"Working with James was great from the beginning. He put my mind at ease with his product knowledge and his creative designs."

Landscape design & stone masonry in Markham.
Astonia Landscaping designs and builds high-end residential landscapes and natural-stone masonry in Markham. Owner James Dennison is a third-generation stonemason, and Astonia has been doing this work since 1975. Every Markham project is owner-led, built by our own WSIB-covered crews with our own equipment, and backed by $5 million in liability insurance. We are a Unilock Authorized Contractor.
- Since 1975
- 3 Generations
- $5M Insured
- WSIB Covered
- Unilock Authorized
Landscaping that belongs in Markham.
Markham holds two very different kinds of property under one municipality, and a stone landscape has to answer to both. In Unionville and along the older heritage streets near Main Street, you have established homes on mature lots where the architecture and the streetscape already have a settled character — work here calls for restraint, natural stone that reads as if it has always been there, and detailing that respects the age of the house rather than competing with it. In the executive enclaves of Cachet and Angus Glen, the homes are larger and newer, the frontages more generous, and the expectation is a designed, cohesive landscape that matches the scale of the architecture. We design for the property in front of us, not a template.
Many of these are established executive homes on settled lots, which usually means mature trees, finished grading and existing hardscape that a new build never has to work around. Protecting healthy specimen trees, tying new stonework into established planting, and matching the grade and drainage already in place takes more planning and more care than a blank site — and it is exactly the kind of work that benefits from owning our own equipment and running our own crews, so there are no subcontractor delays and no guesswork on a property where mistakes are visible for decades.
Markham homeowners making a once-in-a-generation investment in their property tend to value the same things we do: craft that lasts, a clean and respectful site, and direct communication with the person responsible for the work. James is on your project and reachable every day. We haul all debris away in our own trucks — no bins parked on the driveway of an established street — and we leave the site tidy each evening, because in a settled neighbourhood the condition of the site matters as much as the finished result.
From first handshake to final reveal.
Initial Consultation
We meet you on-site to walk the space, understand how you want to live in it, and talk through your vision and investment — no obligation.
Design & 3D Review
Our designer measures and plans your space, then renders it in 3D so you can see it before we break ground. We refine every detail together.
Breaking Ground
Our own crews and equipment start at 7:00 AM, keep the site clean every day, and brief you each morning and evening — no subcontractor gaps, no bins.
Project Completion
After a final walkthrough, the only thing left behind is your finished space — built to gather on for generations.
Why homeowners in Markham choose us.
Owner-led
Daily communication from James, from the first handshake to the final reveal.
Our own equipment
Small and heavy machines, run by our own crews — no subcontractor delays.
No unsightly bins
We haul every bit of debris away in our own trucks, every day.
$5M insured
Liability coverage above the industry average, for your peace of mind.
WSIB covered
A fully covered, professional crew on every project.
Unilock Authorized
Warranty-grade materials and professional installation standards.
Kind Words
Homeowners across the GTA, on the Astonia experience.
Five decades of referrals across the GTA & Durham — and a Unilock Authorized Contractor. Read more on Google & Houzz.
"The natural stone work and landscape job that James and his crew did is beautiful, outstanding work. The quality is outstanding — we would recommend this company to anyone."
"Astonia was a delight from start to finish. The crew showed up early and worked long days to finish on time. We are now enjoying the most amazing front yard. Outstanding results!"
"As a repeat client, we selected Astonia to transform our simple backyard into a relaxing space amongst a natural setting that will bring us many years of pleasure."
Landscaping in Markham, answered.
We design and build across the GTA & Durham region — including Toronto, Etobicoke, Mississauga, Brampton, Oakville, Vaughan, Markham, Newmarket, Aurora, King City, Whitby, Oshawa, Bowmanville and the surrounding areas.
Every project is different — from focused stonework to a full landscape transformation — so we provide a clear, detailed proposal after an on-site consultation rather than a generic price. Most of our work is a meaningful, lasting investment in your property.
Timelines depend on scope, and you receive a realistic one at the design-review stage before we break ground. Because we own our equipment and run our own crews, we work efficiently — starting at 7:00 AM and keeping the site clean every day.
Yes. We carry $5 million in liability insurance — above the industry average — our crews are fully WSIB covered, and we are a Unilock Authorized Contractor.
Yes. Our designer visits your home to measure and plan the space, then renders your project in 3D so you can see it before any work begins. We review and refine it together until it is right.
No unsightly bins on your driveway — we haul everything away in our own trucks and leave a tidy site every day.
Astonia is led by James Dennison, a third-generation stonemason with five decades of craft. You get the expertise of a large company with the warmth and accountability of a family business, owner-led from start to finish.
Your Markham project starts here.
Book a free on-site consultation. We design, build and plant the whole space — then haul it all away when the last stone is set.
$5M insured · WSIB-covered crews · 3rd-generation craftsmanship since 1975




