House overlays in synastry: partner planets in your houses

House overlays are the second layer of synastry after inter-aspects. One person's planets are placed into the houses of the other person's chart to see which areas of life the partner enters, and with which functions. An aspect answers the question of how two planets interact; an overlay answers where it happens. The method depends heavily on birth time, and that is its main limitation.

How an overlay works

Take the house cusps of chart A and place the planets of chart B on them. B's Sun is at 10°15′ Scorpio; if A's second house cusp falls at, say, 8° Scorpio, B's Sun is in A's second house. Repeat for each of B's planets, then do the reverse: A's planets in B's houses.

Overlays are read from the point of view of the person who owns the houses. A partner's planet in my house describes how that person touches the corresponding area of my life and how I experience it. A partner's Saturn in my tenth house concerns my career and public role, not theirs. So the two halves of an overlay, B's planets in A's houses and A's planets in B's houses, give two different pictures, and both are needed.

Why this layer is unreliable without exact birth times

House cusps depend on the time and place of birth. The Ascendant moves through the whole zodiac in about a day, which averages out at roughly one degree every four minutes. The rate varies a lot between signs of short and long ascension, but the order of magnitude holds: a birth time that is half an hour off shifts the Ascendant and the other cusps by several degrees, and in some signs by more than ten.

For overlays this means a partner's planet near a cusp can easily move from one house to the next. "Their Venus is in my seventh house" can become "in my sixth" because of a carelessly recorded time. The practical rule follows: to put B's planets into A's houses you need A's accurate birth time. B's time matters much less for this layer, because it only affects the position of B's Moon (which moves about 13° a day); the other planets barely move in a day.

If neither birth time is known, it is better to skip house overlays entirely and stay with planet-to-planet aspects. A noon chart produces nominal houses, and conclusions drawn from them do not hold.

The second limitation is the house system. Placidus, Koch, equal houses and whole sign houses divide the circle differently, and a planet near a boundary can land in a different house depending on which one you use. The angles (Ascendant, Descendant, MC and IC) are the same across the quadrant systems, so they can be trusted more than the intermediate cusps.

Which houses to look at first

For a couple, the houses tied to personal relationships and shared life carry the most weight:

• 7th house: partnership and the kind of person someone looks for.
• 1st house: personality and body.
• 5th house: romance, play, pleasure, children.
• 8th house: intimacy, shared resources, deep mutual dependence.
• 4th house: home, family, a sense of safety.
• 10th house: career, status, public role.

The other houses work too, but they describe daily routine, study, friends and areas far from the couple's shared life. The 12th house is a special case: a partner's planets there are traditionally read as something hidden, or something hard to put into words.

Planets on the angles

The strongest overlay is a partner's planet within a few degrees of my Ascendant, Descendant, MC or IC. It is not just in a house; it sits on an axis of the chart, and both people tend to feel it. Here overlays and inter-aspects coincide: B's planet on A's Descendant is at the same time in opposition to A's Ascendant, and a planet on the IC opposes the MC.

That is also why the angles demand an even more accurate birth time than the other houses. A few degrees of error, and a planet "on the Ascendant" ends up in the twelfth house.

Double overlays

An overlay is called double when the same theme appears from both sides: B's planet in A's seventh house and A's planet in B's seventh, or each person's Moon in the other's fourth. The repetition works like a mutual aspect: the theme involves both partners rather than one. A one-sided overlay describes an asymmetry, where an area of life is touched for one partner only.

A worked example: partners A and B

Partner A: Ascendant 11°40′ Libra, MC 14°05′ Cancer, so the Descendant is at 11°40′ Aries and the IC at 14°05′ Capricorn. Partner B: Ascendant 7°25′ Aquarius, MC 28°10′ Scorpio, so the Descendant is at 7°25′ Leo and the IC at 28°10′ Taurus. The planets are the same as in the inter-aspects example.

B's planets in A's houses:

• B's Moon at 16°50′ Capricorn is 2°45′ past A's IC: in the fourth house, on the angle.
• B's Mars at 25°10′ Aries is 13°30′ past A's Descendant: in the seventh house. Exactly where the boundary with the eighth falls depends on the house system and on how accurate the time is.
• B's Sun at 10°15′ Scorpio is 28°35′ past A's Ascendant, near the boundary of the first and second houses. This is exactly the case where half an hour of error in A's birth time changes the house.

A's planets in B's houses:

• A's Mars at 9°05′ Leo is 1°40′ past B's Descendant: in the seventh house, on the angle.
• A's Moon at 3°10′ Cancer is 35°00′ past B's IC: in the fourth house or already in the fifth, depending on the fifth house cusp.
• A's Saturn at 22°30′ Capricorn is 14°55′ before B's Ascendant: in the twelfth house.

Each partner's Mars sits in the other's seventh house. That is a double overlay: for both of them, the partner is the one who acts and takes the initiative in the relationship. A's Mars is also on B's Descendant, and it shows up among the inter-aspects as an opposition to B's Ascendant with an orb of 1°40′. Two methods point to the same thing, and that agreement gives the reading something solid to stand on.

The Moon is not symmetrical. B's Moon sits right on A's IC, so for A the theme of home and family is strongly engaged. A's Moon in B's chart is far from the angle and near the boundary of the fourth and fifth houses, so for B the same theme is quieter or takes a different form. This is the difference between a one-sided overlay and a double one.

B's Sun near the boundary of A's first and second houses is the least reliable part of the example. It is better left uninterpreted until A's birth time has been checked.

Overlays and aspects together

Overlays do not replace aspects. A partner's planet in my fifth house with no aspect to my planets describes a background, not an event in the relationship. When the same planet also closely aspects my Sun or Venus, background and contact combine into one theme.

The working order is: aspects and repeating themes first, then overlays for them. The overlay suggests in which area of life an aspect you have already found will show. Only angular planets and double overlays are worth looking at independently of aspects. The next methods, the composite chart and the Davison chart, build a single chart out of two, and houses mean something different there.

Compare two charts