Get Fast, Permit-Ready Structural Plans for ADUs

Structural engineers specializing in ADUs delivering code-compliant plans in as little as 2-3 weeks. Serving Seattle, Bellevue, Tacoma, Spokane, and all of Washington. Unlimited plan-check revisions within our engineering scope* at no extra cost.

Licensed WA Engineers

2-3 Weeks Delivery

Permit Guarantee*

Highly Responsive

Fixed Transparent Pricing

150+ ADUs Permits Approved

(844) 750-0773

Call (844) 750-0773

Licensed Washington Engineers|WA PE License #24002154 - Amarendra Prasad, PE

3000+

Projects Completed

2-3 Weeks

Average Delivery

Guaranteed*

Permit Approval

5.0

Google & Yelp Rating

OUR SERVICES

We provide structural engineering for all ADU types, from garage conversions to new detached units, throughout Washington.

Which ADU Type Will Add the Most Value to Your Property?

Junior ADU (JADU)

Units typically under 500 square feet, created by converting a portion of the primary residence. Commonly used for extended family or rental purposes.

Attached ADU

Units attached to the primary residence, often constructed as an addition or garage conversion.

Detached ADU

Stand-alone structures built on the same lot as the primary residence, offering greater privacy and flexibility.

Basement ADU

ADUs created within the basement of the primary residence, maximizing existing usable space.

Garage ADU

Units constructed within or above an existing garage. A popular ADU option in Seattle, Bellevue, and Tacoma.

Multi-family ADU

Secondary units designed for multi-family residential properties such as duplexes or apartment buildings.

Same-day quote • 2-3 weeks delivery • No hidden fees

Don't Have Plans or Architectural Drawings Yet?

No problem! We work with a network of trusted, design partners and licensed architects who can help you design your project from scratch. Once your design plans are ready, we'll handle all the structural engineering seamlessly.

Architect/Designer Referrals

Coordination Support

Expert Guidance

HOW IT WORKS

Get Your ADU Permitted in 3 Simple Steps

1

Fill Out Our Form & Schedule Free Consultation

Complete our quick form and schedule a call with a dedicated project manager. Share your ADU design plans and project description. Don't have plans yet? We can refer you to trusted architects and designers at no extra cost, who can help!

2

Get Same-Day Quote

After reviewing your ADU design plans, we'll provide a transparent fixed quote the same day--typically within a few hours. Most ADU projects ranges from $2,500-$5,500 for structural plans and structural calculations.

3

Receive Permit-Ready Plans in 2-3 Weeks

We deliver complete structural permit sets. *If building departments have comments related to our scope, we handle all revisions--no extra fees, no limits.

SUCCESS STORIES

What Our Clients Are Saying

See why homeowners and industry professionals across Washington trust us with their projects.

"ProStruct Engineering prepared the structural plans for my home remodel, which required extensive consideration due to the age of my house and its location near the beach. Nithin, the project manager, was incredibly responsive, quickly facilitating changes requested by the city during the review cycles. Their expertise and willingness to consult throughout the construction process will be invaluable. I'm genuinely grateful for their professionalism and support."

S

Sandra

"The engineer checked thoroughly for issues related to our foundation. He gave unbiased opinion and very constructive recommendations to mitigate the issues. Compared to the sales person from various foundation contractors, this advise would help us avoid the over engineering and save more than $30k."

Z

ZF Zhan

"Prostruct was great! Responsive, prompt, great communication. I am looking forward to going into the permitting process with them since I know to expect good results and communication."

V

Vatche Bezdikian

"I just received notice that I will now have my permit to build a bathroom and bedroom as a remodel in my garage. Josh was great and Nithin and his team helped me through the process. YAY!"

D

Dee Sherm

"The PM was prompt and the engineer that came to assess structure was courteous. He was able to give us a report including all the details he discussed with us in person. The PM is knowledgeable of the general construction process as well. Would definitely send business their way again, should a structural assessment need arise again."

H

Hiren Patel

"We contracted ProStruct to look at the integrity of some retaining walls. Nithin, Josh, and Jesse were swift with their communication and very knowledgeable. We will be using them again in the future!"

W

Wade

"Easy process! Great communication every step and the inspector was able to come out and inspect our foundation very quickly. Overall impressive company who I would recommend!!"

T

Tamara Lee

"Very smooth experience. Accommodated my timelines and helpful reviews. Thanks"

M

Mallikarjuna Vallem

Trusted by homeowners and AEC industry professionals across Washington

Fast delivery • Permit guarantee* • Fixed Transparent Pricing

Built for Speed, Clarity, and Permit Success

Why Clients Choose ProStruct Engineering

2-3 Week Express Delivery

Don't wait months for plans. We deliver complete, permit-ready structural plans and engineering drawings in just 2-3 weeks so you can start building and generating rental income faster.

Permit Revision Guarantee*

If building departments have comments related to our scope of work*, we'll revise plans at no extra charge--no matter how many rounds it takes. We stand by our work until your permit is approved.

Transparent Pricing: $2,500-$5,500

Most ADU projects range from $2,500 to $5,500 depending on size, complexity, and foundation requirements. No hidden fees. You'll receive a detailed quote within 24 hours.

Your Own Dedicated Project Manager

Every project includes a dedicated project manager at no additional cost. They act as your single point of contact, coordinating with our engineers and collaborating with third-party professionals--including architects, contractors, and others--on matters within our scope to ensure clear communication, faster decisions, and a seamless project experience.

Serving All Across Washington

We're the trusted ADU structural engineers for homeowners and AEC industry professionals in Seattle, Bellevue, Tacoma, Spokane, Vancouver, Olympia, and all surrounding Washington cities. Local expertise, fast service.

COMMON QUESTIONS