A slipped slate is one of the most common roof faults on older houses. You see a slate sitting lower than its neighbours, or a gap where one used to be, or a broken piece in the gutter. Sometimes it’s a one-off after a storm. Sometimes it’s the start of something bigger.
This guide explains why slates slip, what nail fatigue means and how to tell a small repair from a roof that needs a proper look.
How slates are held on
Each slate on a traditional roof is nailed to timber battens, usually through two holes. The slates overlap so that each nail is covered by the slates above. Underneath, older roofs may have bitumen felt or no underlay at all. Breathable membranes only appeared in the UK in the late 1990s.
Good slate lasts a very long time. Checkatrade gives natural slate a life of 100 years or more (Checkatrade). The nails and battens don’t always last as long.
What nail fatigue means
Nail fatigue is the name for slates slipping because their nails have corroded. Older nails were often iron. Over decades, damp in the roof makes them rust and thin until they snap or pull through. The slate then slides down out of place.
Because the nails across a roof are usually the same age, they tend to fail around the same time. That’s why one slipped slate is worth noticing.
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One slate or the whole roof?
A single slipped slate after high winds may just need refixing. Signs that point to a wider fixing problem include:
- slipped slates across several parts of the roof, not just one spot
- new slips appearing every year or so
- many small metal clips (tingles) holding slates in place from past repairs
- broken slate pieces regularly found in gutters or on the ground.
Look at the ridge and hips too. Loose or cracked ridge pieces often show up at the same time as slipped slates on an ageing roof. Battens can also rot, especially where the roof has been damp for years. A survey looks at both the slates and, from the loft where it’s safe, the underside of the roof.
Why it matters
A gap in the slates lets rain reach the battens and underlay. On roofs with old felt or no underlay, water can reach the roof timbers and ceilings quickly. Slipped slates can also fall, which is a risk to anyone below. On a terrace, debris may land in a neighbour’s garden or a valley gutter and block it.
What a survey checks
A roof survey records the number and spread of slipped, cracked and missing slates, the state of ridges, hips and valleys, and what can be seen of the underlay and battens from the roof space. Where applicable, a drone gives close-up photos of slopes that can’t be seen from the ground. The written report explains whether the pattern looks local or roof-wide, with recommendations prioritised by urgency.
If you’re buying a house with an old slate roof, a pre-purchase roof survey helps you understand what you’re taking on. See also how long roofs last.
Quick answers
Can I refix a slipped slate myself?
Please don’t climb on the roof. Slate is easy to break and dangerous to walk on. Note where it is from the ground and get it looked at.
Does nail fatigue mean the slates are worn out?
Not necessarily. Good slates can often outlast their fixings. A survey looks at the condition of the slates as well as how they’re held.
What are the metal clips on my slates?
They’re usually tingles or clips used to hold refixed slates. A few are normal. Many of them across a roof suggest repeated slipping.
Related services
More advice
- How Long Does a Roof Last? Slate, Tile, Flat
- Victorian Terrace Roofs in London: Common Defects
- Storm Damage to Your Roof: Evidence for a Claim
- Winter Roof Checklist for Homeowners
- All advice
This guide is general information about roofs and roof surveys. It isn’t legal, insurance or structural engineering advice; for those, speak to a suitably qualified professional.