Kampala gets roughly 1,200mm of rain a year, and it does not arrive gently. It arrives in intense afternoon events, twice a year, on ground that is often a red clay with poor infiltration and a habit of moving when it gets wet. Buildings here fail at the roof edge, at the ground, and at the junction between them.
Overhangs are not decoration
The single cheapest durability measure available is a generous roof overhang. A 900mm eave keeps driving rain off the wall face, keeps water away from window heads, and shades the glass in the bargain. We specify 1,200mm or more wherever the plan allows it. Flush-eave buildings look sharp in a render and stain within two rainy seasons.
Size gutters for the storm, not the year
Annual rainfall figures are useless for sizing rainwater goods. What matters is peak intensity. Kampala regularly sees short-duration intensities above 100mm/hr. A 100mm half-round gutter on a long roof plane will simply overtop. We size to the peak event, use 150mm gutters as standard on anything over about 60 m² of catchment, and put outlets at both ends rather than one.
Get the ground right
- Finished floor level a minimum of 300mm above surrounding ground
- A hard apron falling away from the building on every elevation
- Surface water taken to a soakaway or attenuation tank, not spread onto neighbours
- Damp-proof course and membrane properly lapped and protected — the most commonly botched detail on site
Store it
Two wet seasons means two chances to fill a tank, and two dry seasons where mains supply gets unreliable. On almost every project we specify rainwater harvesting sized to carry the building's non-potable demand through the dry months. On a house, 20,000–25,000 litres is a reasonable target. It pays for itself, and it takes load off a stressed municipal system.
The detail everyone skips
Wall-to-roof junctions on parapet designs. Parapets look clean, and they are a permanent liability in this climate unless the upstand, flashing and outlet detail are drawn properly and inspected on site. If a client wants a parapet, they get it — and they get a drawing of that junction at 1:5, and a site visit when it is being built.
