By Lawrence Reinholt, Roofing Guides Editor
Updated September 2026
Quick answer: Albuquerque's development ordinance allows ADUs by right in R-1 zones, with detached units capped at 750 sq ft. A casita roof needs the same details as a house: proper slope to outlets or gutters, drip edge and flashing at every wall. For attached additions, the tie-in with the existing roof is where most leaks start, so it deserves the most attention.
Part 1 of 5
Flat or pitched?
Flat roofs with parapets and canales suit Pueblo and Territorial homes and usually get TPO or spray foam over tapered insulation. Pitched roofs match shingle, metal or tile houses and shed water naturally. Either works; the choice is mostly about matching the house.
Part 2 of 5
Drainage on a small roof
A small flat roof still needs slope to its outlet, and a canale or scupper sized for monsoon bursts. Water from a casita roof also has to go somewhere away from its own foundation and the main house. See flat roof ponding for why slope matters.
Part 3 of 5
The tie-in with the main house
Where an addition meets the existing roof, the new roofing has to be woven, welded or crickted into the old so water keeps moving. Tying into a failing old roof only moves the leak, so the existing roof at the joint is checked first. See casita and ADU roofing.
Questions about your own roof? Call and talk to a roofer.
Call (505) 636-9496Part 4 of 5
Matching materials
Matching shingle color, metal finish or tile profile makes an addition look original. Where an exact match is not available, a complementary material that looks intentional is better than a near miss.
Part 5 of 5
Plans and permits
A casita or ADU is permitted as a building project, and the roof is inspected with it. Reviewing the roof details on the plans before building is the cheapest time to fix drainage or flashing problems.
FAQ
Common questions on this topic
Detached ADUs in R-1 zones are limited to 750 sq ft.
Usually, or complement it deliberately.
Either; match the house and plan drainage.
At the tie-in with the existing roof.
Yes; roof details are easiest to fix before building.
If the old roof is near the end of its life, it can be the right time.
The project is permitted as a building; the roof is part of it.