Trusted Renton ADU Builders for Detached and Attached Units
Want a rental unit, guest house, or more room for family? BB-Builders Pro is a team of ADU builders serving Renton. We design, permit, and build detached backyard cottages and accessory dwelling unit additions. State law now allows up to two ADUs per lot, so there is more room to add value than ever. We handle the full build, from site evaluation to final walkthrough, on your schedule.
Trusted Family Owned Remodeling Service
Our licensed crew has built detached and attached ADUs across Renton and King County with careful, lasting craft.
We design detached backyard cottages and attached accessory units shaped to your lot and how you plan to live in them.
Local zoning and the two-ADU law can seem like a maze. We run every permit step so your build passes all code review.
We choose sturdy, energy-smart materials that cut upkeep, stand for decades, and keep your monthly utility bills down.
From the opening consult and 3D renderings to the final walkthrough, we guide every phase of your ADU build with care.
BB-Builders Pro handles every part of your ADU project, from first sketch to final sign-off in Renton. Our full services include:
Place a freestanding backyard cottage on your Renton lot, a strong fit for rental income, family, or a quiet guest retreat.
Turn underused interior space into a fully livable attached ADU, adding a second home within your existing footprint.
Planning for later? We build yard additions and outbuildings set up to become a future detached ADU when you are ready.
We craft bespoke ADU floor plans and layouts built around your Renton lot, your budget, and the way you plan to use it.
We handle each building permit, zoning sign-off, and code check, keeping your ADU project moving along smoothly and legally.
Already own an older ADU or home extension? We take on renovations, interior updates, and energy-efficient improvements too.
Testimonials
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We meet you at your Renton property, hear out your goals, and give clear guidance on the right ADU or home plan for the lot.
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Our design team builds full blueprints and 3D renderings, so you can view your ADU or addition in real detail well before we ever dig.
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We manage each building permit, zoning rule, and code check, so the legal paperwork never becomes your problem to solve.
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Our crew clears and preps the ground, then builds with real care, keeping the site clean, efficient, and easy on your routine.
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After we finish, a thorough inspection and walkthrough confirm that every last detail meets our safety and quality marks.
An ADU is a secondary home on a single-family lot, either attached to the main house or built as a separate detached structure. Renton allows up to two ADUs per lot, including junior ADUs, under code adopted in 2025. Both attached and detached units are permitted, giving homeowners more flexibility than before.
An ADU adds rental income, housing for aging parents, or a private guest space. It uses land you already own, so it builds value without buying more property. With two units now allowed per lot, the earning and living options are wider than before.
Yes. Renton runs a Permit Ready ADU Program with plan sets already reviewed for city code. Using one can cut time and cost from the design and permit stage. We build from these plans or draw a fully custom design, whichever fits your lot best.
Yes. Every ADU in Renton needs a building permit, plus zoning and code review. One catch: a Renton mailing address does not always mean city jurisdiction, since some areas fall under King County. We confirm the right office first, then prepare and manage the full application.
Cost depends on size, type, and finishes. A conversion of existing space runs the least, while a large detached cottage costs the most. Utility connections and site work add to the total. We give you one written estimate after a free on-site visit.
Most ADUs take a few months from permit approval to move-in. Design and permitting add time up front, though a pre-approved plan speeds that stage. Detached units usually take longer than conversions. We map out the full schedule before work begins.
Yes. Renton no longer requires owner-occupancy for newly built ADUs, so a second unit works as long-term rental income. That makes an ADU a real investment option. Short-term rentals follow separate city rules, which we can point you to.
A detached ADU can reach 1,000 square feet, or 60 percent of the primary home’s living area, whichever is less. Attached units and junior ADUs follow their own caps. Lot size and setbacks also shape the limit. We design to the largest unit your property allows.
Renton generally limits a detached ADU to about 16 feet, though state parity rules can allow more. Height ties to your zone and the main home’s limit. We plan the roofline early so the design clears review without costly changes.
Not always. Some ADUs share water and power with the main house, while others need separate connections depending on size and layout. Separate meters help if you plan to rent. We assess your utilities during the site evaluation.
Usually yes. Adding livable square footage raises your assessed value, so property taxes typically go up. The added rental income or home value often outweighs the increase. The King County assessor sets the exact change after the build.
Simple Financing Options
Discover the perfect financing solution for your remodeling project. We provide tailored options to suit your budget and ensure your dream home becomes a reality.
Contact us today for a free consultation, and let’s begin transforming your house into the home you’ve always wanted.
Contact us today for a free consultation, and let’s begin transforming your house into the home you’ve always wanted.