HOME ADDITION PLANS
Home addition plans, priced on what actually has to be drawn
An addition is never drawn on its own. The set has to show how it connects to the house: the wall you open up, the roof it ties into, the rooms it changes. We price that honestly and tell you why before you pay.
- ✓ Existing and proposed plans
- ✓ Foundation and roof tie-in details
- ✓ Elevations of the whole house face
- ✓ Energy compliance for new space
- ✓ Engineer coordination when needed
What home addition plans cost
We charge $1 per square foot of drawn area, with a $1,200 minimum. The drawn area is the new space plus the existing rooms the set has to show, which is usually more than the addition itself.
Here's a real one. A 272 sq ft sunroom addition we drew in New Jersey in 2026 carried 1,480 sq ft of drawn area: the set had to cover the dining room and kitchen wall it opened into, the existing roof it framed against, and the elevations of the whole rear of the house. The quote showed that math line by line before any money changed hands.
| Project | Drawn area | Fixed fee | What sets the fee |
|---|---|---|---|
| Bump-out or small room additionProject minimum | under 1,200 sq ft drawn | $1,200 | Project minimum |
| Primary suite addition with existing rooms shown$1 per sq ft | 1,500 sq ft | $1,500 | $1 per sq ft |
| Second-story addition over a 1,400 sq ft house$1 per sq ft | 2,800 sq ft (both levels) | $2,800 | $1 per sq ft |
Additions are priced on drawn area even when they're under 1,200 sq ft; the per-sheet rule applies only to new detached construction.
What the drawing set includes
On top of the standard sheets, an addition set has to answer how new meets old:
A-1Site plan
The addition's footprint against your setbacks and lot coverage limit, which is where additions most often get stopped.
A-2Existing and proposed floor plans
Demolition, the new walls, and every existing room the addition changes.
A-3Elevations
The full face of the house the addition sits on, so plan check sees the finished building, not a box.
A-4Tie-in sections and details
Foundation and roof connections, flashing, and the transition between old and new wall assemblies.
SStructural, when required
New beams over opened walls and second-story loads usually need an engineer. We draft to their design.
E / P / ENMEP and energy
Circuits, fixtures and the energy compliance forms (Title 24 in California, REScheck or IECC elsewhere).
What the fee doesn't cover
We'd rather you hear about these now than at plan check. None of them are hidden fees of ours; they're paid to other people, and we tell you up front which ones your project needs.
- Structural engineering
- Most additions that open a bearing wall or add a floor need an engineer's design and seal. You hire them directly; budget roughly $1,200 to $1,800 on a typical house job, and we carry the coordination.
- Surveys
- Needed when your addition sits close to a setback or your city asks for one. We'll tell you which kind.
- Permit fees
- Paid to your city.
Questions people ask before they order
How much do home addition plans cost?
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At ArchWorkPro, $1 per sq ft of drawn floor area with a $1,200 minimum. Drawn area includes the existing rooms the addition ties into, so the fee is often based on more than the addition's own size; your quote shows the math.
Why is the drawn area bigger than my addition?
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Because plan check needs to see how the addition connects to the house: the wall that opens, the roof it frames against, and the rooms it changes. A 272 sq ft sunroom we drew in 2026 needed 1,480 sq ft of drawn area for that reason.
Do I need an engineer for an addition?
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Often, yes, when you remove part of a bearing wall, add a second story, or build in a high-wind or seismic zone. We tell you when we quote and coordinate with the engineer you hire.
Can you match my existing house?
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Yes. Send photos of every side and any old plans you have; we draw the existing house from those plus your measurements.
How long do addition plans take?
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Usually 5 to 10 business days once we have measurements, photos and any engineer input. Your quote states the date.
Related: Permit sets explained · As-built drawings of your house · For owner-builders · Price rules
Get your addition quoted
Send photos, rough dimensions and a sketch of what you want to add. We reply within 2 working hours with the drawn area, a fixed fee and a delivery date.
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