Choosing the Best Roof Type for Your ADU: A Novice's Guide

When planning an accessory dwelling unit (ADU), one of the most important design choices you’ll make is the roof type. The roof not only protects the structure from the elements, but it also defines the overall style, cost, and functionality of your ADU. Choosing the right roof type early can save money, simplify permitting, and improve the livability of the space. Here’s a guide to help you weigh your options:

1. Consider Your ADU’s Purpose and Style

Start by thinking about how your ADU will be used. Is it a rental, a guest house, or an office? The function will influence your design choices.• Detached ADUs: Often benefit from a pitched roof to match the primary home and add curb appeal.• Garage Conversions or Additions: Low-slope or shed-style roofs can create a modern look while minimizing structural changes.• Tiny Homes / Studios: Compact gable or shed roofs maximize usable interior space and allow for lofts or vaulted ceilings. Matching the architectural character of your main house can help the ADU blend into your property and pass design review more easily.

2. Understand the Most Common Roof Types

Here are the most common roof styles used on ADUs:• Gable Roof — A classic triangular shape with two sloped sides. Affordable, simple to frame, and good for rain and snow runoff.• Hip Roof — All four sides slope downwards. Provides excellent stability and wind resistance, ideal in storm-prone areas.• Shed Roof — A single sloping plane. Modern-looking, easy to frame, and perfect for maximizing natural light with high clerestory windows.• Flat or Low-Slope Roof — Clean, modern aesthetic and cost-efficient. Can provide a rooftop deck, though they require excellent waterproofing. Each type has different framing requirements and can affect your project’s engineering and permitting needs.

3. Factor in Local Building Codes and Climate

Before settling on a design, review your local building department’s zoning and building codes:• Snow and rain loads may require a minimum roof pitch.• Wildfire-prone zones may require Class A fire-rated roofing.• Height limits could restrict roof pitch if you’re close to the maximum allowable height.• Setbacks and design review might require the ADU roof to match the primary residence. Your designer or drafting professional can help navigate these requirements.

4. Think About Cost and Construction Complexity

Roof complexity directly impacts construction costs. Simple gable or shed roofs are typically the most affordable to build, while hip roofs and multi-slope combinations cost more in both materials and labor. If your budget is tight, opt for a straightforward roofline — fewer valleys, dormers, and transitions mean fewer potential leak points and a faster build.

5. Plan for Long-Term Efficiency

A roof isn’t just about looks — it affects energy performance too. Consider:• Overhangs for shade and rain protection• Cool roofing materials to reflect sunlight• Insulation and attic ventilation for comfort and energy savings• Solar panel placement if you plan to add PV later a thoughtful roof design can reduce your long-term operating costs.

Here is a table going over the different types:

Roof Type	Description	Key Benefits	Relative Cost
Gable Roof	Two sloped sides forming a triangle	• Classic, widely accepted look• Easy to frame & build• Excellent water/snow runoff• Allows attic or loft space	💲 Low–Moderate
Hip Roof	All four sides slope downward	• Very stable & wind-resistant• Performs well in harsh weather• Attractive, finished appearance	💲💲 Moderate–High
Shed Roof	Single sloping plane	• Modern, sleek design• Quick to build• Maximizes wall height• Great for vaulted ceilings	💲 Low–Moderate
Flat / Low-Slope Roof	Nearly level surface	• Clean, modern aesthetic• Can be used as rooftop deck• Fast and simple to frame	💲 Low–Moderate (needs waterproofing)
Combination / Complex Roof	Mix of multiple roof forms	• Highly customized look• Can match main house exactly• Adds architectural interest	💲💲💲 High (more labor & materials)

Final Thoughts

Choosing the right roof type for your ADU is a balance between style, cost, climate, and code compliance. Take time to explore your options early, and work with a professional designer or drafting service to ensure your plans meet local requirements. With the right roof, your ADU will look great, perform well, and add lasting value to your property.