Why drainage matters more here
Phuket rainfall comes in short, intense bursts. A roof that sheds a drizzle perfectly can be overwhelmed in minutes when a storm hits. When water cannot get away fast enough, it finds the weakest point: over the top of a gutter, back under a flashing, or ponding on a flat roof until it finds a gap in the membrane.
Pitched roofs and gutters
- Gutters sized for tropical rainfall, with enough outlets that no single one carries too much roof
- Gutters laid to a fall towards outlets, with no sagging sections holding water
- Valleys and abutments flashed properly, with flashings lapped in the direction water flows
- Ridge and hip tiles bedded and mechanically fixed, not just mortared
- Leaf guards where trees overhang, and safe access for cleaning
Flat roofs and roof terraces
Flat roofs and terraces are where we find the most drainage faults. A ‘flat’ roof must not be flat: it needs a definite fall to every outlet, so water never stands for long. We check falls with a level rather than by eye, because a few millimetres of backfall is enough to leave permanent ponding.
Membranes must be dressed into outlets, not stopped short of them, and upstands at walls and parapets need to rise well above the finished surface. Every flat roof also needs an overflow — a second way out for water if the main outlet blocks with leaves or debris.
Downpipes and where the water goes
Downpipes should be securely fixed, jointed so they do not leak against the wall, and discharge somewhere sensible: into a drain, a gully or a soakaway, never onto a walkway or against the base of a wall. On hillside and low-lying plots, where that water goes next matters just as much; see Kamala and Surin and Bang Tao and Laguna.
Signs of a drainage problem
Staining on ceilings below terraces, water marks on fascias and soffits, streaking down walls below gutters, standing water on flat roofs a day after rain, and plants growing in gutters are all warning signs. Inside, moisture readings on any ceiling below a flat roof or terrace that looks suspect can confirm a leak before it stains badly. Our guide to damp in villas explains how we trace them.
Getting it checked
Roof and drainage checks are part of every villa pre-handover inspection, including the roof void where it is accessible. If you are building, the best moment to check falls and membranes is before tiling — see construction stage inspections. For roofs that are hard to reach, our guide to drone roof inspections explains when an aerial survey helps.
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