How to Choose a Curtain Walling Contractor: What to Check and Who to Shortlist

To choose a curtain walling contractor, find out who will actually design, fabricate and install the wall, ask for named projects at your package size, height and system, get test evidence for your configuration and a written position on fire stopping and design responsibility, then check the programme against glass and coating lead times. Send every tenderer the same information so the prices can be compared. BDF Architectural is a curtain walling contractor and wrote this guide, so it is a contractor's view, not an independent one. Regulatory points apply to England, with sources at the end. For what curtain walling is and how to specify it, see our specification guide.

Who to shortlist as a curtain walling contractor

We do not rank companies, and we are one of them. Keep a company on the list only if it can show:

• Comparable work: named projects close to your package size, building height and system
• A clear delivery model: who designs, fabricates and installs, and what is sub-let
• Capacity: a named team and a fabrication slot in your programme window
• Written answers on fire and design, including who owns the slab edge
• Whatever your procurement route requires, such as insurance levels or prequalification

Fabricator, installer or system company: who holds what

A "curtain walling company" or "curtain walling manufacturer" can be doing any of these jobs:

• System company: designs and tests the profiles, gaskets and fixings as a system and publishes the data, as Schüco and Jansen do. It answers for its system, not for your façade.
• Fabricator: cuts, machines and assembles the frames to the system company's rules.
• Installer: fixes and seals the wall on site, sometimes as a sub-contractor to the fabricator.
• Contractor or sub-contractor: takes the package under contract and answers for whatever it sub-lets.

One company can hold several roles, and no model is automatically better; the contract must say who answers when a fault crosses fabrication and installation. Ask each tenderer to name the fabricator, installation team and any design consultant.

Check experience at your package size, height and system

Experience only counts if it transfers. Compare each record on package size, building height and use, system type (stick or unitised, capped or structurally glazed), the specific system, and site conditions. A package much larger or smaller than a contractor's usual work can stretch it, so ask what else it will be running during your window.

Ask for named projects and references

• Project name, location, year and main contractor or client
• The company's actual scope: design, supply, fabrication or installation
• The system used and the approximate package size
• A contact who managed the package on the client side

Ask how the contractor handled design information, slippage and defects. Photographs show a finished building, not who did what. That applies to our own project pages too, including Pentonville Road, Islington (2024) and Prescot Street, Whitechapel (2025).

Agree who carries design responsibility

Curtain walling design is usually split between the architect, the structural engineer and the sub-contractor, and problems start when nobody writes the split down. Use a responsibility matrix covering framing and bracket calculations, fixings, thermal and condensation calculations, glass design, fabrication drawings and fire-stopping details. Ask whether design liability is on a reasonable skill and care or a fitness for purpose basis.

Under the Building Regulations 2010, a company that carries out design work in the course of business is a designer, with designer duties alongside any contractor duties. Designers and contractors doing part of the work must consider directly related work and report compliance concerns to the principal designer or principal contractor respectively.

Ask for BS EN 13830 test evidence for your configuration

BS EN 13830 is the curtain walling product standard, and our specification guide covers its test methods. When choosing a contractor the question is narrower: do the reports apply to this façade? Ask for test reports and classifications, not a brochure, and for written confirmation that your spans, glass sizes and details sit within the tested scope, with any departures listed.

If the specification calls for project testing, such as a laboratory mock-up or site water tests, check that each tender states what is included, where it sits in the programme and who pays for retesting after a failure.

Fire compliance on relevant and higher-risk buildings

Regulation 7(2) requires materials that become part of the external wall of a relevant building to be European Classification A1 or A2-s1, d0. A relevant building has a storey at least 18 metres above ground level and contains one or more dwellings, an institution or a room for residential purposes. Regulation 7(3) exempts some items, including window frames and glass, seals, gaskets, fixings and sealants, while Approved Document B states that window spandrel panels and infill panels must comply. Ask each tenderer for a schedule of the materials in the wall, with their classifications and any exemption relied on.

Who owns slab-edge fire stopping?

The Building Regulations set the outcome and do not allocate slab-edge fire stopping to a trade, so your contract must. Approved Document B Volume 2 (paragraphs 8.22 and 8.23) says fire resistance should be maintained where a compartment floor or wall meets an external wall, with fire stopping at the junction, and that an external wall with no fire resistance should be restrained at floor level to limit movement away from the floor in a fire. (Volume 1 covers dwellings.) Ask who designs the detail, who supplies and installs it, what test evidence covers your gap and movement, and who inspects it before it is hidden. Where the façade itself must resist fire, see fire-rated curtain walling.

Higher-risk buildings

For design and construction, a new building is a higher-risk building if it is at least 18 metres high or has at least 7 storeys and either contains at least two residential units or is or contains a care home or hospital, with some exclusions. Building control approval from the Building Safety Regulator is needed before work starts. After approval, any change to an agreed document is a controlled change, and for a major change, work on that part must stop until the regulator approves it. A late system or glass substitution can therefore cost programme. Ask tenderers what records they will hand over for the golden thread.

Building Safety Act competence duties

The dutyholder and competence rules that followed the Building Safety Act are in Part 2A of the Building Regulations 2010, in force in England since 1 October 2023. Before using anyone for building or design work, you must take all reasonable steps to satisfy yourself that they have the required competence, which for an organisation means organisational capability, and can plan, manage and monitor the work. Where the work relates to a higher-risk building, you must also ask about any serious sanction in the previous 5 years and consider any available information on misconduct. On higher-risk building work, a written record of those steps goes to the client. GOV.UK guidance says meeting a standard does not guarantee meeting all legal obligations, so treat certificates as support, not proof.

Test the programme: glass, coating, cranage and access

• Lead times: order dates for glass and coating, especially large, coated or laminated units and special colours, and the approval dates that protect them
• Sequencing: by elevation, floor or zone, and what must be complete before each starts
• Cranage: who provides the crane or hoist and how much lifting time is assumed
• Access and logistics: scaffold, mast climbers or mobile platforms, delivery windows and storage

Ask for a programme showing these dates. A finish date with no order dates behind it cannot be checked.

Interfaces with roof, rainscreen and floors

Give tenderers an interface matrix and ask them to mark what they include wherever another package begins:

• Roof: head details, flashings and the tie-in to the roof membrane
• Rainscreen and other cladding: closers, membrane laps and the cavity barrier line
• Floors and structure: brackets or cast-in channels, slab tolerances, movement and floor finishes at the sill

Insurance, warranties and prequalification

Ask for what your contract and procurement route require, ask every tenderer the same, and see current documents.

• Insurance: the types, limits and expiry dates you require; if design is included, ask about professional indemnity cover and any fire safety or external wall exclusion
• Collateral warranties or third-party rights: issue your form with the tender so objections surface early
• Prequalification: where your process uses schemes such as Constructionline, SSIP member schemes or ISO 9001, check scope and expiry with the issuer

What to send so tenders compare like for like

• Elevations, sections and the performance specification
• The fire strategy, and whether the building is relevant or higher-risk
• Structural and slab-edge information, including loads, movement and tolerances
• Design responsibility and interface matrices
• Programme dates, logistics constraints and who provides cranage and access
• Testing, contract, warranty and insurance requirements
• A pricing schedule and a required list of exclusions and qualifications

Red flags when choosing a curtain walling contractor

• It will not name who fabricates or installs, or what is sub-let
• "System compliant" with no test report or confirmation of your configuration
• Slab-edge fire stopping marked "by others" with no named owner
• A low price resting on exclusions for access, cranage, testing or design
• A system or glass substitution offered without revised performance evidence
• Reluctance to answer questions on competence, sanctions or insurance exclusions