No. Profiled metal sheeting and concrete tiles differ in thickness, weight, fixing methods, lap details, and underlay requirements. Combining them under one item risks inaccurate pricing, inconsistent installation rates, and potential misunderstandings about sequencing, detailing, and coordination. The Standard System requires separation to ensure fair representation of scope, resources, and performance expectations.

Yes, and significantly so. While the roof area is still measured in square metres, the pitch directly influences tile overlaps, fixing density, underlay performance, and rainwater runoff design. Steeper pitches may increase wastage, complicate access and safety measures, and demand additional tile courses. The BOQ should clearly indicate pitch zones and measure each as a separate item. Grouping different pitches under a single rate risks cost distortion and non-compliance with manufacturer guidelines.

Double-lapping is not standard practice unless specified. It increases material quantity, reduces effective coverage, and adds significant labour. Therefore, it must be either described in the relevant roof covering item or measured as a separate or extra-over item. If introduced by site instruction or design development, the variation must be accompanied by updated fixing details, tile gauge spacing, and lap dimensions to allow for accurate pricing and compliance with wind load resistance requirements.

They are measured separately under the Carpentry or the Roof Structure trade. Roof coverings only include the external finish (tiles, sheeting, slates, etc.) and their direct fixings. Battens, purlins, trusses, and counter-battens are structural or support components that must be itemised with dimensions, spacing, and timber treatment where applicable. This allows for precise coordination between the roofing and structural teams and ensures accountability for installation responsibilities.

Not if it is factory-laminated and forms an integral part of the roof sheeting product. In this case, the insulation is deemed included, but the BOQ must describe the type, thickness, thermal performance, and bonding method to support correct rate build-up. If insulation is laid as a separate layer (e.g., bulk fill, rigid boards, or blankets), it must be measured independently with detailing of overlaps, support grids, and fixings.

It is measured separately in square metres. Underlay is a functional barrier—either vapour-permeable or impermeable—and must be described with type, weight (gsm), location, and number of layers. It is installed as a distinct operation with separate fixings and sequencing and thus cannot be assumed within the roof covering rate. The BOQ should also include overlaps, sealing methods, and any detailing at valleys, hips, or upstands.

No. The measured roof area reflects the net covered surface, and all standard lap allowances (side and end laps) are deemed included in the rate. However, where non-standard overlaps are specified—such as increased end laps due to rainfall intensity or wind uplift zones—these must be described in the BOQ. The contractor’s rate must then allow for additional material, fixings, and cutting, which justifies either a higher base rate or an extra-over item.

Absolutely. Fixing systems must be clearly stated in the description, especially where they differ from conventional methods. Concealed clip systems reduce visible penetrations but require more precise setup, specialised fixings, and often limit thermal movement flexibility. Omitting this detail may result in under-pricing, incompatibility with insulation layers, or improper coordination with guttering and flashings.

They must be measured separately in linear metres under “Hips” and “Ridges.” These elements involve more intricate setting out, require mechanical or mortar fixing, and often come with their own dedicated system kits (e.g., dry ridge systems). Descriptions should include tile type, fixing method, and whether ridge tiles are interlocking or require bedding and pointing.

Verge tiles and dry verge systems are measured separately in linear metres, as they involve specialist detailing for wind resistance, water runoff, and aesthetic continuity. The BOQ should identify whether the verge is a traditional bedded system or a clip-on dry verge product, as each has different material and labour requirements.

The moment a cladding system transitions from a pitched surface to a vertical one, it must be measured separately under Wall Cladding. Even if the material is identical, vertical cladding involves different installation methods, fixing orientations, and lap detailing. The BOQ should state the extent of each plane and describe changes in orientation clearly to avoid confusion in scope allocation.

No. Gutters and rainwater disposal systems—regardless of material—are measured separately in linear metres under Rainwater Goods. These items require their own accessories (brackets, outlets, stop ends), fixing procedures, and maintenance considerations. The BOQ should describe the profile, size, and material to ensure compatibility with roof coverings and sufficient allowance for thermal movement.

If the ventilation is achieved via proprietary components—such as ridge roll vents, mesh inserts, or ventilated closures—these must be measured separately in linear metres. If the ventilation is fully integrated into a system such as dry-fix ridge tiles, and the BOQ description explicitly states so, it may be included. Either way, the ventilation detail must be clear in the specification to ensure compliance with building regulations and manufacturer performance guarantees.

Yes—if the increased laps and fixings were not part of the original BOQ or drawings and are the result of a documented uplift analysis or Engineer’s instruction, this is a legitimate variation. Increased laps reduce the effective coverage of each tile and require more fixings and time to install. The variation must be measured as a separate or extra-over item, with revised tile quantities and fixing descriptions supported by the wind loading report.

Yes. Any change in roof pitch after tender affects both material use and labour methodology. Steeper slopes can increase tile wastage due to cutting angles, require additional safety measures, and may demand modified fixing methods. The change represents an alteration to the basis of pricing, and a revised rate is justifiable. The affected areas should be remeasured with the new pitch noted, and rates adjusted to reflect the increased complexity.

No. Changes made without client or consultant instruction are not grounds for cost recovery. If the fixing method was not described in the BOQ, standard fixing is assumed. Concealed systems typically involve additional labour and higher-cost clips, but unless the change was pre-approved, the contractor assumes the risk. The lesson here: always formalise design or aesthetic substitutions through written instruction before pricing or implementation.

Generally, no — this kind of remedial work does not qualify for remeasurement under the standard BOQ rules, unless a specific provisional item was allowed for reinstatement due to follow-on trades. If the damage was caused by other subcontractors (such as M&E teams), the correct route is not to pay the roofing contractor again via remeasurement, but rather to process a backcharge against the party responsible, to be treated as a recoverable cost — not as extra work payable to the roofer through normal remeasurement.

Yes. Site-rolled standing seam systems involve on-site forming machines, longer panel lengths, more precise alignment, and higher installation labour. If the substitution was Architect-approved and formally instructed, the contractor is entitled to reprice based on the changed specification. The QS must remeasure the affected roof areas and include revised descriptions covering seam width, fixing system, substrate preparation, and underlay requirements.

Despite their elevation and decorative function, these elements should still be measured under Roof Coverings if they are clad with profiled metal sheeting traditionally used for roofing, and if they include underlays, flashings, or standard roof fixings. The defining principle is the material and fixing method, not the accessibility or whether the element forms part of the main roof envelope.

The SSMBW confirms that roof coverings include “materials for covering pitched or flat roofs, including underlays, fixings and flashings.” The fact that these are non-accessible or high-level canopies does not exclude them from this trade—unless the material, method of fixing, or detailing clearly shifts it into a different category, such as architectural cladding or bespoke metal fabrications (in which case it may then fall under Cladding or even Metalwork).

This is a layered system with both waterproofing and aesthetic overlay functions. The correct measurement approach is to split the items across their functional trades:

• The bitumen-based membrane should be measured under Waterproofing, not Roof Coverings, since it is a flat roof waterproofing layer.
• The aluminium interlocking panels—even though installed on roof battens—are not part of the functional weatherproofing layer. They serve as cladding and should therefore be measured under Cladding, not Roof Coverings.

Per SSMBW and the Cladding trade rules, where materials are non-traditional roof coverings (e.g., timber slats, decorative metalwork), and their function is aesthetic rather than protective, they fall under Cladding.

SSMBW does not require a deduction for reused materials unless explicitly supplied by the Employer—which is not the case here. The covering is still being laid as part of the contract scope, and its full area must be measured.

You should measure the full area of roof covering, regardless of whether new or reused tiles are used, under the standard Roof Coverings item. However, the description must clearly state that the tiles are to be a mix of reused and new, and that the contractor is responsible for salvaging, sorting, and relaying.

Where significant effort is required to salvage and clean tiles, a Provisional Sum or separate item under Preliminaries or Dayworks may be appropriate to cover additional labour or risks.

This comes down to whether the components are part of a standard roof covering assembly or are specialist details required to accommodate structural movement. Here’s how to approach it:

• 1. Roof sheeting that continues across the expansion joint is measured as normal Roof Coverings—no special treatment required in terms of quantity or rate.
• 2. The flexible membrane and movement-compatible flashing system, however, should not be included in the standard roof covering rate. These are additional components designed specifically to allow for structural movement and should be measured separately under Flashings and Special Roofing Details.
• 3. If the expansion joint detail is highly bespoke (e.g., a custom prefabricated cap or proprietary movement system), it may be best measured as a Provisional Item, with full detailing in the BOQ description.

Per SSMBW, flashings and detailing to accommodate expansion, contraction, or movement must be expressly measured and described when not part of a standard junction. Including them within the general roof covering rate would result in under-pricing.