Building on Koh Samui means planning for intense rainfall, high humidity, strong sunlight and prolonged heat. These conditions influence how a property is designed, which materials are selected and how the work is carried out.
Long-term performance depends on details that are often concealed beneath the finished surfaces: drainage routes, waterproofing, movement joints and the junctions between different building elements.
Give water a controlled route
Waterproofing can keep water out of a building, but it does not remove the water arriving at it. Roof water, terrace runoff, pool overflow and surface water all need a planned route to a suitable discharge point.
Roofs and terraces require appropriate falls towards outlets. Thresholds, balconies, planters and retaining walls need particular attention so that water does not collect against the building or build pressure behind it.
Drainage must also remain accessible for cleaning. Leaves, soil and other debris can block outlets, so the design should consider what happens when a drain becomes obstructed, including safe overflow routes where appropriate. Simply diverting water elsewhere without considering its destination can transfer the problem to another part of the property.
Follow the waterproofing system’s instructions
A waterproofing product is only one part of a complete system. Its performance depends on correct surface preparation, compatible primers, specified coverage and thickness, treatment of corners and joints, and proper detailing around drains and pipe penetrations.
Installation should follow the manufacturer’s current instructions for the exact product supplied in Thailand. Product formulations, approved systems and application guidance can differ between countries, so instructions from an overseas website should not automatically be assumed to apply locally.
Temperature, humidity, substrate moisture and the weather forecast also matter. Recoating and curing times must suit the actual conditions, and newly applied materials may need protection from rain before they are ready for exposure.
Protect the membrane after installation
Waterproofing needs protection throughout the remaining construction work. A membrane can be correctly installed and subsequently damaged by tools, scaffold feet, sharp debris, drilling or later fixings.
A puncture or poorly sealed penetration can create a route for leakage. Where the specified system requires protection boards, screeds or other protective layers, these should be installed before subsequent work or backfilling takes place.
Membranes intended to remain exposed must be suitable for that exposure, including sunlight and any expected foot traffic. Inspection and appropriate testing should take place before waterproofing is concealed, with any damage repaired using the manufacturer’s approved method.
Allow finished surfaces to move
Concrete, render, tiles and stone change dimension as temperatures and moisture conditions vary. Concrete and cement-based finishes also shrink as they cure and dry.
Control joints help manage shrinkage cracking, while movement joints accommodate expansion, contraction and movement between building elements. Their positions and details should be planned as part of the structure and finish design.
Structural movement joints must continue through the finishes rather than being bridged with rigid render, tiles or grout. Large tiled areas, external terraces, changes in material and junctions around columns or walls require suitable joint detailing.
Flexible sealants must be selected and installed for the expected movement and exposure. Joint width, depth, backing material and preparation all affect performance. A narrow line of sealant cannot compensate for an incorrectly designed joint.
Choose materials for their actual exposure
External coatings, sealants, metal fixings and timber should be selected for heat, moisture and sunlight, with salt exposure considered where relevant. Products suitable for sheltered interiors may not perform well on exposed roofs, terraces or façades.
Ventilation, shading and air-conditioning design also influence comfort and moisture control. Condensation and trapped humidity need to be considered alongside protection from rain.
Plan for insects and pests
Service penetrations, roof spaces, drainage openings and gaps around doors can provide entry routes for insects and other pests. These details should be addressed during construction, while they remain accessible.
Suitable screens, sealed service openings and well-fitted doors help limit entry. Screening must preserve the ventilation or drainage capacity of the opening and remain accessible for cleaning.
Termite protection should be considered where appropriate, particularly around timber and concealed building elements. Avoiding standing water and allowing access for inspection and maintenance also helps reduce pest problems.
Design for maintenance as well as handover
A property needs to perform through repeated wet seasons and years of daily use. Accessible drains, inspectable joints, protected membranes and maintainable services make it easier to identify and resolve small issues before they become larger repairs.
At Samui Modern Construction, we consider these details alongside the finished appearance, because the quality of a building depends on both.
