Shed Roof Assessment — Soluna, Ko Pha Ngan

Proposal: Replace the hip roof (30°, four-sided slopes) with a mono-pitch shed roof at 14° using Bluescope Snap Lock standing seam.
Orientation: High wall on East (pool side, 73° azimuth), slope descending toward West.
Overhangs: East (pool) 4.0m · West 1.5m.
Two options: A — Pure 14° skillion (continuous slope). B — 3m flat at W + 14° rise to E (green roof + lower E wall).
Roofing: Bluescope ZACS Cool Snap Lock T-310, concealed clip-fix standing seam — Carlos confirmed, 14° minimum for Thailand.

Shed spans 9.45m E–W. W wall raised so W eave = 3.0m with continuous slope (Option A). East overhang 4.0m, West overhang 1.5m. 14° minimum — Bluescope Snap Lock per Carlos.

Pitch	W Wall	E Wall (A)	Height Δ	E Eave A	W Eave	E Wall (B)	E Eave B	Notes
10°	3.26m	4.93m	1.67m	5.64m	3.0m	4.40m	5.10m	Original proposal — below Snap Lock min
12°	3.32m	5.33m	2.01m	6.18m	3.0m	4.69m	5.54m	Below Snap Lock min
★ 14°	3.37m	5.73m	2.36m	6.73m	3.0m	5.0m	6.0m	Snap Lock minimum — Carlos confirmed
15°	3.40m	5.93m	2.53m	7.00m	3.0m	5.10m	6.17m	Some tiles also OK
20°	3.55m	6.99m	3.44m	8.44m	3.0m	5.90m	7.35m	Extreme east height

Option A (pure skillion): W wallH = 3.0 + 1.5 × tan(θ) | E wallH = W wallH + 9.45 × tan(θ) | E eave = E wallH + 4.0 × tan(θ)
Option B (flat + rise): E wallH = W wallH + 6.45 × tan(θ) | E eave = E wallH + 4.0 × tan(θ) | W eave = 3.37m (flat, no drop)
Bluescope Snap Lock ≥ 14° (Thailand conditions). Clay/concrete tiles ≥ 15°.

Hip Roof

Current Design — 30° hip

Four-sided slopes, ridge at center

Option A

14° Skillion — Pure Slope

Continuous 14° slope · E overhang 4.0m · W overhang 1.5m

Option B ★

Flat + 14° Rise — Green Roof

3m flat at W + 14° Snap Lock rise to E · green roof on flat

East Elevation (Pool Side, 25m)

Hip Roof

Hip — East Elevation

Hipped ends slope down · 2.42m eave

Option A

14° Skillion — East

Clean roofline at 6.73m eave · Powerlouvres

Option B ★

Flat + Rise — East

Lower E wall (5.0m) · 6.0m eave · Powerlouvres

North Elevation (Short End, 9.45m)

Hip Roof

Hip — North End

Hip slope from all sides

Option A

14° Skillion — North

Continuous slope: low W (3.37m) → high E (5.73m)

Option B ★

Flat + Rise — North

Flat W zone + 14° rise to E · green roof visible

Hip Roof

Hip Interior — Symmetric Peak

Raked ceiling, ridge beam at center

Option A

14° Raked Ceiling

Continuous 14° slope · 2.36m stack effect

Option B ★

Flat + 14° Raked Ceiling

Cozy 3.37m flat zone → rising to 5.0m at E

Passive cooling via Breezway Powerlouvres: Option A: 2.36m height difference between W entry (3.37m) and E Powerlouvres (5.73m) creates strong stack effect. Option B: 1.63m height differential (3.37m → 5.0m) — still effective, with the flat W zone providing a cozy, intimate ceiling height. Both options: hot air rises along the sloped ceiling and exits through automated louvres on the high east wall. (Breezway, Architropics)

Solar panels as roof insulation: A UC San Diego study found that solar PV panels reduce heat reaching the roof by 38% and keep ceilings 5°F (2.8°C) cooler. The panels act as roof shading — the sun beats on the panels instead of the roof surface, and wind flowing between the tilted panels and roof removes trapped heat. (UC San Diego)

Sun hours = average direct sun on wall at equinox. Hip: ~1.0m overhangs, 30° pitch. Option A: E=4.0m, W=1.5m, 14° pure slope. Option B: same overhangs, 3m flat + 14° rise. Option B W eave is higher (3.37m vs 3.0m) giving slightly better W wall shading.

Facade	Azimuth	Hip: eave / sun hrs	Option A (14°): eave / sun hrs	Option B: eave / sun hrs
East (pool)	73°	2.42m	5.2h	6.73m	0.8h	6.0m	1.2h
West	253°	2.42m	5.0h	3.0m	5.0h	3.37m	4.5h
North	343°	~3.0m	1.5h	~4.2m	1.1h	~3.8m	1.2h
South	163°	~3.0m	1.8h	~4.2m	1.4h	~3.8m	1.5h

Solar panels: Option A: ~244 m² unbroken W-facing slope at 14° (~49 kWp, peak generation in afternoon matching AC load). Option B: ~161 m² on sloped section only (panels not suited for flat membrane) (~32 kWp, still excellent). Hip roof: ~130 m² fragmented across 4 slopes at 30°. Panels also reduce roof heat by 38% (UC San Diego).

Option B combined benefit: Solar panels on the 14° slope generate electricity and reduce roof heat by 38%. The flat western zone hosts a green roof (75 m²) providing additional thermal mass and insulation. Combined with Powerlouvre thermal exhaust, this creates a four-layer cooling system: green roof insulates W → solar panels shade E slope → sloped ceiling channels hot air → Powerlouvres exhaust it.

Hip Roof

Hip — Rain Drainage

Water drains to all 4 sides · gutters needed everywhere

Options A & B

Shed — Rain Drainage

ALL water drains West (away from pool) · E side stays dry

Hip Roof (Current) — 30°

Wall height3.0m (all sides)

Ridge height5.73m

E eave (pool, ~1m ov)~2.42m

W eave (~1m ov)~2.42m

Interior peak5.73m at center

Solar area~130 m² (fragmented)

RoofingClay/concrete tiles

DrainageAll 4 sides

Thermal ventNo height diff

Option A — 14° Skillion

E wall (high)5.73m

W wall (low)3.37m

E eave (4m ov)6.73m

W eave (1.5m ov)3.0m

Interior ceiling5.73 → 3.37m slope

Solar area~244 m² (~49 kWp)

RoofingSnap Lock 14°

DrainageWest only

Thermal vent2.36m stack

Option B — Flat + 14° Rise ★

E wall (high)5.0m

W wall3.37m

E eave (4m ov)6.0m

W eave (flat)3.37m

Interior ceiling3.37m flat → 5.0m

Solar area~161 m² (~32 kWp)

Green roof75 m² (3m × 25m)

DrainageSlope W → flat → gutter

Thermal vent1.63m stack

Option A — Pure 14° Skillion

Advantages

E eave 6.73m vs 2.42m — pool side headroom nearly tripled
Simpler construction — no ridge beam, wall-to-wall rafters
~2× solar capacity — 244 m² unbroken slope vs 130 m² hip
Roof heat −38% — solar panels as roof shading
Strong stack effect — 2.36m height diff for thermal ventilation
Pool side stays dry — all rain drains west
Modern Japandi aesthetic — clean single roofline
Bluescope Snap Lock — concealed clip-fix, 15yr warranty

Considerations

E wall 5.73m — very tall, significant material + wind bracing
E eave 6.73m — very tall columns on pool side
W eave drops to 3.0m — continuous slope lowers W entry
All rain to one side — oversized west gutter required
Engineering rework — Yuki ~80% done on hip design
Carlos scope note — raising walls 500mm was already called significant

Option B — Flat + 14° Rise (Preferred)

Advantages

Lower E wall (5.0m) — 0.73m shorter than Option A, less material + wind load
Higher W eave (3.37m) — flat section gives better W entry headroom
Green roof 75 m² — thermal mass, insulation, Japandi aesthetic
Four-layer cooling — green roof + solar panels + slope channels + Powerlouvres
Cozy + dramatic zones — 3.37m flat ceiling (bedrooms) → rising raked ceiling (living)
Pool side dry — all rain drains west via flat section to gutter
Bluescope Snap Lock on slope — concealed clip-fix, 15yr warranty
E eave still 6.0m — excellent pool-side shade

Considerations

Two roofing systems — flat membrane + Snap Lock (more complexity)
Flat roof drainage — must slope slightly (≥1%) to gutters, ponding risk
Green roof weight — ~80–150 kg/m² wet, structure must support
Less solar area (161 m²) — still 24% more than hip, but 34% less than Option A
Junction waterproofing — flat-to-slope transition needs careful detailing
Stack effect 1.63m — weaker than Option A's 2.36m (still effective)
Engineering rework — same as Option A, plus green roof structural calc

BlueScope ZACS Cool — Snap Lock T-310

TypeConcealed clip-fix standing seam

CoatingAZ70 aluminium-zinc + Cool

Thickness0.35mm / 0.47mm (premium)

Warranty15 years (ZACS Cool)

FixingClip system (no screws through metal)

InsulationUp to 50mm PU foam (sandwich)

Min pitch14° (Thailand conditions)

SarkingRequired under sheets

Carlos Notes

Reference projectBaan Thai (~8 months ago)

Site visitCan take Eliya to see it

Fixing methodDo NOT screw through sheet

Lap jointsNeeded for long rafter spans

PurlinsEngineering needed for span

Sarking qualityMust be good quality

Thermal expansionClip system allows movement

Color Options

For Japandi aesthetic + tropical heat: lighter = cooler. Confirm COLORBOND availability with Carlos.

Japandi picks: Natural Brown, Silver Grey, or Cream from the ZACS line are the safest choices — warm, minimal, and widely available. If COLORBOND is available, Surfmist or Dune would also work beautifully. Lighter colors = better solar reflectance = cooler house.

Pricing Estimates (Option B: Flat + Rise)

Snap Lock area: ~261 m² (6.45m slope + 4m overhang × 25m). Flat membrane: ~113 m² (3m flat + 1.5m overhang × 25m). Total roof: ~374 m². Prices are estimates — actual BOQ from Carlos/Yuki needed.

Item	Est. THB/m²	Area (m²)	Est. Total	Notes
Snap Lock material (0.47mm)	400–600	~261	~130K–157K	Slope + E overhang
Clips + accessories	50–100	~261	~13K–26K	Concealed fix clips, flashings
Sarking (underlay)	30–60	~261	~8K–16K	Required per Carlos
PU insulation (50mm)	150–250	~261	~39K–65K	Optional sandwich panel
Flat membrane	~500	~113	~57K	W flat zone + overhang
Purlins + structure	200–400	~374	~75K–150K	Steel, engineered for span
Installation labor	150–300	~374	~56K–112K	Clip-fix faster than screw-fix
Total (no PU insulation)		~370K–500K	Material + labor, excl. structure
Total (with PU insulation)		~410K–565K	Add ~39K–65K for PU foam

Saves Cost (vs Hip)

No ridge beamMajor saving

No hip raftersEliminates HRS1/HRS2

Simpler raftersWall-to-wall span

Snap Lock fixingClip-fix, faster install

15yr warrantyBluescope ZACS Cool

Adds Cost

E wall (A: 5.73m / B: 5.0m)Taller × 25m

Wind bracingTaller = more force

Flat membrane (B)~113 m² waterproofing

Green roof (B)Structure + planting

Redesign feesEliya + Yuki

Net Assessment

StructuralSimpler overall

Materials~Neutral

LaborSnap Lock = faster

Design reworkSignificant

Long-term valueSolar + cooling ROI

Key questions before committing:
1. Option A vs B — pure 14° skillion or flat + rise? (B preferred: lower E wall, green roof, better W headroom)
2. Bluescope Snap Lock color — get samples from Thai supplier. Natural Brown, Silver Grey, or Cream recommended for Japandi + heat.
3. PU insulation — sandwich panel (50mm PU bonded) or separate sarking + ceiling insulation?
4. E wall height (A: 5.73m / B: 5.0m) — Carlos noted 500mm raise is significant. Both options raise walls. Structural + cost implications?
5. Green roof (Option B) — structural loading ~100 kg/m² wet. Yuki needs to calc for 75 m² flat zone. Drainage + waterproofing spec.
6. Yuki engineering — ~80% complete on hip. What's the rework cost/timeline for shed?
7. Flat-to-slope junction (B) — critical waterproofing detail. Carlos/Yuki need to spec the transition.
8. Solar panel spec — west-facing 14° tilt. Get quote from installer. Option A: 244 m², Option B: 161 m².
9. Carlos reference visit — take Eliya to see Baan Thai Snap Lock roof (~8 months old).
10. Timeline — V5 plans near-final. Roof type change is fundamental. When is point of no return?

Baan Suriya Chan · 25m × 9.45m, rotated −17° from true North.
Hip roof data from engineering plans S1-05 (Yuki/Dontapo Pechmai) and architectural V4 (Eliya, 12.02.26).
Option A: 14° continuous slope, W wall 3.37m, E overhang 4.0m, W overhang 1.5m, W eave 3.0m.
Option B: 3m flat at W + 14° rise, W wall 3.37m, E wall 5.0m, E eave 6.0m, W eave 3.37m, green roof 75 m².
Bluescope Snap Lock: ZACS Cool T-310, AZ70 coating, concealed clip-fix, 15yr warranty, 14° min pitch.
Solar panel heat study: Kleissl et al., UC San Diego, Solar Energy journal.
Powerlouvre specs: Breezway Powerlouvre System.
For interactive solar analysis: Solar Overhang Simulator · Roof Height Visualizer