Summary

Selecting the right roof tile type is a decision that affects the building for decades. The key variables are the existing roof structure's load capacity (can it carry the proposed tile weight?), the required minimum pitch (different tiles have different minimum pitch requirements), local planning constraints (particularly in conservation areas where clay or slate may be required to match existing), and budget. Cost ranges from around £20–30/m² for concrete interlocking tiles to £70–100/m²+ for natural Welsh slate — but lifespan differences mean the long-term cost per year can be comparable.

BS 5534:2014+A2:2018 is the key British Standard for slating and tiling of pitched roofs. It covers minimum pitch, lap requirements, fixing specifications (including the increased use of mechanical fixing with nails and clips following Amendment 1 in 2016), and underlay requirements. The Amendment 1 changes are significant: in most wind zones across the UK, far more tiles now require mechanical fixing (nailing or clipping) than was previously the standard — a fully-bedded or dry-fixed roof per the old standard may now be non-compliant.

The difference between a roof that lasts 30 years and one that lasts 60 years is often not the tile itself but the installation quality: correct minimum pitch, correct lap, correct batten sizing, correct fixing, and a quality breathable underlay. A cheap concrete tile correctly installed will outlast an expensive slate installed on too shallow a pitch.

Key Facts

  • BS 5534:2014+A2:2018 — the UK standard for slating and tiling of pitched roofs and vertical cladding; specifies minimum pitches, laps, and fixing requirements
  • Concrete interlocking tiles — most common UK roof tile; minimum pitch typically 17.5° (low-pitch types go to 12.5°); weight 40–55 kg/m²; lifespan 40–60 years; cheapest option
  • Clay plain tiles — traditional double-lap tiles, 265x165mm; minimum pitch 35°–40°; weight 65–75 kg/m²; lifespan 60–100+ years; required in many conservation areas
  • Clay interlocking tiles — single-lap; minimum pitch typically 30° (some down to 22.5°); weight 35–55 kg/m²; lifespan 60–100+ years
  • Natural slate — Welsh, Spanish, or Chinese; minimum pitch 20°–25° (Welsh); weight 25–35 kg/m²; lifespan 75–150 years; premium cost; Welsh slate is preferred for quality and appearance
  • Fibre cement slate — manufactured to resemble natural slate; minimum pitch 20°–25°; weight 20–25 kg/m²; lifespan 30–40 years; lower cost than natural slate; lighter
  • Reclaimed tiles/slates — salvaged materials for heritage repairs; must match existing in size, colour, and profile; check for frost damage (spalling) before use
  • Rafter loading — changing tile type significantly affects the loading on rafters and wallplates; going from concrete interlocking to clay plain tiles (much heavier and requiring closer batten spacing) may require a structural check
  • Batten sizing — 25x50mm sawn softwood batts for tiles up to 70 kg/m²; 38x25mm for lighter slate; batten gauge (spacing) set by the tile manufacturer's data sheet based on pitch and lap
  • Underlay — BS 5534 requires a suitable underlay under all roof coverings; breathable (vapour-permeable) underlay is now standard; non-breathable (traditional felt) still permitted in ventilated roof designs
  • Wind uplift — Amendment 1 (2016) significantly increased the proportion of tiles requiring mechanical fixing; in most UK wind zones, a meaningful proportion of tiles (often all of them in exposed areas) must be nailed or clipped
  • Batten fixing — BS 5534 requires that tiling battens be fixed to every rafter with two nails minimum
  • Planning restrictions — in conservation areas, national parks, and for listed buildings, the tile type may be restricted to match the local vernacular; check with the local planning authority before re-roofing
  • Code 4 lead — used for valleys, soakers, and flashing; minimum 1.8mm; detailed per Lead Sheet Association (LSA) guidance
  • Ridge and hip tiles — can be dry-fixed (using a proprietary clip system) or mortar-bedded; dry-fixed is preferred as mortar eventually fails; mortar-bedded ridges are the most common call-back item on newly tiled roofs

Quick Reference Table

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Tile Type Minimum Pitch Weight (kg/m²) Approx. Cost (m²) Lifespan
Concrete interlocking (standard) 17.5° 40–55 £15–25 40–60 years
Concrete interlocking (low pitch) 12.5° 40–50 £20–30 40–60 years
Clay plain tile 35–40° 65–75 £30–55 60–100+ years
Clay interlocking 22.5–30° 35–55 £25–45 60–100+ years
Natural slate (Welsh) 20–25° 25–35 £60–100 75–150 years
Natural slate (Spanish) 20–25° 25–35 £35–55 60–100 years
Natural slate (Chinese) 20–25° 25–35 £20–35 30–50 years
Fibre cement slate 20–25° 20–25 £25–40 30–40 years

Note: material costs only; installation adds £30–70/m² depending on complexity.

Consideration Concrete Clay Plain Natural Welsh Slate Fibre Cement
Conservation area use Often not permitted Yes Yes Sometimes
Low pitch suitability Good (specialist types) Poor Moderate Moderate
Weight (structural impact) Medium High Low Very low
Colour stability Fades over time Very good Excellent Variable
Maintenance Low Low-medium Low Low
Availability of matching tiles Moderate (discontinued profiles) Good Specialist Good

Detailed Guidance

Concrete Interlocking Tiles

Concrete interlocking tiles are the most commonly installed roof tile in the UK and have been since the 1950s. They interlock at the side and lap at the head, providing a single-lap covering. Major manufacturers include Marley (Ludlow, Mendip, Eternit), Redland (49, Richmond), and Sandtoft (20-20).

Advantages: lowest material cost; wide range of profiles and colours; reasonable lifespan; easy to source matching tiles for repairs.

Disadvantages: colour can fade and algae growth makes older roofs look patchy (treatments are available but not always effective); minimum pitch typically higher than some alternatives; heavier than slate.

Common failure modes: cracked tiles from physical damage (falling branches, foot traffic); delaminating surface treatment on older tiles; ridge and hip mortar failure (the most common repair requirement).

Installation key points:

  • Always check the specific tile manufacturer's fixing guide for the minimum pitch, batten gauge, and fixing specification
  • Nail or clip as required by BS 5534 wind uplift calculations (most roofs in the UK now require a significant proportion to be nailed)
  • Ensure the batten gauge is set correctly from the tile's data sheet — wrong gauge means tiles don't lap correctly

Clay Tiles

Clay plain tiles are the traditional UK roof tile, particularly in south-east England, East Anglia, and parts of the Midlands. They are 265mm x 165mm, double-nib hanging tiles with a minimum pitch of 35–40°. Their long lifespan and authentic appearance make them the preferred tile in conservation areas.

Clay interlocking tiles (pantiles in East Anglia and the north-east; Roman, Riven, and other profiles) have a lower minimum pitch than plain tiles and are associated with different regional vernacular traditions.

Key considerations:

  • Weight: clay plain tiles at 65–75 kg/m² are significantly heavier than concrete interlocking tiles; always carry out a structural assessment before replacing concrete tiles with clay plain tiles on an existing structure
  • Batten spacing: plain tiles require 100–115mm gauge (very close), meaning many more battens are needed than for interlocking tiles
  • Source: for conservation areas, sourcing matching clay tiles for partial re-roofs can be difficult; specialist salvage yards are often necessary for period properties

Natural Slate

Natural slate is quarried from metamorphic rock. Welsh slate (from Penrhyn, Ffestiniog, or Preseli quarries) is the highest quality, with exceptional durability and a characteristic blue-grey appearance. Spanish slate is a lower-cost alternative; Chinese slate is the cheapest but has variable quality and is prone to delamination.

Assessing existing natural slate for repair vs replacement:

  • Tap each slate: a dull thud indicates delamination (the slate is breaking down) — replace
  • Sound slates ring clearly when tapped
  • A general rule: if more than 15–20% of slates need replacing, a full re-roof is more economic than continued patching
  • Nail sickness: the nails fixing old slates to the battens corrode over time (often after 50–80 years); when nails corrode, slates slide down and fall off without warning — nail sickness is a major reason for full re-roofing of old natural slate roofs

Minimum pitch: Welsh slate can be laid to as low as 20–25° pitch with the correct headlap; Spanish and Chinese slate typically 25–30° minimum.

Fixing: every slate fixed with two nails at the head (centre-nailing for smaller slates); copper or stainless steel nails (not galvanised, which corrode faster); batten gauge set from the slate length and headlap per BS 5534

Fibre Cement Slate

Fibre cement slates are manufactured to replicate natural slate in profile and appearance but are made from Portland cement reinforced with cellulose fibres. Major manufacturers include Cedral, Marley Eternit (Rivendale, Birkdale), and Swissline.

Advantages over natural slate: lighter weight; more uniform size and thickness; lower cost; easier to work with on site.

Disadvantages: shorter lifespan (30–40 years vs 75+ for quality natural slate); can look artificial at close inspection; cannot be used in all conservation areas.

Installation: similar to natural slate; nail-fixed through pre-drilled holes; copper or stainless steel nails; correct headlap per manufacturer's specification.

Roof Structure Load Assessment

When changing tile type, a structural assessment should be carried out — particularly when moving to heavier tiles (e.g. from concrete interlocking to clay plain). The assessment considers:

  1. Existing rafter size and span — checked against Approved Document A span tables for the new load
  2. Existing wallplate condition — the wallplate (timber plate on top of the wall that carries the rafter feet) should be checked for rot
  3. Batten spacing requirement — closer batten spacing (as with clay plain tiles) means more battens; more battens = more load; this is often the critical additional load beyond the tile self-weight
  4. Point loads — hip rafter, valley rafter, and ridge board loads change with tile weight

For most domestic re-roofs within the same tile category (like-for-like), a formal structural calculation is not required. For significant weight changes, consult a structural engineer.

Frequently Asked Questions

How do I match a concrete tile for a repair when the original profile is discontinued?

This is a common and frustrating problem. Start with the manufacturer — most major manufacturers maintain a list of discontinued products and sometimes have old stock or can suggest the closest current equivalent. If not, specialist salvage yards (particularly those near housing estates built in a specific era) sometimes hold stock of discontinued tiles. As a last resort, the closest match from current production is used — an exact match is rarely achievable on older properties.

My flat-profile concrete tiles are lifting at the edges — what's happening?

This is usually the tiles becoming unclipped over time (if they were clipped) or nail sickness (if they were nailed). In windy conditions, the wind lifts the free tail of the tile. The fix is to re-clip or re-nail the affected tiles, and to assess whether a wider programme of re-clipping is needed (check a representative sample across the roof). Ridge mortar failure that is allowing roof movement can also cause this.

Is Welsh slate worth the premium over Spanish or Chinese slate?

For a permanent installation expected to last 100+ years, Welsh slate is strongly preferred — it has a proven track record of very long life, it is more resistant to delamination, and it has a superior appearance that tends to look better over time. Spanish slate from quality quarries (Cupa, Pizarras del Norte) is a reasonable alternative at lower cost. Chinese slate has very variable quality — some grades are excellent, others delaminate within 20 years. If using Chinese slate, insist on a certified grade from a reputable supplier with a manufacturer's warranty.

Do all roof tiles need to be mechanically fixed now?

Following BS 5534:2014 Amendment 1 (2016), the fixing requirement has increased significantly. In most wind zones and most situations across the UK, a significant proportion of tiles must now be nailed or clipped rather than relying on head-nib and interlock alone. The exact requirement depends on wind zone, altitude, exposure, and tile type — each manufacturer publishes a fixing specification for their tiles for each wind zone. Always check the specific tile's fixing guide before installation.

Regulations & Standards