From building plan to CLT panels: panel grid, junctions, calculation and bill of materials
How a request for a house in CLT runs through FlowCraft: the architect's plan, a 3D model with one panel per wall and storey, the junctions to the system's details, the calculation of wall and floor, the heat loss and the bill of materials.
FlowCraft automates entire business processes, from the request that comes in to the invoice that goes out. For a CLT producer or builder, that starts with the architect’s plan.
How a request runs
The same house as in the video, step by step.
1. The architect’s plan comes in
A request comes in by email, with the plan as a PDF. The platform reads the floor plans of the ground floor, the first floor and the attic, the section and the four elevations. The section gives the floor levels and the 40-degree roof pitch; the elevations give the height of every window and door.
2. A 3D model with the panel grid
On the plan, the 3D model of the house grows on the existing basement. Then the CLT panels go onto the walls, floors and roof.
Panel height, maximum length, thickness and joint rule are settings. With panels up to 2.95 m high and 16.5 m long, every wall becomes one horizontal panel per storey, with the openings routed out. That holds for the load-bearing internal walls too.
3. The junctions, as the system’s details prescribe
Floor and wall meet as a platform (Stora Enso, Construction details 04/2012, 5.1): the CLT floor bears on the wall and runs to its outer face, and the first-floor wall stands on the floor. The facade leaf with wood-fibre insulation stands on the basement wall and runs past the floors without a break to the underside of the roof; the hollow-core slabs run under the CLT wall up to the insulation.
Two system rules apply to this house. At the eaves, the CLT roof panel rests on a bevelled eaves lath on the attic floor, above the wall (Stora Enso 6.1). The roof runs as a folded plate from eaves to ridge without a purlin (Stora Enso 6.7); the attic floor ties the two eaves together.
4. In the BIM viewer
The section along the line of Section AB sits beside the architect’s drawing. Every panel is an element: you click it and see its size, system, weight, cut-outs and where it sits on the plan.
5. The calculation of wall and floor
A finite-element analysis on the real panels, through every layer. The front-facade wall panel takes the wind and the load of roof and wall, with its door and window cut out. The floor panel spans 6.0 and 4.3 m over three supports.
KLH 180 meets deflection and stress, but its natural frequency is too low. The platform chooses the thickness that passes every check: KLH 240 in seven layers.
| Check | Result |
|---|---|
| CLT wall, deflection under wind (limit H/300) | 0.64 ≤ 9.3 mm |
| CLT wall, compression in the vertical layers | 2.2 ≤ 15.4 N/mm² |
| CLT wall, buckling (hand calculation) | 0.08 ≤ 1 |
| CLT floor, natural frequency KLH 180 | 6.7 Hz < 8 Hz ✗ |
| CLT floor, natural frequency KLH 240 | 8.38 ≥ 8 Hz |
| CLT floor KLH 240, w_inst imposed (L/300) | 3.1 ≤ 20.0 mm |
| CLT floor KLH 240, bending · rolling shear | 4.3 · 0.14 N/mm² |
Wind to EN 1991-1-4 (26 m/s, terrain II), checks to EN 1995-1-1, material values from KLH (ETA-06/0138, DoP 2025).
6. Heat loss and cooling load per room
With the U-values of the build-up, the platform calculates the heat loss of every room to EN 12831-1. For the summer, EnergyPlus calculates the cooling load on a design day in Brussels, with the front facade facing north-west.
| The house | |
|---|---|
| heat loss (outside −8 °C) | 5,505 W |
| cooling load, peak | 5,676 W |
| heating demand per year | 6,308 kWh |
| cooling demand per year (26 °C) | 1,543 kWh |
| U external wall · pitched roof · window | 0.18 · 0.21 · 1.1 |
| Heat loss per room | |
|---|---|
| living area and kitchen (20 °C) | 1,780 W · 25.8 W/m² |
| study (20 °C) | 254 W · 28.4 W/m² |
| entrance hall and stairs (18 °C) | 312 W · 15.6 W/m² |
| toilet (18 °C) | 34 W |
| shower (24 °C) | 224 W |
| bedroom 1 (18 °C) | 262 W · 15.7 W/m² |
| dressing room (18 °C) | 86 W · 8.6 W/m² |
| bedroom 2 (18 °C) | 253 W · 16.8 W/m² |
| bathroom (24 °C) | 771 W · 44.1 W/m² |
| utility room (18 °C) | 137 W · 11.8 W/m² |
| bedroom 3 (18 °C) | 277 W · 25.1 W/m² |
| landing (18 °C) | 192 W · 8.4 W/m² |
| attic (16 °C) | 1,220 W · 11.7 W/m² |
Outside −8 °C (NBN EN 12831-1 ANB), 309 m² heated floor area.
7. The bill of materials
The bill of materials comes from the same model as the calculation: every panel with its size, thickness, area, weight and the openings routed out of it.
| Part | Count · quantity |
|---|---|
| wall panels ground floor, 100 mm | 26 · 202.0 m² |
| wall panels first floor, 100 mm | 14 · 165.2 m² |
| wall panels attic, 100 mm | 4 · 42.5 m² |
| floor panels first floor, 240 mm | 5 · 110.6 m² |
| floor panels attic, 180 mm | 4 · 105.2 m² |
| roof panels, flat roof of the rear extension, 180 mm | 2 · 31.8 m² |
| roof panels, pitched roof, 160 mm | 10 · 168.1 m² |
| eaves laths GL24h | 4 · 19.9 m |
| panels net · gross | 825.4 · 972.2 m² |
| panels volume · weight | 119.0 m³ · 59.5 t |
Net is the panel itself after its cut-outs, gross the rectangle it is routed from. Only the two attic gables are split in two, because they are taller than 2.95 m. The walls include the load-bearing internal walls.
Design values and sources
What the plan does not show, the platform calculates with these values. Each of them is a setting.
| CLT | KLH (ETA-06/0138, DoP 2025): λ 0.12, E 12,000 N/mm², rolling shear 50 N/mm², fc,0,k 24 N/mm²; up to 2.95 × 16.5 m; wall 100 mm 3s 30 / 40 / 30; first floor 240 mm 7s, attic 180 mm 5s, roof 160 mm |
| junctions | Stora Enso, Construction details 04/2012: platform (5.1), eaves lath (6.1), ridge without purlin in a folded plate (6.7). System rules of this house: the floor runs to the wall’s outer face; at the eaves a bevelled GL24h lath on the attic floor; the roof as a folded plate without a purlin. |
| base | facade leaf with wood-fibre insulation on the basement wall (top −0.40); the hollow-core slabs run under the CLT wall up to the insulation and bear 100 mm on the 400 mm basement wall (assumption) |
| roof planes | at the ridge and in the valleys every roof panel is cut vertically on the ridge or valley line, so two panels meet in one joint; this holds for roof planes of the same pitch (assumption) |
| panel grid | one horizontal panel per wall and storey, up to 16.5 m long, openings routed out; roof from eaves to ridge |
| insulation | wood fibre STEICOflex 036 λ 0,036 · PIR Idelco α-therm SARKING XTRA λ 0,022 on the roof |
| wind and snow | EN 1991-1-4: 26 m/s, terrain category II · EN 1991-1-3: 0.5 kN/m² |
| floor | imposed load 2.0 + 0.5 kN/m² (EN 1991-1-1); deflection L/300, natural frequency ≥ 8 Hz, point load 1 kN ≤ 1.5 mm (chosen limit) |
| heat | inside 20 °C living area and study, 24 °C bathroom, 18 °C other rooms, 16 °C attic; thermal bridges + 0.05 W/m²K |
| windows and ventilation | windows U 1.1 and g 0.5; balanced ventilation with 85 % heat recovery; airtightness n50 1.5 h⁻¹ |
| summer | EnergyPlus, design day Brussels 29.0 °C, cooling to 26 °C, no solar shading; front facade facing north-west |
Does this fit the way you work?
How does a building plan become a production list at your company today, and how much time does that take? We are glad to come and see you about it. Half an hour is enough to see whether this fits. Book a conversation.