Compositions

A composition is the layered build-up of a wall, slab or roof: render, insulation, masonry, plaster, each with a thickness and a function.

Caution

Layers are not modelled in 3D. They are data. There are no nested groups, and nothing changes about how a wall rebuilds, mitres or takes openings.

They show up in two places: sections and plans, where each layer is hatched separately, and IFC, as IfcMaterialLayerSet.

This was a deliberate decision. Modelling layers as geometry multiplies the object count, and every corner, opening and joint then has to be solved four times instead of once.

Define one

Constructions — the layers icon in the Project palette header, or Plugins → Archeform.

Each row is a layer:

Column	What it is
Name	what it is called in schedules and in IFC
Thickness	in millimetres
Function	structure, substrate, insulation, membrane, finish, air
Priority	0–100, defaults from the function
Colour	which status colour set to hatch it in
Hatch	pattern, or blank to follow the function

Applying a composition sets the element’s thickness to the sum of its layers, so the two can never drift apart.

Compositions are saved in a library shared across projects. The file lives outside the extension folder, so updating Archeform does not touch it.

Constructions dialog

Which side is outside

The first layer in the list is the exterior. Geometrically that is the left face relative to the direction the wall was drawn.

Since you do not always draw walls in a consistent direction, each wall has an Exterior side switch in its dialog — left or right of the drawing direction. It changes only which way the layers are read; the geometry does not move.

The convention — first layer outermost — is the usual one, so a build-up copied from an office standard reads the same way round.

Priorities

Priority decides what happens where two elements meet. A layer passes through layers of lower priority and stops at the first one of equal or higher priority.

Function	Default priority
Structure	80
Substrate	60
Insulation	40
Air gap	30
Membrane	20
Finish	10

In practice: a partition’s masonry runs through the plaster of the wall it meets and stops at that wall’s masonry — which is how it is built and how it should be drawn.

Caution

Priorities above 80 will drive a layer through the structural layer and out the other side. Stay inside the range in the table unless you know exactly what you are asking for.

Junctions between a partition and a wall are handled. Junctions between two walls at a corner are not — the calculation is right but the drawing is not, so the feature is switched off rather than shipped half-working.

Roofs

A roof has no single reference plane. Each plate — two on a gable, four on a hip, any number on a skeleton roof — has its own slope, and the layers are perpendicular to that plate rather than to the ground.

Archeform works this out per plate, so a composition applied to a hip roof is drawn correctly on every face.

Applying one

Two ways:

• Per element — the Composition dropdown in the wall, slab or roof dialog. Several selected elements take it together.
• As a default — set it with nothing selected and new elements of that kind get it.

In IFC

Exports as IfcMaterialLayerSet: one IfcMaterial per layer name, thickness in the file’s own units, function mapped to the IFC category, and priority as a ratio from 0 to 1.

Open the file in your favourite BIM or IFC viewer and the layers are listed with their thicknesses, usually on a Material tab. Some viewers read the materials but do not display the layering at all — that is a limitation of the viewer, not a defect in the data.

Written by Plugins → Archeform → Add Layers to IFC… after export; see Material layers.

See also

• Hatching
• Walls
• Material layers