What a house system actually does
The twelve zodiac signs are fixed: each covers exactly thirty degrees of the ecliptic, the same for every chart, every location, every era. The twelve houses are not fixed. They must be calculated — and different methods of calculation produce different results.
A house system is the mathematical rule that distributes twelve house boundaries (called cusps) across the chart wheel, starting from the Ascendant (the degree of the zodiac rising on the eastern horizon at birth). Every system agrees on where the Ascendant falls. They disagree on how to divide the remaining space.
This matters because a planet's house placement — which life domain it speaks to — depends entirely on which side of the cusp it falls.
The major systems
Placidus — The default in most contemporary Western software, including Veyra. Placidus divides the sky by the time it takes a given degree of the ecliptic to travel from the horizon to the meridian, producing unequal house sizes that vary by latitude. At extreme latitudes (above roughly 60°N or 60°S), Placidus produces distorted or impossible houses; other systems handle polar charts more gracefully.
Whole Sign — The oldest system in the Western tradition, used throughout Hellenistic astrology from roughly 200 BCE. The entire sign containing the Ascendant becomes the first house; the next sign becomes the second; and so on around the wheel. Every house spans exactly thirty degrees. It is mathematically simple, works at any latitude, and is increasingly used by practitioners working from traditional sources.
Equal House — Each house begins exactly thirty degrees from the Ascendant, measured in ecliptic longitude. The houses are equal in size but do not align with whole signs. The Midheaven may fall in any house from the ninth to the eleventh, rather than anchoring the tenth.
Koch and Porphyry — Two additional quadrant-based systems with their own approaches to dividing the space between horizon and meridian. Both are in active use; neither has displaced Placidus in mainstream practice.
When the choice matters
For most chart positions, house systems agree. The Sun in the fifth house under Placidus is likely in the fifth under Whole Sign. The disagreement concentrates at the edges: planets near house boundaries may fall in different houses under different systems.
Saturn at 27° of what Placidus calls the second house might sit squarely in the third under Whole Sign. That difference is not trivial — the two houses carry different topics (resources versus communication), and the reading shifts accordingly.
Different astrologers hold different positions — sometimes strongly held — on which method is more accurate. This is not an error to be resolved. The tradition has used multiple systems for two thousand years; the debate reflects genuine theoretical disagreement about how to locate planetary topics in lived experience.
Using house systems responsibly
Name the system. Any interpretation of a chart should specify which house system was used, because a reader working from a different system may see a different picture for the same planet.
When a planet sits within two or three degrees of a house cusp, treat it as genuinely ambiguous. Check it in at least one other system. If it changes houses, read both possibilities — this is information, not an error.
The sign a planet occupies is never affected by the house system. Signs are stable. Houses are method-dependent.