Great Windows is your local business service provider in top window installation service, proudly serving Markham and surrounding areas of Ontario, CA. We are offering high-quality replacement windows and doors, competitively priced with a level of service second to none.
We live in Markham, we work in Markham, we shop in Markham, when we do your custom windows and custom doors we give you the attention and customer service that you would expect from a neighbor because, quite simply, we are your neighbors.
Great Windows is there to offer you top quality replacement windows and replacement doors, installed to the highest standards with a level of customer service at a cost-effective price point that will mean that you will want to refer us to your friends and neighbors. We rely on customer referrals to grow our business and we’re pretty good at getting those customer referrals. We must be doing something right!
We believe that buying replacement doors and windows doesn’t have to be difficult.
- An initial consultation that will tell you what you need to know in a way you need to know about replacement windows and doors.
- An easy to understand quote that itemizes everything so that you can see what you’re paying for what
- Aggressive pricing
- Top flight customer service before, during and after installation

Our Process Window Installation Service
When you call or email us we book a consultation appointment where initial measurements for all replacement windows and doors are taken. We provide you with a detailed and itemized quote that includes everything, there are no surprises. We are available for quotes 7 days a week.
Once you accept our quote we typically request a 35-50% deposit (depending on the size of the project) ahead of ordering from the manufacturer. We also measure the window and door openings again prior to ordering the replacement windows and doors. We employ specialist window installers and it is their job to ensure quality so they measure again to ensure accuracy. We accept cash, cheque, and credit card for payment.
Installation dates are typically 6 weeks out and we book a date once you give us the go ahead. We install windows and doors in all seasons (leaving aside monsoon rains or snowstorms), you will lose energy when we install anyway and we do our best to leave the opening unenclosed for as short a time as possible.
We follow up three months later to ensure that everything is to your satisfaction. We never hide from our work.
Windows
OK, so you’ve got casement windows, double hung, single hung, picture or fixed and on and on. Go take a look at our products to get a better idea of what on earth we’re talking about.
Entry Doors
The door, the sidelight or sidelights, the colour, the amount of glass, the patterns on the glass. It’s ok, we’ll walk you through it, if you’ll pardon the pun!
Patio/Garden/French Doors
Nope, it doesn’t get simpler, sliding doors or gliders (or scratchy non gliders if the kids are dragging dirt in from outside), French doors, garden doors or patio doors. Steel or vinyl. We prefer vinyl.
Great Windows
20-15 Heritage Road
Markham ON
L3P 3T1