Costs and rent

Status: rough order of magnitude, 27 Sep 2026, revised 21 Oct 2026: rents are now all-inclusive (operating-model.md), the estate runs one shared grid and one water plant (utilities.md), the gate, guards and intercom are priced line by line (security-and-access.md), every house has an attached two-car garage instead of an open carport, the layout now gives every house a 9 m garden and the estate a park and a sports centre, with no pond (site-plan.md), and the padel courts play in an enclosed hall and a standby generator backs up the battery (utilities.md); the third layout puts 7 m between neighbouring houses, a round ring road with two roundabouts and a natural park in the middle, moves the club to the edge and adds a water tower; on a parcel of 20,000 m² (12.5 rai) that design held 14 houses. Revised 3 Nov 2026: the four corner houses are a new Type C (5 bed, about 300 m², a three-car garage and a private pool), an 8 m green belt inside the wall carries a perimeter trail with outdoor fitness stations, green lanes run between the plots, and the 14-house flagship site grows to what the design needs, 16.9 rai; the park gets places to sit and play (a table tennis table, a picnic lawn, a second pavilion, a seating circle, benches, flowering shrubs and more trees) (site-plan.md). All figures are THB at 2026 prices and are estimates. They come from model/cost_model.py and its hourly energy model model/estate_energy.py; the full generated output is model/results.md. Change an assumption in the script and re-run it rather than editing numbers here. Bracketed numbers such as [5] refer to sources.md.

The answer

Type A ranges run from the pilot to the flagship estate; Types B and C are built only on the flagship. The rent includes all maintenance and repairs, electricity up to 500 kWh a month (Type B 600, Type C 800 including its pool pump), water up to 30 m³ (Type B 36, Type C 50), garden care (and for Type C the care of its pool) and the estate services, including the 24-hour guarded gate.

For comparison, a standard-spec Type A on the same land, in the same small gated estate with the same 24-hour gate post and a plain garage with a roller shutter, would cost about 7.3 M and need about 48,000 THB/month for 5 % net, let the normal way: its tenant pays about 6,400 THB a month more for electricity, water, AC cleaning, small repairs, purifier filters and garden care. The premium specification plus full service adds about 5.6 M THB per house (+76 %) and about 52,700 THB/month of rent: about 27,700 for the better building and 25,000 for running it. The padel hall and the standby generator count as premium: a normal-spec estate would have neither.

A useful sanity check: the model's standard house (7.3 M, 48,000/month) sits above what the market shows today: a Hang Dong 3-bed at 5.5 M renting for 30,000 gives 6.5 % gross and about 4.1 % net.[7] About a quarter of the difference is the guard: a 24-hour gate post costs about 4,000 THB per house per month in a 12-house estate and about 300 in a 150-house one (security-and-access.md). Most of the rest is what estate houses rarely have: the 9 m garden on a wider plot, 7 m between houses, the park and the club, and a closed garage where most have an open carport. So the model is calibrated at the normal end, and small gated estates carry a cost that big ones spread thin; the question is the premium end.

What the layout choices cost

The second layout gives every house a 9 m garden, puts a park and a sports centre in the middle and drops the retention pond; then the padel courts moved into an enclosed hall and a standby generator was added; the third layout puts 7 m between neighbouring houses, curves the road into a ring with two roundabouts, keeps the middle as a natural park with the club at the edge, and adds a water tower; the latest step makes the four corner houses Type C, widens the belt inside the wall to 8 m for a perimeter trail, adds green lanes between the plots and fitness stations, and lets the site grow to 16.9 rai, and the park gets places to sit and play (site-plan.md). Step by step, a flagship Type A house:

The third layout is mostly land. Wider plots (16 and 19 m instead of 13 and 16), the ring and its roundabouts, and a club zone of its own east of the ring take the site from 11.8 to 17.7 rai: at 4.8 M a rai that is about 1.47 M per house. The larger site also needs more fill, road, wall, stormwater tank and landscaping; with the water tower (about 1.0 M) and a water plant 0.3 M cheaper because it no longer needs a booster station, the estate infrastructure grows by 7.5 M, about 0.38 M per house. With fees and contingency that is about 2.0 M per house and 10,300 THB a month of rent. Land is therefore the lever that matters most for this layout: at 3.0 M a rai, an outer Hang Dong price, the rent falls by about 8,700 a month.

On a 20,000 m² parcel the design held 14 houses, and each one cost more (the step before the corner houses, 21 Oct 2026). The same layout (7 m between houses, the ring with two roundabouts, the natural park, the club and the water tower outside it) fitted 20 houses only on about 24,000 m² or more; on 20,000 m² it fitted 14 (then 8 Type A and 6 Type B), with a natural park of about 2,100 m². Each house still carried about the same land (1,395 m²), because the ring, the club and the gate take the same room for 14 houses as for 20. What changed was the share of the fixed costs: the club, gate, water plant, sewage plant and generator cost almost the same for 14 houses, so the infrastructure share rises from 3.54 to 4.41 M per house; the guards from 3,600 to 5,200 THB a month per house; full service (the technical team, consumables, repairs) from about 6,800 to 8,800, and the estate systems' service and reserves from 4,400 to 5,600. Against 20 houses on 17.7 rai, a Type A house cost about 1.1 M more and needed about 12,000 THB a month more rent. The 200 kVA generator, the 250 kVA transformer and the battery are sized for 14 houses.

The corner houses, the trail and the lanes take the site to 16.9 rai (3 Nov 2026). The flagship keeps 14 houses, now 8 Type A, 2 Type B and 4 Type C, and the parcel grows to what the design needs: 27,054 m² (167 × 162 m) instead of 20,000. The four corner plots take the whole free corner of the site (about 897 m² on average, against 416 m² for a Type A plot); the belt inside the wall is 8 m instead of 2 m and carries a 2.5 m perimeter trail of about 606 m with 10 outdoor fitness stations (seven on the trail, three in the park); 4 green lanes run between the plots, one in every row (to the trail from the outer rows, to the park from the inner rows); the natural park grows to about 3,500 m². A Type A house now carries 1,784 m² of land instead of 1,395 (5.51 M instead of 4.31 M). The estate infrastructure grows from 61.7 to 70.7 M: more fill (1.9 M), the trail, lanes and fitness stations (2.5 M, est.), the places to sit and play in the park (0.87 M, est.), longer roads and wall, a larger stormwater tank, park and landscaping on the larger site (about 3.6 M together) and a 170 kWh battery instead of 160. With fees and contingency a Type A house costs 19.87 M instead of 17.84 M and needs 144,000 THB a month for 5 % net instead of 131,000; the whole estate costs about 311 M instead of 263 M.

The park, the sports centre, the padel hall, the pool, the courts and the stormwater tank cost about 22.6 M for the estate, about 1.6 M per house; the places to sit and play in the park (a table tennis table, a picnic lawn, a second pavilion, a seating circle, 9 benches, 28 flowering shrubs and 25 park trees) another 0.87 M (est.), about 0.06 M per house; and the perimeter trail, the green lanes and the fitness stations another 2.5 M, about 0.18 M per house (line by line in results.md). The sports centre with its badminton hall is 7.7 M, priced from turnkey sports halls in Thailand (a 6-court badminton hall of 1,060 m² from 8.5 M[65]) and sports floors;[66] the padel hall is 4.5 M at the same rate per m² for a 9 m high hall (the padel federation asks for at least 6 m clear over the court and suggests 8 m[69]), plus 1.6 M for the two courts.[67] Running them adds about 2,600 THB a month per house against the first layout: service and reserves for the halls, pool and courts, a third gardener for the park and the larger gardens, a second cleaner. The park furniture (table tennis table, picnic tables, pavilion, benches) carries a care and replacement reserve of about 40,000 THB a year (est.), about 240 THB per house per month. The standby generator (200 kVA for 14 houses) is 1.7 M installed and about 640 THB per house per month for service, test runs and its replacement reserve (utilities.md).

If the rent test says no, the largest single savings in this group are the sports hall (a gym in a small pavilion with outdoor courts only: about 5.0 M, 2,200 THB a month of rent with 14 houses), the padel hall (courts in the open: 4.5 M, 2,000 a month) and the generator (battery and roofs only: 1,500 a month). With 14 houses the club weighs more on each rent, so these choices matter more than they did with 20.

What the market pays today

Three-bedroom houses for rent in Chiang Mai, September 2026:

Realistic Chiang Mai residential yields are about 5.5 to 6.5 % gross and about 4 to 5 % net; houses carry heavier maintenance than condos (roofs, gardens, pumps, several AC units).[7] New-build supply is not scarce: Chiang Mai may need more than four years to clear its existing housing stock.[20]

Reading: normal new 3-bed estate houses let for 20,000 to 38,000. Only the top of the market (branded lakeside estate, pool houses) reaches 55,000 to 90,000. Our Type A needs 80,000 to 144,000 all-inclusive, about 76,000 to 140,000 in bare-rent terms: at the very top of that band and, on the flagship estate, above it. The corner Type C, with its own pool, needs 194,000 against 55,000 to 90,000 for the pool houses listed above.[6] It has to earn its place there with something a tenant can see and feel, not with finishes alone.

What a developer told us (November 2026): in a meeting with the team, a Chiang Mai real-estate developer said that rents of 80,000 to 120,000 THB/month are achievable in Chiang Mai for a house of this kind, and that 150,000 is possible. This is one developer's view, given verbally; it is not a listing, a signed lease or a rent test, and the developer has not said which houses, tenants or locations it rests on. If it holds, the pilot (80,000 at 5 % net), the lean estate (101,000) and the Type A in a 30-, 40- or 50-house estate (112,000, 106,000, 101,000) sit inside the range the developer calls achievable; the Type A in a 20-house estate (126,000) and on the 14-house flagship (144,000) sit between that range and the 150,000 the developer calls possible, the flagship just under it. The flagship Type B (158,000) and the corner Type C (194,000) need more than even the possible figure; no Type C comes down to 150,000 at any size up to 50 houses, and in the 50-house estate it needs about 151,000, just above it (Estate size). Open: ask the developer for the comparable lets behind the figures (address, size, rent, what the rent includes, tenant type, how long they took to let) and add them to the table above as sourced listings.

Where the money goes (flagship estate, Type A)

The house alone (base + upgrades, without the garage) comes to about 30,000 THB/m², inside the 25,000 to 40,000+ THB/m² band quoted for premium, architect-designed Thai houses.[2]

The specification upgrades, per Type A house

Type C's upgrades come to 5.20 M, of which 1.10 M is its private pool with deck and fence (spec.md §6b). The first draft's home battery (225,000) and hybrid inverter are gone: the estate's central battery and the water plant sit in the infrastructure line. Items marked "Estimate" are engineering judgement; replacing them with quotes is the first task of phase 1 (plan.md).

Running costs: what full service and shared utilities cost

Per house per month, from the model:

Rounded to 10 THB, so a column may be 10 off its total. Type C's private pool is cared for by the estate team: about 36,000 THB a year for care, chemicals, salt and water top-up, plus a pool reserve (pump, filter and salt cell every 8 years, resurfacing every 15) in its component reserve (est.). Management (8 % of collected rent) and one month of vacancy a year come on top. The first draft carried guards, gardeners, pool, cleaning and office as one estimate of 4,000 THB per house per month; they are now priced separately: one 24-hour gate post plus a night patrol at a quoted guard rate (security-and-access.md), and the gardens, pool, cleaning and office line by line in results.md. The first draft carried a 1 % maintenance reserve (about 5,000 THB a month); the model now prices full service bottom-up, component by component (operating-model.md). Electricity is cheap for the landlord because the estate makes 76 % of its own power: its PEA bill is about 980 THB per house per month (utilities.md).

What the tenant gets for the rent

No bills, no repairs. Priced as a tenant would pay on their own, the rent covers about 4,200 THB a month: electricity for the reference family (450 kWh, which PEA would bill at about 2,000 THB[33]), water (about 300 THB at the PWA tariff[43]), AC cleaning (about 450 THB a month at Chiang Mai prices[39]), small repairs and garden care. A family in a normal leaky house pays about 6,400 THB a month for the same things, because it uses about 800 kWh (about 3,700 THB[33]).

Monthly cost to the tenant, all in:

So moving from a standard house in the same estate to this one, a family stops paying about 6,400 THB a month in bills and upkeep but pays about 32,000 to 96,000 THB a month more in rent: about 25,000 to 89,000 more in total. Against a normal house in a large estate (20,000 to 38,000[5]) the gap is wider, because that rent does not carry a guard post shared by only 12 or 14 houses.

Air. Even a basic HEPA positive-pressure setup has held indoor PM2.5 around 10 or lower on very polluted days;[17] a ducted ERV in an airtight house should do better in every room, which phase 1a of the plan measures. A family in a normal house runs 3 to 4 purifiers for three months and still breathes outdoor air through the gaps. This is the benefit the premium tenant pays for; it is not measurable in THB but it is measurable in µg/m³, and the house shows it on the dashboard.

Power and water that stay on, quiet, security. The estate battery carries every house and the water plant through PEA outages; a guarded gate where nobody gets in unless the tenant has said yes on the intercom (security-and-access.md); laminated glass and multipoint locks; sealed windows against traffic and dogs; no pump cycling in the garden.

Cash savings cover only a small part of the premium. The rest must be paid for air, comfort, quality and never having to deal with the house. That is the market test.

Levers that change the answer

From the model's sensitivity table (flagship Type A, all-inclusive rent for 5 % net):

No single lever closes the gap to normal-market rents: even fully value-engineered, the house needs about 135,000 THB/month all-inclusive for 5 % net. The reverse view makes the same point: if the market only pays 70,000 THB/month, a house may cost at most about 4.9 M all-in for a 5 % net yield, which is 75 % below the flagship Type A; at 60,000 the ceiling is about 2.9 M.

Structural levers, worth more than any line item:

1. Rent to the right tenant. Corporate leases (relocation packages, schools, consulates, NGOs) on 2 to 3 year terms, priced against pool villas and branded estates, not against estate houses.
2. Decide what the rent includes. All-inclusive is the base case. Billing every kWh at the PEA residential rate instead of including an allowance lowers the rent needed by about 2,700 THB/month on the flagship.
3. Accept a lower yield for a better asset. At 4 % net the pilot needs 69,000 THB/month all-inclusive. Whether that is acceptable is an investor decision, not an engineering one.
4. Bring the running costs down with data. The component reserve is the largest running cost; the one-model-per-system rule, durable materials and the pilot's measured service costs are how it comes down. Sharing the technical team with other B4L buildings would cut the team cost per house.
5. Spread the fixed costs over more houses. The guard post, the technical team and the estate systems cost almost the same for 12 houses as for 30. The lean estate pays about 4,000 THB per house per month for one gate post, the 14-house flagship 3,400 for the same post (20 houses would pay 2,400); a larger estate, or a gate shared with a neighbouring development, brings that down. The next section works this through for 14 to 50 houses.
6. Never sell. Selling houses is ruled out by design (operating-model.md): it would recover capital but turn the project into a land-allocation development (selling ten or more sub-parcels needs a licence[29]) with developer obligations, including bank guarantees for infrastructure maintenance under the 2569 amendment.[21]

Estate size: 14 to 50 houses

The same design in a bigger estate makes every house cheaper, mostly because the club, the gate and the plants are shared by more houses. model/scale_study.py rebuilds the layout for 20, 30, 40 and 50 houses with the same plots, the same 7 m between houses, a Type C house at each of the four corners, the ring road with its two roundabouts, the natural park, the 8 m belt with the perimeter trail, green lanes every 3 to 4 houses, one club and one gate: the rows get longer and the ring is stretched east to west, on the smallest site that passes the layout checks. Fill, roads, wall, cables, water main, stormwater tank, park, trail, lanes, fitness stations and landscaping come from the measured quantities of each layout. The water plant, the water tower, the sewage plant, the grid connection, the generator, the battery room, the technical team and the office grow with the six-tenths rule[72] (est.), the night patrol gets a second guard above 30 houses (est.), and the gate, the club and the workshop stay as they are. Land stays at 4.8 M THB/rai. The full table is in model/scale_results.md.

The 50-house variant

The 50-house layout drawn from the same geometry code (MOOBAN_HOUSES=50, see scripts/layout.py): 29 Type A, 17 Type B and 4 Type C houses on 54,918 m² (34.3 rai, 339 x 162 m), rows of 13, 12, 12 and 13 houses, with 10 green lanes, a perimeter trail of about 950 m, 14 fitness stations and 11 places to sit and play in the park (site-plan.md). The same estate as an interactive isometric view: estate-view-50h.html; its key figures come from model/results-50h.md, the full cost model run for this layout. The utilities and gate sketches are drawn for it too.

Most of the saving comes early: going from 14 to 30 houses lowers the Type A rent by about 32,000 THB/month, going on from 30 to 50 by another 11,000. Per Type A house, the infrastructure share falls by 2.7 M THB from 14 to 50 houses and the land share by 2.3 M, because the park, the club, the roads and the trail are shared by more plots (land per house including its share of the common areas goes from 1,784 m² to 1,036 m²). Guards fall from 5,200 to 1,900 THB per house per month, estate systems from 6,300 to 3,400 and the common services from 5,900 to 2,900. Every size has exactly four corner houses; the Type C rent falls with the rest, from 194,000 to 151,000. The technical team, the consumables and the component reserve hardly move (16,800 to 14,300), because they are work done in each house.

What the table leaves out:

• The club stays the size it is. One pool and two padel courts are busier with 50 families. A second padel hall over two more courts (6.1 M THB, priced like the first) adds about 700 THB/month to the Type A rent at 50 houses and 2,700 at 14.
• Land price per rai. A 30 to 35 rai parcel may cost less per rai than a 17 rai one, or may only be found further out; the levers table above shows what land at 3.0 or 6.5 M/rai does.
• The shape of the site. The 50-house layout is 339 x 162 m, a long rectangle with a narrow park. A squarer parcel would need a different road plan (two loops, or a ring with a spine), which the model has not drawn.
• Letting 30 to 50 premium houses. Even at 50 houses the Type A needs about 101,000 THB/month all-inclusive, still above the branded lakeside and pool houses listed above (55,000 to 90,000[5][6]), though inside the 80,000 to 120,000 a developer told us is achievable, and the Type C about 151,000, just above the 150,000 the developer called possible (see "What a developer told us" above). Finding 50 tenants at that rent in Chiang Mai is a bigger test than finding 14, in a market that may need more than four years to clear its existing housing stock,[20] and the estate earns nothing while houses stand empty. Building in phases (the club, the plants and the first row first) keeps the empty houses down but brings back part of the fixed-cost burden on the first houses. The rent test and the two-house pilot (plan.md) answer the demand question before any of this is decided.

So a bigger estate lowers the rent a Type A house needs by about 30 % at 50 houses and brings it into the range the developer named, but it does not reach the rents of the listings we found, and it raises the capital from about 311 M to 774 M THB.

Assumptions to confirm (not yet sourced)

• Vacancy one month a year, management 8 % of rent, insurance 0.15 %.
• Guards at 22,500 THB per guard position a month plus VAT, from a Bangkok quote;[45] a Chiang Mai quote replaces it in phase 1b. Gardens, pool, cleaning and office: staff and materials estimated line by line in model/cost_model.py.
• Gate, intercom and CCTV kit from catalogue and package prices,[50][51][52][59] not quotes.
• Full-service costs: the technical team's size and wages, consumables, and every component's price and life in the replacement reserve (all in model/cost_model.py).
• Energy: household and common loads in model/estate_energy.py, the PEA tariff class of the estate connection,[33] whether the estate may export,[34] and whether supplying tenants through the estate grid needs an ERC licence.[35]
• Land and building tax at 0.30 %, the "other use" band that covers rental property;[25] it would be 0.02 % if the local office treats monthly residential leases as residential, which saves about 2,000 THB/month per house. To confirm with a Thai tax adviser.
• Foreigners cannot normally hold land in their own name,[22] so the owning entity (Thai company, lease structure) needs legal design before any land deposit.