Ultimate Guide to ADU Exterior Design & Finishes in Southern California

The exterior of your accessory dwelling unit (ADU), casita, or guest house is the first impression visitors or potential tenants will have of your property. Building an ADU is an exciting project that not only adds value to your property but also provides extra space for family, friends, or rental income. However, one key consideration is often underestimated: the exterior design of your ADU. How well it integrates with the main house can significantly impact the overall aesthetics and the long-term satisfaction you derive from your investment.

In this extensive look at ADU and casita exterior styles in Greater San Diego, we will explore various aspects of what to consider in order to build a welcoming and attractive guest house that blends with the rest of the property… while also measuring up to California’s strict building code & energy requirements, which further influence the design and construction of ADUs in the region.

Blending your ADU with your Primary Home

When it comes to ADU exterior design and finishes, it’s important to consider the overall cohesion with your main dwelling and the surrounding environment. Many jurisdictions and home owners associations (HOAs) require that the exterior of your ADU match or be compatible with the architectural style of your main home and neighborhood.

When the ADU is designed to complement the architectural style, color palette, and materials of the primary home, it can look like a natural extension of the existing property, rather than an out-of-place addition. Traditionally constructed or “stick-built” homes can be readily customized to blend with the primary structure style, while manufactured and modular prefab ADU options are less flexible in terms of design.

How closely can the exterior of the ADU match the main home?

Essential Integration: Blending without Overwhelming

Refined Integration: Meeting Rigorous Standards

Seamless Integration: A Precise Match for a Perfect Extension

Snap ADU Exterior Match Summary

Read more about custom ADUs.

Exterior ADU Design Styles in Greater San Diego

In Greater San Diego, we see a wide range of exterior home styles. All of the featured photos in this article are ADUs designed & built by SnapADU, so click any photo to see more about the project. You can also learn more about the ADU design build approach.

Contemporary ADU

Contemporary ADU style is characterized by its sleek and modern design, with clean lines, minimalistic aesthetics, and a focus on functionality. The style of home that is commonly built in track homes in San Diego is often referred to as “contemporary” architecture. The exteriors of these homes often include materials such as stucco, fiber cement board siding, and asphalt shingles. Contemporary ADUs are versatile and are the most common style built by homeowners in San Diego.

Mediterranean ADU

Mediterranean and Spanish styles are characterized by tiled roofs, stucco walls, and dark windows and doors. Decorative tile or stone work, wrought iron details, and vibrant colors typically show up in Mediterranean ADUs. This style is popular in San Diego and are known for their timeless and elegant aesthetic.

Modern ADU

If you’re looking for a sleek ADU, modern style is a popular choice. Clean lines, minimalist design, and a mix of materials such as stucco, metal, and glass are typical characteristics of modern ADUs. Flat or low-slope roofs, large windows, and open floor plans are also common features in modern ADUs, creating a sense of openness and lightness. You may consider using materials like fiber cement board siding with a smooth finish, metal roofing for a sleek and contemporary look, and large, expansive windows or multifold doors.

Craftsman Style ADU

Craftsman style is an iconic design that emerged from the Arts and Crafts movement, celebrating handwork and design simplicity. In Greater San Diego, Craftsman ADUs embody a nostalgic and warm charm, showcasing intricate details and high-quality materials. Distinct features of the Craftsman style include overhanging eaves, exposed rafters, decorative braces, and a mix of materials like wood, stone, and brick. Typically, these ADUs sport deep color palettes with contrasting trim, multi-pane windows, and a prominent front porch supported by square columns. The Craftsman aesthetic encapsulates a blend of function, comfort, and timeless beauty.

Cottage ADU

Cottage style is all about quaintness and charm, often featuring elements such as wood siding and decorative trimwork. Soft color palettes with pastel hues, flower boxes, and details like trimmed doors and windows can add a touch of whimsy to a cottage-style historic ADU. Cottage style may feature covered porches with traditional swing doors or Dutch doors. Read more about historic ADUs.

Farmhouse ADU

While not as prevalent in San Diego, some homeowners opt for a white and black farmhouse look. Farmhouse style is characterized by its rustic charm and simplicity. In a farmhouse ADU, you can expect to see elements such as board and batten siding, metal roofs, and large covered porches. Neutral color palettes with pops of bold accents, such as red doors or black window frames, are common in farmhouse-style ADUs, creating a cozy and welcoming ambiance.

Not sure if you are any of these styles? Not to worry, many ADUs fall between categories and you can browse more ADU exteriors for inspiration. We create custom ADU plans, too.

Siding Styles: Enhancing Durability and Aesthetics

The right siding style can greatly impact the durability and aesthetics of your ADU’s exterior. In Greater San Diego, there are several popular siding styles to choose from, each with its own advantages.

Stucco

Stucco with a light sand finish is a common choice for ADUs in Southern California, including Greater San Diego. This type of siding offers a smooth and clean appearance, with a textured surface that adds depth and visual interest to the exterior. Stucco is known for its durability and resistance to the elements, making it an excellent choice for the region’s warm and dry climate. Additionally, stucco can be easily painted in a wide range of colors, allowing you to customize the look of your ADU to match your preferred style.

Clapboard / Lap Siding

Clapboard or lap siding, made of fiber cement board, is another popular choice for ADU exteriors. This type of siding replicates the look of traditional wood siding but offers superior durability and low maintenance. Fiber cement board is resistant to rot, pests, and fire, making it a practical choice for ADUs in Southern California. Clapboard lap siding typically comes in a range of colors and can be installed horizontally or vertically, allowing for creative design options.

Board & Batten

Board and batten siding is a timeless and classic choice for ADUs, especially in farmhouse or cottage-style designs. This type of siding features wide vertical boards (the “boards”) paired with narrower vertical strips (the “battens”) that cover the seams between the boards. Board and batten siding made of fiber cement board offers the same benefits as clapboard lap siding, including durability and low maintenance. It can be painted in various colors to achieve the desired look.

Santa Barbara Stucco

Smooth Santa Barbara finish is a type of stucco finish with a smooth, polished texture that creates a clean and refined appearance. The finish is achieved by applying multiple layers of stucco, followed by a fine sanding process to create a smooth and even surface. Santa Barbara finish is often used in Mediterranean, Spanish, and Spanish Colonial style ADUs, and it can be customized with various colors to achieve the desired aesthetic. This type of finish adds a touch of elegance and sophistication to the exterior of a building, creating a timeless and classic look.

Quick question: Can I paint stucco?

Stucco is a cement based product where the color is mixed into the stucco as it is being readied for application. Paint is typically a latex-based product that simply covers a surface. Both have beneficial qualities to protect your ADU. With a painted surface, the paint itself provides a water-resistant layer over the substrate to expel water. With a stucco system, the stucco itself is actually porous and will absorb water. However the stucco is layered on top of a waterproof membrane which expels the water. The stucco itself primarily serves to protect the membrane.

Stucco is beneficial in that it can last decades without any need for maintenance. Paint, on the other hand, requires reapplication every few years. Stucco is susceptible to staining, which can be difficult to remove or even re-color. Paint can easily be touched up in a localized area or over an entire wall with little ability to tell that work was done. Lastly, it is worth noting that it is possible to paint over stucco. This is typically undertaken for cosmetic reasons as opposed to providing additional protection against moisture.

Roof Styles: Lines for your Exterior

The style and structure of the roof are vital components that significantly influence overall character and and style of the accessory dwelling unit. The roof also needs to harmonize with the main house and the floor plan layout.

Here are some of the most common roof styles you might consider for your ADU:

Gable Roof ADU

This is one of the most popular roof styles, featuring two sloping sides that meet at a ridge. Its triangular shape offers a timeless aesthetic suitable for various architectural styles.

Hip Roof ADU

A hip roof slopes on all four sides, converging at a single point or ridge. This design is often chosen for its stability and elegant appearance.

Shed Roof ADU

Shed or single sloped roofs are another option for ADUs, particularly for modern or minimalist designs. This type of roof features a single slope, usually angled towards the back of the ADU, creating a sleek and simple look.

Flat Roof ADU

As the name suggests, flat roofs appear level, providing a sleek and modern appearance, often favored for urban designs or where rooftop amenities are desired.

Construction Note: Roof Construction Methods

Once you’ve settled on a style, the next step is understanding how your roof will be constructed. Two primary methods dominate residential construction:

Roof Trusses: These prefabricated structural components are popular in residential construction due to their efficiency and cost-effectiveness. Trusses allow for easier installation of utilities and can span longer distances without the need for intermediate supports. An advantage of using roof trusses are that they allow for easier installation of plumbing, wiring, and HVAC systems with minimal interference. Trusses create open spaces between their members, making it convenient to route utilities through the roof structure. They also can achieve longer spans without the need for posts to support them when compared to a hand framed roof. The main disadvantage is that the pitch of the exterior roof will be steeper than the interior ceiling. This is usually not that noticeable.

Hand-Framing: This traditional method involves constructing the roof on-site, piece by piece. While it offers greater flexibility and customization, it is more labor-intensive and can be more expensive than using trusses. The advantage of hand framed roofs is that they can achieve taller interior ceiling heights and allow for a uniform roof and ceiling pitch. Smaller systems like wires and plumbing lines can be drilled through the framing member to conceal in the ceiling. The major disadvantage is that larger systems like HVAC duct work requires a soffit to be built (a soffit is a boxed our section of a ceiling, typically next to a wall).

Roofing Types: Protecting Your ADU with Style

The roofing type you choose for your ADU not only protects your home from the elements but also contributes to the overall style. In Greater San Diego, you have several popular roofing types to consider, each with its own unique features and style options.

Asphalt Shingles

Asphalt shingles are a common and cost-effective roofing option for ADUs in Southern California, and come standard on in our ADU home features. They are available in a wide range of colors and styles, including architectural or dimensional shingles that mimic the look of wood shakes or slate tiles. Asphalt shingles are durable, lightweight, and relatively easy to install and maintain, making them a popular choice for ADUs in the region.

Tile Roof

Terra cotta tile roofs are a classic choice for ADUs in San Diego, particularly in Mediterranean or Spanish-inspired designs. Terra cotta tiles are made from natural clay, which is fired at high temperatures to create durable and weather-resistant tiles. They are known for their distinctive reddish-brown color and can be installed in various patterns, such as mission or barrel tiles, to add character and charm to your ADU.

Metal Roof

Metal roofs are gaining popularity in ADU design, particularly for modern or contemporary styles. Known for durability, energy efficiency, and low maintenance, metal roofs are available in a wide range of colors, finishes, and profiles, including standing seam, corrugated, or ribbed panels. Metal roofs can add a sleek and modern look to your ADU, and their reflective properties can help reduce heat gain making them a good choice in hot climates.

Energy Code Note: Solar

Some new construction ADUs require solar, which should also be planned on the roof in most cases. ADU design-build companies work closely with solar installation experts to ensure that the roof structure can support the solar panels and that the electrical wiring and connections are properly integrated into the ADU design. This may involve planning for additional space for inverters and other electrical components.

Entry Styles: Creating Space with Covered Entries and Patios

The entry of your ADU is an important design element that sets the tone for the overall aesthetic of your home. Covered entries and patios not only provide protection from the elements but also add an inviting and functional element to ADU exteriors by providing a space for outdoor seating, relaxation, and entertainment.

Covered patios or porches are another popular option for ADUs in Greater San Diego. They provide a shaded outdoor space for relaxation, entertainment, or dining, and can be designed to flow seamlessly with the overall style of your ADU.

Door Styles: Making a First Impression

The style of doors you choose for your ADU can significantly impact its overall aesthetic appeal. Adding a pop of color on the door can also give the accessory dwelling unit a bit of personality. There are several styles to consider depending on the design and functionality of your ADU.

Swing Doors

Swing doors are the most common type of doors used in ADUs. They are hinged on one side and swing open or closed, creating a traditional and familiar look. Swing doors can be customized with various materials, finishes, and designs to match the overall style of your ADU. They are available in a wide range of styles, such as solid wood, glass, or panel doors, and can be painted or stained in different colors to complement your ADU’s exterior.

Sliding Glass Doors

Sliding glass doors are a popular choice for ADUs with a focus on indoor-outdoor living. They provide a seamless transition between the indoor and outdoor spaces, allowing natural light to flow into your ADU and providing panoramic views of the surrounding environment. Sliding glass doors are typically made of aluminum or vinyl frames and can be customized with different types of glass, finishes, and hardware options to match the style of your ADU.

French Doors

French doors are a classic and elegant choice for ADUs that exude a sense of charm and sophistication. They are typically made of wood or fiberglass and feature multiple glass panels with decorative grids or mullions. French doors can be used as entry doors, patio entrances, or interior doors, and can be painted or stained in various colors to enhance the aesthetic appeal of your ADU.

Multifold Doors

Multifold doors, also known as bi-fold or accordion doors, are a popular choice for ADUs that aim to create a seamless indoor-outdoor connection. They consist of multiple panels that fold and stack against each other, creating an open and expansive view. Multifold doors are typically made of aluminum or wood frames and can be customized with different finishes, glass options, and panel configurations to suit your ADU’s style and space requirements. Multi-panel doors are another more cost effective option (two moveable doors in center, two fixed doors at sides).

Building Code Note: Doors

Local and state building code will also dictate certain requirements for doors, such needing at least one swing door for egress (in addition to any sliding glass doors you may have).

Window Styles and Colors: Adding Functionality and Style to Your ADU

The window styles and colors you choose can also greatly impact the overall appearance of your ADU’s exterior. Recessed windows with modern or traditional frames in black or white can create a sleek and contemporary look, while windows with grids or decorative trimwork can add charm. The size and placement of windows should also be carefully considered, as these openings play a crucial role in the functionality, aesthetics, and energy efficiency of your ADU.

Here are some window styles and colors commonly used in ADU exterior design in Greater San Diego:

Window Frame Color

Black or white window frames are a popular choice for ADUs with modern, contemporary, or minimalist styles. Black frames create a sleek and bold look, while white frames provide a clean and crisp aesthetic. These contrasting colors can add a modern and sophisticated touch to your ADU’s exterior, creating a visual focal point and enhancing the overall curb appeal.

Recessed Windows

Recessed windows are a design feature that adds depth and interest to the exterior of an ADU. These windows are set back into the wall, creating a recessed area that provides visual appeal and can also offer functional benefits, such as improved energy efficiency and increased privacy. Recessed windows can be used in various architectural styles and can be customized to suit the overall aesthetic of the ADU. Some HOAs may require them.

Window Grids

Grids, also known as mullions or grilles, are decorative elements that divide windows into smaller sections, creating a distinctive look. You’ll see grids used in different patterns and styles, such as colonial, prairie, or modern, to add character and charm to your ADU’s exterior. Grids can be made of wood, vinyl, or metal, and can be customized in different colors to match your ADU’s overall color scheme.

Building Code Note: Windows

Local and state building code will also dictate certain requirements for windows, such as egress windows in bedrooms and maximum allowable openings on walls along property lines or other structures. Windows will also largely impact calculations related to Title 24 energy standards.

Decking & Railing: Enhancing Outdoor Living Spaces

Decking and railing options can also be important considerations for your ADU exterior, especially if you have a raised foundation or a second-story balcony. The color, finish, and design of decking and railing can greatly impact the overall aesthetic of your ADU’s exterior and should be chosen carefully to achieve the desired look and feel. Here are some options commonly used:

Decking

Decking materials commonly used in ADUs include wood, composite, or PVC. Composite and PVC decking offer durability and low maintenance. Decking can be customized with different colors, finishes, and patterns to complement your ADU’s exterior style and create a cohesive outdoor living space.

Railing

Railing is an essential safety feature for raised decks or balconies in ADUs. Wood, metal, or even glass are commonly used railing materials. Wood railings provide a classic and traditional look, while metal railings offer a sleek and modern aesthetic. Railing styles can vary, including horizontal, vertical, or custom designs, and can be painted or stained to match your ADU’s exterior color scheme.

Building Code Note: Decks

Note that while ADUs enjoy reduced setbacks, decks do not and must adhere to underlying side & rear setbacks. Keep this in mind when planning the location of your ADU and deck on your site.

Other Trimwork Details: Adding Character and Charm

In addition to the main exterior elements mentioned above, there are other trimwork details that can add character and charm to your ADU’s exterior:

Accents

Plant-on accents are decorative elements that can be added to the exterior walls of your ADU to create visual interest and add texture. Plant-on accents can be made of various materials, such as wood, stone, or fiber cement board, and can be installed in different patterns or designs, such as shingles, panels, or trim. Accents can be painted or stained in different colors to complement your ADU’s overall design theme and can add a touch of uniqueness and character to your ADU’s exterior.

Stone Accent

Shutters

Shutters are decorative elements that are installed on the exterior of windows and can add a touch of elegance and charm to your ADU’s exterior. They can be made of wood, vinyl, or metal, and are available in various styles, such as louvered, raised panel, or board-and-batten. Shutters can be painted or stained in different colors to match your ADU’s color scheme, and can be functional or purely decorative, depending on your preference.

Eaves

Eaves are the overhanging edges of the roof that provide protection from the elements and can also add visual interest to your ADU’s exterior. You’ll notice eaves designed in different widths and styles, such as boxed, open, or decorative, and can be painted or stained to match your ADU’s exterior color scheme. Eaves can also be used to conceal gutters and downspouts, creating a clean and streamlined look.

Gutters

Traditional Gutters: In the temperate climate of San Diego, traditional gutters are a common sight on residential homes with pitched roofs. These systems, crafted from materials such as aluminum, vinyl, or steel, are designed to capture rainwater from the roof and direct it through downspouts. This setup is essential for safeguarding the home’s foundation from water damage, protecting the landscaping, and maintaining the integrity of the exterior walls. Homeowners often choose traditional gutters for their affordability and the ease with which they can be blended into the home’s design, offering both functionality and aesthetic appeal without the need for frequent maintenance due to San Diego’s mild weather.

Torch Down Roofing with Internal Drains: Torch down roofing with internal drains, meanwhile, is an excellent option for San Diego homes with flat or low-slope roofs. This method involves layers of modified bitumen adhered with a torch to create a durable, waterproof surface. The internal drains are a key component, cleverly integrated into the roof to channel water away discreetly. These drains connect to pipes inside the walls, terminating in spouts close to the ground, allowing for a clean, uncluttered look without visible gutters. This system is particularly suited to modern or commercial buildings where aesthetics dictate a minimalist exterior. It’s also a practical choice for residential areas where homeowners prefer a more streamlined roof appearance and wish to avoid the traditional look of external gutters.

Rafter Tails

Rafter tails are a decorative element commonly used in ADUs to add character and charm to the exterior. These exposed ends of roof rafters can be seen beneath the eaves of the ADU, providing an opportunity for customization and personalization. Rafter tails come in various shapes, sizes, and styles, allowing homeowners to choose a design that complements the overall aesthetic of their ADU, whether it be modern, traditional, or rustic.

Trellises

A trellis is a framework of horizontal or vertical bars that can be attached to the exterior walls or used as freestanding structures in your ADU’s outdoor spaces. Trellises are commonly used for climbing plants, such as vines or flowers. Foliage can add a natural and organic touch to your ADU’s exterior. Trellises can be made of wood, metal, or vinyl, and can be customized in different styles, such as modern, rustic, or traditional, to suit your ADU’s overall design theme. You would typically add these after the construction portion of the ADU, likely when working on landscaping and other finishing touches.

Climate & Code Considerations: Make Sure Your ADU Measures Up

With the warm Mediterranean climate and occasional wildfires in San Diego County, choosing materials that are fire rated, energy-efficient, and low-maintenance is not only beneficial, but required in many cases like high fire zones. It’s crucial to comply with local building codes and regulations when it comes to ADU exterior design and finishes. Different cities and counties have specific requirements and restrictions on materials, colors, heights, setbacks, and other design elements.

Title 24

ADU designs in Southern California must comply with Title 24 energy standards. Title 24 is a set of energy efficiency requirements that aim to reduce the energy consumption of buildings, including ADUs, and promote sustainable construction practices. These standards cover various aspects of the ADU exterior design, including insulation, windows, doors, roofing, and lighting. For example, Title 24 requires a certain level of insulation in walls, roofs, and floors to minimize heat gain or loss and improve energy efficiency. Windows and doors must meet specific performance standards to limit heat transfer and reduce reliance on artificial lighting. Roofing materials must meet certain reflectance and emissivity requirements to reduce heat absorption and minimize the urban heat island effect.

Fire Rated Construction

Another important consideration that comes into play in certain situations is fire-rated construction of the ADU. California has strict building codes and regulations related to fire safety, especially in wildfire-prone areas. Building codes may require ADUs to be constructed with fire-resistant materials and design features to minimize the risk of fire spread. One common fire-resistant design feature is boxed eaves, which are typically constructed with non-combustible materials to prevent the spread of fire from the exterior to the interior of the ADU. Boxed eaves provide an additional layer of protection, as they encase the roof overhangs. This prevents embers from igniting the eaves and potentially spreading the fire to the ADU’s structure.

Working with a knowledgeable and experienced design-build company can help ensure that your ADU meets all the local building codes and regulations while achieving the desired aesthetic and functional goals.

Get expert advice on designing your ADU exterior

As a general contractor specializing in ADUs, we have hands-on experience in designing, permitting and constructing ADU exteriors in many styles. We take pride in delivering high-quality ADU exteriors that not only meet your design preferences but also can be built within your budget.

Our team is here to provide you with expert guidance, valuable insights, and unbiased advice on the latest options and associated costs. You can browse our Exterior Material Catalog for an idea of the finishes we already offer. We can also custom-source items as needed for your project. We guide you through the entire design & selection process, providing recommendations and suggestions based on your property constraints, preferences, budget, and local building codes. Request a Discovery Call.