Home Additions
Des Moines, IA
An addition in Des Moines is judged against your lot’s house type, its setbacks and, on some streets, a historic review. The city charges a flat permit fee and assigns one inspector for every trade. Here is what the Permit and Development Center asks for before and during the build.
- Des Moines at a glance
Des Moines lots and homes in numbers
Des Moines grew from 502 residents in 1850 to 214,133 in 2020. Owners occupy 60.5 percent of its homes. The addition figures come from city house type checklists, the accessory housing page and the fee schedule.
502 to 214,133
Residents, 1850 to 2020
60.5%
Owner-occupied rate
2024 IRC
Residential code since 2026
115 mph
Wind speed homes design for
$257.50
Flat addition permit fee
40 feet
Rear setback, House Type B
35%
Lot coverage cap, Type B
1,000 sq ft or 50%
ADU cap, whichever is larger
- Permits and rules
Adding on in Des Moines: setbacks, plans and inspections
Yes, an addition needs a permit, and Des Moines charges a flat $257.50 plus $77.25 per trade. Setbacks and lot coverage come from your house type and zoning district. Plans follow the city’s combined new home and addition checklist.
Setbacks and lot coverage
Each house type sets its own limits by district. On a House Type B lot in N3a or N3b, the rear setback is 40 feet and interior sides are 7 feet, 15 feet combined. The street side is 15 feet, and the front is 25 feet with averaging. Buildings may cover 35 percent of the lot, impervious surfaces 50 percent.
Site plan and drawings
The site plan needs a north arrow, property lines, lot dimensions, every structure with its setbacks, and impervious surface areas. Floor plans, all exterior elevations and cross sections from footing to roof come next. The city wants enough detail that someone with no knowledge of the project could build it.
Footings, frost and winter pours
Addition footings go below the city’s 42-inch frost line. Under the metro cold weather policy, no concrete goes in on frozen ground. Pours also stop when the predicted temperature falls below 10 F in the next 24 hours. Fresh concrete must not freeze for 48 hours or until it reaches 500 psi.
Energy and code rules
Additions follow the 2024 IRC, in effect since January 1, 2026, and the 2015 International Energy Conservation Code. The plan set needs an energy review showing how prescriptive compliance is met. The city’s checklist still cites the 2018 IRC, so we confirm current values with the Permit and Development Center.
Accessory dwelling units
Des Moines allows ADUs in the N, NX, A, DXR, RX1 and RX2 districts. One can be up to 50 percent of the house’s floor area or 1,000 square feet, whichever is larger. It must sit at least 5 feet from every lot line and stay no taller than the house. No extra parking is required, and state law SF 592 bars owner-occupancy rules.
Inspections and historic lots
Additions are in the Residential Combination Inspection program, so one assigned inspector handles every trade. Request visits through the city portal. If your lot sits in a Local Historic District, exterior changes need a Certificate of Appropriateness, at $10, before work begins.
- Our process
How Busy Builders builds your Des Moines home addition
We start with your lot: its zoning district, its house type and the setbacks left to work with. Plans follow the city’s addition checklist, from site plan to energy review. Footings go below 42 inches, and one assigned city inspector sees every stage. Licensed electricians, plumbers and HVAC contractors we coordinate tie the addition into your home’s systems. We also build attached garages, storm shelters and safe rooms as part of an addition when asked.
Busy Builders is a registered Iowa contractor, DIAL C140184. Additions, full remodels and basement finishes make up most of the more than 100 projects we complete each year.
- Setbacks measured before design starts
- Footings below the 42-inch frost line
- Garages, shelters and safe rooms on request
Lot check to final
- Achievement
Trusted Home Addition Contractors in Des Moines
Since 2020, Busy Builders has completed more than 1,285 projects across Central Iowa.
- Frequently Asked Questions
FAQs About Home Additions In Des Moines
What does a home addition cost in Des Moines?
Additions start at about $300 per square foot. Final costs vary by scope, materials, complexity and location within our service area. Size, foundation type, the roof tie-in and how far the home’s systems must extend drive the total. City fees are flat: $257.50 for the building permit and $77.25 per trade permit.
How close to my property line can I build an addition in Des Moines?
It depends on your house type and zoning district. Take House Type B lots in N3a and N3b. They need 40 feet at the rear and 7 feet on each interior side, 15 feet total. The front needs 25 feet, with averaging. Show Me My House gives your district, and the city checklists confirm your numbers.
What if my addition can't meet the setback?
You can ask the Zoning Board of Adjustment for relief. As of January 1, 2026, a variance costs $310 and an exception $230. Each adds a notice fee of $3 for every property within the notice area. Any board decision must go in with your permit plans, per the city’s submittal checklist.
Does an older Des Moines lot follow different rules?
It can. The house type checklists ask whether a lot was platted before December 15, 2019, the date tied to pre-existing situations in section 135-10. The same forms flag lots in historic districts. Older lots that do not fit today’s dimensions may fall under those pre-existing rules, so we check before we design.
Who inspects an addition in Des Moines?
A single city inspector, assigned through the Residential Combination Inspection program. That person handles the building inspections and every trade inspection for the addition. You request each visit online, and your inspector’s contact information is on Show Me My House.
Can you build a storm shelter or garage as part of an addition?
Yes, when you ask. We build storm shelters, safe rooms and attached garages to the spec of the job as part of an addition, not as standalone projects. One of our finished two-story additions has an upper deck with metal railings and exterior finishes matched to the original house.
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