Pitched vs Flat Roofs: Hidden Costs in Building These Houses

A collage of Park Road Affordable Housing Project in Nairobi (left) and a file photo of a pitched roof
A collage of Park Road Affordable Housing Project in Nairobi (left) and a file photo of a pitched roof
PDU Delivery/Designing Buildings

Roofing is one of the key aspects of constructing a house that architects should pay attention to its detail. The roof also defines the general structure of the house. 

Whether building a residential home or a commercial office building, an owner ought to decide which type of roof is right, between a pitched and flat one.

A pitched roof has a peak, or what a layman would call a triangular shape at the top to create tall attics on the inside. On the other end, a flat roof is considered almost complete or completely level. 

They are designed with a slight slope that leans towards the building’s gutter system. Joel Cenas, a civil engineer and construction expert say that a flat roof has a 0 gradient while a pitched roof has a surface sloping at above 20 degrees. 

An image of Affordable Housing Project
Apartments under the affordable housing project located at Park Road, Ngara in Nairobi.

The pros and cons of the two are analysed through two perspectives; upfront cost and life span

Upfront Cost 

In as much as pitched roofing systems demand more in initial upfront installation, this cannot be compared to the flat roof which needs a lot of details. 

From the slab to other accessories such as the ethylene propylene diene monomer (EPDM) synthetic rubber used in construction, thermoplastic polyolefin and PVC roofing.

Life span

A pitched roof also lasts longer, from 20 to 50 years, depending on what shingles and roofing material an owner settles for. 

It is easier to maintain as they are designed to manage precipitation which reduces the beating a roof is subjected to. 

A flat roof lasts nearly 10 years and needs constant maintenance and repairs especially for buildings in rainy areas or during the rainy season. It ought to be inspected at least once a year. 

Even though they have a slight undetectable slope as aforementioned, they’re not good at redirecting rain whose water ends up puddling at various rooftops leading to leakages. 


The debate here is centered around the homeowner's taste and reasons for constructing the building. 

For those designing a contemporary, modern design, a flat roof is more appealing as the pitched system does not fit such an architectural design. 


File images of residential houses in Nairobi

A flat roof also offers more usable cohesive space for the entire building. Nonetheless, some owners also love the triangular attic of a pitched system. 

If the foundation was well constructed, a flat roof can be converted into another storey. 

Other Advantages of Pitched Roofing System 

The other advantages a pitched roof holds over a flat system are better thermal mass, allowing for ventilation, providing ample time to install insulation and solar panels.

One can also collect rainwater through an external drainage system (guttering).