When Irene Akoth moved into her rented apartment within Nairobi County, she expected the usual sounds of urban living - neighbours opening doors, children playing outside and the occasional traffic sounds.

Instead, barely had she settled in than her home became a construction site. The landlord began adding another structure to the two-storey building. The drilling and hammering soon became part of the daily routine. Construction materials were moved around the compound, workers came and went, and dust found its way into spaces that were supposed to be homes. For Akoth, the biggest concern was not the noise. It was the children.

With young children living in the building, the sight of construction materials, tools and workers moving around freely raised an uncomfortable question: How safe is a home when construction is taking place directly above it?

Akoth's experience is not unique. Across Nairobi and other rapidly developing urban areas, property owners are adding rooms and floors to existing buildings to squeeze more rental income from their pieces of land. For landlords, the attraction is understandable.

Instead of buying another plot, one can add units to an existing property and increase monthly income. For tenants, however, the same investment decision can transform a quiet home into a chaotic health hazard.

And while the additional rental income may seem attractive on paper, experts warn that building upwards is not simply a matter of putting up walls on an existing surface. Important questions to answer are whether the existing structure can support the additional load, whether the extension has the required approvals, whether construction is being supervised by qualified professionals and whether tenants are being adequately protected from construction-related risks.

In February 2025, the National Construction Authority Executive Director Maurice Akech cautioned landlords against extending buildings upwards while tenants were occupying them, saying it was illegal.

However, he explained that for a vertical extension, work could take place while the existing part was occupied as long as it was properly secured and safe routes were maintained.

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For tenants like Akoth, that warning raises another question: If it is illegal to construct upwards while people are living in the building, what should a tenant do when the landlord starts building anyway?

According to architect, contractor and Director at Space Consult Kelvin Laichena, a landlord cannot treat an occupied building as an ordinary construction site when planning to add another floor.

"It is illegal to extend a building upwards while people are occupying the lower floors. The safety of the occupants has to come first. Before an extension is undertaken, the existing structure has to be assessed and the necessary approvals obtained. You cannot simply decide that because there is space on the roof, you can add another floor."

The warning is significant because tenants are often the least informed people in the entire construction process. A landlord may know what is being built. The contractor may know what drawings have been approved. The architect and engineer may know the structural calculations, but the tenant below may only know that workers have arrived and that something is being built.

Under Kenya's Physical and Land Use Planning (Building) Regulations, anyone intending to make alterations or additions to an existing building is required to submit building plans before obtaining development permission. The regulations also require buildings to conform to approved plans, zoning regulations and the registered use of the land.

That means one cannot simply assume that because the original building was approved, any additional floor or rooms can automatically be added.

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If it is illegal to construct upwards while people are living in the building, what should a tenant do when the landlord starts building anyway?

Unauthorised development

Under National Construction Authority (NCA) Sanctions, failure to comply may attract a fine of Sh3 million, a prison sentence of up to three years, or both.

Physical and Land Use Planning Act also warns that commencing unauthorised development or extensions without a permit attracts county fines of up to Sh500,000, imprisonment for up to two months, or both under national planning laws

The National Building Code, 2024, which is now the country's current building framework, also sets requirements for structural safety and professional involvement in building design and construction.

That aside, when planning to extend upwards, there are many factors to consider, not just the additional rent you will collect at the end of the project. For instance, there are architectural and engineering fees, construction materials, labour, approvals, professional supervision, possible structural reinforcement, additional water and sewerage requirements, electricity, drainage and maintenance costs. But before all those calculations, there is one fundamental question: Can the existing building safely carry another floor?

Dennis Onyango, a structural engineer, says this is where some property owners can make a costly mistake.

"You cannot look at a building and conclude that because it has been standing for years, it can automatically carry another floor. Before an additional storey is constructed, the existing structure has to be assessed, including the foundations, columns, beams and slabs. The engineer has to establish whether it can safely accommodate the proposed additional load," Eng Dennis says.

The engineer says an existing building is a complete structural system, meaning changes to one part can affect the entire structure.

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The rental market has expanded to suit the tenant more.

"The biggest concern is when the desire to create more rental units takes priority over structural assessment. When you add another floor, you are changing the loads acting on the building. If that change is not properly designed and supported, you can create serious structural problems."

The National Building Code requires structural designs to provide adequate structural resistance, serviceability, durability and reliability, with structural design falling within the work of qualified professionals.

For tenants, however, the problem is that they are rarely in a position to know whether such assessments have been carried out. One may watch workers carrying bags of cement and steel bars onto the roof but have no way of knowing whether the foundations and columns below were designed to support the additional weight.

Children can make the situation even more worrying because construction sites contain hazards that adults may recognise but children may not.

Loose building materials, tools, nails, exposed electrical connections, piles of sand and other equipment can become dangerous when construction and residential life are taking place in the same compound.

There is also the risk of falling objects, dust and debris reaching occupied areas. This does not mean every landlord adding another floor is putting tenants in danger. A properly designed, approved and professionally supervised extension can be a legitimate way of increasing the value and income potential of a property. The concern is what happens when an owner skips the necessary steps.

The Physical and Land Use Planning Act defines building operations to include structural alterations and additions to buildings.

County governments consider factors such as the proposed building's use, height, density, plot coverage, access, parking, ventilation, lighting and adequacy of infrastructure when considering development. This is important because adding more units to existing ones does not only affect the structure, it can also increase the number of people using the same water supply, sewerage system, parking spaces, access routes and other facilities.

A property that was designed for a particular number of residents may have to accommodate many more after an extension. For tenants already living in the building, the consequences can be immediate. Imagine working from home while concrete is being drilled overhead from early morning. Imagine trying to put a baby to sleep while workers are hammering above the ceiling. Imagine hanging clothes outside only to find them covered in construction dust.

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Or imagine children wanting to play in the compound while parts of it are occupied by construction materials.

These may not appear to be structural emergencies, but they affect the quality of life for people who have paid for the place they are living in, therefore, communication should form part of any major construction project in an occupied residential building.

Tenants should be informed about the nature of the work, how long it is expected to take and which areas may be affected. Where access routes, parking, water or electricity are likely to be disrupted, occupants should receive adequate notice.

Safety concerns

Construction areas should also be properly separated from residential areas, particularly where children live. The regulatory framework provides mechanisms for dealing with ongoing developments without breaching approved plans.

The Physical and Land Use Planning (Development Control Enforcement) Regulations define non-compliant development to include development undertaken without permission or contrary to the conditions attached to that permission.

For tenants who suspect that construction is being undertaken without the necessary approvals, the safest approach is not to attempt to determine structural safety themselves. They can first raise their concerns with the landlord or property manager, and where there are serious or immediate safety concerns, seek help from the relevant county authorities or other competent bodies. The financial side of the story is equally important.

According to Jane Kariuki, a property investment expert, landlords should be careful not to calculate the returns from an extension simply by multiplying the expected monthly rent by the number of new units.

"The mistake some landlords make is to look at the additional rent without calculating the full cost of creating those units. You have construction, professional fees, approvals, utilities, possible reinforcement of the existing structure and financing costs. All those expenses have to be factored into the expected rental income," she says.

The expert says more rooms do not automatically translate into a more valuable property.

"More rooms do not necessarily mean more value. If an extension is poorly designed, creates congestion, reduces parking spaces or puts pressure on water and drainage systems, it can actually make the property less attractive. The question should be whether the additional development improves the property's income and value sustainably," she adds.

That calculation is particularly important for landlords who are financing construction through loans or other forms of borrowing. If the project takes longer than expected, construction costs rise or the new units take time to fill, the expected payback period can stretch. Kariuki also notes that landlords should also consider the people already occupying the building.

"The tenant is not a construction contractor or a structural engineer. If you are developing a property while people are living there, you have to think about their safety and the disruption. You cannot simply look at the additional rent and ignore the people already occupying the building."

There are also lessons for people searching for rental homes.

Prospective tenants often focus on rent, location, security, water, parking and the size of the house. Construction plans rarely make it onto the checklist.

But where a building appears incomplete or construction is already taking place, a prospective tenant can ask the landlord whether more floors are planned and how long the work is expected to continue. If construction has already started, tenants can ask which areas will be affected and what measures have been put in place to protect residents.

They should also look for obvious safety concerns, including unsecured construction areas, exposed electrical wires, loose materials and blocked access routes.

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wonyando@ke.nationmedia.com