranty (National House Building Council)
- Covers the first 10 years
- Year 1: Builder should fix all defects
- Years 2-5: Coverage for structural defects
- Years 6-10: Coverage for structural defects (more limited)
- Cosmetic cracks in year 1 are typically the builder’s responsibility to address
LABC Warranty and Other Providers
Different warranty providers have different terms, but generally:
- Year 1 is the main defect rectification period
- Structural issues are covered longer than cosmetic ones
- You need to report issues within the warranty period
- Some issues have thresholds (cracks over a certain width or pattern)
What to Do
- Keep records of all cracks you notice
- Photograph and measure them
- Note dates and growth patterns
- Contact your builder in writing about concerns during the first 12 months
- If ignored, escalate to your warranty provider
- Don’t assume something will be addressed later; report it during year 1
When to Get Professional Assessment
You don’t need a surveyor for every crack in a new build, but do consider professional advice if:
- You’re seeing horizontal or diagonal cracks (rather than vertical)
- Multiple cracks are appearing in patterns
- Cracks are growing noticeably after 6 months
- You notice sticking doors or windows
- Doors or windows that used to work fine are now difficult to operate
- There’s visible displacement along any crack
- You’re unsure whether something is normal settling or a defect
- Your builder is dismissing concerns that worry you
A structural survey costs £200-400 but can identify genuine problems and protect your interests.
Common Concerns Explained
“My new house is settling unevenly. Is it going to collapse?”
No. Uneven settling is common and buildings are designed with safety factors to handle it. The cracks you see are usually minor compared to the stresses the structure is designed to withstand. That said, extremely uneven settling (very wide cracks, significant displacement) does warrant investigation.
“Why is the builder not fixing these cracks?”
They probably will during the first 12 months if they’re genuine defects. Minor cosmetic cracking is often considered normal and not a defect. However, if cracks are numerous, growing rapidly, or accompanied by other issues, the builder should address them.
“I paid a lot for this house. Why are there cracks?”
New materials cracking as they settle is completely normal, even in expensive homes. It’s not a reflection of quality. However, persistent or serious defects after the builder has had time to address them would be a concern.
“Should I sell and buy an older house instead?”
No. Older houses have their own issues (dry rot, structural movement over decades, hidden defects). New houses cracking in their first year is expected. Most settle down after 12-18 months and require only cosmetic repair.
What You Can Do
Monitor Carefully
- Take photos monthly
- Measure widths with a ruler
- Keep records with dates
- Look for patterns rather than individual cracks
Report Issues Early
- Contact your builder about genuine concerns during year 1
- Be specific about which cracks and when they appeared
- Provide photos and measurements
- Follow up in writing
- Don’t wait until near the end of your warranty period
Distinguish Between Normal and Abnormal
- Fine hairline cracks: normal, cosmetic only
- Small vertical cracks under 5mm: usually normal
- Cracks growing noticeably: abnormal
- Horizontal or diagonal cracks: investigate
- Multiple cracks forming patterns: investigate
- Cracks with displacement: abnormal
Manage Your Expectations
- Most new build cracks are cosmetic and cost little to repair
- Don’t panic over minor cracks; they’re expected
- But do take note of patterns and growth
- Be prepared to escalate if something seems wrong