Why Do Roof Slates Slip?

A slipped roof slate is one of the more obvious roofing defects a homeowner may notice.

Sometimes the slate remains partly in position. In other cases, it may fall completely from the roof and become visible on the ground below.

A slipped slate does not automatically mean the whole roof needs replacing.

In many cases, the problem can remain localised and suitable for repair.

The important part is understanding why the slate moved and whether the surrounding roof is still performing properly.

There are several possible causes.

Common reasons include:

Deteriorating fixings
Cracked or broken slates
Age-related wear
Severe weather
Movement within the roof
Previous poor repairs
Installation issues

Sometimes more than one factor is involved.

A slate may have weakened gradually over time and then finally move during strong winds or prolonged wet weather.

Deteriorating Fixings

One of the most important causes of repeated slate movement is deterioration of the fixings holding the slates in place.

The slate itself may still be in reasonable condition.

However, if the fixing has corroded, loosened or failed, the slate may begin to move.

This is particularly relevant on older roofs.

Where one fixing fails in isolation, the repair may remain straightforward.

Where slates are repeatedly slipping across several areas, wider fixing deterioration may need to be considered.

Broken or Cracked Slates

A slate can also move because the slate itself has failed.

Cracks can form through:

Ageing
Impact
Movement
Previous damage
Weather exposure

A cracked slate may no longer sit securely in position.

Where the surrounding roof remains sound, individual replacement may be all that is required.

Weather Exposure

Slate roofs are designed to cope with normal British weather, but strong winds can expose materials that have already become vulnerable.

A sound, well-secured slate should not simply fall because it rains.

However, ageing fixings or already-damaged slates may be more likely to move during severe weather.

This is why problems sometimes become visible immediately after a storm even though the underlying weakness developed gradually.

Coastal and Exposed Properties

Properties in more exposed parts of Devon can experience stronger winds and driving rain.

That does not mean slate is unsuitable for these locations.

It simply means weakened materials may become more noticeable sooner.

A slate roof in a sheltered urban position may age differently from one on exposed higher ground or near the coast.

Actual condition remains more important than location alone.

Ageing Slate Roofs

Natural slate can remain serviceable for a very long time.

In some cases, the slates themselves may outlast other components of the roofing system.

This is why an older slate roof should not automatically be assumed to need replacement.

The visible slates may remain perfectly usable while fixings, flashing or other components begin to deteriorate.

Our guide to how long a roof lasts explains this distinction in more detail.

What Happens When Several Slates Start Slipping?

One slipped slate may be an isolated problem.

Repeated slippage across several sections can indicate something broader.

This may include:

Ageing fixings
General deterioration
Previous repair problems
Movement within the roof
A roof approaching the point where larger-scale work should be considered

The pattern matters.

Repeated failures in unrelated parts of the roof deserve a more complete assessment than one isolated defect.

Does a Slipped Slate Always Cause a Leak?

Not necessarily.

A slate may move without immediately producing visible water ingress.

However, the gap can leave the materials beneath more exposed to rain.

If water reaches the underlay, it may travel before becoming visible inside the property.

This means an internal damp patch may not appear directly below the slipped slate.

It is still sensible to address visible slate movement before further deterioration develops.

Can One Slipped Slate Be Repaired?

Often, yes.

Where one slate has moved and the surrounding roof remains in good condition, localised repair may be enough.

The repair should still take account of why the slate slipped.

Simply replacing it without considering the fixing or surrounding area may not be enough if the underlying cause remains.

What If the Same Area Keeps Failing?

Repeated failure in the same section may indicate that the issue is not limited to one slate.

Possible causes can include:

Fixing deterioration
Poor previous repairs
Movement
Problems around junctions
Defects in nearby roof components

At this point, the surrounding section deserves closer investigation rather than repeated isolated patching.

Slate Problems Around Chimneys

Slate roofs often meet chimney stacks.

These areas rely on flashing and other details to prevent water ingress.

If damp appears near a chimney, possible causes include:

Slipped slates
Damaged flashing
Deteriorating mortar
Weathered brickwork
Other nearby junctions

The slate covering and chimney area should therefore be considered together.

Our chimney repair service provides more information.

Slate Problems Around Valleys

Roof valleys carry significant quantities of water between adjoining slopes.

Slates close to a valley can be affected by movement, previous repairs or deterioration in the valley itself.

A leak in this area may therefore not be caused by the slate alone.

Our guide to roof valley leaks explains why these areas are especially important.

Slate Problems Around Rooflights

Rooflights create additional junctions in a slate roof.

These rely on suitable detailing and flashing.

If water appears around a rooflight, the visible slate may not be the only possible cause.

The surrounding flashing, seals and adjoining materials should also be considered.

Can Slates Be Reused?

In some situations, serviceable natural slates can potentially remain in use during repair work.

Whether that is appropriate depends on:

Their condition
The extent of the work
The existing roof construction
The cause of the problem

The aim should be to retain sound materials where practical rather than replacing them unnecessarily.

What Is Nail Sickness?

The term “nail sickness” is sometimes used to describe older slate roofs where metal fixings have deteriorated and slates begin to slip.

The phrase can be useful descriptively, but the key issue is the condition of the fixing system.

If only one or two fixings have failed, localised repair may remain practical.

If slates are slipping repeatedly across the roof because fixings are widely deteriorated, more extensive work may be required.

Does Nail Sickness Mean the Slates Are Bad?

Not necessarily.

The slates themselves may still be serviceable.

The problem may lie mainly with the fixings.

This is one reason why an older slate roof should be properly assessed before assuming that all of the visible roofing material needs replacing.

Storm Damage to Slate Roofs

Strong winds can displace already-vulnerable slates.

Following severe weather, homeowners can look from ground level for:

Slates on the ground
Visible gaps in the covering
Slate fragments
New internal damp
Changes around ridges or chimneys

Never climb onto the roof yourself to investigate.

If something appears to have changed, a professional assessment is the safer option.

Can Loose Slates Damage Gutters?

Yes.

A falling slate can land in or near a gutter and potentially cause damage or blockage.

Fragments can also accumulate in the rainwater system.

If slate debris appears in the guttering or on the ground, the roof should be checked for the source.

Our guttering service covers cleaning and repairs where required.

When Is Slate Repair Usually Appropriate?

Repair is generally more appropriate where:

Only one or a small number of slates are affected
The surrounding covering remains sound
Fixing problems are localised
The cause can be clearly identified
Previous repairs have not become widespread

In these circumstances, localised repair can preserve the wider roof effectively.

When Might a Slate Roof Need More Extensive Work?

Broader work becomes more relevant where:

Slates are repeatedly slipping across several areas
Fixings are deteriorating widely
Many slates are cracked or damaged
Leaks occur in several locations
Repairs are becoming increasingly frequent

At this stage, the complete roof should be considered rather than treating each slipped slate individually.

Our guide to signs your roof may need replacing explains this decision in more detail.

Slate Roof Replacement

Replacement should not be recommended simply because a slate roof is old.

It becomes more relevant where deterioration is widespread and localised repairs are no longer a practical long-term option.

The existing property, roof pitch, character and materials should all be taken into account.

This can be particularly important on older or period buildings.

Slate Roofing on Older Devon Properties

Older Devon homes can contain roofing materials and details that have developed over many decades.

A slate roof may include:

Historic repairs
Replacement slates
Chimneys
Rooflights
Extensions
Altered junctions

These elements can all affect the way the roof performs.

Understanding the existing construction is therefore important before major work is planned.

What Should Homeowners Do If They Find a Slate on the Ground?

Do not attempt to climb onto the roof.

Instead:

Look safely from ground level for an obvious gap.
Check indoors for any signs of water ingress.
Move vehicles or belongings away from areas where further material could potentially fall.
Arrange an assessment if the source is unclear.

Finding one slate does not automatically mean the roof has suffered major damage, but it should not be ignored.

Slate Roof Maintenance

Homeowners can monitor a slate roof without accessing it directly.

Useful signs to watch for include:

Slipped slates
Missing sections
Slate fragments on the ground
Repeated internal damp
Changes after storms
Problems around chimneys
Blocked gutters

Our roof maintenance checklist for Devon homes covers broader routine observations.

Slate Roofing Services Across Devon

Bramwell Roofing Devon provides slate roofing services throughout Devon, including localised repair and replacement where appropriate.

Where slipped slates form part of a broader roofing problem, our roof repair services can help investigate the cause.

Need Help With Slipped or Damaged Roof Slates?

If you have noticed a slipped slate, found slate fragments on the ground or are concerned about repeated movement across an older roof, Bramwell Roofing Devon can assess the condition and discuss the available options.

Call 01392 308173 or 07598 001 200, or contact Bramwell Roofing Devon online.

Frequently Asked Questions