Installing Slate in High-Wind Areas: What a Coastal Slater Does Differently

I've put slate on roofs across the west coast of Scotland, the Orkneys and the exposed headlands of Cornwall and Wales — places where the wind doesn't knock politely, it shoulders the door. Twenty years of that, and the one lesson I keep coming back to is this: slate is not the problem. The fixing is. A good slate roof will outlast three generations of the house under it. It's the nail, the edge, and the last three courses that let the wind in.

What the wind actually does to a slate roof

Wind works on a slate roof in three ways. First, it lifts: a gust gets under the lower edge of a tile, and the tile behaves like a little wing. Second, it tears: the airflow curls around the eaves, the gable and the ridge, and pulls at the edge of the tile from the outside. Third, it drives: it pushes rain horizontally, up and between the laps — the one direction a lap joint was never designed to stop.

Lift, tear, drive. A tile is not usually "blown away" in one piece. It gets lifted at a corner, torn sideways, and eventually driven off. So every installation detail has to answer a single question: can this tile be lifted?

And the tiles that can be lifted are almost always in the same three places: the eaves course (wind gets under the bottom edge), the gable edges (wind accelerates around the corner), and the ridge (the airflow curls over the top). That's where the extra fixing goes.

1. Two nails in the headlap, not one

On a sheltered roof, one nail per tile is the traditional practice, and it's fine. On an exposed site I nail every tile twice. The second nail doesn't hold the tile "twice as well" — it holds the tile in two places, so the tile can't rotate around the first nail when a gust catches the corner. One nail, the tile swings. Two nails, it can't.

Both nails go into the headlap — the part of the tile covered by the course above — and never into the exposed face. The metal matters too. On the coast I use copper or stainless steel, sized so the head pulls flat without cracking the slate. A rusted nail is a loose nail, and a loose nail is a handle for the wind. The nail vs hook methods are laid out in the fixing methods guide, and the metal comparison in copper vs stainless steel. The wind-country conclusion, in one line: don't save money on the fixings.

2. Shorter tile, shorter lever

The longer the tile, the longer the lever the wind has to work with. When a gust lifts a tile, the tile pivots around its top edge, and a 500×250 tile gives the wind a longer arm than a 400×250. So on open hillsides, at the coast, on any roof the weather can reach without a tree in between, I drop the working size: 400×250 (or 450×250 where the site is only partially exposed), and I never use 600×400 on an exposed roof. The sizes guide covers coverage and cost; the wind rule is simply: short beats long.

3. Heavy tiles at the bottom — ballast

Weight is a silent helper on a windy roof. The lower courses — the first three rows up from the eaves — are where the wind gets its first purchase, and they're the rows I give the most weight. I lay heavier slates there: a thicker grade, or simply the denser tiles out of the batch. 34 kg per square metre of real slate already sits on the roof; put more of it where the wind starts. It costs nothing extra if you choose the tiles in the sort — it's just giving the heavy ones the job they're best at.

4. Eaves, gables, ridge: the edges are where it starts

Walk any roof after a storm and the tiles that are missing are almost always near an edge, not in the middle. The middle of the roof is protected by the surrounding tiles; an edge has nothing behind it.

At the eaves, the first course sits on the open edge of the roof. I nail it with both nails, and I tuck a lead or aluminium drip strip under the lower edge so the wind can't get up underneath the slab. On truly open sites that eaves course gets hooks as well.

At the gable, the wind accelerates around the corner and tries to lift the verge from outside. I bed the verge tiles in mortar, or set them on hooks, and bring the gable flashing out wide enough that the wind can't get in behind it. A verge that "looks" secure but isn't fixed is the first thing a storm finds.

At the ridge, the airflow curls over the top and pulls on the ridge tile from above. On a wind roof the ridge is never just balanced — it's fixed with ridge screws or nails into the timber, or bedded in mortar. The water-side details of all these edges live in the eaves, ridges, hips and valleys guide; here the wind question is the same as everywhere: can this be lifted?

5. Snow and wind: the winter that breaks roofs

Wind by itself a slate roof handles fine. Wind plus snow is a different beast. Snow settles on the roof and seals the laps — that part is good. But then the wind blows the snow off in patches, and where the roof is exposed again the rain arrives at the same speed, driven into a lap that has just been wetted and frozen. When the water freezes it cracks the edges of the slate and loosens the nail here and there, and the next storm does the rest.

So for a snow-and-wind area I add three things: keep the pitch at 30° or above on open sites (see the minimum pitch guide), deepen the headlap by 15 mm over the sheltered standard (headlap calculation), and make sure the roof can breathe — a counter-battened, vapour-permeable assembly as described in deck, battens and underlayment. A ventilated roof dries out overnight; a sealed roof sits wet for a week, and that's when the battens begin to go.

6. The details that live in my tool bag

Four habits, not options:

• A 6 mm washer on every nail. A rubber or nylon washer under the head spreads the pressure, stops the slate cracking, and beds the tile down a little tighter. It costs pennies and it's the closest thing I know to glue for a windy roof.
• Hand-driven nails. I don't use a nail gun on the coast. A gun is fast but it leaves the heads standing proud, and a proud head is a handle for the wind. Hand-set heads pull flush.
• A 150 mm offcut in the bag. I keep a spare piece of slate about 150 mm long for gauging laps and setting out — the wind doesn't respect a memory, it respects a number.
• Staggered vertical joints, kept tight. The gap between adjacent tiles is where wind-driven rain likes to sit, so I keep the side joints as tight as the slate allows, and never line the head joints up. The why is in the joint spacing guide — the stagger is the weathertightness, not the gap.

One last thing I tell every client on a wind slope: a slate roof isn't afraid of the wind — it's afraid of the one tile nobody pressed down. Two nails, a short lever, weight at the bottom, edges that can't be lifted, a roof that breathes. Do those six and the gale will come and go while the house stays dry.

Quick answers: slate in the wind

• Roofing Slate Fixing Methods: Nails and Hooks — the methods behind the two-nail rule.
• Copper Nails vs Stainless Steel Nails — why the nail metal is a wind detail.
• How to Calculate Roofing Slate Headlap — adding the 15 mm of wind allowance.
• Roof Deck, Battens and Underlayment — the ventilated assembly that dries the roof.
• Slate Layout and Vertical Joint Spacing — why the stagger is the weathertightness.