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  • Writer's pictureBarry Shaw

ADU Types and Costs

As a follow-up to previous article on ADU’s in Arvada, Broomfield, Erie, Superior and Lafayette along with other Northern Colorado cities, associated construction costs are addressed here.

Building costs will of course vary somewhat depending on site conditions, the extent/size of the ADU accessory building and the quality of materials selected.

Our architectural designs for the ADU building incorporates our (30) years tenure as Architects and General Contractors, to incorporate creative design that reflects our Client’s needs, as well as producing a set of plans that responds to a project that can be built in a timely, cost-effective and quality manner.

An ADU project that is a detached accessory dwelling, Cottage, is typically located in the backyard of a home and is like a mini-house. It will require ‘four sided’ foundations, whole-home framing, ‘four-sided’ exterior finish materials, etc. Thus, the cost of this will be the most expensive type of ADU, but will provide the most ‘independence’.

The next type of unit, a Carriage House design, would typically be a second story addition to the Garage. This unit would be able to utilize some of the existing foundation footings (although upgrades of spaced concrete pads would likely be needed). As well, in order to ensure an open space in the garage, large beams would need to span across the garage walls. Notwithstanding this, a reduction of about 10% in costs can be achieved.

The third level of cost for construction of an ADU, attached to the home or garage in the shape of a three sided addition, is the Granny-Flat ADU design. It is about 20% less cost of the detached unit. This type of ADU could respond well to a Client’s request for possibly an elderly family member to have direct access to the primary residence, as well as the family to have direct access to the elderly person, if needed.

For more specifics on possible designs, construction cost estimates and what is allowed on your property, let us know of your interest and we will provide you with a half hour complimentary consultation. Best Always! Barry R. Shaw AIA, G.C. BSA Inc. Design & Construcion


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