Skip to main content
+1 647-466-6989
Luxury custom home in Thornhill built by AVL Custom Homes

Old Thornhill · Royal Orchard · Uplands · Bayview Glen

Custom Home Builders in Thornhill

Custom homes in Thornhill, by referral — on both sides of Yonge Street, with Vaughan or Markham permits and Don River valley planning.

Custom Home Services Plan Your Build
One community, two cities

Your side of Yonge Street decides who issues the permit.

Thornhill is not a municipality of its own. The part west of Yonge Street is in the City of Vaughan, and the part east of Yonge is in the City of Markham. Building permits come from Vaughan’s or Markham’s building department depending on your address, and each city has its own zoning rules and Committee of Adjustment.

Both cities protect the historic core. Old Thornhill along Yonge Street is covered by heritage conservation districts in Vaughan and in Markham. Work on a property inside a district usually needs heritage approval, and new homes are reviewed for how they fit the historic street.

Outside the core, Thornhill grew in the 1960s and 1970s. Royal Orchard, Uplands, Bayview Glen and German Mills have many split-levels and two-storey homes on medium to large lots, and some ravine properties along the East Don River and German Mills Creek. These valleys are regulated by the TRCA.

AVL builds custom homes by referral. Many Thornhill clients first work with us on a renovation or the Annual Home Maintenance Plan before planning a new house.

AVL in Thornhill

Home maintenance, renovations and custom homes by referral.

Thornhill’s 1960s and 1970s houses are solid but dated. We help owners keep them healthy, update them or replace them.

Annual Home Maintenance Plan

Yearly condition reports and seasonal visits for Thornhill homes on both sides of Yonge, from $119/month.

Split-level renovations

Open layouts, new stairs and updated systems for 1960s and 1970s split-levels.

Additions

Second-storey and rear additions that meet Vaughan or Markham zoning.

Custom homes by referral

New homes on Thornhill lots, including heritage and ravine properties.

Why Thornhill needs care

Two sets of rules and a historic core.

The same street name can sit under different rules in Thornhill. Knowing which city, district and watershed apply avoids delays.

Right municipality

We confirm whether Vaughan or Markham reviews your project before drawings start.

Heritage guidelines

Inside a district, design choices follow the district plan.

Valley lots

TRCA set-backs and slope reviews apply on many ravine properties.

Lasting care

Our maintenance plan keeps the finished home in good shape.

Thornhill requests

What Thornhill families want in a new home.

Thornhill clients often have multi-generation households and large extended families.

  • Main-floor bedrooms for parents or grandparents.
  • Large dining areas for family gatherings.
  • Separate entrances for lower-level suites.
  • Quiet, efficient heat pumps and good ventilation.

Care that continues after the build

Thornhill homeowners tend to stay for a long time. AVL connects Design | Build | Protect, so the team that built or renovated the house can maintain it.

Explore the Maintenance Plan On-Demand Maintenance
Service Area

Serving Thornhill in Vaughan and Markham

Municipal check

Vaughan or Markham zoning confirmed for the address.

Heritage review

District guidelines checked near Old Thornhill.

Valley mapping

TRCA regulated areas and slopes mapped early.

Thornhill approvals

Approvals that can apply in Thornhill.

Which approvals you need depends on your side of Yonge and your exact lot.

Building permit

From the City of Vaughan or the City of Markham.

Committee of Adjustment

Each city has its own committee for minor variances.

Heritage approval

For properties in the Thornhill heritage conservation districts.

TRCA permit

For regulated areas along the Don River branches and creeks.

How we build in Thornhill

Four steps, whichever city you are in.

Our process is the same in Vaughan and Markham; only the forms and reviewers change.

1. Address review

Municipality, zoning, heritage and TRCA mapping confirmed.

2. Design and budget

Plans developed to fit the rules and your budget.

3. Approvals

Permit, variance, heritage and TRCA applications as needed.

4. Construction

Building, inspections and handover.

Owner Preparation Guide

Preparing for a Thornhill consultation.

Useful documents

  • Survey or lot plan.
  • Property tax bill showing Vaughan or Markham.
  • Any heritage or TRCA letters.
  • Photos of the house, yard and trees.

Key choices

  • Renovate or rebuild.
  • Rooms and suites you need.
  • Budget and timing.
  • Ongoing maintenance after move-in.
Thornhill questions

Frequently Asked Questions

Is Thornhill in Vaughan or Markham?

Both. Thornhill west of Yonge Street is in the City of Vaughan, and Thornhill east of Yonge is in the City of Markham. Your address decides which city issues the building permit.

Is my Thornhill home in a heritage district?

Old Thornhill along Yonge Street is covered by heritage conservation districts in both Vaughan and Markham. Properties inside them usually need heritage approval for exterior changes and new homes.

Does the TRCA regulate my lot?

Lots near the East Don River, German Mills Creek or other Don tributaries may be in the TRCA regulated area, which can require a permit and set-backs from the slope.

Can I add a suite for my parents?

Often yes. Both Vaughan and Markham allow additional residential units in many houses, subject to zoning and the building code. We check the rules for your lot.

Does AVL maintain homes in Thornhill?

Yes. The Annual Home Maintenance Plan is open to every home in the GTA, on either side of Yonge Street.

Google feedback

What our clients say.

Reviews from our Google Business Profile.

5.0

Google Rating · 15 Verified Reviews

Write a ReviewView All on Google

Antony He

2 months ago

Got the Gold Plan with AVL Custom Homes about 4 months ago. I wanted to wait and see if it was actually worth it before leaving a review.

We ended up having some random issues around the house recently, and Ali literally took care of everything. He dealt with the contractors directly, coordinated everything, and got the issues fixed so we didn't have to deal with the headache ourselves.

The reports they send are great, and they actually do what they promised. Having someone who knows the house, keeps track of things, and takes care of issues when they come up has given us a lot of peace of mind.

Definitely recommend AVL if you want reliable home maintenance and someone you can actually count on.

kosoku ko

8 months ago

We hired AVL Custom Homes to manage and complete a full house renovation, including our kitchen, bathrooms, and flooring. From the start, they were easy to work with and very organized. Communication was clear, and we always knew what was happening next.

We also chose them for project management, and that turned out to be the right decision. Scheduling and coordination were handled smoothly, and the accounting was very transparent. As with any renovation, there were some unexpected costs, but everything was clearly explained in advance and there were no hidden charges. Ali was very knowledgeable and took the time to explain issues and suggest practical, cost-effective solutions when challenges came up.

Overall, the project was well managed from beginning to end, and we are very happy with the final result. We would recommend AVL Custom Homes to anyone looking for a reliable company to handle a full home renovation.

Ali Ahadian

8 months ago

After several poor experiences with unreliable contractors, I was referred to AVL Custom Homes and immediately noticed a difference in their professionalism and technical expertise. Ali and his team consistently identify issues accurately and propose practical, cost-effective solutions.

I started with their Oversight Plan and later upgraded to the Concierge Plan after seeing their reliability, even for small issues and in difficult weather. Along with higher-level service, it brings real peace of mind for a busy homeowner. Based on this experience, I have also entrusted them with the maintenance of my office. I would recommend AVL Custom Homes to anyone seeking dependable and professional property oversight.

Brian Chan

9 months ago

I have relied on AVL Custom Homes for years and wouldn't trust anyone else with my properties. They have handled everything for me—from a full custom build and residential renovations to commercial services and ongoing property maintenance. They even provide home oversight, which gives me total peace of mind.

I'll be honest: their pricing is a little higher than the market average, but the quality of work and the level of responsibility they take make it worth every penny. They are experts who know their job inside and out, and they always take the time to explain every detail. If you are looking for a professional in the GTA who delivers high-quality results and zero stress, AVL is the best choice.

Raymond Reid

8 months ago

We recently signed up for the Gold Plan with AVL Custom Homes, and the first 'House Condition Report' was eye-opening. While scanning the house with a thermal camera, the team discovered a hidden leak in an exterior wall caused by a faulty roof downspout. We had no idea this issue existed for years!

The level of detail Ali and his team put into the deep inspection was impressive. It’s clear they truly care about the long-term health of the homes they manage. I highly recommend this service to any homeowner who wants professional, deep-dive maintenance and real peace of mind.

Verified reviews via Google Business Profile · View all reviews on Google

Planning a new home in Thornhill?

Explore Design & Build Custom Homes, review the custom home cost guide, understand permit-ready planning, or contact AVL Custom Homes to confirm your municipality, approvals and budget.

Plan your Thornhill home