NOTE Nº 0169 · REV B

Roof Tiles & Slates: Coverage, Fixings & Ventilation

How many tiles or slates per m² for each type, BS 5534 nailing and clipping rules, dry-fix systems, and eaves-to-ridge ventilation requirements.

By The Renovation Notes Team · 9 min read · Published 25 August 2025 · updated within the last month · Sources checked 30 September 2026

Black and white photo of a tiled roof featuring a dormer window, showcasing architectural details.

In short

Large-format concrete interlocking tiles cover about 10–11 tiles/m², clay plain tiles about 60/m² and natural slates roughly 13–20/m² depending on size and headlap. Under BS 5534:2014+A2:2018, mortar can no longer be relied on to resist wind uplift, so tiles, slates and ridge, hip and verge units need mechanical fixings.

Choosing between tiles and slates is rarely just an aesthetic call. Coverage rates, weight, fixing schedules and ventilation strategy all interact, get one wrong and you’ll be back on the roof within a decade. This guide works through each factor using the figures roofing contractors and building inspectors actually use.

Tiles and Slates Per m² by Type

Coverage is driven by the minimum headlap, the amount of each unit hidden beneath the one above, which in turn depends on roof pitch and exposure zone. The table below shows typical ranges for the main product families at a 35° pitch in a sheltered location; reduce headlap (and raise coverage) only with manufacturer approval and within BS 5534 limits.

Product type	Units/m² (approx.)	Weight (kg/m²)	Min pitch	Typical batten gauge (mm)
Concrete interlocking tile (large format, 420 × 330 mm)	10–11	45–54	17.5–25°	up to 345
Concrete double-roman / pantile (420 × 330 mm)	about 10	44–47	22.5–25°	up to 345
Clay plain tile (265 × 165 mm)	60	about 64	30–35°	up to 100
Natural Welsh slate (600 × 300 mm)	about 13	30–35	25°	250–263
Natural Spanish slate (500 × 250 mm)	18.5–20	25–30	20°	200–213
Fibre-cement slate (600 × 300 mm)	about 13	14–18	20°	250–263
Reconstituted stone slate	14–22	45–70	22.5°	Varies

The concrete and clay figures are manufacturers’ published data. Marley’s Modern concrete tile, for example, has a maximum gauge of 345 mm and covers 9.9 tiles/m² at a 75 mm headlap.¹ Marley’s Acme clay plain tile covers 60 tiles/m² at a 100 mm gauge and weighs 64 kg/m² laid.² The slate figures are worked from the gauge formula below, assuming a 75–100 mm headlap and a 3–5 mm gap between slates: a 600 × 300 mm slate at a 250 mm gauge covers about 13/m², and a 500 × 250 mm slate at a 200 mm gauge about 20/m².

Gauge = (exposed length) = (slate/tile length − headlap) ÷ 2 for slates; for single-lap tiles it equals the full exposed height. Always take batten gauge from the manufacturer’s technical data sheet verified against BS 5534 Section 6.

Nailing and Clipping: BS 5534 Requirements

BS 5534:2014+A2:2018 (Slating and tiling for pitched roofs and vertical cladding) is the current governing standard.³ Among the changes BSI lists for it, reliance on the tensile strength of mortar bedding to resist wind uplift has been withdrawn, so tiles, slates and ridge, hip and verge units all need mechanical fixings, to a specification set by a wind uplift calculation.³ In practice that means:

For tiles: single-lap interlocking tiles are typically nailed at the head and clipped at the tail, or held by the manufacturer’s own clip system, with the number of fixings set by the wind uplift calculation for the site. Double-lap plain tiles are nailed through the holes near the head.

For slates: natural slates are usually fixed with two copper or stainless-steel nails each, or with stainless-steel hooks, into treated softwood battens sized for the rafter spacing; fibre-cement slates also take a copper disc rivet at the tail.

Nail and batten sizes come from the manufacturer’s fixing specification. For its Acme clay plain tile, for example, Marley recommends 38 mm × 25 mm battens on rafters at up to 600 mm centres and 38 mm × 2.65 mm tile nails.²

BS 5534 Annex A sets the pressure test that decides which zones an underlay may be used in, while the worked wind uplift and fixing calculations sit in Annex K (mapped against BS EN 1991-1-4 UK National Annex).³ The standard divides the UK into geographical wind Zones 1 to 5.⁴ The zones are used chiefly to decide which underlays may be used where; the fixings for the tiles or slates themselves come from the site’s wind uplift calculation, which also takes account of height, exposure and roof pitch.

Practical costs for fixings per 100 m² roof:

Annular-ring shank nails (stainless, 3.35 mm × 30 mm, 1,500-pack): £25–£40
Aluminium or stainless tile clips (bag of 250): £18–£30
Copper nails for natural slate (1 kg, approx. 500 nails): £12–£20

Dry Verge and Dry Ridge Systems

Traditional mortar at verges and ridges is now seen as a weak point: settlement and shrinkage can make it crack and fall out, sometimes within a relatively short time, letting water in.⁵ Dry-fix systems eliminate mortar entirely, and BSI noted in 2018 that more than half of the UK’s new and refurbished roofs already used dry-fixed ridge and hip systems.⁶ The specification they are judged against is BS 8612:2018, which covers dry-fixed ridge and hip systems and dry-fixed verge systems on both new and existing roofs.⁶

Dry verge: Interlocking plastic caps are clipped over the edge of the tiles at the gable, giving a secure fixing without mortar.⁵ Avoid purely push-fit systems in severe exposure; specify mechanically fixed units with stainless screws. Material cost: £4–£8 per linear metre.

Dry ridge: The ridge tiles are each screwed or clipped to a timber ridge batten held on metal brackets, and a flexible ridge roll dressed onto the tiles on either side seals the joint. Vented versions leave a continuous gap beneath the roll that can provide the high-level ventilation a cold roof needs. Material cost including carrier, clips and roll: £12–£20 per linear metre.

Eaves and Ridge Ventilation

Roof ventilation is a Building Regulations Approved Document C matter rather than a Part L one: paragraph 6.10 sends you to BS 5250, although the 2013 Approved Document still names the 2002 edition rather than the current BS 5250:2021 (Management of moisture in buildings).⁷⁸ For a cold pitched roof (insulation at ceiling level):

Eaves: ventilation equivalent to a continuous 25 mm opening along each eaves (25,000 mm² per metre run), typically provided by over-fascia vents or ventilated soffit panels, with eaves trays or rafter vents keeping a clear air path past the insulation.
Ridge: corresponding outlet is required at or near the ridge, minimum 5 mm continuous equivalent open area per pitch, which NHBC states as a free area of not less than 5,000 mm²/m against 25,000 mm²/m at the eaves.⁹ Vented dry ridge systems, high-level tile vents or purpose-made ridge vent tiles can all provide this, provided their declared free areas add up to the requirement.
Counter-battens: where the breather membrane is laid taut over sarking boards or rigid insulation rather than draped between rafters, counter-battens lift the tiling battens so that water and air can pass beneath them.

For warm roofs (insulation between and/or above rafters), vapour control on the warm side of the insulation becomes essential, and there is no roof void to ventilate. That is not the same as needing no ventilation at all: under a high-resistance underlay such as bitumen felt, BS 5250:2021 still wants a ventilated void of at least 25 mm between insulation and underlay, plus roughly 15 mm for underlay drape, so 40 mm in practice.¹⁰

Ventilation tile or vent unit rates: in-line tile vents roughly £16–£50 each depending on profile and type; over-fascia vent strips about £1.30–£2.80 per metre.

Material Cost Summary

Material	Supply cost (£/m², 2026)	Notes
Concrete interlocking tiles	£8–£16	Budget to mid-range; includes clips
Clay plain tiles	£22–£45	Handmade clay at top end
Natural Welsh slate	£30–£60	Source and grade dependent
Natural Spanish/Portuguese slate	£18–£35	S1 grade preferred for UK exposure
Fibre-cement slate	£10–£18	40-year BBA-certified products
Reconstituted stone slate	£25–£55	Region-specific aesthetics

These are material-only supply costs; add roofing labour at £18–£28/m² for tile work and £22–£35/m² for natural slate on typical domestic projects. Scaffolding and associated costs are additional.

Relevant Standards and Guidance

BS 5534:2014+A2:2018, primary standard for all slating and tiling
BS 8612:2018, dry-fixed ridge, hip and verge systems
BS 5250:2021, moisture management including roof ventilation
NHBC Standards Chapter 7.2, pitched roofs (warranties require BS 5534 compliance)
Approved Document C, site preparation and resistance to moisture
Approved Document L (2021 edition), conservation of fuel and power, thermal performance

When specifying any roofing system, the wind uplift and fixing calculation to BS 5534 (worked examples in Annex K) should be carried out or confirmed by the roofing contractor and retained as part of the building file, increasingly expected by building control bodies and warranty inspectors.³

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.

References (10)

Figures in this note were checked against the sources below on 30 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

1technicalsupplier figureMarley Ltd, a data sheet.RN-MQ1XYAMarley Modern flat interlocking concrete tile: size 420mm x 330mm, cover width 292mm nominal, hanging length 397mm. Minimum pitch 22.5 degrees smooth finish at 75mm headlap, 17.5 degrees smooth at 100mm headlap, 30 degrees granular at 75mm headlap, 25 degrees granular at 100mm headlap; maximum pitch 90 degrees. Minimum headlap 75mm at 22.5 degrees and above, maximum gauge 345mm. Covering capacity 9.9 tiles/m2 at 75mm headlap, 10.7 tiles/m2 at 100mm headlap. Weight of tiling 50kg/m2 (0.49 kN/m2) at 75mm headlap, 54kg/m2 (0.53 kN/m2) at 100mm headlap. Battens 2.9 lin.m/m2 at 75mm headlap, 3.1 at 100mm; batten size 38 x 25mm to 450mm rafter centres, 50 x 25mm to 600mm centres. Tile nails 50mm x 3.35mm.
2technicalsupplier figureMarley Ltd, a data sheet.RN-8QKBLYMarley Acme single camber clay plain tile: 265mm x 165mm, cover width 165mm nominal. Minimum pitch 30 degrees, maximum 90 degrees. Minimum headlap 65mm on a roof, 35mm vertical tiling. Maximum gauge 100mm roof, 115mm vertical. Covering capacity 60 tiles/m2 at 100mm gauge on a roof, 53 tiles/m2 at 115mm gauge vertical. Weight of tiling 64kg/m2 (0.63 kN/m2) at 100mm gauge roof, 56kg/m2 (0.55 kN/m2) at 115mm gauge vertical. Battens 10.0 lin.m/m2 at 100mm gauge roof, 8.7 lin.m/m2 vertical; batten 38 x 25mm to 600mm rafter centres. Tile nails 38mm x 2.65mm.
3technicalstrongBSI (British Standards Institution), a standard.RN-FCTWJDSTATUS: CURRENT. BS 5534:2014+A2:2018 published 28 February 2018. Full title is 'Slating and tiling for pitched roofs and vertical cladding. Code of practice' - NOT the older 2003 title 'Code of practice for slating and tiling', which is a common stale citation. Gives recommendations primarily for the design, performance and installation of new build pitched roofs including vertical cladding, and for normal re-roofing work including repairs, using slates, tiles, shingles and shakes and their associated components. The A2:2018 amendment reworked wind loads and uplift resistances of the roof covering and underlay around the Eurocodes and withdrew reliance on the tensile strength of mortar bedding to resist wind uplift, which is why mortar-bedded ridges and verges alone no longer satisfy the code. Batten grading rules sit inside this standard (clause 4.11 and its annex), not in BS 4978, BS 5756 or BS EN 14081.
4technicalstrongBritish Board of Agrement.RN-DFUI2FThe document that settles what BS 5534's geographical wind zones are actually called. Table 3 is headed 'Zones of applicability according to BS 5534:2014, Clause A.8' and gives Zones 1 to 2 at a 345 mm batten gauge with battened lap, and Zones 1 to 5 at 250 mm battened lap, taped laps, integrated taped laps or with counter battens. They are NUMBERED 1 to 5, not lettered, so any note quoting a lettered exposure zone for roof fixings is wrong. Table 2 gives declared wind uplift resistances of 1119, 2165, greater than 1932, 2949 and 1932 Pa for those five conditions, and note (2) fixes the minimum design wind pressure for Zone 1 at 820 Pa. Validity is limited to a well sealed ceiling as defined in BS 9250:2007 clause 3.7, ridge height 15 m or less, pitch 12.5 to 70 degrees, site altitude 100 m or less and insignificant topography; otherwise uplift must be calculated from BS 5534. Counter batten allowance applies to any counter batten 11 mm deep or more, and NHBC does not accept wind zones based on counter battens on an unsupported roof. Also confirms BS 8000-6:2023 as the live workmanship code. Note the UKAS suspension of BBA accreditations from 26 Feb 2026 when weighing this source.
5technicalsupplier figureMarley, guidance.RN-N11KICA roof tile maker's guide to dry verge systems. It explains why mortar verges deteriorate and how clip-on dry verge units replace them.
6technicalstrongBSI, a standard.RN-DQAH47Published 31 January 2018, this is the standard behind every dry ridge and dry verge claim. It applies to dry-fixed ridge and hip systems connected to timber ridge or hip battens, ridge boards or hip rafters, and to dry-fixed verge systems installed with slating or tiling, for both new buildings and renovations. It sets minimum performance requirements for fixing resistance, weather-tightness and durability with guidance on ventilation, and includes the performance tests, calculation methods and acceptance criteria. Cite it when a note says mortar bedded ridges have been superseded by mechanically fixed dry systems.
7technicalstrongBSI, a standard.RN-DVFEWEBS 5250:2021, published 31 July 2021, is the current code of practice for managing moisture in buildings and the reference for cold roof and warm roof condensation risk, roof void ventilation and the choice between high resistance and low resistance underlays. It replaced the earlier condensation code of practice and is the standard the NFRC and the Approved Documents point to when a note discusses interstitial condensation in a loft or a boarded roof.
8technicalvery strongMinistry of Housing, Communities and Local Government.RN-NPO8FJThe statutory figures behind a damp diagnosis, and the numbers to quote when a note explains why ground levels or a bridged damp proof course cause rising damp. Paragraph 5.2 requires that in an external wall the damp-proof course should be at least 150mm above the level of the adjoining ground (Diagram 8) unless part of the building protects the wall, and that in an external cavity wall the cavity should be taken down at least 225mm below the level of the lowest damp-proof course, or a damp-proof tray provided (Diagram 9a). For suspended timber ground floors it requires a ventilated air space of at least 75mm from the ground covering to the underside of any wall-plates and at least 150mm to the underside of the suspended timber floor or insulation, with ventilation openings on two opposing external walls of not less than 1,500mm2 per metre run of external wall or 500mm2 per square metre of floor area, whichever is greater; for suspended concrete floors the clear ventilated space is at least 150mm with the same opening sizes. Section 2.39 onwards covers radon, referring to BRE Report BR 211 for protective measures. The 2013 edition was published on 3 September 2013 with changes in effect from 1 October 2013.
9technicalstrongNHBC, guidance.RN-GSDAA1August 2022, first issue, one page. NHBC performance standard 7.2.15 requires roofs to have adequate precautions against condensation. Section 12.4.3.2 of BS 5250 gives the method for deciding whether a roof covering is air permeable: the covering is deemed air permeable if the airflow at a differential of 10 Pa exceeds 17.4 m3/h Ar, where Ar is the tested area of the outer weatherproof covering in m2 as defined in BS 5534:2014+A2:2018; below that it is air impermeable. Where air impermeable coverings are used on a COLD pitched roof with an LR underlay, provide ventilation openings to the roof void per BS 5250 sections 12.5, 12.6 and 12.7, plus ventilation openings to the batten space above the underlay created with minimum 25 mm deep counter battens, free area not less than 25,000 mm2/m at eaves level and 5,000 mm2/m at ridge level. The same batten-space figures apply on a WARM pitched roof with an LR underlay, with an air and vapour control layer at ceiling level. This is the cleanest in-tier statement of the 25,000 and 5,000 mm2/m opening figures, i.e. 25 mm continuous at eaves and 5 mm at ridge. The live URL 403s to plain scripted fetches on some paths but answers 200 with a browser user agent; the Wayback copy reads cleanly.
10technicalvery strongMinistry of Housing, Communities and Local Government.RN-ISI2YI2024 government hygrothermal modelling assessment of sprayed foam on domestic timber roofs, and an unusually quotable secondary source for BS 5250:2021's prescriptive roof guidance. Risks are low only where an OPEN CELL, moisture permeable insulant is used with an air and vapour control layer on the warm side and a space left between insulation and underlay, ventilated from the eaves where a high resistance underlay is used. For a WARM pitched roof with a high resistance underlay such as bitumen felt: each ventilated void should be at least 25 mm deep, ventilated at high and low level, plus a 15 mm allowance for underlay drape, giving 25 + 15 = 40 mm. For a low resistance underlay, option 1 is an AVCL plus an unventilated counter batten air gap for air permeable coverings; option 2, where an AVCL is impracticable, follows the HR guidance. It also states plainly that official moisture guidance is Approved Document C, that AD C was last fully revised in 2004 with 2010 and 2013 amendments, and that AD C REFERENCES THE 2002 EDITION OF BS 5250, not the current 2021 edition. It names BS EN ISO 13788:2012 (the Glaser method) as the calculation method referenced by the 2002 edition, and notes the Glaser method may underestimate risk because it cannot simulate heat and liquid transport, unlike BS EN 15026:2007.