diff --git a/domain/property/__init__.py b/domain/property/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/domain/property/properties.py b/domain/property/properties.py
new file mode 100644
index 00000000..b7a5aae5
--- /dev/null
+++ b/domain/property/properties.py
@@ -0,0 +1,25 @@
+from __future__ import annotations
+
+from collections.abc import Callable, Iterator
+from dataclasses import dataclass
+
+from domain.property.property import Property
+
+
+@dataclass
+class Properties:
+    """A first-class collection of Property objects — the unit of bulk operation
+    in services (CONTEXT.md: Properties). Services take and return `Properties`
+    rather than bare lists so batch operations read clearly.
+    """
+
+    items: list[Property]
+
+    def __iter__(self) -> Iterator[Property]:
+        return iter(self.items)
+
+    def __len__(self) -> int:
+        return len(self.items)
+
+    def filter(self, predicate: Callable[[Property], bool]) -> "Properties":
+        return Properties([p for p in self.items if predicate(p)])
diff --git a/domain/property/property.py b/domain/property/property.py
new file mode 100644
index 00000000..856eb3e3
--- /dev/null
+++ b/domain/property/property.py
@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Literal, Optional
+
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from domain.property.site_notes import SiteNotes
+
+SourcePath = Literal["site_notes", "epc_with_overlay"]
+
+
+@dataclass(frozen=True)
+class PropertyIdentity:
+    """Identifies a single Property within a portfolio.
+
+    Keyed by `(portfolio_id, uprn)` or `(portfolio_id, landlord_property_id)` —
+    a UPRN is permanent but each portfolio gets its own Property against it
+    (CONTEXT.md: UPRN).
+    """
+
+    portfolio_id: int
+    postcode: str
+    address: str
+    uprn: Optional[int] = None
+    landlord_property_id: Optional[str] = None
+
+
+@dataclass
+class Property:
+    """The Ara modelling aggregate root for a single dwelling (ADR-0002).
+
+    Holds identity plus the source data the pipeline reasons about. Enrichments
+    (geospatial, solar) and modelling outputs (baseline performance, plans) are
+    added by later slices — this is the minimal-and-growing shape for First Run.
+    """
+
+    identity: PropertyIdentity
+    epc: Optional[EpcPropertyData] = None
+    site_notes: Optional[SiteNotes] = None
+
+    @property
+    def source_path(self) -> SourcePath:
+        """Which of the two disjoint source paths models this Property (ADR-0001).
+
+        Site Notes alone, or the public EPC (with Landlord Overrides, once that
+        slice lands). When both exist the newer wins (Recency Tie-Break); on an
+        equal date the survey wins, as it reflects on-site observation.
+        """
+        if self.site_notes is not None and self.epc is not None:
+            epc_date = self.epc.registration_date or self.epc.inspection_date
+            if self.site_notes.surveyed_at >= epc_date:
+                return "site_notes"
+            return "epc_with_overlay"
+        if self.site_notes is not None:
+            return "site_notes"
+        if self.epc is not None:
+            return "epc_with_overlay"
+        raise ValueError(
+            "Property has neither Site Notes nor an EPC; no source path to model from"
+        )
+
+    @property
+    def effective_epc(self) -> EpcPropertyData:
+        """The EpcPropertyData the modelling pipeline scores against.
+
+        Path 1: the Site Notes' surveyed data. Path 2: the public EPC (Landlord
+        Overrides overlay is a later slice — returned as-is for now).
+        """
+        if self.source_path == "site_notes":
+            assert self.site_notes is not None
+            return self.site_notes.to_epc_property_data()
+        assert self.epc is not None
+        return self.epc
diff --git a/domain/property/site_notes.py b/domain/property/site_notes.py
new file mode 100644
index 00000000..04267735
--- /dev/null
+++ b/domain/property/site_notes.py
@@ -0,0 +1,23 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from datetime import date
+
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+
+
+@dataclass
+class SiteNotes:
+    """A Domna survey of a single Property (CONTEXT.md: Site Notes).
+
+    Committed by the domain to being full-coverage — it carries every EPC field
+    the modelling pipeline needs, expressed as an `EpcPropertyData`. When present
+    (and not older than the public EPC) it is the complete source of truth for
+    the Property; the public EPC is then irrelevant (ADR-0001).
+    """
+
+    surveyed_at: date
+    epc: EpcPropertyData
+
+    def to_epc_property_data(self) -> EpcPropertyData:
+        return self.epc
diff --git a/infrastructure/postgres/property_table.py b/infrastructure/postgres/property_table.py
new file mode 100644
index 00000000..0b91a2ad
--- /dev/null
+++ b/infrastructure/postgres/property_table.py
@@ -0,0 +1,23 @@
+from __future__ import annotations
+
+from typing import ClassVar, Optional
+
+from sqlmodel import Field, SQLModel
+
+
+class PropertyRow(SQLModel, table=True):
+    """Defensive view of the FE-owned ``property`` table.
+
+    The schema and migrations for ``property`` are owned by the front-end
+    Next.js repo; this declares only the identity columns the modelling backend
+    reads/writes, so FE-owned migrations to other columns don't ripple into us.
+    """
+
+    __tablename__: ClassVar[str] = "property"  # pyright: ignore[reportIncompatibleVariableOverride]
+
+    id: Optional[int] = Field(default=None, primary_key=True)
+    portfolio_id: int
+    postcode: str
+    address: str
+    uprn: Optional[int] = Field(default=None)
+    landlord_property_id: Optional[str] = Field(default=None)
diff --git a/repositories/epc/epc_postgres_repository.py b/repositories/epc/epc_postgres_repository.py
index 52873dce..b0a8070c 100644
--- a/repositories/epc/epc_postgres_repository.py
+++ b/repositories/epc/epc_postgres_repository.py
@@ -134,6 +134,16 @@ class EpcPostgresRepository(EpcRepository):
             )
         return epc_property_id
 
+    def get_for_property(self, property_id: int) -> Optional[EpcPropertyData]:
+        row = self._session.exec(
+            select(EpcPropertyModel)
+            .where(EpcPropertyModel.property_id == property_id)
+            .order_by(EpcPropertyModel.id)  # type: ignore[arg-type]
+        ).first()
+        if row is None or row.id is None:
+            return None
+        return self.get(row.id)
+
     def get(self, epc_property_id: int) -> EpcPropertyData:
         p = self._session.get(EpcPropertyModel, epc_property_id)
         if p is None:
diff --git a/repositories/epc/epc_repository.py b/repositories/epc/epc_repository.py
index db479c85..fb83bdbc 100644
--- a/repositories/epc/epc_repository.py
+++ b/repositories/epc/epc_repository.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
+from typing import Optional
 
 from datatypes.epc.domain.epc_property_data import EpcPropertyData
 
@@ -24,3 +25,6 @@ class EpcRepository(ABC):
 
     @abstractmethod
     def get(self, epc_property_id: int) -> EpcPropertyData: ...
+
+    @abstractmethod
+    def get_for_property(self, property_id: int) -> Optional[EpcPropertyData]: ...
diff --git a/repositories/property/__init__.py b/repositories/property/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/repositories/property/property_postgres_repository.py b/repositories/property/property_postgres_repository.py
new file mode 100644
index 00000000..c1b631dd
--- /dev/null
+++ b/repositories/property/property_postgres_repository.py
@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+from sqlmodel import Session
+
+from domain.property.property import Property, PropertyIdentity
+from infrastructure.postgres.property_table import PropertyRow
+from repositories.epc.epc_repository import EpcRepository
+from repositories.property.property_repository import PropertyRepository
+
+
+class PropertyPostgresRepository(PropertyRepository):
+    """Hydrates the Property aggregate from the FE-owned ``property`` row plus the
+    EPC slice (via an injected `EpcRepository`). Reads only from repos — no
+    external IO — so a hydrated Property is a pure function of repository state
+    (ADR-0003).
+    """
+
+    def __init__(self, session: Session, epc_repo: EpcRepository) -> None:
+        self._session = session
+        self._epc_repo = epc_repo
+
+    def get(self, property_id: int) -> Property:
+        row = self._session.get(PropertyRow, property_id)
+        if row is None:
+            raise ValueError(f"property {property_id} not found")
+        identity = PropertyIdentity(
+            portfolio_id=row.portfolio_id,
+            postcode=row.postcode,
+            address=row.address,
+            uprn=row.uprn,
+            landlord_property_id=row.landlord_property_id,
+        )
+        return Property(
+            identity=identity,
+            epc=self._epc_repo.get_for_property(property_id),
+        )
diff --git a/repositories/property/property_repository.py b/repositories/property/property_repository.py
new file mode 100644
index 00000000..0a9045be
--- /dev/null
+++ b/repositories/property/property_repository.py
@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+
+from domain.property.property import Property
+
+
+class PropertyRepository(ABC):
+    """Loads and saves the Property aggregate.
+
+    Composes the aggregate whole from the FE-owned ``property`` identity row plus
+    its source-data slices (EPC today; Site Notes / enrichments as later slices
+    land). Aggregates load whole — never half a Property (ADR-0002).
+    """
+
+    @abstractmethod
+    def get(self, property_id: int) -> Property: ...
diff --git a/tests/domain/property/__init__.py b/tests/domain/property/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/domain/property/test_property.py b/tests/domain/property/test_property.py
new file mode 100644
index 00000000..01d7edfd
--- /dev/null
+++ b/tests/domain/property/test_property.py
@@ -0,0 +1,127 @@
+"""Property aggregate — source-path precedence and Effective EPC resolution.
+
+The two disjoint source paths (ADR-0001): a Property is modelled either from its
+Site Notes alone, or from the public EPC (with Landlord Overrides, once that slice
+lands). When both exist, the newer wins (Recency Tie-Break).
+"""
+
+from __future__ import annotations
+
+import json
+from datetime import date
+from pathlib import Path
+from typing import Any
+
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+from domain.property.properties import Properties
+from domain.property.property import Property, PropertyIdentity
+from domain.property.site_notes import SiteNotes
+
+_JSON_SAMPLES = Path(__file__).resolve().parents[3] / "backend/epc_api/json_samples"
+
+
+def _epc(inspection: str = "2023-12-01") -> EpcPropertyData:
+    raw: dict[str, Any] = json.loads(
+        (_JSON_SAMPLES / "RdSAP-Schema-21.0.0" / "epc.json").read_text()
+    )
+    return EpcPropertyDataMapper.from_api_response(raw)
+
+
+def _identity() -> PropertyIdentity:
+    return PropertyIdentity(
+        portfolio_id=1, postcode="A0 0AA", address="1 Some Street", uprn=12345
+    )
+
+
+def test_source_path_is_epc_with_overlay_when_only_epc_present() -> None:
+    # Arrange
+    prop = Property(identity=_identity(), epc=_epc())
+
+    # Act
+    path = prop.source_path
+
+    # Assert
+    assert path == "epc_with_overlay"
+
+
+def test_source_path_is_site_notes_when_only_site_notes_present() -> None:
+    # Arrange
+    prop = Property(
+        identity=_identity(),
+        site_notes=SiteNotes(surveyed_at=date(2024, 6, 1), epc=_epc()),
+    )
+
+    # Act
+    path = prop.source_path
+
+    # Assert
+    assert path == "site_notes"
+
+
+def test_recency_tie_break_newer_site_notes_win_over_older_epc() -> None:
+    # Arrange — EPC inspected 2023-12-01; survey is newer
+    prop = Property(
+        identity=_identity(),
+        epc=_epc(),
+        site_notes=SiteNotes(surveyed_at=date(2025, 1, 1), epc=_epc()),
+    )
+
+    # Act / Assert
+    assert prop.source_path == "site_notes"
+
+
+def test_recency_tie_break_older_site_notes_lose_to_newer_epc() -> None:
+    # Arrange — survey predates the EPC's inspection date
+    prop = Property(
+        identity=_identity(),
+        epc=_epc(),
+        site_notes=SiteNotes(surveyed_at=date(2020, 1, 1), epc=_epc()),
+    )
+
+    # Act / Assert
+    assert prop.source_path == "epc_with_overlay"
+
+
+def test_effective_epc_follows_the_selected_source_path() -> None:
+    # Arrange
+    survey_epc = _epc()
+    public_epc = _epc()
+    site_notes_property = Property(
+        identity=_identity(),
+        site_notes=SiteNotes(surveyed_at=date(2025, 1, 1), epc=survey_epc),
+    )
+    epc_property = Property(identity=_identity(), epc=public_epc)
+
+    # Act / Assert
+    assert site_notes_property.effective_epc is survey_epc
+    assert epc_property.effective_epc is public_epc
+
+
+def test_property_with_no_source_raises() -> None:
+    # Arrange
+    prop = Property(identity=_identity())
+
+    # Act / Assert
+    try:
+        _ = prop.source_path
+    except ValueError:
+        pass
+    else:  # pragma: no cover
+        raise AssertionError("expected ValueError when no source is present")
+
+
+def test_properties_collection_iterates_and_filters() -> None:
+    # Arrange
+    with_epc = Property(identity=_identity(), epc=_epc())
+    without = Property(identity=_identity())
+    properties = Properties([with_epc, without])
+
+    # Act
+    with_source = properties.filter(lambda p: p.epc is not None)
+
+    # Assert
+    assert len(properties) == 2
+    assert list(properties) == [with_epc, without]
+    assert len(with_source) == 1
+    assert list(with_source) == [with_epc]
diff --git a/tests/repositories/property/__init__.py b/tests/repositories/property/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/repositories/property/test_property_repository.py b/tests/repositories/property/test_property_repository.py
new file mode 100644
index 00000000..2456a670
--- /dev/null
+++ b/tests/repositories/property/test_property_repository.py
@@ -0,0 +1,49 @@
+"""PropertyRepository hydrates the aggregate whole from the property row + EPC slice."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Any
+
+from sqlalchemy import Engine
+from sqlmodel import Session
+
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+from infrastructure.postgres.property_table import PropertyRow
+from repositories.epc.epc_postgres_repository import EpcPostgresRepository
+from repositories.property.property_postgres_repository import (
+    PropertyPostgresRepository,
+)
+
+_JSON_SAMPLES = Path(__file__).resolve().parents[3] / "backend/epc_api/json_samples"
+
+
+def test_get_hydrates_identity_and_epc_slice(db_engine: Engine) -> None:
+    # Arrange
+    raw: dict[str, Any] = json.loads(
+        (_JSON_SAMPLES / "RdSAP-Schema-21.0.0" / "epc.json").read_text()
+    )
+    epc = EpcPropertyDataMapper.from_api_response(raw)
+    with Session(db_engine) as session:
+        row = PropertyRow(
+            portfolio_id=7, postcode="A0 0AA", address="1 Some Street", uprn=12345
+        )
+        session.add(row)
+        session.commit()
+        property_id = row.id
+        assert property_id is not None
+        EpcPostgresRepository(session).save(epc, property_id=property_id)
+        session.commit()
+
+    # Act
+    with Session(db_engine) as session:
+        repo = PropertyPostgresRepository(session, EpcPostgresRepository(session))
+        prop = repo.get(property_id)
+
+    # Assert
+    assert prop.identity.portfolio_id == 7
+    assert prop.identity.uprn == 12345
+    assert prop.epc == epc
+    assert prop.source_path == "epc_with_overlay"
+    assert prop.effective_epc == epc