House Size, Program & Design

Treat design as an early, high-leverage affordability decision. Show how size, plan efficiency, and complexity multiply costs across structure, envelope, MEP, and finishes, and define "worth it" features vs low-value complexity.

How this fits in the series

Builds on: A1 (cost elements and baseline)
Leads to: A6 (labor and materials), A7 (alternative construction)

Core concepts and execution implications

Size multiplies cost across most systems.
- Can quantify which systems scale with size for the baseline project.
Livability often comes from layout efficiency, not more area.
- Can compare plans by usable function, not just square footage.
Complexity creates cost via labor hours, errors, and rework.
- Can identify complexity drivers and remove them intentionally.

Connections

Cost elements: B07-BuildCost; secondary: B06-SoftCosts
CROs: CRO-SIZE, CRO-SIMPLIFY, CRO-STANDARDIZE
Decision authorities: City council, planning commission, code bodies, design review boards, builders
Performance framework: Thermal (C2), Thermal/Moisture Mechanisms (E2) — size and geometry affect thermal bridging risk
Cross-series: P5 The House as a System (size and geometry affect heat/air/moisture interactions)
Cross-series: P9 Heat Flow & Thermal Bridging (geometry drives thermal bridge locations)
Explore in Affordability Framework →

Cost elements in this session

Building construction — size and materials (B07-BuildCost)

Size drives structure, envelope, MEP sizing, and finishes. Every additional square foot cascades into every subsystem.

💡 Square footage is a multiplier. Bigger cascades into every subsystem, not just framing.

💡 Livability isn't size. Good layouts can feel bigger than they are.

⚠️ Size creep as "small" decisions — a few hundred extra square feet cascades into every trade.

⚠️ Misplaced "value" upgrades — spending goes to visible upgrades instead of high-payoff livability.

Decision authorities: City council, planning commission, code bodies, appraisers.

Explore in AF: Build Cost (B07) → CRO-SIZE

Building construction — labor and geometry (B07-BuildCost)

Corners, offsets, rooflines, and non-repeating details drive labor hours. Simple geometry reduces labor and envelope area.

💡 Shape is cost. Simple geometry reduces labor and envelope area.

⚠️ Complexity creep — design features add labor and coordination cost without proportional value.

⚠️ Articulation mandates — design review standards emphasizing variation increase cost without measurable benefit.

Decision authorities: Design review boards, municipalities, HOAs.

Explore in AF: Build Cost (B07) → CRO-SIMPLIFY

Soft costs (B06-SoftCosts) — secondary

Repeat plans and details reduce design time and production errors. Standardization saves on design and production learning curve.

💡 Standardization saves twice. Design + production learning curve savings.

⚠️ Too many one-off plans — SKU proliferation increases soft costs and mistakes.

Explore in AF: Soft Costs (B06) → CRO-STANDARDIZE

Common high-leverage plan moves

Three design decisions that reduce cost without reducing livability:

Stack plumbing vertically
Align kitchen/bath wet walls across floors. Reduces pipe runs, fittings, and labor hours significantly.
Simplify the roofline
Fewer valleys, hips, and dormers = fewer transitions, less flashing, faster framing, and fewer leak opportunities.
Compact the envelope
Reduce exterior wall area per square foot of floor. A simple rectangle encloses more space with less wall than an articulated plan.

Barriers & levers

Top barriers blocking the CROs in this session. Full barrier table in the Affordability Framework.

CRO-SIZE barriers

MIN_UNIT_SIZE — Minimum dwelling unit size in zoning or code prohibits smaller, lower-cost homes. Authority: City council, planning commission.
MIN_ROOM_SIZE — Minimum room size requirements force larger overall footprints. Authority: Code bodies.
PARKING_INDUCED_SIZE — Parking requirements indirectly enforce larger units via garages and circulation. Authority: Municipality.
APPRAISAL_BIAS — Appraisal and market norms penalize small units, reducing financing feasibility. Authority: Lenders, appraisers.

CRO-SIMPLIFY barriers

ARTICULATION_MANDATES — Design review standards emphasizing articulation increase labor, waste, and detailing cost. Authority: Design review boards.
AESTHETIC_ONLY_RULES — Aesthetic requirements not tied to performance force cost without measurable benefit. Authority: Municipalities, HOAs.
FIRE_ZONING_COMPLEXITY — Fire or zoning rules indirectly force articulation and offsets on simple forms. Authority: Fire marshal, zoning authority.
NO_SIMPLE_ARCHETYPES — Lack of pre-approved simple building archetypes forces each project to reinvent geometry. Authority: Municipality.

CRO-STANDARDIZE barriers