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How long does it take to build a home addition?

Adding on to your home is a major time commitment. But it’s also exciting to watch as the structure takes shape and comes together. If you’re considering a home addition, understanding how long the build will take is an important part of the planning process.

Here at Lamont Bros., our team of design and construction pros has built dozens of home additions across the Portland metro area. We’ve seen additions come together in a matter of weeks, while others can take over a year. Want to know how long your addition will take to build? Keep reading to find out.

This article will discuss the timeline for the construction of a home addition, broken down into 3 phases. By the time you finish reading, you should have a better understanding of the time it takes to build an addition. Here are the different phases we will discuss:

Addition Construction Timeline

If you’re working with a qualified contractor to build an addition to your home, they will provide you with a set of design plans from an in-house designer or independent architect. These plans should outline the entire scope of work, including what changes will be made, what methods will be used, and which products and materials will be required.

Having a set of design plans will help your project manager predict the timeline for your home addition more accurately. There are several factors that can affect the timeline of an addition. By using the plans as a guide, your project manager can create a schedule that will give you a better idea of how long the project will take to complete.

This article uses a standard 14-week schedule for a single-story, ground-level addition as an example. Depending on the size, scope, and complexity of your addition, it may take shorter or longer.

Phase 1: Foundation (3 weeks)

During the first phase, your team will begin by laying down the concrete foundation of the addition. As the base layer of the entire structure, it’s important to put in the necessary time and effort to prepare, construct, and inspect the foundation before moving on to the rest of the project.

Week 1: Preconstruction Meeting & Excavation

You’ll meet on-site with your entire team to discuss the project ahead. If you work with a design-build firm like Lamont Bros., the build team may give you a presentation that covers their construction schedule, site protection plan, and any safety concerns that you need to be aware of.

They should also explain how your addition project could impact your daily routine during the construction phase. This is your chance to ask any questions you may have and to communicate any house rules to the contractors.

Following the preconstruction meeting, your team will get to work excavating the construction site. During this process, they will use heavy machinery to clear a level space for the foundation.

To begin working on the foundation of an addition, the ground below must be level.

Week 2: Forms & Form Inspection

Concrete forms are temporary structures used to contain and shape concrete as it sets and hardens. They are traditionally made of wood and function as a mold for the foundation. Forms are assembled on the construction site prior to pouring the concrete. This process generally takes an entire week.

Once built, an inspector will ensure that the forms are built to code and ensure that the steel rebar is placed correctly. It is important to note that this inspection comes before the concrete itself is poured. This is because it is much easier to adjust the forms and rebar than it is to demolish and re-pour concrete later on.

Week 3. Concrete

By the start of the third week, the first permanent structure for your addition is on its way. Your build team will fill the foundation forms with concrete and allow them to dry. Typically, the concrete needs about 7 days to dry before framing can begin. During this week, you won’t see much construction activity except the occasional check-in.

The concrete is poured and ready for framing.

Phase 2: Rough-In (5 weeks)

During the rough-in phase of a home addition, the major structural and utility components are installed. This stage can be exciting for homeowners as they get to see their vision for the new space starting to take shape. Since these components make up a major part of the project’s design, it is common to see a lot of progress in a relatively short amount of time during this phase.

Weeks 4-5. Framing

It usually takes a minimum of two weeks to complete the framing of an addition. During this process, your construction team will use lumber to craft the floors, walls, and roof trusses that form the structure of the addition.

The framer in charge of the job must pay close attention to detail and adhere to strict construction code requirements. Additionally, they must also consider the placement of every door, window, and exterior vent in the framing structure.

Stud walls during installation.

Week 6. Roof & Sheathing

After the framing process is finished, the next step is to install both the roofing and sheathing. This can often be done at the same time.

The team responsible for the roofing will install the shingles to protect the newly constructed structure from weather elements. Simultaneously, the other team will install the sheathing, which serves as both a weather barrier and provides additional structural support to the frame walls.

Week 7. Trades/Utilities

Once the interior of the addition is enclosed, it is time for the rough-in installation of the electrical, plumbing, and HVAC systems. This stage of the construction process requires the involvement of several subcontractors. Therefore, you’ll probably see a few new faces during this time.

During the rough-in installation, the subcontractors will primarily work on the major systems that run inside the walls. The plumbers will install the water supply and drainage lines. The electricians will be responsible for installing the electrical boxes, wiring, and any appliance hookups. Similarly, the HVAC installers will be adding the ducts, vents, and piping required to distribute hot and cold air throughout the building.

Week 8. Inspection

Before moving on to the third and final phase of the build, the completed rough-in structure requires an inspection. The purpose of the inspection is to ensure that the structure and rough-in utilities are properly installed and meet building code requirements.

If the inspector identifies any issues or code violations during the rough-in inspection, the construction team will need to make any necessary corrections before proceeding with the project.

Phase 3: Finish Work (6 weeks)

During the final 6 weeks of your addition build, it may feel like the project has slowed down. Don’t be discouraged — finish carpentry is a construction art form that requires extreme care and fine attention to detail. You’ll get to watch the space go from a shell to a home as your build team works tirelessly to put the finishing touches on your addition.

Weeks 9-10. Exterior Siding, Trim, Paint

The exterior of the addition is often the final step in the process. The exterior siding in an important part of the building envelope, and when installed correctly, can protect your home for over 50 years.

Once the exterior trim and paint are complete, your build team will address any lingering issues, fix the items on your final punch list, and close out the job.

Week 11. Insulation & Drywall

With the utilities installed and approved, it’s time to close up the walls. Insulation goes in first to ensure that your addition can maintain a good internal temperature and stay energy efficient.

Then comes the drywall, which will take up most of the week due to its lengthy installation process. The higher-quality drywall finish you’ve requested, the longer the installation will take to complete.

Drywall installation can take a long time depending on the addition’s size.

Weeks 12-13. Trim, Flooring & Paint, 95% Walkthrough

The following two weeks will consist of finish carpentry work. This will include everything from door and window casings to installing new plumbing fixtures. At the end of the two weeks, the trim, flooring, and paint should be fully installed.

At the end of the 11th week, you’ll do your 95% walk-through. The purpose of this meeting is to tour the addition in a state of substantial completion. You’ll get to see the project in its ending phase and provide a final punch list to your build team of things to fix before closeout.

Week 14. Final Inspection & Photos

Before your addition is officially ready to live in, it will need one final inspection. The purpose of this inspection is to ensure build quality and code requirements. It’s also an opportunity to check for things that might have been overlooked in previous inspections.

Lastly, a professional photographer may come and photograph your completed addition to memorialize the project. You’ll get to keep a set of the final photos to show your friends and family.

Ready to meet with a designer about your Addition?

After reading this article, you should have a better understanding of the various stages involved in building a home addition, as well as a clearer idea of the timeline for completing your own project. However, don’t stop there! We recommend that you also take a look at our Additions Portfolio to gather inspiration from real addition projects by Lamont Bros.

If you’re ready to start planning your home addition project, click the link below to connect with a member of our design team. We offer free video consultations to help you navigate the remodeling process and create a space that meets your needs.