28. House design for a hot and wet climate

House design for a hot and wet climate

Many of the houses that I see around Thailand seem very badly designed for the climate.

The traditional design was much more suitable.

  • Raised on stilts to avoid risk of flooding, and keep the living space above ground hugging mosquitoes

  • Thatched roof with a wide overhang, provides waterproofing, but also essential insulation against the sun.

  • Lattice screen walls / windows allow the breeze to blow through. Shutters to keep out the coldest winds.

Iron sheet roofs replaced the thatch, and without any insulation turned the living space into an oven in the daytime, but cooled down quickly at night.

Many modern houses have adopted a western style design that I think simply don't suit the climate or lifestyle.

Heavily (over) engineered in concrete

Lack sufficient insulation

Limited roof overhang to prevent wall exposure to sun and dry space in rain.

Complex roofs with multiple failure points – many severely underegineered.

Not designed for natural ventilation and cooling.

Not designed to place solar energy / hot water facilities

Not designed to capture rainwater for toilets etc.

Proposed Design

This house needs a school room and a cafe area in addition to a separate living space. Kitchen serves both cafe and living space. Bedrooms with the potential for homestay accommodation.

I am still looking for a site, but I am looking for a naturally dry site, not filled in paddy or with a potential flood risk.

Plan of house



Remove loose topsoil. A perimeter strip foundation reinforced concrete, built up to retain infilling stone. Fill the whole veranda base with fist size rough stone, to 0.5m above finished ground level. House proper raised another 30cms

Strip foundations also below walls at end of long hall that support water tanks above.

Concrete channels to hold drains for kitchen and bathrooms (drains not to be embedded in concrete)

Enough fine stone on top of rough stone to give a hard level surface.

Damp proof membrane

Poured reinforced concrete floor with a slight camber from the centre to the edges, Veranda floor with slightly more marked camber to outer edge.

(Note that this floating raft is an effective design in earthquake prone areas, as it decouples the house structure from lateral ground movement)

Wall structure

Although the images show steel uprights within the wall structure these are not needed, and may even reduce the house strength by decoupling walls at the corners. Block walls which interleave at junctions are much stronger than walls which but up to a steel or concrete pillar.

The only advantage would be building walls within a dry environment.

The proposed wall is built of lightweight foamed concrete block. Metal ties will be set in the wall as it is built. These ties are used to hold a covering of galvanised wire netting over the wall which is embedded in a cement plaster.

This produces a dramatically stronger wall at very little cost. If you look at the plan you will see that all internal walls are in the form of a very wide H. This produces a rigid structure, and with the wire netting, one that is shock-proof.

The wire netting also makes the walls much more secure.



Natural ventilation is encouraged by large air vents that can be opened above the main windows to the outside, and at a higher level to the central hall on the inside. The central hall also has large air vents above the level of the main roof.

Openings screened and close with internal shutters, security grills.



These are shown as double doors to the outside. Exact size depends on what is available at the time. Also depends on whether to have security doors opening outwards (are they needed?), glass doors sliding or open inwards.

Roof Structure




This is a simple structure with the lower roof using galvanised Z purlins supported on the walls.

I would like to use two layers of aluminium sheeting with insulation between the two.

Questions here relate to expansion of aluminium sheeting. Conduction of heat through the Z purlins. Type of insulation to use. Methods of sealing ends against vermin (probably a fiber reinforced cement mortar will work well.)

Hopefully verandah overhang will be determined by length of sheets available to avoid cutting if possible.

The same Z pulins are cut and bolted to make the upper roof structures – retains the galvanising at the joints better than welding so has much longer life expectancy.

Rainwater collection

Rainwater collected from the upper roof is held in tanks above the toilets, with potential to use for showers. Potential to provide water for hot water tanks if base above level of lower roof.

Rainwater from the lower roof is collected in tanks whose base is half room height and tops below roof height. This is used to feed the toilet cistern.

A lower tank underneath this collects water for use in the garden.

Hot water




Solar heating used for passive heating of water in tanks at the higher level above toilets. Used for hot water in kitchen and bathroom.

The header tank will need a pump to feed


Comments and suggestions gratefully received!!

It costs far less to put things right at the design stage.