How Bilby works
Greenhouses and other outbuildings
Greenhouse object or budget-only building
The planner offers garage, carport and greenhouse objects. A generic storage/outbuilding allowance can be added in the budget, but it is not a fourth selectable planner building. A greenhouse receives a structure/base allowance plus ordinary preparation of its own pad in the completed projection.
Ordinary greenhouse scope
The native greenhouse model describes aluminium framing and 3 mm horticultural glass, normal doors and vents, manufacturer base/anchoring, delivery and professional assembly. Its initial structure model assumes an already prepared pad; the completed budget adds an ordinary groundwork allowance. Heating, water and electricity, furniture, growing systems and premium orangery construction remain separate. Generic outbuilding references describe simple unheated timber storage with ordinary supports/base, not a habitable dwelling.
Geometry and assumed extras
A level pad in a price specification is not a conclusion about the terrain.
| Input | Unit | Origin |
|---|---|---|
| Greenhouse footprint | m² | Planner width × depth |
| Shorter side and shape ratio | m / ratio | Derived from geometry |
| Storage-building area | m² | Editable budget assumption; default 15 |
| Services and fit-out | SEK | Optional scope/quote |
Size tiers and fallback
Native greenhouse totals for up to 8, 15 and 25 m² are respectively 25,000/40,000/65,000; 35,000/55,000/85,000; and 50,000/80,000/125,000 SEK. The normal envelope starts at 4 m², has a shorter side of at least 1.5 m and at most a 4:1 ratio. Ordinary ground preparation adds max(8,000/15,000/25,000, area × 350/650/1,100). A fallback greenhouse structure uses max(20,000/35,000/60,000, area × 3,500/6,500/12,000); inspect its component receipt because its structure/base scope differs from the native tier. Generic storage is max(45,000/70,000/110,000, area × 4,500/7,000/11,000). Optional basic secondary-building services/fit-out use 10,000/25,000/60,000 SEK.
Illustrative greenhouse and storage allowance
A fictional 2.5 × 4 m greenhouse is 10 m² and uses the native middle tier: 35,000/55,000/85,000 SEK. Its ordinary ground allowance reaches the minimum 8,000/15,000/25,000, giving 43,000/70,000/110,000 SEK. A separate optional 15 m² storage building at national reference rates is 67,500/105,000/165,000 SEK. Do not add another legacy secondary-foundation line for the same included base.
Check the product and pad
Tier changes can make cost jump when area crosses a boundary. Colour does not necessarily change the estimate. Major slope, rock, foundation design and heated use exceed ordinary scope. The allowance bands are scenarios, and missing dimensions can cause a provisional fallback. Obtain a scoped product/assembly quote and reconcile preparation separately; a registry reference is not proof that a stored older total was calculated from that formula.
Method review
Code reviewed 18 October 2026: greenhouse standard V1 and September 2026 national building references. The model distinguishes the manufacturer base from formation of the ground below it. Willab Garden’s installer information supports the assembly-scope distinction, not the modelled tier totals. Supplier documentation for the selected product is the controlling scope evidence; assembly, transport and foundation conditions must be stated in the quote.
The review date covers this explanation and its implemented method. Price and data dates are stated separately in the article.