Module 4 · Lesson 7
Bigger Is Not Always Better
Four reasons to resist maxing out your ADU's square footage: cost curves, yard value, privacy, and layout efficiency.
"Build the biggest thing the city allows" sounds like obvious advice. It's often wrong. Four reasons to resist the max.
1. The cost curve doesn't care about your rent curve. Construction cost rises almost linearly with size — every added foot costs real money. Rent doesn't follow: it rises in steps (studio → 1BR → 2BR) and flattens between them. A 950 SF 2BR often rents within a few percent of a 1,150 SF 2BR that cost $70K more to build. Build to the top of a rent step, not past it.
2. Your yard is worth money too. A maxed-out ADU can turn two homes with pleasant outdoor space into two homes staring at each other across a strip of concrete. Usable yard raises the rent of the ADU, preserves the value of the main house, and keeps daily life pleasant. Appraisers notice; so do tenants.
3. Privacy shrinks as buildings grow. The bigger the ADU, the closer it presses toward the main house and the neighbors' fences. Distance is the cheapest privacy feature there is — spend some square footage on it.
4. Layout efficiency beats raw area. A 700 SF unit with zero wasted hallway outperforms a 900 SF unit with a long corridor and awkward corners. Every foot of hallway is money spent on space nobody enjoys. Good designers deliver small units that live large; size can't fix a bad plan.
The takeaway question: not "how big can I go?" but "what's the smallest size that fully serves my goal?" That number — plus a great layout — is almost always the best investment on the lot.
Key takeaways
- Rent rises in steps (studio → 1BR → 2BR) while cost rises with every foot — build to the top of a step, not past it.
- Usable yard adds value to both homes; don't pave your lot's biggest amenity.
- Distance between buildings is the cheapest privacy feature available.
- A tight, efficient layout beats extra square footage every time.