Serving Missoula, the Bitterroot Valley and Western Montana Mon to Fri, 7am to 6pm  ·  (406) 207-2524
More room, same house

Home Addition Contractors in Missoula, Montana

Bedroom additions, second stories, primary suites and mudroom bump-outs for growing Missoula families, built on frost-depth footings, tied into the existing structure correctly and finished so the seam between old and new disappears.

Missoula families outgrow their houses faster than they can afford to move, especially with what a fourth bedroom costs in the Rattlesnake or Farviews right now. An addition lets you stay on the lot you like and in the school you chose. Constructive Brothers builds additions as one continuous carpentry job: we pour the foundation on footings below frost, frame the new walls and roof to the local snow load, tie the new floor and roof into the old structure with proper flashing and ledger details, and carry the project through siding, windows, insulation, drywall and trim. The existing house stays weather-tight the whole time because we do not open the connection until the new shell is closed in.

Site conditions in the valley shape how an addition gets built. Lots near the Clark Fork and Bitterroot have high water tables and gravelly soils that call for wider footings or engineered fill, while South Hills and Grant Creek lots often slope enough to need stepped foundations. Setbacks, lot coverage and height limits vary by zoning district, so we check the rules with the city before drawing anything. Second-story additions on 1950s ranches are common and worth doing carefully: the existing walls and foundation have to be evaluated for the new load, and the roof comes off in a window of dry weather with a plan to have it dried in fast. Every addition gets a fixed-scope quote, an engineer's stamp and the same crew from footing to final.

Home additions in Missoula generally cost $275 to $450 per square foot, so a 400 square foot bedroom and bath addition lands around $110,000 to $180,000, with foundation conditions, a second-story versus ground-level build and the bathroom count driving most of the spread.

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Why Us

Why Missoula Homeowners Choose Us for Home Additions

Foundations that match the old one

New footings next to a 1940s foundation have to be dug below frost and, on soft valley soils, sometimes wider than the original. We match bearing elevations and pin the new stem wall to the old one so the two do not settle at different rates and crack the connection.

A roofline that looks original

The giveaway on a bad addition is the roof. We match pitch, overhang and fascia depth to the existing house, tie the new rafters into the old ridge or valley with the framing the snow load requires, and flash the intersection with ice-and-water membrane and step flashing.

Weather-tight during the build

We build the new shell, roof it and side it before cutting the opening into your existing wall. Your family lives in a dry, heated house through the whole project instead of behind a tarp during a September cold snap.

Zoning and permits handled

Missoula's setback, lot coverage and height rules decide what you can build before design starts. We check your zoning district, confirm what is allowed, prepare the permit set with the engineer and handle the plan review so you are not redrawing after a rejection.

Our Process

How a Home Additions Project Runs

Feasibility and zoning check

Before you spend money on drawings, we confirm setbacks, lot coverage and height limits for your parcel and look at how the addition would tie into the existing foundation and roof.

Design, engineering and quote

We work with your designer or a local draftsman on plans, get the structural engineering stamped, and give you a fixed-scope quote with allowances for finishes before anything is submitted for permit.

Foundation, frame and dry-in

Excavation and footings go in during thawed months, followed by the stem wall, framing, roof and siding. The new shell is weather-tight before we open the wall into the existing house.

Tie-in, finish and final

We cut the connection, blend the floors and ceilings, and run mechanical, insulation, drywall, trim, flooring and paint through both the new and the patched old space. Final inspection and walk-through close it out.

Recent Work

Home Additions We've Built

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FAQs

Home Additions Questions, Answered

Is a second-story addition or a ground-level addition cheaper?
Ground level is usually cheaper per square foot if you have the yard, because the existing house barely gets touched. A second story avoids losing yard space and can be the only option on a small Northside or Westside lot, but it requires evaluating whether the existing foundation and walls can carry the load, and it usually means living elsewhere while the roof is off. We price both if the lot allows it.
How long does an addition take?
A single-room ground-level addition takes eight to twelve weeks on site. A second story or a primary suite with a bathroom runs three to five months. Add four to eight weeks before that for design, engineering and Missoula permit review. Because footings need thawed ground and the roof tie-in needs dry weather, we schedule most additions to start between April and August so the shell is closed before the snow.
Will the addition match the rest of the house?
That is the whole point of doing it as carpenters. We match siding profile and exposure, window style and trim, roof pitch and overhang, and interior details like casing and baseboard so the addition reads as part of the original house. On a 1920s bungalow that might mean lap siding with a specific reveal and fir trim; on a 1970s split-level it means matching the T1-11 or replacing it all so nothing has to match at all.
Do additions need a permit and engineering in Missoula?
Yes to both. Any addition needs a building permit from the City of Missoula or Missoula County, and the plan review will want stamped structural drawings for the foundation, beams and roof, plus energy code compliance for insulation and windows. Electrical, plumbing and mechanical work each get inspected. We prepare the permit set, coordinate with the engineer and schedule every inspection, and we keep the approved paperwork for your records and your eventual buyer.
Service Areas

Home Additions Across Missoula and the Bitterroot

Based in Missoula. One crew and one standard of work from Frenchtown to Hamilton, up the Blackfoot and over to Seeley Lake.

Related Services

Often Paired With This Work

Add the room your family needs without moving

Free on-site walkthrough. A fixed-scope quote in writing. Work that passes inspection the first time.

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