337 sq ft Master Suite Addition
in Renton, WA
A master bedroom suite addition to an existing two-story home in Renton. Adds a 205 sq ft bedroom with sliding glass door to a new 138 sq ft deck, a luxury bathroom with 42"×60" walk-in shower, and a walk-in closet. R-60 roof insulation exceeds code by 58%. Blower door target of 2 ACH@50Pa — less than half the code requirement. Includes an EV-ready 40A/240V garage circuit for future electric vehicle charging. Built by Evercrest LLC.
Floor Plan
Master Bedroom (205 sq ft) — connects to existing home through two infilled window openings. 72"×84" sliding glass door to new deck.
Master Bathroom (43 sq ft) — 42"×60" walk-in shower, linen closet, pocket door entry.
Walk-in Closet (37 sq ft) — positioned between bedroom and bathroom.
Deck (138 sq ft) — new outdoor space with 36" safety railing, 6×6 PT posts, 2×12 joists. Crawl space access below.
Note on plans: construction limited to master suite — no other work on existing rooms.
North Elevation
North elevation shows the addition relative to the existing two-story home. New construction clearly marked with new horizontal/vertical siding. The new roof cap with built-in damper sits at the transition between old and new roof lines.
Existing windows and structure remain untouched. The 36" railing on the new deck visible at the lower right.
West Elevation
West elevation shows the addition's side profile. New horizontal and vertical siding wraps the addition. Foundation vents visible along the base for the new crawl space.
The new deck extends from the bedroom with a 36" high railing. Below, new crawl space with R-38 insulation provides mechanical access and airflow.
South Elevation
South elevation gives the full view of the two-story existing home with the single-story addition extending from it. Floor levels clearly marked: second floor at 8'-7", first floor ceiling at 7'-7".
The new deck is visible at the base, and all new windows are called out with size specifications for permitting.
Building Section
Roof: R-60 — 2" R-12 closed-cell spray foam + 12" R-48 fiberglass batt. Exceeds code R-38 by 58%. New roof cap with built-in damper at ridge.
Walls: 2×6 framing, R-21 cavity + 2" R-12 CCSPF. 1/2" GWB typical. Finish per elevation over 1/2" OSB sheathing.
Floor: 2×12 HP joists @16" OC on new floor beam. LUS hangers at connections.
Crawl Space: R-38 insulation under new floor. ABU post bases with 1/2"×4" strong bolts. New posts on new footings tied to existing stem wall.
Building Specifications
Permit
Status: Under Review
Authority: King County
Codes: 2021 IRC, WSEC 2021
Project Team
General Contractor: Evercrest LLC
Architect: National Design Project LLC, Everett WA
Engineer: Alex Mostursenko, PE #36923
Understanding Home Additions in Renton
A home addition extends your existing structure — adding bedrooms, bathrooms, or living space without building a separate unit. Renton falls under King County jurisdiction (unincorporated areas) with R-4 zoning allowing up to 35% lot coverage. Additions require structural engineering to tie new and existing foundations, and must meet current energy codes even when the original home was built to older standards. Evercrest LLC handles everything from design through King County permitting and construction — for additions, attached ADUs (AADUs), and backyard cottages (DADUs).
Home Additions in Renton — FAQ
Home additions in the Renton area typically cost $300–$450+ per square foot depending on scope, finishes, and how the new structure ties to the existing home. Master suite additions with high-performance insulation like this project (R-60 roof, spray foam walls) are at the higher end but deliver significant long-term energy savings. Evercrest LLC provides fixed-price contracts.
King County typically reviews residential addition permits in 3–6 months. Evercrest LLC handles all submissions, plan revisions, and inspector communication throughout the process.
R-60 means the roof insulation is 58% better than the code-required R-38. This project uses 2" of closed-cell spray foam (R-12) plus 12" of fiberglass batt (R-48). Combined with a blower door target of 2 ACH@50Pa (less than half the code limit of 5), the addition will be dramatically more energy-efficient than a code-minimum build.
Per IRC R309.6, this project includes a dedicated 40A/240V circuit with 1" conduit from the electrical panel to the garage. This means you can install a Level 2 EV charger in the future without rewiring — just plug in the charger. It's a low-cost addition during construction that adds real value.
Yes. Renton's R-4 zoning allows up to 35% lot coverage. This 12,672 sq ft lot is currently at 21.8% coverage — well within limits. The addition connects to the existing home through two infilled window openings, maintaining the structural integrity of both old and new.
Yes. Evercrest serves King County (Seattle, Renton, Bellevue, Kent, Auburn), Pierce County (Puyallup, Tacoma), and Snohomish County (Everett, Lynnwood, Bothell). We handle additions, attached ADUs (AADUs), backyard cottages (DADUs), and remodels in all jurisdictions.
Ready to Add a Master Suite in Renton?
Evercrest LLC handles design, engineering, permits, and construction — one team from start to finish.
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