Structural Design Tips for Building an ADU

An accessory house, or an Accessory Dwelling Unit, (ADU Structure), is also often referred to as a backyard cottage, an in-law unit, or a granny flat. In the simplest of terms, an accessory house refers to a “tiny home” that is generally built on the same property as the property owner’s dwelling. People who own accessory houses, in many cases rent them out month to month, because they make an excellent source of extra income. That is unless you are saving your accessory home for college kids or family members when they come into town to visit.

However, there are some very important factors for Structural Design for ADUs that you should consider before building yours, to ensure that you don’t run into any costly snags or hold-ups in the construction process.

We will share some important site layout, utility, and structural design tips, with you. And also share some other general tips that could end up saving you a ton of time and money!

Keep your state’s Property Development Standards in mind when building your ADU

Whether you already own an ADU that you plan to renovate, or you are planning to build one from scratch on your property, one of the first things that you want to look into is your area’s property development standards, so that everything is allowed, and everything flows smoothly for you once you have started. You will need to stay in compliance with your area’s local zoning, housing, and building codes to avoid complications later in the process.

Each state may be a little different, so make sure and check your area for information about local ordinances that need to be met before starting your project. These zoning, housing, and building codes are set to ensure that your accessory house complies with state and international building standards. If this seems confusing to you, here are a few examples of how zoning, housing, and building codes can come into play while planning your ADU project:

A few examples:

1. Density Constraints for Housing Development: Your ADU will have to fall within certain density constraints. These constraints are calculated to determine your actual available land area, with a few important factors figured in like physical constraints, potential infrastructure dedications, like streets and stormwater management structures, and practical design considerations.

2. Structural Design: Another factor that may come into play, depending on the location, is the height of your ADU. Some areas will need you to stay within set maximum height requirement when you build your accessory dwelling unit.

Tip: A good place to start if you know nothing about the structural engineering process, is by hiring an experienced contractor or consulting with your local government officials. Either one will work with you to let you know what the standards are that you must follow in your area, and tell you what building permits you may or may not need.

3. Site Conditions: Another factor that you want to keep in mind while you are making your land and structural analysis, is the site conditions where your structure will be constructed.

For example:

Is your backyard sloped or flat?

Do you have areas of standing water after heavy rain? Does your ground need to be leveled or built up in any areas?

By paying close attention to the site conditions beforehand, you can reduce a ton of potentially very costly expenses later on down the road.

4. Parking Requirements: Another factor that could come into play when you are planning your project is parking. You may be required to provide an off-street parking area for your accessory dwelling unit. However, if your ADU is close enough for tenants to access your area’s public transportation, or if you live in an architecturally or historically significant area, you may not have to worry about this. 

PLEASE NOTE: This is another reason that it’s a good idea to hire an experienced contractor or speak to local officials before starting to build your ADU.

5. Access Requirements: Your accessory house will need to be easily accessible, with safe access to the street. You may even need to install a walkway leading from the street to the unit, but for the most part, a clutter-free path between your home and the property line is required.

Architectural Design Tips for an ADU Structure

There are a few architectural design tips for an ADU that we should also alert you to, that may help your construction project flow a little smoother. Factors like utility connections, site conditions, and even privacy concerns come into play while planning a construction project for a dwelling. They are all things that you won’t want coming back to haunt you later! Here are the most important architectural design tips for an accessory dwelling unit:

Privacy Concerns: Privacy concerns should be taken into consideration when you are planning your accessory house project. Granted, that privacy will be more of an issue depending on who will be staying in your ADU, but in general, you want to give strangers complete privacy, completely cut off, if possible, from your primary housing.

Privacy Tips: Privacy issues can be solved in several different ways, such as; using privacy screens, plants, trees, window blinds, or even privacy fencing, when you can manage it.

Utility Connections: A Well Thought Out MEP Package is Important

Why a Well Thought Out MEP Package is Important

An MEP Package is short for a mechanical, electrical and plumbing engineering package. The reason for having a well-thought-out MEP package is important, is because your MEP package essentially controls the main factors that work together to make your accessory house livable. If you have an accessory house already, and you are only renovating, chances are that you won’t have to install any new utilities. In most cases you can tap into existing water, making it unnecessary to install and additional service meters. The plumbing fixtures in most cases can even be tied into the existing plumbing system, but your septic system may need to be approved by your local health department.

Design Requirements for Accessory Homes

Most areas will have design requirements for accessory houses, like requiring bathrooms and kitchens to be installed. Heating systems are also an issue that you need to plan out ahead of time if you are building your ADU from scratch. If any of these factors are a grey area to you, it is highly advised to consult with structural and MEP design consultants or speak with your local building department officials to make sure that your accessory home is installed up to code.

Living Space Requirement Tips for ADUs

One more factor that you need to consider is living space requirements. If you have a limited space that is being used for your accessory dwelling unit, you should think about things like closet space, the size of your appliances, and space for furniture. You want your tenant to have enough room to move around in and not be cramped. Making use of shelving, cabinets, storage rooms outside or under stairs, and avoiding the use of big bulky furniture having tables and chairs that fold up out of the way, etc., are all ways that you can free up a ton of living space to make your tenants more comfortable.

Fire Regulations for Accessory Homes

In ADU Design the fire regulations of your area will have to be taken into consideration when you plan yours. Your local fire regulations may require that a sprinkler system be installed in the unit. Just speak with your local fire department and/or building officials to find out what the fire regulations are for your area so that you can follow them accordingly when planning your unit. You may even get a break on insurance for installing a sprinkler, and it’s always better to be safe than sorry anyway.

Just speak with your local fire department and/or building officials to find out what the fire regulations are for your area so that you can follow them accordingly when planning your unit. You may even get a break on insurance for installing a sprinkler, and it’s always better to be safe than sorry anyway.

Structural Design for ADU

Investing in renovating your existing accessory home or building an accessory home can both be a wise investment. Hiring a professional contractor or speaking to local officials about the design and construction of your new investment is always the best way to make sure that everything flows and turns out smoothly once you decide to get started on your project.

We wish you the best of luck with all of your endeavors. We hope that this Design Tips for ADUs will help you plan the perfect project. And saves you some trouble and some unexpected costs if you were planning an accessory house project in the near future!