How to Slate a Roof

Slating a roof is one of the most durable and attractive ways to weatherproof a home. Natural slate offers a long service life, excellent resistance to the British climate, and a timeless finish that suits both period and contemporary properties. Laying slate correctly is a skilled job, yet with a clear understanding of the method, the materials, and the rules that apply in the UK, homeowners can make informed decisions, specify good work, and judge quotations with confidence. This guide explains the full process from survey and design through to the final ridge, with realistic costs, safety advice, and best practice that aligns with current UK expectations.

What slating involves

A slate roof is a layered system. Above the rafters sits a breathable underlay that keeps out wind driven rain and controls draughts. Timber battens are fixed horizontally over the rafters at a precise spacing known as the gauge. Each slate is fixed to a batten with nails or hooks. Courses overlap so rain always falls onto a lower slate and away. At edges, junctions, and the ridge, special details and preformed components provide a neat, secure finish. The success of the whole roof depends on correct headlap for the pitch and exposure, on straight setting out, and on fixings suited to the location.

Choosing slate for UK conditions

Natural slate varies by origin, thickness, and colour. Welsh slate is widely regarded for strength and consistency. Spanish and Portuguese slates offer good quality at a lower price point. Brazilian and Chinese slates are also available and can be suitable when carefully selected. Slates are supplied in standard sizes such as 600 by 300 millimetres or 500 by 250 millimetres. Thicker slates are better for exposed sites. On coastal or high ground, choose a slate and fixing specification rated for high wind uplift and driving rain. Man made fibre cement slates are an alternative with consistent sizing and lower cost, though most homeowners choose natural slate for the longest lifespan and character.

Safety and access

Roof work must be planned with safe access. A properly erected scaffold with guard rails, working platforms, and ladder access is essential for a full re slate. Roof ladders are used to spread load on the slates during installation. Edge protection and debris control matter in built up areas. Personal protective equipment such as gloves, eye protection, and non slip footwear is a basic requirement. Hot works are rarely needed for slating, which reduces fire risk compared with some flat roof systems, but cutting dust should be controlled and disposal of old materials managed responsibly.

Planning and building regulations

Replacing a roof like for like usually falls under permitted development. If the property is listed or in a conservation area the local authority may require you to retain the original material and colour, and formal consent may be needed before work starts. Building regulations apply when more than a quarter of the roof covering is replaced. This brings thermal requirements into play, so insulation upgrades are normally required. The roof structure must be checked for loading, fixings must resist expected wind uplift, and ventilation must control condensation. Competent contractors can self certify compliance or you can use local authority building control.

Survey and design before work begins

A good slating job begins on paper. The contractor should confirm roof pitch, measure spans and rafter centres, and assess exposure. The pitch and exposure together dictate the minimum headlap and therefore the gauge. The slate size is chosen to suit that gauge with sensible waste. Eaves and ridge details are agreed, along with valleys, hips, and abutments. On older homes the structure may need repairs to rafters or wall plates. The survey should highlight rotten fascias, perished underlay, or failing mortar so the quote covers the real scope rather than leaving costly surprises.

Stripping out and preparing the deck

The old covering is removed in a controlled sequence and sent to licensed waste facilities or reclaimed if suitable. Any defective boards or sarking are replaced. Rafters are checked for straightness and treated where needed. New eaves support trays or tilting fillets are fitted to prevent underlay sagging into the gutter. Breathable underlay is rolled out horizontally from eaves to ridge with adequate overlaps. Temporary fixings hold it in place until battens are installed. The work area must remain watertight at the end of each day. Neat temporary coverings prevent rain entering the home during changeable weather.

Battening and setting out

Battens must be the correct thickness and grade for slating and are fixed with appropriate nails into rafters. The gauge is calculated from the chosen slate size and headlap. The first batten at the eaves and the last batten at the ridge are set with care so courses finish evenly. A chalk line helps maintain straight courses. On complex roofs a setting out plan saves time and avoids awkward cuts at verges and valleys. Battens are cut tight to abutments and supported so they do not spring when nailed. Every cut end is kept off the gutter line to avoid water tracking back.

Fixings and why they matter

Copper nails are the standard for natural slate because they resist corrosion. Aluminium or stainless steel may be specified in certain environments. Nail length is chosen so the point ends flush with the batten and does not protrude. On exposed sites slate hooks provide excellent wind resistance and reduce nail breakage, particularly on thinner slates. The choice between nails and hooks is not aesthetic alone. It is a technical decision based on wind loads, slate thickness, and local practice. Using the correct fixing pattern reduces rattling in storms and helps the roof meet design life expectations.

Laying slates course by course

Work begins with an under eaves or eaves course so that the main slates above present a clean lower edge. Each slate is graded by thickness before fixing so the flatter, thicker slates are used low down and at edges where they resist weather best. Slates are punched or pre holed and then fixed with two nails at the correct head position so they sit flat and tight on the batten. Joints are broken bond so vertical joints in one course are not aligned with those above and below. Cuts are made cleanly with a slate cutter. Sharp, crisp edges shed water better and look professional. Progress continues up the slope maintaining bond and gauge to the ridge line.

Verges, abutments, and valleys

At verges the slates are finished flush with the barge board or projecting slightly under a dry verge system. Mortar verges still exist on older homes but modern dry verge systems provide better long term security with fewer maintenance demands. Where the slate meets a wall, stepped or secret flashings in lead or appropriate alternative are installed so water is turned onto the slate surface and away. Valleys can be open metal, formed in lead or preformed troughs, or they can be closed where slates meet neatly over a valley board. The chosen detail must suit the slate size and gauge and must be secured so wind cannot lift the edges.

Ridges and hips

Ridge lines can be finished in traditional mortar bedded ridges or in modern dry ridge systems that use mechanical fixings and ridge rolls. Dry ridge is widely chosen today because it allows ventilation at the highest point while resisting wind and storm damage without ongoing repointing. Hips can be slate and lead, or you can use mechanically fixed hip tiles that match the ridge. The key requirement is that water is channelled away from the joint and fixings remain serviceable for the life of the roof.

Ventilation, insulation, and condensation control

A slate roof must be detailed so moisture from the home can escape without condensing within the roof space. Ventilation can be provided at the eaves and ridge or through discreet slate vents that connect to ducting if needed. When a re roof triggers building regulations, insulation levels are upgraded. The chosen build up must consider vapour control layers, airflow paths, and the risk of thermal bridging. Getting this right protects timbers, maintains indoor air quality, and keeps heating costs under control.

Typical costs for slating in the UK

Costs vary by region, access, and specification. As a broad guide, supply and fit of natural slate on a straightforward roof typically ranges from £120 to £200 per square metre. Premium Welsh slate and complex details will be higher. Fibre cement slates are often installed in the £90 to £140 per square metre range. On a typical three bedroom house a full re slate can sit between £12,000 and £25,000 depending on size, scaffold, insulation upgrades, and the number of hips, valleys, and roof windows. Small patch repairs to replace broken slates generally start from £150 to £300, while re fixing a short run of ridge or a small valley repair may cost £400 to £800. Always ask for a written specification that lists slate origin and size, underlay type, batten size and grade, fixing type, ridge and verge systems, insulation upgrades, and waste removal, so you can compare quotations fairly.

Quality checks before handover

A finished slate roof should present straight lines, even gauges, and clean edges with no visible nail heads. Eaves should project sufficiently to shed water into the gutter without overshoot. Flashings should be tight to the masonry and dressed neatly with no buckling. Valleys should have correct clearances so debris does not trap water. Vent components should be present where specified. Inside the loft you should see dry timbers, free airflow at the eaves, and a tidy underlay with no sagging. A competent contractor will provide warranties for materials and workmanship and, where required, certification for building control.

Common mistakes to avoid

The most frequent issues arise from inadequate headlap for the pitch, poorly spaced battens, or wrong fixings for the site exposure. Thin slates placed at verges or low down at the eaves can lift or break. Mortar only ridge and verge details on very exposed sites tend to fail early. Cutting slates with grinders produces heat and dust that can weaken edges and mark the surface, so mechanical slate cutters are preferred. Skipping ventilation when insulation is upgraded often leads to condensation problems that show as damp timbers and mould.

Maintenance and longevity

A well installed natural slate roof can last a century or more with light maintenance. Periodic checks after storms, clearing of gutters and valleys, and prompt replacement of occasional broken slates will keep it performing. Lead flashings can last decades when detailed and fixed properly. Dry ridge and verge systems reduce routine repointing. If you see slipped slates, rusting nails, or widespread delamination on older roofs, a planned re slate may be more economical than repeated patching.

When to use a professional roofer

Small repairs can be handled by experienced homeowners, but full slating requires trained hands. Professionals bring safe access, correct setting out, and fixings that match local wind zones. They also understand the interaction between insulation, ventilation, and underlay. For listed buildings, an experienced heritage roofer can source matching slates and use traditional details that satisfy conservation officers while keeping the building weather tight.

Conclusion

Slating a roof is a precise craft. The right slate, correct gauge and headlap, quality battens, and corrosion resistant fixings come together to create a long lasting covering that suits the UK climate. Add sound junction details, thoughtful ventilation, and compliance with building regulations, and you have a roof that will protect your home for generations. Whether you are commissioning a full re slate or planning improvements, understanding the steps and standards involved helps you brief contractors clearly, assess quotations on more than price alone, and secure a result that is both beautiful and resilient.