BS 8000-6:2023 Explained

1) Who does BS 8000-6 apply to?

• New roofs being covered with clay tiles, concrete tiles, natural slates or fibre-cement slates.
• Re-roofing and refurbishment work on domestic and commercial buildings.
• Vertically tiled or slated walls, including associated battens, counterbattens and accessories.

What it’s not: BS 8000-6 is not primarily a structural design standard. It is a workmanship standard explaining how specified roofing materials and systems should be checked, prepared, laid, fixed and finished on site.

2) The big idea in plain English

A well-designed roof can still fail if it is poorly installed. BS 8000-6’s core message is:

• Good workmanship starts before laying begins. Materials, drawings, working instructions and the roof structure should be checked first.
• The roof should be properly set out. Batten gauge, coursing, overhangs and junctions need planning before tiles or slates are fixed.
• Every layer matters. Underlays, battens, fixings, flashings and accessories all contribute to performance.
• Details require care. Eaves, ridges, hips, verges, valleys, abutments and penetrations are common defect locations.

If you remember one thing: roof quality depends as much on preparation and workmanship as it does on the materials selected.

3) Materials, checking & storage

BS 8000-6 requires roofing materials to be checked before installation and stored so they remain suitable for use.

• Check products: tiles, slates, battens, underlays and fittings should match the project specification and be undamaged.
• Check identification: products should carry the appropriate manufacturer labelling, certification or conformity information.
• Store safely: materials should be kept on firm, clean ground and protected from damage, contamination and traffic.
• Protect timber: battens and counterbattens should be supported to prevent sagging, twisting and saturation.

Materials stored on the roof should be distributed carefully to avoid overloading or unbalancing the structure.

Client takeaway: damaged, unmarked or poorly stored materials should not simply be installed because they have already arrived on site.

4) Preparing the roof before work starts

Before roofing work begins, the installer should check that the structure and adjoining construction are ready.

• Rafters and trusses: should be sound, securely braced and reasonably true.
• Roof pitch and alignment: should suit the selected tile or slate and the required headlap and sidelap.
• Fascias and gutters: should be correctly positioned to form the eaves datum and receive rainwater.
• Flashings and valleys: concealed elements should be positioned before they are covered by slating or tiling.

The work should also be coordinated with other trades so that flashings, penetrations, insulation and fire-stopping are completed in the correct sequence.

Client takeaway: roofing should not start over a defective or poorly aligned structure in the hope that the roof covering will hide the problem.

5) Underlays, battens & setting out

Underlays and battens form the supporting system beneath the visible roof covering and require careful installation.

What this means in practice

• Underlay direction: underlay is normally laid parallel to the eaves with the correct overlaps for the roof pitch and construction.
• Drainage: unsupported underlay should be draped so water drains beneath battens and into the gutter.
• Avoid damage: punctures and tears should be repaired before the roof covering is installed.
• Batten quality: battens should be the specified size, correctly marked and fixed to every support.

Battens should be set out in straight, regular courses, with joints centred on supports and staggered appropriately.

Client takeaway: irregular batten gauge or poorly positioned underlay laps can affect both the appearance and weather performance of the finished roof.

6) Tiles & mechanical fixing

Clay and concrete tiles should be laid in regular courses and mechanically fixed in accordance with the design, BS 5534 and the manufacturer’s recommendations.

• Set out before laying: roof width, verge overhangs and available tile shunt should be assessed in advance.
• Do not exceed gauge: the manufacturer’s maximum batten gauge should not be exceeded.
• Mechanical fixing: every tile should be mechanically fixed as a minimum, subject to the appropriate fixing specification.
• Perimeter restraint: perimeter tiles should receive enhanced fixing because edges are more exposed to wind uplift.

Small cut tile pieces at hips, valleys and abutments should be securely fixed or bonded to adjacent full tiles using suitable proprietary methods.

Client takeaway: mortar or adhesive should not be used as a substitute for the required mechanical fixing of the roof covering.

7) Eaves, ridges, hips, verges & valleys

The most vulnerable parts of a tiled or slated roof are usually its edges and junctions.

• Eaves: tiles or slates should project correctly into the gutter and remain in the same plane as the main roof.
• Ridges and hips: should have the correct cover, bedding where used, and mechanical restraint.
• Verges: overhangs, undercloaks, mortar or dry-fix components should be neatly aligned and securely fixed.
• Valleys: underlays, valley linings and adjacent roof coverings should be installed to permit unrestricted drainage.

Dry-fix ridge, hip and verge systems should be installed in accordance with the relevant product requirements and manufacturers’ instructions.

Client takeaway: poor workmanship at one junction can compromise an otherwise well-laid roof.

8) Natural slates, fibre-cement slates & heritage roofs

BS 8000-6 includes separate workmanship guidance for natural slate and fibre-cement slate roofing.

• Sort and prepare: natural slates should be checked, graded and prepared before laying.
• Maintain headlap: batten gauge and slate size should provide the specified minimum headlap.
• Fix carefully: nail holes, hooks and mechanical fixings should suit the slate type and roof exposure.
• Traditional roofs: historic and reclaimed materials may require a conservation-led approach rather than standard modern detailing.

Client takeaway: natural slating is a skilled trade. Sorting, gauging, fixing and detailing all affect both appearance and long-term durability.