Glass Facades and Curtain Walls: What Developers Should Know Before Commissioning

A curtain wall is a non-structural glass and aluminium envelope hung from a building's frame; it carries its own weight and resists wind and weather, but not the building's load. Commissioning one well means getting five things right early: the system type, the glass specification for Nairobi's climate, the engineering behind the fixings, a contractor who fabricates and installs to specification, and a clear scope with maintenance access designed in. Decisions made at concept stage decide how the facade performs for the next thirty years.

This guide is written for developers, contractors and architects specifying glass facades in Kenya. It covers what to know before you go to tender.

What is a curtain wall, and how is it different from a glass facade?

"Glass facade" is the general term for any building exterior dominated by glass. A curtain wall is the specific system most large glass facades use: aluminium mullions and transoms fixed to the floor slabs, with glass panels (and sometimes opaque spandrel panels) infilled between them. Because it hangs from the structure rather than sitting on the ground, it "curtains" the building.

Smaller glass frontages, shopfronts and single-storey elevations often use structural glazing or framed systems rather than a full curtain wall. Which is appropriate depends on the building height, the span between floors, and the wind loads.

See: facades and curtain walls in Nairobi

Stick or unitised: which system should you specify?

Stick systems are assembled on site, mullion by mullion, then glazed. They suit low to mid-rise buildings, irregular elevations and projects where site access is straightforward. They are more flexible and usually lower in upfront cost, with more of the work happening on site.

Unitised systems are fabricated as complete panels, glass included, in the workshop, then craned into place and hung on brackets. They suit taller buildings and tight programmes: faster on site, better quality control because assembly happens under cover, less scaffolding. The trade-off is more engineering and fabrication upfront and less tolerance for late design changes.

For most mid-rise commercial projects in Nairobi, the choice comes down to programme pressure and site logistics. Discuss it with the facade contractor before the design is fixed, because the system affects the slab edge details and the structural brackets.

What glass should a facade in Nairobi use?

Nairobi's climate is kind in some respects and demanding in others: strong equatorial sun and UV, significant temperature swings between day and night, heavy rain in season, and dust. The glass specification has to respond to all of it.

• Solar control and low-emissivity coatings reduce heat gain and glare, which is the difference between a comfortable building and one that fights its own air conditioning all day. On an east or west elevation this is not optional.
• Double glazing (insulated glass units) improves thermal and acoustic performance. Where noise or heat is a concern, it earns its cost.
• Laminated glass holds together if broken and is the right choice wherever glass is overhead, at height where falling glass is a risk, or where security matters.
• Toughened glass is the minimum for any panel that can be reached or impacted.
• Laminated toughened combines the two and is common in facades for exactly that reason.

The glass choice affects weight, which affects the mullion sizing and the brackets, which affects the structure. Specify the glass early.

See: tempered vs laminated glass explained

Who engineers the facade, and what must it withstand?

A curtain wall is engineered, not just fitted. Someone has to calculate the wind loads, size the mullions and transoms, design the brackets that transfer the facade's weight to the slabs, and detail how the system moves with the building as it expands, contracts and deflects.

Ask every prospective contractor who does that engineering, and whether the design will be checked by a structural engineer. Ask about water management: how the system drains rain that gets past the outer seals, because on a curtain wall it will, by design. Ask about fire stopping at each floor. A contractor who can answer these fluently has done it before. One who cannot has not.

How do you choose a facade contractor in Kenya?

The facade is the most visible element of the building and among the most technically demanding. The contractor selection deserves more scrutiny than almost any other package.

Check, in this order:

1. Comparable completed work. Facades on buildings you can identify and visit, at a similar scale. Ask for the client contact.
2. In-house fabrication. A contractor with its own workshop controls quality and programme. One that subcontracts fabrication adds a layer where specifications drift.
3. Engineering capability. Who designs the system, and can they produce calculations and shop drawings?
4. Installation crews. Their own, trained on the system, or subcontracted?
5. Registration and compliance. Appropriate registration with the construction authority, insurance, and a record of working to specification on institutional or corporate projects.
6. A written scope covering system, glass, finishes, engineering, installation, warranty and programme.

A firm that has delivered facades for banks, corporate clients and large developments has already passed the scrutiny those buyers apply. That track record is worth more than the lowest tender.

See: how to choose a glass and aluminium contractor

See: facade projects by Husseini Builders

What should the scope and warranty cover?

For a facade package, expect the written scope to include:

• The system (stick or unitised) and the aluminium profiles, with finish and colour.
• The glass specification per elevation: type, thickness, coatings, whether laminated or toughened.
• Engineering, calculations and shop drawings, and who checks them.
• Brackets, fixings and interfaces with the structure, including who supplies the cast-in channels or anchors.
• Water management, drainage and fire stopping details.
• Installation method, access and scaffolding or crane requirements.
• Testing, if specified (water tightness testing is common on larger facades).
• Programme with milestones tied to the main contract.
• Warranty on the system, the glass, the seals and the installation, with durations stated.

Design maintenance in from the start

Glass facades need cleaning and, eventually, seal replacement and occasional panel replacement. Decide at design stage how that will happen: building maintenance units, abseil points, or accessible ledges. Retrofitting access is expensive and sometimes impossible. A good facade contractor will raise this without being asked.

Next step

Husseini Builders has fabricated and installed glass facades, curtain walls and structural glazing across Kenya for over three decades, in-house, for corporate, institutional and residential developments. If you are commissioning a facade, we are glad to review the drawings and discuss the system and glass specification before you go to tender.

See: for developers and contractors

See: request a quote