A build-up is a named stack of layers — brick, insulation, boards — that you assign to a wall, a roof, a ceiling or a floor slab. Its U-value is computed from the layers, and assigning it sets that element’s thickness, so the drawing and the construction stay one thing. Open them under ⚙ → Build-ups & U-values, or from the Build-up row in any selected element’s panel.
Build-ups are free.
Making one
The dialog groups build-ups by what they clothe — Walls, Roofs, Ceilings, Floor slabs — and a new one starts either From a preset or Blank. Layers are added from the material groups: Masonry & concrete, Timber, Insulation, Boards, Finishes and Cavity. Each layer carries a thickness in millimetres, and the U-value updates as you type.
Layers run outside → inside. If a material you need is not listed, Custom… takes a Material name and its Thermal conductivity λ, W/(m·K).
Named products
Insulation and board layers can be picked from Products — real manufacturers’ products, each carrying the λ its maker declares and a link to the document that declares it. That is the Gridsnap materials library, and the same data feeds the public U-value calculator, so the two can never disagree about a λ.
On the drawing
Label on plan calls the build-up out beside the element it belongs to — the way a wall type is annotated on a working drawing.
What the U-value is, and is not
It is computed in the EN ISO 6946 form, from typical material conductivities and fixed surface resistances. Treat it as indicative: it is a design number for comparing options and sizing insulation, not a certified assessment, and it is not a compliance calculation.
Two honest limits worth knowing:
- A timber-frame layer is handled as a composite with an effective λ, not as a proper fraction-weighted bridged calculation.
- Windows and doors carry typical figures by type — the document does not model glazing build-up.
What this doesn’t do
- No per-layer hatching on the drawing yet; the layer order is stored for it.
- No condensation or interstitial analysis.
- A build-up never moves geometry. It writes its summed thickness into the element; the walls, the 3D and the drawings know nothing else about it.
Next
Heat loss totals U × A over the whole envelope, and quantity takeoff measures the materials these build-ups declare.