Assembly Builder SRS — G-7 Layer-by-Layer TACK

Foundation: BBC · DATA_MODEL · BIM_COBOL · MANIFESTO · TestArchitecture

Stack BUY items into sub-BOMs with layer composition. The Assembly MAKE path — material layers, U-value calculation, and template save/recall using the same m_bom schema.

Version: 1.0 (2026-03-19, session 35) Depends on: BIM_Designer.md §18.2 Principle 4, §18.5 MAKE path; BIM_Designer_SRS.md §11 material_layers, §14 InferenceEngine; BOMBasedCompilation.md §4 tack convention; DATA_MODEL.md m_bom + m_bom_line schema Scope: The Assembly MAKE path — stacking existing BUY items into sub-BOMs with layer composition, U-value calculation, and template save/recall. Gate: G-7 (depends on G-4 Save/Recall, feeds G-9 ORDER View + G-10 Promote)

Pattern source: BIMsmith Forge (300K materials, layer-by-layer assembly). Our equivalent uses the same m_bom + m_bom_line schema that drives the entire pipeline — assembly templates are data, not code.

Rules are DATA, not code. Assembly templates, material properties, and layer compositions live in component_library.db tables. Adding a new wall type = SQL INSERT into material_layers. Adding a new assembly = SQL INSERT into m_bom + m_bom_line.

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1. Assembly Types — What Can Be Assembled

Three categories of assemblies map to construction practice:

Category	Example	material_layers rows	m_bom_line rows	U-value?
WALL	Basic Wall:Exterior - Brick on Block	6 layers	6 BOM lines	YES
ROOF	Basic Roof:Live Roof over Wood Joist Flat Roof	6 layers	6 BOM lines	YES
FLOOR	Floor:Residential - Wood Joist with Subflooring	2 layers	2 BOM lines	YES

Current seed data: 20 distinct layer_set_name values in material_layers (60 rows total): 9 walls, 2 roofs, 2 ceilings, 7 floors.

Additional assembly types (CEILING, STAIR) follow the same pattern but may not have material_layers rows — they use m_bom_line children directly.

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2. Data Model

2.1 Assembly Template = m_bom + m_bom_line

An assembly template is an m_bom record whose children (m_bom_line) are the layers. The m_bom itself has no component_type column — the component_type lives on each m_bom_line child. Each layer line has:

m_bom_line column	Assembly meaning	Example
child_product_id	Material product (FK → M_Product)	BRICK_110
sequence	Layer order (outside → inside)	0, 1, 2, 3
role	Layer function	CLADDING, CAVITY, INSULATION, LINING
allocated_width_mm	Layer thickness (= wall-normal direction)	110
allocated_depth_mm	Same as parent depth (wall length)	parent
allocated_height_mm	Same as parent height (wall height)	parent
component_type	BUY (leaf material) or MAKE (sub-assembly)	BUY

Constraint: SUM(allocated_width_mm) across all layers = parent m_bom.aabb_width_mm. This is the thickness invariant.

2.2 material_layers → Assembly Template Mapping

material_layers in component_library.db provides the seed data:

-- material_layers schema
layer_set_name  TEXT    -- e.g. "Basic Wall:Exterior - Brick on Block"
sequence        INTEGER -- 0-based layer order
material_name   TEXT    -- e.g. "Masonry - Brick"
thickness_m     REAL    -- layer thickness in metres (SH) or mm (TE)
is_ventilated   INTEGER -- 1 if air gap / ventilated cavity

Unit ambiguity (known): The thickness_m column contains mixed units — metres for some templates, mm for others, even within the same prefix: - Basic Wall:Exterior - Brick on Block → 0.092 (metres) - Basic Wall:Wall-Partn_12P-70MStd-12P → 12.5 (mm) - Basic Roof:Live Roof over Wood Joist Flat Roof → 0.064 (metres) - Basic Roof:Roof_Flat-4Felt-150Ins-50Scr-150Conc-12Plr → 4.0 (mm)

Prefix is unreliable. The DAO uses magnitude check as primary strategy: - If MAX(thickness_m) for a layer_set < 1.0 → values are in metres → multiply by 1000 - If MAX(thickness_m) for a layer_set ≥ 1.0 → values are already in mm

All thicknesses normalised to mm on read.

2.3 Material Thermal Properties (new table)

U-value calculation requires thermal conductivity per material. New table:

CREATE TABLE IF NOT EXISTS ad_material_thermal (
    material_name     TEXT PRIMARY KEY,     -- FK-ish to material_layers.material_name
    conductivity_w_mk REAL NOT NULL,        -- λ (W/m·K)
    description       TEXT,                 -- human label
    source            TEXT DEFAULT 'CIBSE'  -- data source reference
);

Seed data (29 materials from material_layers, standard values):

Material	λ (W/m·K)	Source
Masonry - Brick	0.77	CIBSE Guide A
Masonry - Concrete Block	1.13	CIBSE Guide A
Misc. Air Layers - Air Space	0.56†	CIBSE (R=0.18 at 25mm)
Air	0.56†	CIBSE (R=0.18 at 25mm)
Insulation / Thermal Barriers - Rigid insulation	0.025	CIBSE Guide A
Rigid insulation	0.025	CIBSE Guide A
Insulation / Thermal Barriers - Semi-rigid insulation	0.038	CIBSE Guide A
Metal - Stud Layer	50.0‡	(bridged: effective R from stud fraction)
Metal Stud Layer	50.0‡	(bridged)
Plasterboard	0.21	CIBSE Guide A
Plaster	0.57	CIBSE Guide A
Gypsum Wall Board	0.21	CIBSE Guide A
Concrete - Cast In Situ	1.40	CIBSE Guide A
Concrete, Cast In Situ	1.40	CIBSE Guide A
Concrete	1.40	CIBSE Guide A
Concrete, Sand/Cement Screed	1.40	CIBSE Guide A
Concrete, Precast	1.40	CIBSE Guide A
Concrete Masonry, Floor Block	1.13	CIBSE Guide A
Wood - Sheathing - plywood	0.13	CIBSE Guide A
Wood - Dimensional Lumber	0.13	CIBSE Guide A
Wood - Flooring	0.14	CIBSE Guide A
Ceramic Tile	1.30	CIBSE Guide A
Masonry - Grout	1.40	(≈ cement)
Roofing Felt	0.19	CIBSE Guide A
Roofing - Barrier	0.50	(generic membrane)
Roofing - EPDM Membrane	0.25	Manufacturer typical
Vapor Retarder	0.50	(generic membrane)
Damp-proofing	0.50	(generic membrane)
Site - Grass	0.50	(soil/turf approximation)

† Air gaps: thermal resistance is fixed (R=0.18 m²K/W for 25mm unventilated cavity per BS EN ISO 6946). The DAO returns R directly, not λ. ‡ Metal studs: effective conductivity depends on stud fraction. Simplified: use bridged R-value based on typical 15% stud area fraction.

---

3. API Signatures

3.1 New DesignerAPI Methods

// ── Assembly Builder (§18.2 Principle 4, G-7) ────────────────────────

/**
 * List available assembly templates for a given category (WALL/ROOF/FLOOR).
 * Returns templates with their layer stacks and U-values.
 *
 * // Implementing BIM_Designer.md §18.2 Principle 4 — Witness: W-ASM-LIST-1
 */
AssemblyListResponse listAssemblyTemplates(String category);

/**
 * Get the full layer stack for an assembly template.
 * Returns layers with materials, thicknesses, and thermal properties.
 *
 * // Implementing BIM_Designer.md §18.2 Principle 4 — Witness: W-ASM-DETAIL-1
 */
AssemblyDetailResponse getAssemblyDetail(String layerSetName);

/**
 * Browse compatible alternative materials for a specific layer position.
 * Filters by role compatibility and returns materials with thermal data.
 * Returns its own response type (not BrowseItemsResponse — different shape).
 *
 * // Implementing BIM_Designer.md §18.2 Principle 4 — Witness: W-ASM-BROWSE-1
 */
BrowseAssemblyLayersResponse browseAssemblyLayers(BrowseAssemblyLayersRequest request);

/**
 * Replace a layer in an assembly with an alternative material.
 * Operates on an in-memory copy — does NOT mutate component_library.db.
 * Returns a new AssemblyDetailResponse with recalculated totals.
 * The caller decides whether to save (via saveAssemblyTemplate or save()).
 *
 * // Implementing BIM_Designer.md §18.2 Principle 4 — Witness: W-ASM-SWAP-1
 */
AssemblyDetailResponse swapLayer(SwapLayerRequest request);

/**
 * Save an assembly as a reusable template (new m_bom + m_bom_line).
 * Per-instance saves go through existing save() → C_OrderLine path.
 *
 * // Implementing BIM_Designer.md §18.2 Principle 4 — Witness: W-ASM-SAVE-1
 */
AssemblySaveResponse saveAssemblyTemplate(SaveAssemblyRequest request);

3.2 New Records

// ── Assembly Builder records ─────────────────────────────────────────

/** Request to browse compatible layers for a position in an assembly. */
record BrowseAssemblyLayersRequest(
    String layerSetName,       // current assembly template
    int layerSequence,         // which layer position to browse alternatives for
    String materialCategory,   // optional filter: "Insulation", "Masonry", etc.
    int offset,
    int limit
) {}

/** Request to swap a layer in an assembly. */
record SwapLayerRequest(
    String layerSetName,       // assembly template
    int layerSequence,         // which layer to replace
    String newMaterialName,    // replacement material
    double newThicknessMm      // replacement thickness
) {}

/** Request to save an assembly as a template. */
record SaveAssemblyRequest(
    String templateName,       // human name for the template
    String category,           // WALL / ROOF / FLOOR
    List<AssemblyLayer> layers // the layer stack
) {}

/** A single layer in an assembly. */
record AssemblyLayer(
    int sequence,              // 0-based order (outside → inside)
    String materialName,       // material label
    double thicknessMm,        // layer thickness in mm
    String role,               // CLADDING / CAVITY / INSULATION / LINING / STRUCTURE
    boolean isVentilated       // air gap flag
) {}

/** Response for browsing layer alternatives. */
record BrowseAssemblyLayersResponse(
    boolean success,
    String layerSetName,
    int layerSequence,
    List<AlternativeMaterial> alternatives,
    String error
) {}

/** A material alternative for a layer position. */
record AlternativeMaterial(
    String materialName,
    double conductivityWmK,
    double defaultThicknessMm,
    String roleCompatibility   // CLADDING / INSULATION / etc.
) {}

/** Response listing available assembly templates. */
record AssemblyListResponse(
    boolean success,
    List<AssemblyTemplateSummary> templates,
    String error
) {}

/** Summary of one assembly template. */
record AssemblyTemplateSummary(
    String layerSetName,       // unique ID (= material_layers.layer_set_name)
    String category,           // WALL / ROOF / FLOOR / CEILING
    int layerCount,
    double totalThicknessMm,
    double uValueWm2K,         // pre-calculated
    String compliance          // UBBL reference or null
) {}

/** Full detail of an assembly template. */
record AssemblyDetailResponse(
    boolean success,
    String layerSetName,
    String category,
    List<AssemblyLayer> layers,
    double totalThicknessMm,
    double uValueWm2K,
    String complianceNote,     // e.g. "UBBL 2012: max 0.60 W/m²K for ext wall"
    String error
) {}

/** Result of saving an assembly template. */
record AssemblySaveResponse(
    boolean success,
    String bomId,              // generated m_bom.bom_id
    int layerCount,
    String error
) {}

---

4. U-Value Calculation

4.1 Formula (BS EN ISO 6946)

U = 1 / R_total

R_total = R_si + Σ(R_layer) + R_se

R_layer = thickness_m / conductivity_w_mk    (for solid layers)
R_layer = min(0.18, 0.18 × gap_mm / 25.0)     (for air cavities; saturates at 25mm)

R_si = 0.13  (internal surface resistance, horizontal heat flow)
R_se = 0.04  (external surface resistance)

For vertical elements (walls): R_si=0.13, R_se=0.04 For horizontal elements (roofs, upward): R_si=0.10, R_se=0.04 For horizontal elements (floors, downward): R_si=0.17, R_se=0.04

4.2 Metal Stud Bridging (simplified)

Metal stud layers use proportional-area method (BS EN ISO 6946 §6.2):

R_bridged = 1 / (f_metal/R_metal + f_insulation/R_insulation)

f_metal = 0.15 (typical 15% stud fraction for 600mm centres, 45mm studs)
f_insulation = 0.85
R_metal = thickness / 50.0 (steel λ ≈ 50 W/m·K)
R_insulation = thickness / 0.038 (cavity fill assumption)

4.3 Compliance Thresholds

From UBBL 2012 (Malaysian Uniform Building By-Laws) and common standards:

Element	UBBL 2012 max U	UK Part L max U	Notes
External wall	0.60 W/m²K	0.26 W/m²K	UBBL is tropical, less insulation
Roof	0.40 W/m²K	0.16 W/m²K
Ground floor	0.60 W/m²K	0.18 W/m²K

Compliance check uses AD_Val_Rule rows with check_method = 'U_VALUE' and jurisdiction-specific thresholds. This is Phase 2 — G-7 delivers the calculator; AD_Val_Rule integration comes with G-9/G-10 governance.

4.4 Implementation: UValueCalculator

/**
 * Stateless U-value calculator. Pure function: layers in → U-value out.
 * No DB access — caller provides layers and thermal properties.
 *
 * // Implementing ASSEMBLY_BUILDER_SRS.md §4 — Witness: W-ASM-UVAL-1
 */
public final class UValueCalculator {

    /** Surface resistance by element orientation. */
    public enum Orientation { VERTICAL, HORIZONTAL_UP, HORIZONTAL_DOWN }

    /**
     * Calculate U-value for a layer stack.
     *
     * @param layers      ordered layers (outside → inside)
     * @param orientation element orientation for surface resistance
     * @return U-value in W/m²K, rounded to 2 decimal places
     * @throws IllegalArgumentException if layers is empty
     */
    public static double calculate(List<LayerThermal> layers, Orientation orientation);

    /** Input record — one layer's thermal data. */
    public record LayerThermal(
        double thicknessMm,
        double conductivityWmK,  // λ; ignored if isAirGap=true
        boolean isAirGap,        // use fixed R instead of λ
        boolean isMetalStud      // use bridged R calculation
    ) {}
}

---

5. DAO Layer

5.1 AssemblyDAO (new)

Reads component_library.db for assembly templates and material properties. Read-only — never writes to component_library.db.

/**
 * DAO for assembly templates and material thermal data.
 * Reads component_library.db. Never writes.
 *
 * // Implementing ASSEMBLY_BUILDER_SRS.md §5 — Witness: W-ASM-DAO-1
 */
public class AssemblyDAO {

    /**
     * Load all layer sets for a category prefix.
     * @param categoryPrefix "Basic Wall" / "Basic Roof" / "Floor" / "Compound Ceiling"
     * @return list of layer set names matching the prefix
     */
    List<String> listLayerSets(String categoryPrefix);

    /**
     * Load full layer stack for a layer set.
     * Normalises thickness to mm.
     * @return ordered list of layers (by sequence)
     */
    List<MaterialLayer> loadLayers(String layerSetName);

    /**
     * Load thermal conductivity for a material.
     * @return conductivity in W/m·K, or null if unknown
     */
    Double getThermalConductivity(String materialName);

    /**
     * Load all thermal properties (batch, for U-value calc).
     * @return map of material_name → conductivity_w_mk
     */
    Map<String, Double> loadAllThermalProperties();

    /**
     * Browse compatible alternative materials for a layer position.
     * Filters by role compatibility (e.g., insulation slot → insulation materials).
     * @param currentMaterial the material being replaced
     * @param role            layer role (CLADDING, INSULATION, etc.)
     * @return compatible M_Product entries
     */
    List<AlternativeMaterial> browseAlternatives(String currentMaterial, String role);

    /** Raw layer from material_layers table. */
    record MaterialLayer(
        String layerSetName,
        int sequence,
        String materialName,
        double thicknessMm,    // normalised to mm
        boolean isVentilated
    ) {}

    /** An alternative material for a layer position. */
    record AlternativeMaterial(
        String materialName,
        double conductivityWmK,
        String description
    ) {}
}

5.2 AssemblyWriteDAO (new)

Writes assembly templates to output.db (per-instance) or to a new BOM file (reusable template).

/**
 * Write DAO for assembly templates.
 * Per-instance: writes to output.db C_OrderLine.
 * Reusable: writes to {PREFIX}_BOM.db m_bom + m_bom_line (via Promote path).
 *
 * // Implementing ASSEMBLY_BUILDER_SRS.md §5.2 — Witness: W-ASM-WRITE-1
 */
public class AssemblyWriteDAO {

    /**
     * Save assembly as per-instance OrderLine data.
     * Each layer → one C_OrderLine child under the wall/roof/floor OrderLine.
     * @return number of lines written
     */
    int savePerInstance(Connection conn, String parentOrderLineId,
                        List<AssemblyLayer> layers);

    /**
     * Save assembly as reusable template (m_bom + m_bom_line).
     * Calls through to Promote path — requires governance gate.
     * @return generated bom_id
     */
    String saveAsTemplate(Connection conn, String templateName,
                          String category, List<AssemblyLayer> layers);
}

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6. Wire Protocol — BlenderBridge Extensions

6.1 New Verbs (Python ← Java)

Verb	Direction	Payload	Action
show_assembly_editor	Java → Python	{layers, totalMm, uValue}	Render layer stack panel in Blender N-panel
update_assembly_layer	Python → Java	{layerSetName, seq, newMaterial, newThickness}	swapLayer() → recalculated response
browse_layer_alternatives	Python → Java	{layerSetName, seq}	browseAssemblyLayers() → product list
save_assembly	Python → Java	{name, category, layers}	saveAssemblyTemplate() → bomId
show_composition	Python → Java	{wallType}	Query material_layers → return layer stack

6.2 Wire Protocol Examples

// List templates
{"action":"listAssemblyTemplates", "category":"WALL"}
→ {"templates":[
     {"layerSetName":"Basic Wall:Exterior - Brick on Block",
      "category":"WALL", "layerCount":6, "totalThicknessMm":417,
      "uValueWm2K":0.35},
     ...
   ]}

// Get detail
{"action":"getAssemblyDetail", "layerSetName":"Basic Wall:Exterior - Brick on Block"}
→ {"layers":[
     {"seq":0, "material":"Masonry - Brick", "thicknessMm":92, "role":"CLADDING"},
     {"seq":1, "material":"Misc. Air Layers - Air Space", "thicknessMm":25, "role":"CAVITY"},
     {"seq":2, "material":"Insulation / Thermal Barriers - Rigid insulation",
      "thicknessMm":50, "role":"INSULATION"},
     {"seq":3, "material":"Masonry - Concrete Block", "thicknessMm":193, "role":"STRUCTURE"},
     {"seq":4, "material":"Metal - Stud Layer", "thicknessMm":41, "role":"STRUCTURE"},
     {"seq":5, "material":"Plasterboard", "thicknessMm":16, "role":"LINING"}
   ],
   "totalThicknessMm":417, "uValueWm2K":0.51}

// Swap a layer
{"action":"swapLayer", "layerSetName":"Basic Wall:Exterior - Brick on Block",
 "layerSequence":2, "newMaterial":"Rigid insulation", "newThicknessMm":100}
→ {"layers":[...updated...], "totalThicknessMm":467, "uValueWm2K":0.28}

// Query composition (existing verb from BIM_Designer_SRS.md §12.3)
{"action":"queryComposition", "wallType":"Basic Wall:Exterior - Brick on Block"}
→ {"layers":[...], "total_mm":417}

---

7. Constraints & Validation

7.1 Thickness Invariant

ASSERT: SUM(layer.thicknessMm for all layers) == parent.aabb_width_mm

When a layer is swapped, the parent AABB is updated to match the new total. This is a schema update (update m_bom.aabb_width_mm), not a geometry operation. The compiler handles the 3D consequences.

7.2 Layer Compatibility

Not every material fits every role. Role compatibility matrix:

Role	Compatible materials
CLADDING	Brick, block, timber cladding, render
CAVITY	Air gap (must be is_ventilated=1 or sealed)
INSULATION	Rigid, semi-rigid, spray foam, mineral wool
STRUCTURE	Block, concrete, timber frame, steel stud
LINING	Plasterboard, plaster, gypsum board
MEMBRANE	Vapour retarder, damp-proofing, EPDM

Phase 1: Advisory only — warn on role mismatch, don't block. Phase 2: Enforce via ad_assembly_manifest.interface_type matching.

7.3 InferenceEngine Integration

Layer placement is a constraint satisfaction problem (BIM_Designer_SRS.md §14):

fits(Layer, Slot) :- thickness(Layer, T), max_thickness(Slot, MaxT), T =< MaxT.
compatible(Layer, Slot) :- role(Layer, R), accepts(Slot, R).
valid_stack(Layers) :- thickness_invariant(Layers), all_compatible(Layers).

Phase 1 (G-7): Direct validation in AssemblyBuilderService (no InferenceEngine). Phase 2 (G-9+): Migrate to InferenceEngine rules with proof trees.

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8. Witness Claims

8.1 Witness Matrix

ID	Witness	What it proves	Acceptance criteria
W-ASM-LIST-1	ListAssemblyTemplates	listAssemblyTemplates("WALL") returns ≥ 7 wall templates	count ≥ 7 (9 wall layer_set_names exist)
W-ASM-LIST-2	ListAssemblyTemplates	listAssemblyTemplates("FLOOR") returns ≥ 3 floor templates	count ≥ 3
W-ASM-LIST-3	ListAssemblyTemplates	listAssemblyTemplates("ROOF") returns ≥ 1 roof templates	count ≥ 1
W-ASM-DETAIL-1	GetAssemblyDetail	Brick-on-Block returns 6 layers, total 417mm	layerCount=6, totalMm=417
W-ASM-DETAIL-2	GetAssemblyDetail	Layer order matches material_layers.sequence	layers[0].seq=0, layers[5].seq=5
W-ASM-UVAL-1	UValueCalculator	Brick-on-Block U ≈ 0.37 W/m²K (±0.05)	0.32 ≤ U ≤ 0.42
W-ASM-UVAL-2	UValueCalculator	Swap insulation 50→100mm reduces U	U_after < U_before
W-ASM-UVAL-3	UValueCalculator	Empty layers list → IllegalArgumentException	exception thrown
W-ASM-UVAL-4	UValueCalculator	Air gap uses fixed R=0.18, not λ/d	R_airgap = 0.18 regardless of thickness
W-ASM-BROWSE-1	BrowseAssemblyLayers	Browse insulation slot returns insulation-compatible materials	all results have insulation-class conductivity (λ < 0.1)
W-ASM-SWAP-1	SwapLayer	Swap insulation 50→100mm → totalMm increases by 50	new_total = old_total + 50
W-ASM-SWAP-2	SwapLayer	Swap recalculates U-value	U_after ≠ U_before
W-ASM-SAVE-1	SaveAssemblyTemplate	Save creates m_bom + m_bom_line	bom_line count = layer count
W-ASM-DAO-1	AssemblyDAO.loadLayers	SH Brick-on-Block normalises metres → mm	all thicknessMm > 1.0
W-ASM-DAO-2	AssemblyDAO.loadLayers	TE-style data (already mm) stays mm	no double-conversion
W-ASM-WRITE-1	AssemblyWriteDAO	Per-instance save creates C_OrderLine children	child count = layer count
W-ASM-THICK-1	ThicknessInvariant	SUM(layers) = parent total for all 20 templates	all 20 pass

8.2 Non-Disturbance

G-7 must not disturb existing gates:

Gate	Guard
G1-COUNT	No changes to extraction pipeline
G2-VOLUME	No changes to verb geometry
G3-DIGEST	Seal set unchanged
G4-TAMPER	No AD_Val_Rule changes
G5-PROVENANCE	No GEO_ prefixes introduced
G6-ISOLATION	No cross-stone contamination

Test strategy: Run ./scripts/run_RosettaStones.sh after implementation. All existing 136/136 must remain GREEN.

---

9. Implementation Plan

Phase 1: Core (this session)

Step	File	What
1	migration/027_ad_material_thermal.sql	Create ad_material_thermal + seed 29 materials
2	AssemblyDAO.java	Read material_layers + thermal properties
3	UValueCalculator.java	Stateless calculator (§4 formula)
4	AssemblyBuilderService.java	Orchestration: list/detail/swap/save
5	DesignerAPI.java	Add 5 new method signatures
6	DesignerAPIImpl.java	Wire to AssemblyBuilderService
7	AssemblyBuilderTest.java	17 witnesses (W-ASM-*)

Phase 2: Wire + Governance (future session)

Step	File	What
8	BlenderBridge verbs	show_assembly_editor + update_assembly_layer
9	AD_Val_Rule rows	U_VALUE check_method + jurisdiction thresholds
10	InferenceEngine	Layer constraint rules with proof trees

File Locations

BonsaiBIMDesigner/src/main/java/com/bim/designer/
├── api/DesignerAPI.java              (add records + methods)
├── api/DesignerAPIImpl.java          (wire to service)
├── assembly/AssemblyBuilderService.java  (NEW — orchestration)
├── assembly/AssemblyDAO.java             (NEW — read component_library.db)
├── assembly/AssemblyWriteDAO.java        (NEW — write output.db)
├── assembly/UValueCalculator.java        (NEW — stateless calc)

BonsaiBIMDesigner/src/test/java/com/bim/designer/
├── AssemblyBuilderTest.java              (NEW — 17 witnesses)

migration/
├── 027_ad_material_thermal.sql           (NEW — thermal properties table + seed)

---

10. Open Questions

#	Question	Default assumption	Blocks
Q1	Should metal stud bridging use simplified 15% or actual stud dims?	15% simplified	W-ASM-UVAL-1 tolerance
Q2	Should browse alternatives query M_Product or just material_layers?	material_layers (simpler, no product mapping needed yet)	W-ASM-BROWSE-1
Q3	Should save-as-template go directly to BOM.db or through Promote?	Through Promote (existing governance path)	W-ASM-SAVE-1
Q4	Unit normalisation: trust layer_set_name prefix or magnitude check?	Prefix first, magnitude fallback	W-ASM-DAO-1

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Spec citation: BIM_Designer.md §18.2 Principle 4 + §18.5 MAKE path. Traceability: TestArchitecture.md §Traceability Matrix — G-7 row to be added after implementation.