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Cost to Build a DADU in Seattle

Building a DADU in Seattle is a promising investment that will raise your property value and create a passive income resource.  But how much does it cost to build a DADU in the Seattle, Metropolitan Area?

Site conditions, materials, and finishes will vary from project to project.  Many construction elements are entirely up to the client, and their choices will affect costs. In contrast, other construction elements can be unexpected and have a fixed price. 

The more informed, organized and realistic you are is the key to staying within your proposed budget. 

To help you understand how the layers of construction can impact your DADU’s budget I will run through the the basic financials of a backyard cottage that we recently completed in South Park. The home is a 450 square foot modular kit home that included a significant amount of customization which raised the total overall budget but also the end value.

The DADU’s shell components were made by Kangaroom Systems from Waco, Texas.  The structure was shipped to Seattle on a flatbed truck in panels to be assembled on the foundation that we built ahead of its arrival. 

Pre-Fab construction is just one method of DADU construction. There are multiple ways to construct your DADU, and the most recent trend in Seattle is the city’s Pre Approved Designs.

Below are ballpark figures for all the main items included in the South Park DADU’s build.  Under the chart we provide additional details for clarification.  

The approximate total cost of our South Park DADU: 257K

PERMITTING

25K

STRUCTURE

50K

FOUNDATION

30K

CONTRACTOR

20K

INSULATION

8K

ELECTRICITY

12K

PLUMBING

14K

HVAC

4K

KITCHEN

15K

BATHROOM

12K

WINDOWS/DOORS

7K

OTHER INTERIOR

10K

APPLIANCES

5K

LANDSCAPE

12K

MISC

10K

SALES TAX

23K

Permitting

25K

Included in the cost of permitting are consultant fees and city fees. Most construction projects will require feasibility, logistical, and engineering reports.  You may need to hire experts in various fields to provide evaluations required to build a structure on your property.  The south Seattle backyard DADU required hiring the following professionals:

Geo Tech

Evaluate the ground for construction recommendations

Structural Engineer

Foundation design and drawings

Architect

Design plans of the exterior and interior

Arborist

Identify exceptional trees on the property

Site Survey

Verify property lines

Site Plan

Rough drawing of the property and placement of the structure.

City Fees

The cost of doing business with the City of Seattle

Foundation

30K

The above average cost of the foundation was due to ground and soil conditions of the property.  Included in this price was land demo, disposal, foundation footings, framing and concrete.  The most significant cost increase resulted from the property’s location in a liquefaction zone. Boring seven-teen 34 foot pin piles into the ground under the foundation was necessary to bring the foundation up to code. 

Structure

50K

The materials and labor required to build the core structure.    The building’s lumber,  siding,  accent windows, front door, metal roof,  fasteners required for assembly were included in the kit.

Utilities

39K

Includes all stages of plumbing and electricity from hooking up to the main house, to rough-in and final finishes. Electrical and plumbing fixtures are mixed into this overall cost, as well as, HVAC, and major appliances.  In this case, appliances included a dishwasher, washer dryer, refridgerator, electric range, and electric on-demand water heater.

Windows, Insulation, Drywall

15K

Spray  foam insulation for the metal roof cost higher than the typical bat insulation. They also chose to have above average dry wall finish which also added to this line item.

Interior Finishes

40K

Interior finishing typically takes longer than the other phases of construction because of the intricacies  of creating an aesthetically pleasing and high functioning space. Labor and materials for cabinets, countertop, doors, window trim, tiling, ceiling, and concrete floor finishing are the most prominent elements of this project’s finishing phase.

Kitchen Includes: Dishwasher, Electric Range, Refrigerator, Cabinets, Countertops, Live Edge Shelf, Kitchen Fan, sink, sink fixtures.

Bathroom Includes: Bathtub with Shower, Shower fixtures, Skirted Toilet, Sink, Mirror and Tile

Exterior

22K

Preliminary landscaping,  downspouts, gutters, exterior paint are included in this cost.  The exterior painting and final landscaping are the remaining elements of construction.  Below photos are a work in progress!

Project Management

22K

Planning, permitting , scheduling, leading, executing, supervising the construction project. This includes working with the city on inspections, coordinating subcontractors, scheduling labor and material delivery, and staging the construction area for safety and efficient usability.

 

Misc

20K

Miscellaneous items: Including, furniture, window coverings, household items. Plus anything from tree removal to repairing your fence where it intersected with construction. It can also include additional utility costs due to the increase of resource consumption during construction.