House Plan Modifications: Adapt a Design to Fit Your Needs

Customize Your House Plan with the Help of Our Residential Designers

Our house plan modification service allows you to customize one of our existing designs to create a home that fits your needs perfectly, without starting from scratch. Whether you want to add a bedroom, expand a garage or reconfigure the layout, our residential designers will guide you through every step of the process.

Not sure whether you need a pre-designed house plan, a modified plan or a fully custom home design? Explore our comparison guide to better understand the differences and choose the solution that best fits your lot, budget and lifestyle.

Meet with a residential designer at one of our Drummond House Plans offices or work with our team online from anywhere in North America.

Get a free modification quote Find a house plan to modify

Gianluca from our Laval office

All of Our House Plans Can Be Modified

Our team can customize any design from our collection to meet your specific needs and preferences.

We strongly recommend planning your modifications before purchasing your house plan. Doing so can help reduce costs, avoid unexpected changes and streamline the design process.

Whether you need additional living space, a different layout, a larger garage or other custom adjustments, our residential designers can help adapt your chosen plan to fit your lot, budget and lifestyle.

Original plan

Original house plan before modification by Drummond House Plans showing the initial design selected by the homeowner.

*If you would like to modify one of our existing plans or create a completely custom home design from the ground up, please contact one of our Drummond House Plans offices or work with our design team online.

Customize your plan and get expert assistance online or through a Drummond House Plans office near you.

Modified house plan customized by Drummond House Plans to better fit the homeowner's lot, budget and lifestyle.

Modified plan

How Much Does a House Plan Modification Cost?

The cost of a modified house plan is calculated using a simple formula:

Base price of the selected house plan

Modification fees

(hourly design rates)

On average, a construction-ready plan that includes custom modifications represents approximately 0.75% to 1.25% of the total construction value of the home.

Transparent Pricing

Our modification fees are based on a transparent approach tailored to the scope and complexity of each project.

Detailed Quote Before Approval

Before any work begins, you will receive a detailed written quote outlining the proposed modifications, associated services and estimated completion timeline for your review and approval.

Request a free quote

House Plan Modification Timelines

The time required to complete a house plan modification can range from a few days to several weeks, depending on a variety of factors, including:

The time of year and current workload
Client review and approval times
The number of modifications requested
Additional changes made during the design process

Because every project is different, we establish a realistic timeline from the beginning to help ensure your expectations are met and your project progresses smoothly.

Our Residential Design Services

Modify an Existing House Plan

Customize one of our 1350+ house plans to fit your lot, lifestyle and budget.

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Custom Home Design

Create a fully custom home designed specifically for your lot, lifestyle and vision

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Home Renovation Plans

Transform your existing home with renovation plans tailored to your needs and goals.

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6 steps to modify your house plan

To avoid expenses and delays it is important that you prepare details for your new construction project before buying your house plan and contacting us. Here are the important information regarding your future home plan that you need to collect prior to contacting us:

Buy the land and verify with your municipality about the rules governing your area such as setbacks, mandatory building materials, etc.
Verify your available financing for the construction of your house or cottage from your banking institution.
List the essential elements of your custom home design. This list varies from one family to another and must include: the desired architectural style, the number of bedrooms and bathrooms, required additional rooms such as an office, a gym, a games room, a sheltered balcony (rear or side), desired type of foundation, etc.
Add photos and / or sketches, as needed.

How to prepare for your project

Choose your plan from one of our house plan collections below: click on the link below and you will access all of our plans. Once on this page, use the filters provided in the left column to obtain a group of plans corresponding to your specific criteria (price, number of rooms, style, etc.).

Find my dream house plan

Choose the regional office nearest you and make an appointment. One or more meetings with a Drummond Design expert will allow us to understand your family's needs in terms of space and lifestyle and ensure that your customized plan will correspond to your exact expectations and your budget. We can also visit your home or site of construction, if you wish ($).

Our 30 regional offices

Within 2 to 5 working days following the receipt of your documents by email or a meeting at one of our 30 Drummond House Plans regional offices, or at a time agreed between us, a written estimate and details regarding our service offer and timelines regarding initial project delivery will be provided for your approval. The delivery time of a construction plan can vary from a few days to a few weeks depending on the time of year. Following the receipt of your preliminary plans, timelines may be readjusted depending on the time required for your reflection and the number of revisions required.

Following the approval of our estimate (STEP 3) as well as acceptance of the delivery timelines of your final plan, sketches can be made for you to ensure that we have the same vision as you have of your project.

We will then proceed with the production of the preliminary plan which may include, among other things, floor plans and elevations of the 4 sides of the house, or any other information relevant to your project.
We will then follow up by emailing or handing over your preliminary plan to ensure that all details are in line with your expectations. If you wish, and we have provided for by agreement, different design options can be presented to you.
At this stage we will make corrections as needed until the entire plan is perfect for you. One to three discussions or meetings are usually enough to allow you to approve the final project.
It is always possible to add various additional services to your plan such as the electrical plan.
At this stage it is also best to get quotes from one or more construction contractors.

Additional services Technical information

The preliminary plan is 100% to your liking? Your Drummond House Plans professional then proceeds to the detailed development of all of the construction drawings for your project.

Receive your final construction plan for your future house or cottage, in small or large format PDF and / or the number of printed blueprints you want, and as agreed to in your estimate.

You now have all the information you need to meet the contractor of your choice and get quotes for your construction work. The Drummond House Plans design team will also be available to answer your questions or those of your contractor before or during the work.

Frequently Asked Questions About House Plan Modifications

Can an Existing House Plan Be Modified?

Yes. All Drummond House Plans designs can be adapted to fit your lot, budget and lifestyle. Our residential designers will review your project and recommend the best solution.

How Much Does a House Plan Modification Cost?

The cost depends on the number and complexity of the changes requested. On average, a construction-ready house plan that includes custom modifications represents approximately 0.75% to 1.25% of the total construction value of the home. We provide a free personalized quote before any work begins.

What Parts of a House Plan Can Be Modified?

Almost anything can be modified, including the layout, square footage, number of bedrooms, garage size, foundation type, exterior appearance and room configuration.

Why Modify a House Plan Before Construction Begins?

Making changes during the design phase is usually faster and more affordable than making changes during construction. Early planning also helps avoid costly surprises.

How Long Does a House Plan Modification Take?

Timelines vary depending on the complexity of the project and current workload. Most modifications are completed within a few days to several weeks.

Can I Work with Your Team Online?

Yes. Our team can guide you through the entire modification process online, wherever you are located in North America.

Can I Add a Bedroom, Expand a Garage or Change the Layout?

Absolutely. These are among the most common modifications we perform. Our designers can help adapt the plan to better suit your family's needs.

Can I Modify a House Plan After Purchasing It?

Yes. However, planning your modifications before purchasing the plan is usually more efficient and can help reduce costs and delays.

Can I Change the Foundation Type of a House Plan?

Yes. Many house plans can be adapted to different foundation types, including full basements, slab-on-grade foundations, crawl spaces and walkout basements.

Can I Increase the Size of a Garage?

Yes. Garage expansions are among the most common house plan modifications. Our residential designers can help adapt the garage size to your vehicles, storage requirements and lifestyle.

What Is the Difference Between a House Plan Modification and a Custom Home Design?

A house plan modification adapts an existing design by adjusting elements such as the layout, garage, square footage or foundation. A custom home design is created entirely from scratch based on your lot, budget and lifestyle.

Want to learn more? Explore our complete guide to custom home plans and compare the different design approaches available.