Low cost house with cafe area and school room

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Low cost house with cafe area and school room

Postby kumphawapi » Sun Jul 17, 2011 5:15 pm

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.
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Re: Low cost house with cafe area and school room

Postby geordie » Sun Jul 17, 2011 7:19 pm

A few issues i would have imediately at a glance would be the aluminium roof on steel purlins !! electrolisis the reaction will eat the roof sheets The z purlins are regarded as a specialist material in the uk so good luck finding A the purlins B anyone with the required skills to assemble a roof from them or form the required gussets for joining the purlins and reinforcing the joints

The thais do have aac blocks but do not like the idea of building without colums so you will have problems convincing them and it would pay to check the blocks have the correct compressive strength
The chicken wire is a great idea i have used it for secure rooms in the past for a gunsmith working from home
it will definately reinforce the walls in every respect including Earquake risk but you could use that on any construction and take it over the colums is the extra expense required ???

A strip foundation is a totally different kettle of fish from a raft foundation you may want to review that

:( There is some truth in the statement that i am a pessimist :( But the labour is as much a challenge as material
you lauch with a statement of how we do it wrong but usually its a case of the best you can with what is available at an affordable rate What you have planned would be covered by someone who builds factory,s with a steel frame to support the roof instaed of aluminium you could use zinc coated steel or coloubond with foam sprayed to the underside to keep out the heat no more expensive than a double roof this would give you the option of welding rebar to the steels along the top of the block courses negating the need for chicken wire
A raft foundation is a simple construction it just needs a hell of a lot of rebar and a hell of a lot of concrete
Better and cheaper to build standard footings an take out a good insurance cover :)
Why the aversion to building on paddy fields BKK has weaker ground than you will find in an unfilled paddy but they build on it using rafts or piles Flooding is preventable at the desighn stage typically by raising the structure
Unfortunately ther are no gurantees history has shown flash floods can destroy property and cost live,s australia being the last biggy when thousands were left homeless in an area not prone to flooding The solar hot water is a goody but try and get the tank in the roof near the collector and have a dump for over production the collectors are a simple diy task and you get a good return from free hot water unfortunately not a resouce most Thais see as a requirement I stayed out in the sticks in a Thai hotel there was a bath with cold water only and the shower did not work they could not see what the problem was :(
Take a look through the forum and see what materials are available (common) and desighn around that saving yourself a lot of headaches
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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Re: Low cost house with cafe area and school room

Postby splitlid » Sun Jul 17, 2011 9:42 pm

i may be wong but arnt those z perlins on the wong way round :|
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Re: Low cost house with cafe area and school room

Postby kumphawapi » Sun Jul 17, 2011 11:34 pm

Corrosion between the aluminium roof and galvanised steel purlins should be prevented by a tape. We might use a thicker plastic strip to form a better thermal break as well.
Industrial construction would use a spacer system to have both sheets on top of the purlin, but for these small spans one sheet below might work - the long term problem could be moisture entering at the room edges but in this climate the space between the sheets is likely to be warm and prevent condensation. The Z purlins are shown in the technical literature fitted either way round, but I know some suppliers specify top flange facing up, with cleats above the web. If Z purlins cannot be sourced this would be galvanised C section, failing that it is a paint job.
One advantage of having both sheets on top of the purlin, so that the purlin is exposed - the most effective anti corrosion method is an annual wipe of all steel work with an oily rag.

The strip foundations are only to support a retaining wall for the stone infill. I don't see any need for reinforced concrete uprights when they don't do anything useful. The block walls with wire covering are more than strong enough by themselves. I'm glad to hear someone else has come across that type of reinforcement.

The last (UK) project was 4 inch concrete raft on very hard ground with minimal reinforcement. Nothing cracked so far. Selecting a site that is not deep silt makes a big difference to construction costs.

The pipes for the hot water are shown on one of the images - they run straight up to the location of the hot storage tank. I think you are right about the need for a system to prevent water getting too hot! (or at least prevent anyone getting scalded). A thermostatic mixer control on the hot output might be the best solution.

The intention is not to employ a builder, just employ labour as needed. Between us we have some useful theoretical and practical skills and experience.

Thanks for your comments - has anyone got experience of natural ventilation in this way?
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Re: Low cost house with cafe area and school room

Postby geordie » Mon Jul 18, 2011 2:32 am

Sounds feasable but i still have the same concerns with the roof Getting a hold of z purlins and electrolisis if you can find aluminium sheets (+ the costs of sheets Phenominal)
I suggest taking a look at fredik,s construction satahip with the roof structure there colourbond and foam sprayed on it
Insulating the two metals with plastic does not work take a look at land rovers range rovers sounds like you are from uk ?
Then there is the minor problem of how you insulate the tech bolts that you screw the sheets with!! they are self drilling/tapping
I am sorry a 4" 100mm slab does not make a raft i have min 150mm with a 6" grid 9mm mesh under my driveway
to take the weight of a cherry picker parking there 7-1/2 tons has cracked in a couple of places on sloping london clay the size of the slabs you intend laying will have the same tendancy,s The stone foundation you have back to front the romans being world leaders in this field still have examples around the gravel goes down first
then the larger rock
You condem water wasted off the roof where my in laws live everyone that can collects the rainwater for drinking in large stone jars Town water is for bathing washing clothes
The ornate roof structures are usually designed to ventilate the interiors my primary school victorian buit had 16-20ft ceilings with opening dormers so natural ventilation has been around a while and works well your idea of a floor duct for services is fine but getting a suitable duct could cause problems and again forward planning you should be able to keep most of the services accesible or maybe add a crawlspace
I got bitten in a condo on the 4th floor that mosi was not low flying
The steel uprights you show are standard to take the weight of the roof keep them in there and put a good pad under them but last i checked over there concrete was more affordable
Galvanizing steel helps but any confining spaces (no air flow) will collect condensation the steel will rot with box metal talk to the owner of a boat trailer it always rots from the inside outwards
At the top of the page is a search that will show a raft foundation being constructed take a look at it or i will try and find it and put a link for you c section is available everywhere in thailand as is box metal for the uprights
You should seriously review the material you want to use as its no good finding out during the construction that the materials will have to be shipped from BKK or chaing mai doubling the cost of the project

The blue cth banner with the the little brickie has a search just put raft foundations the one i liked was developer 3d which is halfway down page 2
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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Re: Low cost house with cafe area and school room

Postby Roger Ramjet » Mon Jul 18, 2011 9:45 am

I have a few issues with both the concrete slab's thickness and the material to be used. Geordie has covered most of the material, so I'll cover the slab. A floating slab needs to be bedded properly, you must use gravel and sand for this. The minimum depth of the slab is 6 inches in the centre, it must be reinforced with both rebar and trench mesh. Around the outside the depth is a minimum of 10 inches and must have double rebar and trench mesh and be linked to the centre of the slab. The distance of the 10 inches of concrete around the outside will vary depending on the soil/rock under it, but it should be at least 3 to 6 foot or 1 metre to 2 metres.
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Re: Low cost house with cafe area and school room

Postby otis-a » Mon Jul 18, 2011 10:39 am

galvanic corrosion issues
nice to hear someone mention this concern
i saw elsewhere in these forum discussions mention of using aluminum (Al) runners on steel (Fe) supports - without discussing how to eliminate galvanic electric currents and subsequent eating of the lessor nobile metal (Al in case of Al-Fe junction)
simple solution just use all steel
avoiding the galv junction requires use of insulating bolting materials and subsequent inspection of each bolt instal to insure all insulators properly placed.
where to park dog when in town? A barking lot... :-)))
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Re: Low cost house with cafe area and school room

Postby kumphawapi » Mon Jul 18, 2011 2:25 pm

The proposed foundations are very similar to a roman road - and the larger stones do go at the bottom ( not to be confused with any paving at the surface )
This does depend on the availability of suitable stone locally. Without local stone then reinforced concrete becomes the cheapest option.
The potash mining operation could produce large quantities of waste stone - if it ever gets going.
But when I talk about over engineering, the present house and school room has 1 inch of cement over the existing silt soil. and has lasted for 40 years.
The general appearance of such a metalled road and footway is shown in an existing street of Pompeii.
(A). Native earth, levelled and, if necessary, rammed tight.
(B). Statumen: stones of a size to fill the hand.
(C). Audits: rubble or concrete of broken stones and lime.
(D). Nucleus : kernel or bedding of fine cement made of pounded potshards and lime.
(E). Dorsum or agger viae : the elliptical surface or crown of the road (media stratae eminentia) made of polygonal blocks of silex (basaltic lava) or rectangular blocks of saxum qitadratum (travertine, peperino, or other stone of the country). The upper surface was designed to cast off rain or water like the shell of a tortoise. The lower surfaces of the separate stones, here shown as flat, were sometimes cut to a point or edge in order to grasp the nucleus, or next layer, more firmly.
(F). Crepido, margo or semita : raised footway, or sidewalk, on each side of the via.
(G). Umbones or edge-stones.
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Re: Low cost house with cafe area and school room

Postby geordie » Mon Jul 18, 2011 5:34 pm

I stand corrected on the roman road as well as a little less guilty :)
when i was a lot younger i was digging a drainage ditch with a tractor and we dug through what was obviously a road of some sort and fitted the description other than it had a bed of gravel first then fist size stones bits of teracotta and i asumme lime or chalk then cobblestones given the area within a mile of hadrians wall we assumed it was roman and i was instructed keep your mouth shut or the achitects will be in and digging for months = no job so it was buried and forgotton about :oops: sort of ! its probably well known about anyway so i do not feel too guilty
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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Re: Low cost house - aluminium corrosion

Postby kumphawapi » Wed Jul 20, 2011 7:26 pm

Galvanic corrosion of aluminium sheeting is only a problem where there is also an electrolyte present, such as areas with blowing salt or sea spray.
The risk is not great in rural areas.
Corrosion doesn't take place in dry environments, so ventilation between the sheets is important.
The galvanised coating on the steel frame will prevent attack of the aluminium, as long as the galvanised coating is in place.

Aluminium needs oversized holes drilled in the sheeting to accommodate expansion movement. Plastic grommets push into these holes and also provide electrical isolation at minimal cost.

The oldest aluminium sheet roof I have first hand experience of is a farm store room built at least 50 years ago. There is no sign of corrosion damage to the sheets even though the area occasionally suffers salt laden gales in winter - about two miles from the sea.

One of the biggest corrosion risks to roof sheeting is galvanised iron sheets being stacked together while moist - how often have you seen them sitting outside in the rain? Under these conditions the galvanised coating quickly becomes a white powder and the future life is greatly reduced.
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Re: Low cost house with cafe area and school room

Postby Smithson » Wed Jul 20, 2011 9:34 pm

I like the idea for ventilation, although I would consider a higher pitch and more vents, also at the ends of the building. You mention shutters to keep out the coldest winds - what part of the country are you thinking of building in?
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Re: Low cost house with cafe area and school room

Postby kumphawapi » Thu Jul 21, 2011 12:41 am

The plan is to build in rural Udon Thani. Several evenings and mornings last Dec and Jan I would have put on the heating if there was any to put on!! I think temperatures were dropping to about 15 degrees celsius some nights, and I was wearing the only warm clothes I could find.
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