An accessory dwelling unit — a small second home on your lot — is one of the few moves that adds usable space and can pay for itself. Here's how to think about whether it makes sense for you.
State law requires most municipalities to allow at least one ADU on lots with a single-family home, either attached or detached, subject to local rules on size, setbacks and parking. Keene and most surrounding towns permit them. The practical questions are lot size, septic or sewer capacity, and where utilities can run — which is exactly what a site visit sorts out.
We build ADUs with the Thermasteel panelized system — steel-and-foam structural panels cut to plan. The shell goes up in days. Rough 2026 ranges for a Monadnock-region build:
A 700 sq ft one-bedroom, turnkey, lands around $150k–$210k for the building. Land, site work, utility runs and impact fees are separate and vary more than the structure does. Model it with the ADU sizer.
Take the finished cost, divide by annual rent times about 0.7 (to account for vacancy, maintenance and taxes). At $1,600/month on a $180k build, that's roughly a 13–15 year simple payback — after which it's income, plus the added property value the whole time.
If you have the lot, the utilities are reachable, and you'd keep it 10+ years, the numbers usually work — and panelized construction shortens the risky, weather-exposed part of the build to a few days. If you'd sell within five years, the value bump matters more than the rent.
Curious what your lot could support? Book a consult — we'll look at siting, utilities and the numbers together.
Tell us the room, a rough budget range and when you'd like to start. We'll come back with next steps and a realistic timeline — no pressure, no mystery pricing.
