Accessory Dwelling Unit’s

When you use the term “ADU”, many people may not understand what you are referring to. Even clarifying that the acronym stands for Accessory Dwelling Unit might not eliminate their confusion. 

Accessory Dwelling Units, more commonly known as ADUs, are secondary housing units that reside on a single-family residential lot. We know the term “accessory dwelling unit” sounds more like an institutional name, but it’s the most commonly used term. ADUs can also be called granny flats, laneway houses, in-law units, etc. ADUs can be tiny houses, but tiny houses are not necessarily ADUs. 

Legally, the ADU is considered part of the same property as the main home, no matter what form the ADU takes. As such, the ADU cannot be sold or bought separately, and the owner of the main home must also be the owner of the ADU. Because ADUs can vary quite a bit in shape and size, it can be helpful to look at the range of common ADU types.


Detached new construction Accessory Dwelling Units
These ADUs are also known as backyard cottages, in-law suites, or laneway houses, depending on the jurisdiction you are in. As you may be able to tell from the name, these are built from the ground up and are not connected to the main house on the property. 

Garage conversion Accessory Dwelling Units
Garage conversion ADUs are created when someone converts their garage into a livable space.

ADUs above the garage
ADUs that are located above the garage or are attached to it fall into this category. These may be called garage apartments or carriage houses depending on your part of the country. Have you watched the show Happy Days? If you remember that show, the character The Fonz was someone who lived in an ADU above the Cunninghams’ garage. 

Basement conversion into ADUs
A basement conversion into an ADU is close to a finished basement. They are commonly referred to as basement apartments, mother-in-law units, or in-law units. These ADUs must have a kitchenette, bedroom, full bath, and a door to enter and exit the premises.

Internal ADUs
When a part of the main house beside the basement is converted into an ADU, it is considered an internal ADU. Interested in creating your own custom ADU? We service in Arvada, Lakewood, Littleton, Golden, and other Denver areas.


Because ADUs are secondary housing units, they are in a category of housing separate from main properties. They are adjacent to the primary housing structures and are significantly smaller than the average house in the US. Usually, they are one of two units that are located on a single-family residential lot. 

The main home is usually finished when ADU construction is begun, which explains why ADU development is primarily done asynchronously by housing developers. ADU development is regulated by municipal land use and zoning restrictions, which strongly affect the uses that are allowed. Still, much more informal ADUs exist compared to those that are permitted. 


ADUs have been built for hundreds of years, but they were less popular during the 20th century. They have now become more common to build. Some cities have experienced high-speed growth in the development of Accessory Dwelling Units. Portland, Oregon, has become the leading city in the ADU movement in the United States. Vancouver is the city with the most ADU’s in North America. The city of Austin, Texas has also started to experience a substantial bump in the development of ADU’s since the passing of legislative zoning changes in 2015.

Two of the most common reasons that lead a homeowner to build an ADU are to provide housing for a family member or to gain extra income through rental payments. Housing flexibility has become more favored because of changes in lifestyle and finances. Though people may still live in their houses for decades, their needs can change more frequently. For instance, ADUs can help aging people by providing a smaller place to live without them having to move to another property.

In many areas, permitted ADUs are allowed to generate rental income legally. Alternatively, homeowners can also move into the ADU and rent out the main home to generate rental income.  We are primarily in Arvada, Lakewood, Littleton, and Golden.


An ADU is a major construction project and Prospect 30 Eight Construction Inc is here to guide you through everything from design, permitting, and building. When homeowners think of building an ADU, many first envision a separate structure from their main house. This is a great option, but not the only type of ADU that is built. That is partly because it’s often the most expensive type of ADU. 

Depending on the type and size of ADU you want and the materials you’d like to use, ADUs can vary greatly in cost. Something to keep in mind is that there are creative ways to build an ADU without building a separate unit. Many homeowners have space that is unused in their primary home, and unused areas including separate bedrooms can be converted into a separate unit. This can be a good solution for homeowners that are looking to downsize or cut costs as they head into retirement. 

First, we will work with you to figure out what is possible for your property. Regulations in your area can determine what we will be allowed to build, and these include factors such as location, yard coverage, and even materials. When we analyze your property, we will reveal the opportunities and limitations in your property and compare them with the city or county requirements. We will manage these complexities and help you understand what is permitted to build and work for your budget. 

There is a vast library of pre-approved designs that are available to choose from, and this can help in making your ADU more cost-effective. Many of these designs are pre-approved, which reduces design costs and eliminates confusion or uncertainty during the process of getting a permit. 

Some people prefer to have more personalized ADUs designed completely from scratch, and this can be done with our design team. Alternatively, after we discuss your housing needs and share our suggestions for floor plans with you, we can talk about upgrades that can offer more personalization. We are also able to provide interior design options that you can consider. 

At Prospect 30 Eight Construction Inc, we know how important transparency is. We believe in fairness and integrity, and that shows in the comprehensive proposals that we give you before you decide to move forward. Our proposals are detailed to include the costs for production, the expected timeline, and the materials that will be used. We do our best to anticipate any setbacks that could potentially occur, and inform you as soon as we can. Whether if you’re in Lakewood, or Golden we will love to help construct your proper ADU.

Our design team represents you. We will help in obtaining the permits and adjust for requirements from the building and planning departments. Once regulations are finalized and we have your approval to proceed, we will meet with you in a pre-production meeting to finalize all the practical details. 

When the design process is finished, our team can start building your ADU. There are a few different ways that an ADU can be built, and the most common ones are conventional stick framing and framing packages. 

Stick framing is used when the building team purchases standard dimensions of lumber from a hardware store and assembles the pieces on site. This method requires more manpower because each piece needs measuring, cutting, and installation. Because it takes longer to construct and needs more supervision, costs can go up and changes in weather can prolong the timeline. 

Framing package involves having the components cut in the factory before they are sent to your home. This lessens the time needed for materials to be assembled on site. Though package pieces are initially more expensive, time and labor costs decrease, so the total building costs can be much reduced. 

We will discuss the building options available to you and can help you determine which would be the best fit for your property and budget. 


ADUs built with Prospect 30 Eight Construction Inc are built with the utmost quality and precision. ADUs can go a long way for family connectivity and the long-term housing plans of homeowners. We build them and work with clients in most areas such as Arvada 0r Littleton. We build them because we know how positively they impact your life, your family members’ lives, and the long-term value of your property. 

Because the landscape for ADUs has been changing so much, it can be helpful to work with a team that not only has the expertise to work through the rules and regulations, but also cares about what you and your family want. As you do your research on the contractors that would be the best fit for your property, you can read reviews from clients we have worked with here

Throughout the process, there is always a member of our team there right beside you from your initial on-site evaluation to the design, approval, on-site construction, all the way through handing you the keys to your brand new Accessory Dwelling Unit. Our ADUs are designed and built to meet all of the Colorado building standards by only using quality products and materials sourced from only the most well-known suppliers and manufacturers.

Call 970-309-4170 or contact us to talk about your ADU. We are looking forward to working with you!


What can be considered an accessory dwelling unit?
There are over 50 different synonyms for Accessory Dwelling Units. An accessory unit is a secondary unit on a property that already has a primary residential unit. 

Does an ADU need to have a kitchen?
Yes, to be considered an Accessory Dwelling Unit, a unit must have a kitchen located in the area. A kitchen is one of the defining features needed for an ADU to differentiate itself from another living space.

Is a permit needed in order to build an ADU?
Yes, you will need a permit from your local building department whenever you want to build on or modify your property. 

Is it legal to build an in-law suite or small house in the backyard? 
Depending on where you live, it can be legal or illegal to build a habitable living space in the backyard. Whether the living space in your backyard can be classified as a house is something else. This classification would depend on your local zoning laws. In many cases, building an ADU will be permissible as long as you obtain the required permits. 

If it’s not permissible in your area, you can consider alternatives such as having a guest house or a detached office. Making a home addition to add an extra bedroom with a bathroom could also be allowed. 

Does a guest house or in-law suite add value to my property?
Yes, a guest house or in-law suite will add value to your property. The next question, of course, is natural: “How much value would it add?” It is impossible to provide a general answer to this question as many different factors need to be considered. If you would like a specific idea of how much value would be added with the addition of an ADU, you should contact professional appraisers who can look for sales comparisons on which to base their appraisals. They can then come up with a value estimate for you.

What is designated an illegal apartment?
An illegal apartment is an Accessory Dwelling Unit built without a permit or an informal Accessory Dwelling Unit. This happens when someone builds an additional housing unit on their property that has not been permitted or has not had its inspections. 

However, there are many subtleties here. For example, was the interior finished habitable living space permitted? Was the additional structure permitted? Was just an oven and kitchen sink that did not get permitted? 

These subtleties are vital to understanding precisely how significant the building code and zoning violations are and how to fix them.