A house overlay occurs when a planet from one person’s birth chart is placed in a house of the other person’s chart. It is a core layer of synastry because it identifies where an inter-personal contact may be experienced, beyond the angular aspect between the planets.
How overlays are calculated
Two birth charts are calculated separately. One person’s planetary longitude is then placed against the house cusps of the other person’s chart. A planet may fall in different houses depending on which partner’s chart is used as the reference. The overlay is directional and should be read from each person’s point of view.
Typical house topics
The fifth house highlights creativity, play and romance; the seventh suggests partnership and negotiation; the eighth involves sharing, vulnerability and resources. The fourth can concern home and family expectations, while the tenth can introduce visibility and professional dynamics. These are thematic locations rather than predictions of a relationship outcome.
Avoiding one-placement verdicts
Birth-time errors and changes in house system may alter overlays. A Venus placement in someone’s seventh house may be interesting, but it should be weighed against aspects, rulers and lived circumstances. House overlays do not establish consent, compatibility or commitment by themselves.
Further relationship techniques
Continue with the Compatibility & Synastry guide, which places zodiac compatibility, interchart aspects and house overlays in a single interpretive framework.