I want to build an ADU! What do I need to know?
Updated: Dec 30, 2019
Accessory Dwelling Unit (ADU), Granny Flat, Casita, Secondary Dwelling Unit, Secondary Apartment.
We’ve had a lot of interest from clients who are considering adding a secondary unit to their properties. We’ve assembled some quick notes to help you through the process.
I want to build an ADU! What do I need to know?
The good news is the City of Austin has relaxed the rules to make adding an ADU to you property easier!
Minimum lot size has been reduced to 5,750 square feet, with SF-3 zoning.
Parking regulations have been relaxed if you are within ¼ mile of an area served by public transit.
Unit size has increased to either 15% or 1,100 square feet of FAR, whichever is smaller.
Ask yourself - Why do I want to build an ADU?
I want a steady rental income to offset my current mortgage.
I want to Air B&B and make a killing during special events!
Sorry! STR’s (Short Term Rental) are limited to 30 days a year, if you’re operating a legitimate STR.
I need a place to move my elderly parents.
I’d like a small office outside the confines of my home.
How do I know if it is allowed on my property?
Does my zoning allow it?
SF-3 zoning with a minimum lots size of 5,750.
SF-2 properties allow one residence only.
Please let us know if you do not fall within an SF-3 zoning district and we can discuss your options.
You can check your property's zoning here.
How much can I build?
Technically either 15% or 1,100 square feet of FAR, whichever is smaller.
The base building and impervious cover is still 40 and 45% respectively, so-
If you have an existing sprawling one story house, or a large amount of concrete drive and walkways on you property the ADU square footage will need to fit within the remaining allowable coverage for building and impervious.
I have trees on my property, close to where I’d like to build- is that a problem?
It depends. The City of Austin has very specific tree protections in place, so a few things would need to be determined before knowing if the tree is really a problem-
What type of tree is it?
How large is the tree?
Is the tree healthy?
Do I need to provide parking?
It depends.
If you live within ¼ mile of an area served by public transit the answer is no.
How much will it cost?
It depends. A few factors that can effect the design and construction of an ADU are:
How close is the ADU to my existing utilities – water, power, and sewer?
Can my existing utilities handle the additional building?
I’d like a roof deck to take advantage of my downtown views!
Smaller doesn’t mean cheaper.
We’ve had people say – “It’s small, so it should be cheaper, no”?
Short answer – NO!
We can explain this in more detail, but the boilerplate “it costs $X.XX amount per square foot”, simply does not work for smaller projects.
I’ve considered modular construction, what do you think?
While modular can work in certain situations, its been our experience that it is not for everybody and:
It depends. Why are you considering modular construction?
Do you live in an area with a scarce labor supply?
If so, then modular construction might be beneficial.
Does it have a certain allure for you? If so, please explain.
I’ve seen a modular company plan that I like, but I want to make modifications.
Modifications are typically not allowed, unless the modification is superficial.
I’ve heard it’s much cheaper than site built construction.
Modular construction is typically not cheaper.
The “it’ll cost $X.XX amount per square foot” you see listed on websites does not factor in:
Local permitting
Foundation design
Shipping
Crane set & install
Utility connections
If you’d like to discuss your project, we’d love to hear from you.
We can provide a low cost project review in which we will put together a brief feasibility report for your project, based on your initial input. Download your “project worksheet” information here.
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