Steel vs Aluminium Windows

Everything a Kenyan homeowner, contractor or building professional needs to know before choosing window frames, from Nairobi and Mombasa to Kisumu, Nakuru, Kiambu, Kirinyaga and every other corner of the country.

Quick Summary

• Steel windows are strong, slim and relatively affordable upfront but are prone to rust and require regular repainting to stay in good condition.
• Aluminium windows resist rust naturally, need very little maintenance and can be powder coated in almost any color or finish, though they cost more upfront.
• In Kenya, aluminium generally costs KES 9,000 to 45,000 or more per square metre while steel typically costs KES 5,000 to 50,000 or more per window, depending on quality and finish.
• For coastal towns like Mombasa, Malindi and Kilifi, aluminium is almost always the better long-term choice because of the salty, humid air.
• For highland regions like Kirinyaga, Nyeri, Nyandarua and Kericho, both materials perform well, though aluminium still wins on long-term maintenance costs.

Why Window Frame Material Matters

Before comparing steel and aluminium, it helps to understand why the frame material is such a big deal in the first place. The frame is not just decorative. It holds the glass in place, seals out water and dust, supports the weight of the window when it opens and closes and takes the brunt of weather exposure every single day, whether that is the intense sun in Garissa, the persistent rain in Kericho or the salty air in Mombasa. A frame that fails prematurely means cracked plaster, water stains, sticking hinges and eventually a full window replacement. Getting this right at construction stage saves you money and headaches later, which is why it deserves as much attention as your choice of roofing or flooring. If you are still finalizing your design, browsing through ready house plans is a good place to see how different window styles and placements affect the overall look of a home before you commit to a material.

Understanding Steel Windows

Steel windows have been used in Kenyan construction for generations and many older buildings in towns like Nakuru, Eldoret and Nairobi still have their original steel frames standing strong decades later. Steel is an iron-based metal that is naturally very strong and rigid, which is why it can support large window panes with slim, elegant frame profiles. This is part of the reason steel windows have made a comeback in modern architectural styles that favor thin black frame lines against glass, a look now common in contemporary homes across Kiambu, Karen and Runda.

The Strength of Steel

Steel's biggest selling point is sheer strength. A steel frame can hold larger glass panels without bowing or sagging over time. This makes it a popular choice for feature windows, large sliding doors and areas where security is a priority since steel is much harder to force open or bend compared to lighter materials.

The Rust Problem

The major weakness of steel is that it is prone to rust. Steel is essentially iron and when iron is exposed to moisture and oxygen over time, it oxidizes and forms rust. In Kenya's varied climate, coastal humidity in places like Mombasa and Lamu, highland rains in areas like Kericho and Kisii and even ordinary morning dew can all accelerate this process if the steel is not properly protected. Once rust sets in, it does not just look unsightly with orange-brown staining bleeding onto your wall paint, it actually weakens the metal structurally over time, causing the frame to become brittle and eventually fail at the joints and hinges.

To manage this, steel windows require a protective coating, usually paint or a galvanized zinc layer and this coating needs to be inspected and reapplied periodically, especially in areas near water bodies or in coastal towns where salt air speeds up corrosion. Skipping this maintenance is the single biggest reason steel windows in older Kenyan homes end up looking worn and stained within a few years.

Understanding Aluminium Windows

Aluminium has become the material of choice for most modern Kenyan homes and commercial buildings, from apartment blocks along Thika Superhighway to residential estates in Nyali, Mombasa and for good reason. Unlike steel, aluminium is naturally resistant to rust because of how the metal reacts with air.

Why Aluminium Does Not Rust

When aluminium is exposed to oxygen, it forms a thin, invisible layer of aluminium oxide on its surface almost instantly. This oxide layer acts as a natural shield, protecting the metal underneath from further reaction with moisture or air. This is fundamentally different from what happens with steel, where rust continues to eat deeper into the metal over time. Because of this natural protection, aluminium window frames can go decades without corroding, even in humid or coastal environments like Mombasa and Kilifi, without needing the constant upkeep that steel demands.

Lightweight Without Sacrificing Strength

Aluminium is significantly lighter than steel, which brings several practical benefits. Lighter frames are easier and cheaper to transport and install, they put less strain on hinges and rollers over time, meaning smoother operation for sliding windows and doors for years and they reduce the overall load on the building structure, which can be an advantage in multi-storey buildings common in Nairobi's Kilimani, Westlands and Upperhill areas.

Despite being lighter, modern aluminium alloys used in window manufacturing are engineered to be strong enough for residential and commercial use, especially when reinforced with the right profile design for larger openings.

The Role of Powder Coating

While aluminium resists rust naturally, manufacturers take protection a step further by applying a powder coating finish. Powder coating is a dry finishing process where fine, electrostatically charged powder particles are sprayed onto the aluminium frame and then cured under heat, causing the powder to melt and form a hard, even, protective layer bonded to the metal surface.

This powder coating serves two purposes. First, it adds an extra layer of protection against scratches, fading and weather damage, extending the lifespan of the frame even further. Second, it allows manufacturers to offer aluminium windows in a wide range of colors and finishes, from classic white and matte black to wood-grain textures, giving homeowners far more design flexibility than bare or painted steel typically allows. Unlike ordinary paint, powder coating does not chip or peel easily and it holds its color under direct sun exposure for much longer, which matters a lot in Kenya's strong equatorial sunlight, particularly in sun-intense regions like Garissa, Turkana and the Coast.

Steel vs Aluminium: Side by Side Comparison

Energy Efficiency and Comfort

Beyond looks and durability, window frames also affect how comfortable your home feels day to day. Metal in general conducts heat, meaning both steel and standard aluminium frames can transfer outdoor heat inward during hot afternoons and let indoor warmth escape during cool evenings. This is more noticeable in aluminium because of how efficiently the metal conducts temperature.

To address this, manufacturers now offer thermal break aluminium profiles, where a strip of polyamide material is inserted between the interior and exterior sections of the frame, breaking the direct path for heat transfer. This keeps interiors cooler in hot regions like Mombasa and the wider Coast and warmer in cooler highland areas like parts of Kirinyaga, Nyandarua and Molo, at a modest added cost of roughly 5 to 10 percent over standard aluminium profiles. Steel windows do not typically come with this thermal break option in the Kenyan market, so they perform similarly to non-thermal-break aluminium in terms of heat transfer.

Security Considerations

Security is often a top concern for homeowners, particularly for ground floor windows in urban areas like Nairobi's Eastlands or peri-urban towns such as Ruiru and Kitengela. Steel's natural rigidity makes it inherently resistant to bending or forcing open, which is why you will still find steel window grilles and burglar-proofing bars used widely across Kenya even in homes with aluminium main windows. Aluminium, being softer than steel, is generally paired with multi-point locking systems, reinforced glass or added steel grilles on vulnerable openings to match the same level of security. If security is your top priority for a specific opening, many homeowners choose a hybrid approach: aluminium for the main window frame and finish, combined with a steel grille or burglar-proof bar fitted behind or in front of it for extra protection.

Maintenance Tips to Extend Window Lifespan

Whichever material you choose, a bit of routine care goes a long way in protecting your investment.

For Steel Windows

• Inspect frames at least twice a year for early signs of rust, especially at joints, corners and areas where paint may have chipped.
• Repaint with a quality anti-rust primer and exterior metal paint every two to three years, or sooner in coastal or high-rainfall areas.
• Keep drainage holes and channels clear of dust and debris so water does not pool against the frame.
• Lubricate hinges and locking mechanisms periodically to prevent stiffness and stress cracking around fittings.

For Aluminium Windows

• Clean frames with mild soap and water every few months to remove dust, salt residue in coastal areas or general grime.
• Avoid abrasive cleaning materials that can scratch the powder-coated finish.
• Check and lubricate rollers and hinges on sliding units once or twice a year for smooth operation.
• Inspect rubber seals and gaskets periodically since these tend to wear out before the aluminium frame itself does.

Which One Should You Choose?

The right choice ultimately depends on your priorities, location and budget.

Choose Steel If

• You want maximum strength and security, especially for ground floor windows or large sliding doors.
• You are working with a tighter budget and can commit to periodic maintenance such as repainting.
• You are going for an industrial or minimalist black-frame aesthetic that is popular in contemporary architecture.
• You are building in a drier, cooler region where corrosion risk is naturally lower, such as parts of the Central Highlands.

Choose Aluminium If

• You live in a humid, coastal or high-rainfall area where rust would be a constant battle, such as Mombasa, Kisumu or Kericho.
• You prefer a low-maintenance option that will still look good years down the line without repainting.
• You want more color and finish options through powder coating to match your home's exterior design.
• You are building a multi-storey structure where lighter materials reduce structural load.

For most residential projects across Kenya today, aluminium tends to be the more practical long-term investment because of its resistance to rust and its lower maintenance demands, but steel still holds its place in specific design and security-focused applications.

Steel vs Aluminium Windows: Cost Comparison in Kenya

Price is usually the deciding factor for most homeowners and it is important to understand not just the upfront cost per window but the full picture including installation, hardware and long-term upkeep. Below is a breakdown of what you can expect to pay in the current Kenyan market, whether you are sourcing in Nairobi, Mombasa, Kisumu, Nakuru or a smaller town like Kutus in Kirinyaga County.

Steel Window Prices in Kenya

Steel windows are generally sold in two categories. Jua kali fabricated steel windows, made locally by artisans using mild steel sections, typically range from about KES 5,000 to KES 35,000 depending on size, design and the gauge of steel used. Imported or factory-fabricated steel windows with better finishing, heavier gauge steel and reinforced security features can cost KES 50,000 and above per window.

The advantage of jua kali steel is affordability, especially for large projects with many window openings where you need to control costs. The trade-off is that quality varies a lot from one fundi to another, so it is worth vetting your fabricator carefully and insisting on proper priming and painting before installation to slow down rust formation from day one.

Aluminium Window Prices in Kenya

Aluminium is priced per square metre rather than per window since the frame profile, glass type and finish all affect the final cost. As a general guide for the current Kenyan market:

• Basic sliding windows (lighter profile, single glazing): roughly KES 9,000 to 15,000 per square metre.
• Mid-range windows (heavier profile, powder-coated, better hardware): roughly KES 15,000 to 25,000 per square metre.
• Premium and high-end systems (thermal break profiles, double glazing, soundproofing, imported brands): roughly KES 25,000 to 45,000 and above per square metre.

On top of the frame and glass cost, expect to budget an additional 15 to 25 percent of the window cost for installation, plus smaller add-ons such as mosquito netting (about KES 1,200 to 2,500 per window) and finishing work like plaster and paint around the frame (about KES 1,500 to 3,500 per window). If your site is far from major towns, factor in transport costs too, which can add another KES 1,000 to 3,000 depending on distance.

Upfront Cost vs Long-Term Cost

This is where the real comparison happens. Steel wins on upfront price, especially for jua kali fabrication and for a homeowner working with a tight construction budget this can be the deciding factor. However, steel comes with a recurring cost that is easy to overlook at planning stage: repainting and rust treatment every few years. Over a 15 to 20 year period, the cumulative cost of maintaining steel windows, buying anti-rust primer, paint, labor for repainting and occasionally replacing badly corroded sections, can add up to a significant amount, sometimes rivaling what you would have spent buying aluminium in the first place.

Aluminium costs more upfront but its near-zero maintenance requirement means that cost is essentially locked in once installed. Cleaning with soap and water once in a while is typically all that is needed to keep aluminium windows looking new for two decades or more. For homeowners planning to stay in a property long-term, or for rental units where you cannot control how well tenants maintain the property, aluminium often works out cheaper over the life of the building even though it costs more on day one.

Which Option Fits Your Budget Bracket

• Tight budget, large number of windows: Jua kali steel windows from a trusted fabricator, with a firm commitment to maintenance, can help you stay within budget without compromising too much on strength.
• Mid-range budget, standard family home: Standard aluminium sliding windows offer the best balance of cost, durability and appearance for most residential projects across Kenya today.
• Higher budget, premium or commercial project: Thermal break aluminium systems with double glazing cost more but deliver better energy efficiency, sound insulation and a longer maintenance-free lifespan, which matters for high-end homes, offices and hospitality projects.

Because your exact window budget depends heavily on your house design, the number and size of openings and your chosen finishes, these figures should be treated as a general guide rather than a fixed quote. Prices in the Kenyan market also shift with exchange rates since much of the raw aluminium and steel used locally is imported, so it is always worth getting a current quote before finalizing your budget.

Budgeting for Your Windows

Window costs vary depending on the material, size, glass type and finish you choose and this can significantly affect your overall building budget. Before you commit to a material, it is worth getting a clear picture of how window choice fits into your total construction cost. You can use our construction cost calculator to get an accurate estimate based on your specific house plan and material preferences, helping you plan your budget with confidence rather than guesswork.

Frequently Asked Questions

Which is better, steel or aluminium windows, for a home in Kenya?

For most residential homes across Kenya, aluminium is the better long-term choice because it resists rust naturally and needs very little maintenance. Steel remains a strong option where maximum strength, security or a specific industrial aesthetic is the priority and where the owner is willing to keep up with repainting.

Do aluminium windows rust in Kenya's coastal climate?

No. Aluminium forms a natural protective oxide layer on its surface when exposed to air, which prevents rust even in humid or salty coastal environments such as Mombasa. This is why aluminium is widely preferred for coastal construction in Kenya.

How much do aluminium windows cost per square metre in Kenya?

Basic aluminium sliding windows cost roughly KES 9,000 to 15,000 per square metre, mid-range powder-coated options cost roughly KES 15,000 to 25,000 per square metre and premium thermal break or double-glazed systems cost roughly KES 25,000 to 45,000 or more per square metre depending on the supplier and finish.

How much do steel windows cost in Kenya?

Jua kali fabricated steel windows typically cost between KES 5,000 and 35,000 per window depending on size and design, while imported or factory-finished steel windows can cost KES 50,000 or more per window.

What is powder coating on aluminium windows?

Powder coating is a dry finishing process where charged powder particles are sprayed onto the aluminium frame and cured under heat to form a hard, even, long-lasting protective layer. It protects the frame from scratches and fading and gives homeowners a wide range of color and finish options.

Are steel windows still used in modern Kenyan homes?

Yes. Steel windows have made a comeback in contemporary architecture because of their slim, strong frame profiles that suit modern black-frame design trends, though they still require periodic maintenance to prevent rust.

Which window material is best for a multi-storey building in Kenya?

Aluminium is generally preferred for multi-storey buildings because it is lightweight, which reduces the structural load on the building, while still offering enough strength for standard residential and commercial openings.

Talk to a Professional Before You Decide

While this guide gives you a solid foundation for understanding steel and aluminium windows, every building has unique structural and design requirements that are best assessed by a qualified professional. Factors such as your local climate, the size of your openings, wind exposure and even your home's architectural style can influence which material and profile will serve you best, whether you are building in Nairobi, Mombasa, Kisumu, Nakuru or right here in Kirinyaga County. Our team is ready to guide you through this decision as part of your overall design process. Consult our engineers today to get expert advice tailored to your specific project before you finalize your window choice.

Final Thoughts

Windows may seem like a small detail in the grand scheme of building a home but the material you choose has a lasting impact on maintenance costs, security, energy efficiency and curb appeal. Steel offers unmatched strength and a striking aesthetic but demands ongoing care to keep rust at bay. Aluminium, protected by its natural oxide layer and enhanced with powder coating, offers a low-maintenance, long-lasting and visually flexible alternative that suits most modern Kenyan homes, from the coastal humidity of Mombasa to the cool highlands of Kirinyaga. Whichever direction you lean towards, make sure it aligns with your climate, budget and long-term maintenance plans so that your windows serve you well for decades to come. Explore our house plans, run your numbers through the construction cost calculator and consult our engineers to bring your project to life with confidence.