Home Addition Plans for Permit
Home addition plans that join new space to your existing house cleanly, from the foundation tie-in to the roof line, ready for permit.
- Stamped by a PE licensed in your state
- Built to IBC, IRC and local amendments
- Plan-check comments answered
More space without moving, planned to fit your house
An addition is never a standalone building. It has to meet zoning on a lot that is already partly built, connect to a foundation and roof that were designed decades ago, and match the floor heights, wall thicknesses and finishes of the house it joins. Home addition plans have to document the existing house as carefully as the new work, or the pieces will not line up in the field.
We prepare plans for single-room additions, primary suite additions, kitchen and family room expansions, bump-outs, sunrooms, garage additions and full second stories. Each set includes the site plan, existing and proposed floor plans, elevations, sections and the structural sheets needed to carry the new loads, sealed by a Professional Engineer licensed in your state where required.
Most additions also touch the existing structure. A new opening into the old house may remove part of a bearing wall, and a second story loads walls and footings that were sized for one. We handle that engineering in house, including beam and header calculations and foundation checks, so the architectural and structural sheets are designed together rather than reconciled later.
What you receive
- Site plan with setbacks and lot coverage
- Existing and proposed floor plans
- Exterior elevations matching the house
- Building sections at the tie-in
- Foundation and framing plans
- Energy notes for the new space
Addition types we design
Whether you are adding one room or a full floor, the plans follow the same principle of fitting new work to existing conditions.
Room additions
Bedrooms, family rooms, offices and primary suites added at ground level, with new foundations, roof tie-ins and openings into the existing house designed together.
Second-story additions
A new floor over an existing house, including checks of the existing walls, beams and footings, new stairs, and the shear walls that carry lateral loads down.
Bump-outs
Small cantilevered or footing-supported extensions that enlarge a kitchen, bathroom or closet, often within setbacks where a full addition would not fit.
Sunrooms and enclosed porches
Enclosing an existing porch or adding a sunroom, with glazing, insulation and the decision on whether the space is conditioned under the energy code.
Kitchen and great room expansions
Additions that open the existing kitchen into new space, typically involving bearing wall removal, a new beam and a reworked roof line.
In-law suites
Bedroom, bathroom and sitting area additions for family members, planned with accessible features and, where wanted, a layout that can later become an ADU.
Your Stamped, Permit-Ready Plans Start With One Upload
Send your drawings or describe the project. A licensed engineer reviews it and sends a clear, fixed-fee proposal, often within hours.
- Free and no obligation
- Reviewed by a licensed PE
- Secure file upload
What home addition plans include
Reviewers need to see both what exists and what is changing. A typical addition permit set includes:
- Site plan showing the existing house, the addition footprint, setbacks, easements and updated lot coverage.
- Existing and proposed floor plans, or a combined plan with a legend for walls to remain, walls to remove and new walls.
- Elevations of every affected side of the house, showing how the new roof, siding and windows relate to the old.
- Building sections cut through the connection between the house and the addition, showing floor heights, roof framing and insulation.
- Foundation plan for the new footings and the doweled connection to the existing foundation.
- Framing plans for floor, wall and roof framing, headers and beams at new openings.
- Energy notes for insulation, windows and air sealing in the new conditioned space.
When new bathrooms, a kitchen or HVAC changes are part of the addition, a plumbing, mechanical or electrical layout is added. Many departments also want to know whether the existing heating system can serve the added area or whether new equipment is proposed. We show that on the plans with a short note and, where needed, a load calculation.
Tying the addition into the existing house
The joint between old and new is where most addition problems start, so we design it deliberately. Floor heights are set so the new floor meets the old one at the same level, or with a step that meets stair rules. The new foundation is connected to the existing one with dowels or detailed so the two can move independently where soils require it.
The roof needs the same care. We decide whether the addition roof ties into the existing roof plane, runs as a separate gable or hip, or sits as a lower shed roof against the wall, and we detail the flashing, valley framing and ventilation that each option requires. Matching roof pitch and eave height keeps the addition looking original instead of attached.
Openings into the house often cut through an exterior bearing wall. We size the new beam and posts, carry the loads down to footings and show temporary shoring notes so the contractor can build it safely. If an interior wall also comes out, our load-bearing wall removal design is coordinated on the same sheets.
Finally, we look at the existing wall where the addition attaches. Siding, sheathing and weather barrier have to be lapped correctly at the transition, and existing windows that end up inside or under the addition are removed or relocated on the plans.
Have a Question? Get a Real Engineer's Answer in Minutes
Skip the guesswork. Chat live with a licensed engineer about your drawings, code requirements or permit comments, free and with no obligation.
- Free and no obligation
- Reviewed by a licensed PE
- Secure file upload
Second-story home addition plans
Going up keeps your yard and avoids setback limits, but it puts new weight on a structure that was not designed for it. Before drawing a second story, we evaluate the existing load path: the bearing walls, the beams and headers that carry them, and the footings beneath. Where the existing framing or foundation is not adequate, we design the reinforcement, such as new posts and footings, sistered joists or added beams.
Lateral design is equally important. A taller building catches more wind and develops larger seismic forces, and those forces must travel through the new upper walls into the existing first-floor walls and down to the foundation. We design shear walls, hold-downs and connections for the full height, often adding sheathing or hold-downs to first-floor walls that were originally unsheathed.
The architectural side has its own challenges. A new stair needs space on the first floor, plumbing and ducts need a path to the upper level, and the zoning height limit may control the roof pitch. We resolve all three before construction drawings begin, and we note the temporary weather protection the contractor will need once the existing roof is removed. If you plan to live in the house during construction, we can sequence the work on the plans so the first floor stays usable for as long as possible.
Code upgrades an addition can trigger
Adding space can require improvements to the existing house, and it is better to know before you budget. Common triggers include:
- Smoke and carbon monoxide alarms. Many jurisdictions require alarms to be installed or interconnected throughout the existing home when an addition is permitted.
- Egress. A new bedroom needs a compliant escape opening, and an addition must not block the escape window of an existing bedroom.
- Septic capacity. Adding a bedroom on a septic system may require health department review of the tank and drain field.
- Electrical service. Additional circuits, HVAC and appliances may exceed the existing panel capacity.
- Energy code. The new space must meet current insulation and window requirements even if the old house does not.
- Stormwater or impervious area limits. Larger footprints can push a lot past local coverage thresholds.
We identify these items during the quote and design so the permit is not delayed by an upgrade nobody planned for. Older homes can also reveal conditions such as undersized framing, deteriorated sills or outdated wiring once walls are opened, and we can revise the plans quickly if the inspector asks for corrections. Where a requirement can be met in more than one way, we lay out the options and their cost implications so you can decide before the plans are finalized.
Home addition plans are needed when you
- Add a bedroom, suite or family room
- Build a second story over your house
- Expand a kitchen into new space
- Enclose a porch or add a sunroom
- Add a bump-out or bay
- Build an in-law suite onto the home
How it works, start to finish
From your first message to stamped drawings, you work directly with the engineering team.
- 1Share your projectSend the address, scope and any drawings, photos or plan-check comments. Two minutes is enough.
- 2Receive a fixed-fee proposalAn engineer reviews the scope and replies with a firm price and delivery date for your home addition plans drawings.
- 3Engineering and draftingWe run the calculations and prepare drawings to the codes your jurisdiction enforces, checked before sealing.
- 4Stamped set deliveredYou receive a sealed PDF set ready to submit, and we answer any plan-check comments within scope.
Codes our addition plans follow
Addition plans are prepared to the codes and local amendments your jurisdiction has adopted:
- International Residential Code (IRC) or your state residential code
- International Existing Building Code (IEBC) where your jurisdiction applies it
- International Energy Conservation Code (IECC)
- ASCE 7 for wind, snow and seismic loads
- NDS for wood framing and ACI 318 for concrete
How licensing works. Engineering drawings must be sealed by a Professional Engineer licensed in the state where your project is located. PE Engineer works with a network of state-licensed PEs, so every set is reviewed and stamped by an engineer with an active license in the state where your project is located. Their name and license number appear on the seal, exactly as your building department requires.
Related services
Foundation DesignFootings, slabs, stem walls, piers and pile foundations designed and PE stamped for your soil, loads and local code.Explore More
Framing PlansFloor, wall and roof framing plans with joist, rafter, header and shear wall design, sealed by a licensed PE for permit.Explore More
Remodel & Renovation PlansKitchen, bath, basement, attic and whole-house remodel plans showing existing conditions, demolition and new work, with structural changes engineered.Explore MoreFrequently asked questions
Do I need an engineer for a home addition?
Small one-story additions can sometimes be built using prescriptive code provisions, but most building departments want engineering when an addition loads existing walls or footings, removes part of a bearing wall, adds a second story, or sits in a high wind, snow or seismic area. We provide both the architectural and structural sheets.
Can you match the style of my existing house?
Yes. We use photos and measurements of your house to match roof pitch, eave heights, window proportions, trim and siding, so the addition looks like it was always there. Elevations show the new work alongside the existing house for your review before plans are finalized.
What do you need to start my addition plans?
Your address, photos of the house inside and out, basic measurements of the rooms near the addition, any existing plans or surveys, and a sketch or description of what you want. If you do not have measurements, we can send a simple guide that shows what to measure.
Will my existing foundation support a second story?
Sometimes, but it has to be checked. We evaluate the existing footings and bearing walls against the new loads and design reinforcement where needed, such as new footings, posts or beams. Photos of the foundation and crawlspace or basement help us assess it accurately.
Can an addition be built close to my property line?
Only within your zoning setbacks, unless you obtain a variance. Walls very close to a property line may also need fire-resistant construction under the building code. We check setbacks and separation on the site plan before designing the layout.
How long do home addition plans take?
Most single-room addition sets are delivered within a few business days of receiving measurements and photos. Second-story additions take longer because the existing structure has to be evaluated. We confirm the schedule with your quote, and rush service is available.
Get your free home addition plans proposal
Tell us where the project is and what you need. Attach any drawings, photos or plan-check comments. A licensed engineer reviews every request.
- Upload your filesPlans, sketches, photos or comments
- Get a fixed-fee proposalUsually the same day
- Receive stamped drawingsSealed by a PE licensed in your state