Drive through any new estate around Nairobi and the silhouette has changed. The pitched roof that defined the Kenyan suburb for forty years is being replaced by a straight line — the flat roof, or more often the hidden roof, a pitch concealed behind a parapet so the house reads flat from the street.
We publish two plans drawn both ways: a 4-bedroom maisonette with a flat roof behind parapets, and a 3-bedroom bungalow with a hip roof at 22°. Here is what genuinely differs, and what does not.
Flat, and hidden, are not the same thing
- A true flat roofA reinforced concrete slab, laid to a fall so water runs to outlets. It is a structural element and a waterproofing problem, and it can be occupied — a terrace, a tank platform, a place to put solar.
- A hidden roofAn ordinary pitched roof in iron sheets, screened by a parapet wall so it is invisible from the ground. You get the modern silhouette on conventional roof construction. Most of what looks flat in a Kenyan estate is this.
The distinction matters because the two carry completely different risk. A hidden roof fails the way a pitched roof fails, which is a known and cheap problem. A concrete slab fails at the membrane, and that is neither.
What the choice changes in the drawing
- The wall lineA parapet keeps the building's outline rectangular, which suits a tight plot: no eaves oversailing a boundary and no gutter discharging onto a neighbour. A hip roof at 22° needs its overhang, and on a narrow side setback that overhang is a real constraint.
- The upper floorFlat roofs make two storeys read as one mass. Our maisonette gets its contemporary line exactly this way — 229.1 m² over two storeys, the roof concealed behind parapets.
- The ceilingA pitched roof gives you the option of a vaulted ceiling and a loft. A slab gives you a flat soffit and the floor above. Both clear the 2 400 mm minimum habitable height; they simply offer different rooms above it.
The part nobody enjoys: water
Every flat roof is a drainage design, and the failure mode is standing water. A slab laid without adequate fall, or with outlets in the wrong place, will pond — and ponding is what turns a membrane defect into a ceiling stain. The fall, the outlet positions and the parapet upstands belong on the drawing, not to the improvisation of whoever is on site that week.
We are not going to quote you a waterproofing price. Membrane specifications and their installed cost move constantly and vary by supplier, and a number invented here would be worth less than the paragraph it sat in. What we will say is that this is the line item where a cheap substitution is most expensive later, and the one most worth naming explicitly in a bill of quantities rather than leaving as a lump sum.
So which one
If your plot is tight, your setbacks are narrow, or you want the upper floor to read as a single modern mass — flat or hidden, and budget the waterproofing properly. If you are on a generous plot, want the loft volume, or want the cheapest reliable roof in the country, a pitched hip roof is still hard to argue with. Our bungalow uses one at 22° and looks entirely current doing it.
Both are drawn to the same code checks and both are stampable. The roof is a design decision, not a compliance one.