An interior specification written for a temperate climate and applied here will fail in a predictable order: first the sheet-material joinery, then the ferrous fixings, then the adhesives, then anything with a laminated edge. It takes two to four years, which is long enough that the connection between the specification and the failure gets lost.
Relative humidity in Colombo sits high year-round and stays there. Near the coast, add salt-laden air. Add the monsoon, when the ambient humidity is effectively at saturation for extended periods and surfaces stay damp because nothing dries. Then add the modern complication: an air-conditioned bedroom next to a naturally ventilated corridor produces a humidity gradient and a temperature gradient across a single door, and the joinery in that doorway spends its life moving.
This is a demanding environment. Here is what holds up.
Timber: species and moisture content matter more than finish
Timber works well here — it has for centuries — provided two conditions are met.
Use a durable species. Teak is the reference point for good reason: naturally high oil content, dimensionally stable, resistant to both rot and insect attack, and it takes the humidity swings without much complaint. Where the budget will not carry teak throughout, it is far better to use it selectively — external joinery, wet areas, anything that moves — and use a cheaper species where conditions are benign, than to use a marginal species everywhere.
Satin and jak both have their place. Rubberwood, which is cheap and widely available, is not a wet-area material and should not be specified as one regardless of what it is treated with.
Insist on moisture content at delivery. This is the specification line most often omitted and most responsible for failure. Timber installed wet will shrink and open its joints; timber installed bone-dry into a humid building will swell and bind. Specify the acceptable moisture content range for the intended location, require it to be measured on delivery, and require the timber to be acclimatised on site before it is worked.
Sheet materials: the standing failure
Standard MDF and standard particleboard should not be used in this climate outside a permanently dry, conditioned space, and arguably not there either. They are hygroscopic, they swell irreversibly, and once the edge banding lifts the swelling accelerates.
The workable alternatives, in rough order of cost:
- Marine or exterior-grade plywood with a genuinely waterproof adhesive. Verify the grade — the label and the glue line are not always the same story. Ask to see a sample boiled.
- Moisture-resistant boards for dry-area carcassing where budget rules out plywood. Better than standard board. Still not a wet-area material.
- Solid timber, for anything with a door or a drawer front that will move.
- Aluminium or stainless carcassing for kitchen and bathroom base units. It looks industrial in the showroom and it is still there in fifteen years.
Whatever the board, the edges decide the lifespan. Every cut edge in a wet or humid area must be sealed before assembly, not after. An unsealed edge inside a cabinet is where the failure starts, invisibly.
Metals: the coastal test
Within a few kilometres of the coast, chloride-laden air changes the calculation entirely.
- Mild steel — including the galvanised sort — has a limited life in exposed coastal conditions. Galvanising helps, and it is consumed. Any exposed mild steel is a maintenance item with a schedule.
- Stainless steel grade 304 is fine inland and marginal on the coast; it will tea-stain in salt air, which is cosmetic but persistent.
- Stainless steel grade 316 contains molybdenum and is the appropriate specification for coastal exterior fixings, balustrades, and anything structural you do not intend to revisit.
- Aluminium performs well, provided it is properly anodised or powder-coated and, critically, is not in direct contact with dissimilar metals. Bimetallic corrosion between aluminium and steel fixings is a common and entirely avoidable failure.
The cost difference between 304 and 316 on a fixings schedule is small in the context of a project. The cost of replacing corroded balustrade fixings on a completed building is not.
Floors
Cement-based terrazzo and polished concrete are excellent here: dimensionally stable, unbothered by humidity, cool underfoot, and repairable. They need a properly formed and located movement joint, which is the detail most often skipped.
Porcelain tile is essentially inert and performs well. The variable is the adhesive and the grout. Use a cement-based adhesive of the appropriate class for the substrate and exposure, and in wet areas specify an epoxy grout — cementitious grout in a shower is a mould substrate.
Natural stone works, with attention to porosity. Dense stones are straightforward. Porous stones in wet areas need sealing and re-sealing, which is a maintenance commitment the client should agree to explicitly.
Engineered timber flooring is viable in conditioned spaces with a competent vapour control layer under it. Solid timber flooring over a ground-bearing slab without a functioning damp-proof membrane will cup. This is not a maybe.
Paint, plaster and the walls behind them
Most interior paint failure here is not a paint failure. It is water arriving at the back of the plaster from a roof, a parapet, a leaking pipe or a bridged damp-proof course, and the paint is simply the first place it becomes visible.
That said, two specification points genuinely help:
- Use a breathable finish on masonry walls that may occasionally get damp. A vapour-tight coating traps moisture behind itself and blows the plaster off in sheets.
- In bathrooms and kitchens, use a paint with genuine mould resistance, and give the room mechanical extraction that actually runs. An extract fan wired to the light switch and left on a two-minute overrun does more for the paintwork than any coating.
Adhesives and sealants: the invisible specification
Silicone in a shower has a life measured in a few years here, not a decade. Specify a sanitary-grade silicone with a fungicide, accept that it is a consumable, and design the junction so it can actually be cut out and replaced — which means not burying it behind a fixed panel.
The same logic applies throughout. Anything with a service life shorter than the building needs to be reachable. That is a design decision, made at the drawing stage, and it is the difference between a building that ages and one that degrades.
