How To Build a Home Addition For Your Home: A Step-By-Step Guide

A home addition is a major renovation investment that requires a tremendous amount of planning and coordination. Between getting building permits and hiring the right general contractor, the process of adding living space to your home has many moving parts. Staying on top of the smallest details (such as what a quote should include) to big-ticket items (such as having a contingency budget) will help keep your renovation project on track.

In this guide, we’ll take you through all the steps involved in a home addition, from defining your needs to overseeing construction, and share useful renovation tips along the way.

1. Define your project’s scope of work

Defining the scope of work is the most important step in planning your home addition. While it may require a lot of work and time, this investment will help ensure the success of your project.

Prerequisite: The desire to expand your home

Tools and technique: Brainstorming, researching, finding inspiration, reading building guides, seeking out expert advice

Outcome: High-level description of the scope of work, list of requirements

To establish a clear direction for your home addition, begin by describing the problem you plan to solve. Take the time to understand your current situation and research what you want out of your renovations.

To get started, here are some questions to ask yourself:

TEMPLATE: Download Billdr’s project scope template

Once you’ve answered the questions above, build your project scope. Use this preliminary document to describe your project to a building expert (an architect, engineer, or interior designer). It should include your vision, goals, and requirements.

Farmhouse home addition
Photo credit: Wyant Architecture

2. Understand your municipality’s requirements

Prerequisite: High-level description of the scope of work, list of requirements

Tools and technique: Expert advice from your municipality

Outcome: Informal approval of the project (Note:you will not submit documentation to the City at this stage)

You can present your home addition project at your municipality’s office to find out if it is eligible for construction. A building permit may be required to move forward with the project. Rules may differ depending on your area and whether renovations involve house modifications, second-story additions, or home additions. To find out how to obtain a permit, here are some questions to ask your municipality:

Here are some documents that may be required when applying for a building permit:

In some cases, you may need to revise your project scope to get approval for a permit. For example, there could be building height restrictions in your area. So, instead of building upwards, you could build the extension sideways, either toward the backyard or on the side of the house.

Photo credit: Go building

3. Identify the experts you need

Prerequisite: High-level description of the scope of work, list of requirements

Tools and technique: Expert judgment

Outcome: List of stakeholders

Depending on the type of home addition that you are undertaking, different design and build professionals can work on your project consecutively, at various stages. As a general rule, the larger the project, the more stakeholders are involved. Usually, when it comes to a home addition, you will work with the following experts:

For a standard home addition project (with a budget of $100,000), an architect and a structural engineer will be involved.

Photo Credit: Go building

4. Hire an architect and design your plans

Prerequisite: High-level description of the scope of work List of requirements

Tools and technique: Meeting, brainstorming, data gathering, negotiations, expert advice

Outcome: Architect (or technologist) contract, high-level estimate

The architect (or architectural technologist) is responsible for providing guidance and bringing your vision to life. They’ll work with you to understand your reasons for extending your home, your style, and your design preferences while maintaining a sense of harmony between your current home and the new layout.

After discussing your preferences with you and taking measurements of your home, they’ll be able to draw a series of plans for various stages of your project.

  1. Sketches: Drawings outlining the layout of the space to be renovated
  2. Preliminary plans: Plans used to obtain a building permit
  3. Construction plans*: Plans explaining the work that needs to be done
  4. Demolition plans (if necessary): Plans showcasing elements that need to be taken out

*Though not mandatory in theory, construction plans are important for describing the work that needs to be done during your renovation, allowing contractors, subcontractors, and suppliers to estimate costs and build quotes, and can also be presented as a legal document for designs that need to be approved by a designated professional.

Photo credit: Dana Webber Design Group

5. Hire a structural engineer and develop plans

Prerequisite: Architecture plans High-level description of the scope of work, list of requirements

Tools and technique: Meeting, brainstorming, data gathering, negotiations

Outcome: Engineer contract

Home addition projects typically require both an architect (or architectural technologist) and a structural engineer. While the architect is responsible for designing the new layout and choosing construction materials and finishes, the structural engineer is responsible for designing and sizing structural elements (i.e. load-bearing components that hold a construction up, whether they are wood, steel, or concrete.)

Structural plans determine the structural elements of your home addition: foundation, concrete slab, load-bearing walls, columns and beams, and lintels above doors and windows. These plans give precise information to the general contractor on how to build the parts of your home addition that holds it up. According to the Law on Engineers, an engineer’s input is mandatory for any construction work related to a building’s structure.

General contractors can recommend a structural engineer that they’ve worked with. However, we suggest hiring an independent one to avoid potential conflicts of interest. Also, keep in mind that a contractor needs an engineer’s recommendations on structural work before being able to provide you with final quotes.

Learn more about the difference between architectural plans and engineering plans.

Billdr's backyard home addition project

6. Submit an application for building permits

Prerequisite: Plans (architecture, structure), Building sheet Certificate of location, On-demand technical sheets (window, door, exterior cladding), Payment

Tools and technique: Data analysis, expert judgment CCU

Outcome: Building permit issued by the city

A building permit is an authorization from your municipality to undertake specific renovation work, including home additions. As part of your home addition, you should aim to obtain a building permit from your municipality as soon as you receive architectural plans. Some areas may also require structural engineer plans for your project to be approved. In general, it takes between two and three months to get a building permit, depending on the municipality and the type of construction work.

7. Request quotes from general contractors

Prerequisite: Plans (architecture, structure)

Tools and technique: Site visits, Reading plans, consulting clients and professionals, Cost calculation, consultation of subcontractors and suppliers

Outcome: Quotes from general contractors

With both architectural and structural plans finalized, you can start receiving quotes from general contractors. To receive accurate quotes, it is important to provide them with complete project plans. If there is missing information, general contractors might have to double down on unnecessary efforts to revise their quotes.

Once documents are received, contractors interested in your project will visit your property to ensure that they fully understand the scope of the project and the environment that they are working with. This step will help them assess and visualize the different components of the construction site (e.g. entries, exits, overall condition of the house) since they impact the cost of the project.

Discussing with your contractor about your objective is a good exercise to do. Sometimes contractors will have new ideas to build upon architectural and/or structural plans and alternatives that could help reduce your costs or improve the quality of the work!

Should I discuss my budget with a contractor?

Short answer is yes!

Discussing your objective with your contractor is a good exercise. Sometimes contractors will have ideas that build upon architectural and/or structural plans to help reduce your costs or improve work quality.

General contractors ask clients about the budget to ensure that their time is well spent. Preparing a quote for a home addition project can take up to one week. Between design plans and actual construction, changes can occur along the way. Keep a contingency plan of at least 15% of your budget to cover for these unforeseen expenses and/or additions to the scope of work.

Curious about how much a home addition should cost? Read our full guide to building a home addition to crunch the numbers per type of extension.

Billdr partners exclusively with general contractors who have their license(s) and civil liability insurance, ensuring that your home is in good hands. To learn more about our vetting process, consult our guide to finding the right contractor for you.

By working with Billdr, you will get access to the portfolios of each general contractor who is interested in your project. In these portfolios, you’ll find their license number, areas of expertise, and photos of recent projects to help you decide who you want to hire.

8. Hire a general contractor

Prerequisite: General contractor’s quote

Tools and technique: Meeting, negotiations

Outcome: General contractor’s contract

After meeting with several general contractors and receiving their quotes, you will have a better sense of who you want to work with. At this stage, you will be able to choose and hire a general contractor to carry out construction on your project.

Once signed, the quote becomes a binding contract. So, before moving forward with the quote, make sure that it includes the following information:

Tips for hiring your general contractor

  1. Make sure that the general contractor has a valid license and liability insurance (minimum $2,000,000) to protect your property and your neighbor’s during construction
  2. View the general contractor’s project portfolio to get a good sense of their experience
  3. Check the general contractor's availabilities to see when work can begin
  4. Verify payment terms
Billdr's living room home addition project

9. Begin construction work

At the beginning of a project, the first few days are dedicated to site mobilization. During this time, the general contractor installs protective measures to secure the site and existing installations (e.g. covering floors), sets up temporary services (e.g. on-site lighting), and secures a waste container, among other things. Afterward, when necessary, their team will carry out demolition work before proceeding with the new construction.

Building a home addition or second-story addition involves several stakeholders. Though a general contractor may have to execute part of the construction, they usually work with specialized subcontractors (e.g. electrician, plumber, excavation company). Their role is to manage those build professionals on-site to get the project done. As the primary contractor, they will also be responsible for ensuring that the work being carried out is in accordance with laws, regulations, and building codes.

Establish a communication channel

There is no such thing as too much communication during a construction project! As soon as the contract is signed, decide on which is the most effective communication channel for both you and your general contractor. This allows for regular construction updates, next steps planning, site visits coordination, invoice and payment follow-ups, and change management. Despite having a trusting relationship with your contractor, we also recommend keeping a written record of your communications to have something concrete to look back on.

Manage mid-project changes

It is not unusual for changes to happen in the scope of work during a construction project. These mid-project changes can include additional work (which may incur extra costs) or canceled tasks (which becomes a credit to your contract’s value).

Changes can become a source of conflict if a process on how to manage them has not been agreed on beforehand. For instance, make sure that any change in the scope of work requires your approval first. This means that the general contractor will need to share the price of the changes before related work can begin so that there are no additional surprise costs at the end.

Review your project scope

Your project’s scope of work serves as a baseline and may change over time. As the project develops, there may be new opportunities or alterations to initial designs. To remain aligned, the scope of work must be reviewed regularly and changes must be communicated to each stakeholder involved in the project.

Monitor the construction schedule

Monitoring a pre-established schedule helps you measure the progress of your project over time. It allows you to identify and document causes of delays in construction if they occur, and plan site visits more efficiently.

Track costs

Tracking your costs allows you to control your budget and account for expenses. Your budget should have a specific amount dedicated to paying for the general contractor’s work and another amount to account for contingencies. You should also keep track of the amount you have spent on changes.

Maintain quality control

Quality control is performed through weekly on-site evaluations to see if work has been completed according to the terms of your project scope. There are key moments where these visits should occur — usually during structural changes, electrical installation, thermal insulation, waterproofing against moisture and water, or concrete pouring.

10. Approve the construction work

The end of your home addition is often signaled by the final approval of the work that has been completed. This process is carried out in 2 stages:

To start, there is the deficiency visit. You will need to visit the construction site with the general contractor in order to see if there are any irregularities and uncompleted work (also known as deficiencies). The contractor’s role is to note and document all the deficiencies that have been found on work that they were responsible for.

Once deficiencies have been corrected, you can take possession of your new home addition! This is the moment when responsibility for the premises transfers from who was in charge of the project (general contractor) to the homeowner (you). Call your insurer to update your home insurance and to add the new extension since it was covered by the general contractor's insurer until now. To learn more, consult our guide on insurance for renovations.

Billdr's kitchen home addition project

11. Complete your home addition project

Once work is completed and all deficiencies are corrected, the contractor will have fulfilled almost all his contractual obligations. To finalize the project, they must give you a letter of guarantee. Once you receive the latter, you can pay your last invoice, which marks the end of your project!

Not ready yet?

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