House construction inspection guide

Before construction and preparing the land

• P00 Documents, drawings and the contract before work starts Every page in this handbook teaches you how to look at something that has already been built — except this one. This page is about the day when nothing has been built yet, so it's the only day when asking for changes costs nothing, and the day that decides what you'll be able to inspect over the next 24 stages, because what isn't written down… · 69 criteria
• P34 Budget, finance and choosing a contractor This whole book teaches you how to inspect work, but no amount of inspection skill helps if you pick the wrong people at the start or run out of money halfway. Most houses that never get finished don't stop because the work is bad — they stop because the money runs out before the work is done. The good news about this page is that everything on it can be done… · 38 criteria
• P55 Soil investigation before designing the foundations Before anyone chooses how long the piles should be or how wide the footings are, there has to be one number first: how much load the soil under the house can carry. The 2023 Ministerial Regulation on building foundations and supporting ground requires a site-specific soil report for three groups of buildings… · 37 criteria
• P56 Sun, wind, rain and site planning at the design stage Stage 1 begins on the day the building is set out, by which time the drawings have already been submitted for a permit. But three things must be decided before that and can hardly be changed later: which way the house faces, which side the windows are on, and how far the eaves overhang. This page uses the recommendations of Energy Label No.… · 22 criteria
• P40 Floor level, land filling and flooding Many people believe the law already sets how much higher the house floor must be than the road. The figures quoted are 10 centimetres above the footpath and 25 centimetres above the road centre line. Those two figures really exist in the Ministerial Regulation, but the paragraph they're in begins with “Prohib… · 59 criteria
• P58 Temporary water and electricity during construction Construction needs water and electricity from day one, but an empty plot has no house number yet, so you can't get permanent meters — you have to apply for temporary ones first. And you must agree clearly before signing the contract who applies, whose name is on the meter, and who pays for water and electricity during constr… · 46 criteria
• P01 Setting out the building and checking the property lines A layout staked out wrong today becomes piles in the wrong position next week, and a house in the wrong place that has to be demolished six months later. Setting-out day is the day when the cost of fixing mistakes is lowest in the whole project, because all you have to move is the string lines. Most impor… · 91 criteria

Piles and foundations

• P02-01 Inspecting piles before driving — what to check when the delivery truck arrives A pile that is cracked, bent or whose concrete hasn't reached strength will crack further during driving, and once it's in the ground it can't be pulled out. The day the pile truck arrives is your last chance to reject the goods at no cost — after that, everything becomes repair work · 20 criteria
• P02-02 Pile rig, hammer and helmet — the wrong tools mean wrong work from the start A hammer that is too light won't really drive the pile down, but it makes the recorded figures look as if the pile has reached refusal when it hasn't reached the hard stratum yet, and a helmet that doesn't fit will crack the head of every pile. The standards set figures clear enough for you to check yourself · 10 criteria
• P02-03 Checking pile verticality — why you need to look along 2 axes, and how A pile can lean in any direction, but a person standing in one place only sees lean perpendicular to their line of sight. If the pile leans towards or away from you, it looks perfectly straight — that's why you must look from 2 directions at right angles to each other, and once the footing is poured over it there's no w… · 5 criteria
• P02-04 The driving record — the only evidence that proves the piles can carry the load Piles are underground and nobody will see them again for the life of the house. The only thing that proves they really reached the hard stratum is the figures recorded during driving. The standard even provides a form for it — if the contractor doesn't have this form, they're not yet following the standard · 18 criteria
• P02-05 Pile eccentricity — measured from what, and how much is too much A footing is designed to transfer the load exactly to the centre of the pile group. If a pile is in the wrong place, the load isn't shared evenly and creates a moment the engineer didn't allow for — and once the footing is poured over it, it can never be fixed. The good news is that there are clear figures for this, measured with a tape meas… · 3 criteria
• P02-06 Pile cut-off level — added and subtracted from what, and how to check it's right When the contractor says “the pile heads are at level”, most homeowners can't check, because they don't know what it was measured from. In fact it's just two additions and subtractions from a permanent benchmark, which you can check with an ordinary calculator. A wrong pile-head level… · 5 criteria
• P02-07 When there's a problem — cracked piles, piles that won't go down, splicing and followers On the day a pile breaks or won't go down, everyone pushes for a quick decision because the pile rig is hired by the day. If you don't know what options the standards allow, you'll be led down the route that's convenient for the contractor, not the one that's safe for the house. The good news is that the standards set out the options… · 19 criteria
• P02-08 Tests and documents — what you must receive before paying the piling instalment There are 3 kinds of pile test, with prices differing tenfold, and each proves a different thing. The cheapest can't prove load capacity at all — the standard says so plainly. If you don't know the difference, you'll be handed a report and believe the house is safe when it… · 19 criteria
• P03 Footing excavations, existing soil and sand bedding The bottom of the pit is the first thing to be covered up: sand goes over it, lean concrete over that, then the footing over that again. Within two or three days nobody will ever see it again for the life of the house — and soft or waterlogged soil at the bottom of the pit is the most common and most overlooked cause of settlement… · 71 criteria
• P04 Reinforcement for footings and stub columns Reinforcing steel is the one thing in the house that is expensive, does the most important job, and can't be seen at all after the concrete is poured. The number of bars, bar sizes, cover, lap lengths, hooks — all of it can only be proven on the day the steel is still exposed. This page goes from the day… · 69 criteria
• P05 Formwork for footings, stub columns and ground beams Concrete has no shape of its own — it takes whatever shape the formwork tells it to. Crooked formwork gives crooked concrete, leaking formwork gives honeycombed concrete, spreading formwork gives footings bigger than designed, and all of this is decided before the first concrete truck arrives. This page divides… · 77 criteria
• P06 Pouring day for footings, stub columns and ground beams Pouring day is the one day when everything inspected over the previous three stages is sealed in for good. The bars you counted, the cover you measured, the formwork you checked — all of it disappears from view within a few hours. This page follows the actual timeline of that day — before the mixer truck arrives · during… · 91 criteria

Structure

• P07 Ground-floor structural columns — steel, formwork and pouring Ground-floor columns are the first part of the house that people can see with the naked eye as they walk past. If they lean, are out of line or have honeycombed surfaces, you'll see it for the life of the house and it can't be fixed by plastering over. Columns are also the part that starts from the benchmarks set on setting-out day… · 86 criteria
• P08 Ground-floor beams and slab — precast planks, cast-in-place slabs and pipes under the floor The ground floor of a house can be built with two systems: precast planks laid on beams, or a cast-in-place slab on grade. Both are called a “floor”, but the steps, the moments you can inspect and the mistakes that can't be fixed are completely different. Precast planks cover… · 209 criteria
• P09 Upper-floor structure — columns, beams and slabs you have to climb up to see The upper-floor structure follows almost the same sequence as the ground floor. What changes is that everything is higher up. You can see the whole ground floor standing on the ground, but upstairs you have to climb the scaffolding, so people automatically inspect less — tradespeople and homeowners alike. This page therefore doesn't… · 83 criteria
• P30 Stairs, guardrails and designing for older people Stairs are one of the most expensive things to fix if they're wrong, because they're concrete cast into the structure. Making the risers equal after casting means chiselling or pouring over, and either way the headroom changes too. The good news is that the law sets out the figures… · 45 criteria

Roofing

• P10 Steel roof structure — steel, welds, paint and fixings The roof structure is the most expensive part of the house to repair, because to reach the steel you have to strip off the whole roof covering first. And it's the only part that takes sun, rain and salt air 24 hours a day with nothing but a thin paint film to protect it. The good news is that the period… · 86 criteria
• P11 Roofing, fascias and waterproofing As far as we could verify in this round, there is no central government standard for roofing that sets the pitch, overlaps or fixing points. All the figures come from each tile model's manufacturer installation guide, and they really differ between models. So this page doesn't force a single central figure… · 139 criteria
• P31 Heat insulation and ventilation under the roof Houses in hot cities take in more heat through the roof than any other way, but what really blocks it sits in a different layer from where most people spend their money. People tend to pay a lot for the roof covering, when the best-value layer is the ceiling and the roof space. The good news about this page is that everything can be decided before… · 40 criteria
• P43 Carports, awnings and roof extensions The Ministerial Regulation allows floor or roof area to be extended by a combined total of no more than five square metres, on condition that the number of columns or beams is neither reduced nor increased. These two conditions sound like a wide loophole, but a carport that can really fit one car has an area of more than five square… · 42 criteria
• P45 Rooftop solar panels Rooftop solar has two completely separate sides. One is the legal side, which since 19 November 2025 has only one condition left: weight. The other is the workmanship side, for which there isn't a single Thai standard, and that's the side that actually fails — the poin… · 50 criteria

Walls and architectural work

• P12 Bricklaying — chalk lines, stiffener columns, lintels and what disappears under the render Unlike the concrete and steel work so far, no DPT or EIT standard specifically governs bricklaying. That means quality depends purely on what the designer drew and the order the tradespeople work in. The good news is that what you need to inspect on this page is visible to the naked eye… · 149 criteria
• P14 Rendering walls — screeds, corner beads, anti-crack mesh and cracks Like bricklaying, rendering has no government standard governing it, so all the figures on this page come from brick manufacturers' manuals (which we read ourselves) and from common site practice. The good news is that almost everything can be checked by eye and by hand, and… · 73 criteria
• P15 Installing frames, doors and windows, and waterproofing around frames Long damp streaks on the wall under a window are one of the things homeowners complain about most after moving in, and one of the hardest to pin on anyone, because the frame installers, bricklayers, renderers, sealers and painters are all different teams. Each team says their wor… · 76 criteria
• P16 Waterproofing bathrooms, balconies and roof decks Of all twenty-five stages of building a house, this is the one where the cost of a mistake jumps the most. A leak before tiling is fixed by re-applying waterproofing in that spot, takes a few days, and nobody loses face. A leak after tiling is fixed by rip… · 74 criteria
• P17 Tiling and floor finishes Tiles are the top of four floor layers and the only one you can see. But what decides whether the floor will be flat, sound hollow or crack in three years lies two layers below, and that work was finished days before the first box of tiles arrived on site. This page starts from the day… · 161 criteria
• P18 Ceilings and built-in work Everything above the ceiling — water pipes, air-con condensate pipes, wiring, junction boxes, insulation and whatever holds the ceiling up — is work nobody will ever see again once the first board goes up. This page gathers what has real figures or written requirements in Thai standards, for you to use… · 163 criteria
• P41 Guardrails for balconies, roof decks and openings I searched Ministerial Regulation No. 55 for the word “guardrail” and didn't find it once. The term that actually exists is “stair guardrail”, which is in a clause that applies to other types of building and was already covered in stage 30. The result is that Thai law doesn't set the height of guardrails or the gaps between… · 42 criteria
• P46 Sound insulation between rooms Noise between rooms is something nobody can argue about once the house is finished, because there's no Thai criterion to say what's right or wrong. The most important point on this page is that no Thai standard sets the sound insulation of house walls. The figures in brochures are the manufacturers', and most don't… · 46 criteria

Building systems

• P13 Chasing walls, embedding pipes, running wiring and the systems hidden in walls This stage is one of the most important hold points of the whole project, because everything on this page gets permanently plastered over, and the work has no appointment day like a concrete pour — it starts quietly and ends quietly within a few days per floor. The good news is that what you need to inspect… · 114 criteria
• P20 Sanitaryware, light fittings and electrical accessories This is the only stage in the whole project where the damage isn't caused by workmanship but by items that don't match what was agreed. Cheap and expensive sanitaryware models look very similar, switches and sockets are even harder to tell apart, and the person who chooses the items and the person who installs them are different peop… · 67 criteria
• P32 Air conditioner The air-con technician arrives when the house is almost finished, so people think it's a late job. But the refrigerant pipes, condensate pipes, wiring and fixing points must be in the walls before rendering. A house that wasn't prepared ends up with pipes running exposed outside the walls and cables clipped along the corners of rooms, which isn't just ugly but… · 49 criteria
• P38 Kitchen gas system The most relevant legislation for gas systems is the 2019 Ministerial Regulation on LPG storage at places of use, which we have now read in full ourselves. And what we found is the thing that must be said before anything else — this law only starts to apply at a tank… · 61 criteria
• P39 Water heaters and hot water A water heater is the only electrical appliance in the house that people touch while wet and barefoot. The unit itself is covered by the mandatory standard TIS 1693-2547 for safety only, but the installation method isn't law — it's a professional association standard plus recommen… · 40 criteria
• P42 Sanitary vent pipes Most houses with smells from the pipes don't have a problem with the sanitaryware but with one pipe that no water flows through and that can't be seen from anywhere in the house: the vent pipe. Thai law mentions only two things about this pipe: a diameter of no less than 2.50… · 41 criteria
• P44 Laundry room and washing machine Nobody draws the laundry room in detail, because in the architectural drawings it's usually just a rectangle labelled laundry. But what has to go in there includes water supply, a drain, a socket, a floor drain and a vent for hot air, all of which mus… · 49 criteria

Finishing and external works

• P19 Painting Painting is a stage where inspecting the finished result tells you nothing — a wall painted with one coat on still-damp render and a wall painted with three coats on fully cured render look identical on handover day. The difference shows up in years one to three, as peeling paint, white efflorescence or mould under the fi… · 101 criteria
• P27 Interior finishing and built-ins Every stage before this was inspected with a tape measure and documents, but this page is inspected by hand and eye, because there's no Thai standard setting tolerances for built-in work. What decides whether the work is good or bad is what the people living in the house touch every day — uneven door gaps, draw… · 78 criteria
• P21 External works, fences, driveways and drainage When the house itself is finished, everyone's attention shifts to the interior finishing details, and the remaining outside work — drains, inspection chambers, fill, driveways — is often finished quickly with nobody watching. But this work is what decides whether the first rainy season after moving in… · 106 criteria
• P28 Landscaping, gardens and swimming pools Garden work is seen as the final job because it's the last thing on site, but everything under the garden — pipes, cables, foundations, ground levels — has to be decided before the first load of soil covers it. So the mistakes on this page have a particular character: they don't make the house fall… · 105 criteria

Throughout construction

• P25 Inspecting materials on site — delivery day Every stage in this book inspects workmanship, except this one page, which inspects materials. Steel of the wrong grade, cement that has sat in a warehouse too long, pipes that don't meet the standard — these three things make every other criterion in the book meaningless, because no amount of good workmanship can make up for the wrong materials… · 36 criteria
• P26 Site safety — what you can see from outside the fence This page differs from every other page in the book in that the homeowner isn't the party with the legal duty — the Ministerial Regulation says “employer”, which means the contractor. But the homeowner has a direct stake in two ways: one accident stops work for weeks, and the si… · 73 criteria
• P33 Termite protection Termite treatment is the work most quietly skipped in a house, because nobody sees what was done, nobody asks, and the result of skipping it doesn't show until year three or four. The two most important moments come before the floor concrete is poured; after that, the only option left is drill… · 40 criteria
• P36 Fire protection at home Ministerial Regulation No. 39 (1994), clause 2, states that four groups of buildings must have fire protection systems, and the term detached house doesn't appear in any of those four groups. One- to two-storey detached houses are therefore not required to — which means nobody will order you to do it. If yo… · 50 criteria
• P37 Lightning protection The law requires lightning protection only for high-rise buildings; houses aren't required — that is, from 23.00 metres up, which ordinary houses don't reach. What does exist, and which we have read ourselves, is DPT standard 4501-51 chapter 6, which specifies the size of every conduc… · 47 criteria
• P47 Keeping animals out of the house There is no Thai law or standard on this for houses at all — not because we couldn't find one, but because we checked and can confirm it. What is actually regulated is food premises, which is a different matter from a home. That means if you don't raise it, nobody… · 45 criteria
• P48 Extra work, omitted work and change orders Extra and omitted work happens in every house, and almost all of it starts with a verbal conversation on site. What makes this different from other topics in the book is that there is no provision in the Civil and Commercial Code specifically on extra or omitted work. What there is… · 43 criteria
• P49 Daily logs and written instructions Section 592 of the Civil and Commercial Code states that the contractor must allow the employer or their agent to inspect the work at any time while it is being done. Visiting the site is therefore not something you have to ask for, nor a favour anyone grants you. As for Section 594… · 45 criteria
• P50 When the contractor walks off the job This doesn't start on the day someone announces they're quitting, but on the day fewer people turn up, materials arrive later and calls go unanswered. This page can do two things. The first is to tell you what the law says, especially Section 593, which states that if the con… · 45 criteria
• P51 Disputes and mediation The most misunderstood point on this page is that there are two clocks, not one. The first is Section 600, which requires defects to appear within one year of handover, or within five years if the work is a structure built on the land… · 46 criteria
• P52 Independent home inspectors We searched, and we'll say it plainly: no Thai law regulates the home-inspector profession for private homes. There's no specific licence, no central register to check names against, and we found no national Thai standard for inspecting homes. That doesn't mean it's forbid… · 47 criteria
• P53 Site-visit calendar The most common mistake homeowners make isn't visiting too little but visiting on the wrong days — going often in the weeks when the walls are being rendered, then not being there on the morning the mixer truck arrives or the afternoon the ceiling is about to be closed. This page isn't a checklist; the checklist for each… · 48 criteria
• P57 As-built drawings and photos before work is covered up A house has three sets of drawings: the permit drawings, the construction drawings, and the drawings that match what was actually built. The third set is the one you use every time you drill into a wall, repair a pipe or extend. But having read the 2016 Contract Committee notification clause by clause, we… · 24 criteria

Handover and after moving in

• P22 Testing systems before handover — electrical, plumbing and leaks Everything on this page and the next two depends on one fact — the homeowner's bargaining power drops off a cliff the day the final instalment is paid. Before that day, asking for a re-test is routine and nobody refuses. After that day, asking for the same thing… · 93 criteria
• P23 Accepting the work and the snag list This stage isn't about construction technique but purely about law. The Civil and Commercial Code states plainly that if the homeowner accepts work that is defective without objecting, the contractor is no longer liable for that defect, except for defects that couldn't be found on… · 68 criteria
• P29 Room-by-room inspection before accepting the house Every stage before this inspected work in progress; this page inspects the finished house as a whole, which is a different kind of job — there's nothing to measure against a standard, only things you have to find before you sign. What makes this round of inspection work isn't knowledge of constru… · 48 criteria
• P24 After moving in and claiming under the workmanship warranty The thing people most misunderstand about home warranties is thinking there's only one clock. In fact there are two, and you have to satisfy both — the first is the window in which the defect must appear, and the second is the one-year limitation period for suing, counted from the day the… · 70 criteria
• P35 Documents and utilities after completion In every stage before this, the contractor handled the paperwork for you, but once the house is finished everything instantly becomes the homeowner's job — and it has to be done in order: without a house number you can't get a house registration, and without a house registration you can't get permanent meters. Where people get stu… · 62 criteria
• P54 Annual maintenance plan Houses don't always fail because they were badly built — many fail because nobody looked after them: gutters never cleaned, silicone never replaced, water stains noticed and left alone. This page covers only two things. The first is the intervals — monthly, every six months, annu… · 42 criteria

Appendices

• symptom Index by symptom Use this page when you've noticed a symptom but don't know which stage it belongs to. Choose the closest symptom, then click through to the relevant stage.
• ask Questions to ask the project engineer This book has 572 criteria labelled ask the project engineer, spread across 61 stages.
• limits Limitations of this handbook All content was compiled by artificial intelligence (AI), with the service provider setting the scope, reviewing it and deciding what goes into the book and what doesn't.

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