License #565275

Customer Reviews

Cornerstone Windows - Customer Reviews

At Cornerstone Windows & Patio Doors, we combine the best window and door products with superior service.

With more than 3 decades of construction expertise, we’ve developed an installation system that eliminates damage to stucco and drywall. Our expert, in-house installers go to great lengths to protect your floors and furniture as they work. Most projects are completed in a single day.

Customers often compliment our installers. We thrive on these wonderful business relationships while serving residents throughout the South Bay and West Los Angeles areas.

People Love Us On Yelp - Cornerstone Windows & Patio Doors 2019 Award Recipient

  • Another satisfied customer!

    Cornerstone Dana

  • Another satisfied customer!

    Cornerstone Dave

  • Another satisfied customer!

    Cornerstone lisa
  • Dear Mr. Szik,

    We recently had the pleasure of inviting Cornerstone to install a sliding patio door and bedroom window. We were pleased enough with the first installation, we extended the invitation for additional windows. Now that we have the new windows, we don’t know why we waited so long. You’re to be commended for assembling such an outstanding work crew and office staff. From the first introduction to Marilyn and Maggie, I knew we had selected the right company. The installation crew was professional, well mannered and a delight to work with (can I adopt them?).

    You have a company you can be proud of.

    Our thanks once again for being the kind of company that we had hoped still existed.


    Peggy M., Wayne S., Palos Verdes Estates
  • Cornerstone Windows’ customer Pam R. tells how her new Marvin Bow Window has transformed the front of her West Los Angeles home.

    Pam R.
  • Dear Tony, Marilyn and Wonderful Installers,

    Thank you for great service and care. I selected Cornerstone because you were local, received no hard sell, liked Marilyn instantly and could trust your company. There are no leaks during this recent deluge and the new windows have also cut down on my heating bill. I’ve never seen workers do their job so quickly and with so much care.

    Thanks again,

    Shirley K., Torrance
  • Dear Tony,

    Donna and I want to thank you for the wonderful job you and your crew did last Thursday. The windows look great and are performing beautifully. We need some really cold weather to test them out. What we appreciate the most is the conduct of your crew. Everyone was polite and performed in a professional manner. They answered any questions and cleaned up. We were impressed by the teamwork and the fact they were able to get everything done in one day. It was obvious the crew had done this before and are a reflection of the owner’s pride in providing service.

    We will recommend Cornerstone to our friends for future installations.

    Dennis and Donna
  • Dear Tony and Marilyn,

    Thank you once again for the beautiful windows, doors, and of course, the outstanding customer service. Our experience with your company is first rate. Quality, Value and Customer service is evident from the order, the product and the install. Thank you Marilyn for your deep empathy and care. Sandy is on her way to recovery. Hope all is well. Hope to see you soon to get the other windows.


    Matt & Sandy H., Rolling Hills
  • Hi Tony,

    I was extremely pleased with your crew, the great quality of the materials and the exceptional work they did on my windows today.

    Your guys were friendly, courteous and very skilled and careful as they did their work. I know the bathroom window and back door were challenging, but they stepped right up and did a great job. I could not be happier with the outcome. The windows and doors look so attractive with the new vinyl trim that it feels like the outside of my house has been remodeled. Thank you so much for working with me on this project. You’ll have my business in the future. I’ll be sure to give referrals too, if I hear of anyone needing window work.

    Thanks again,

    Camille, Torrance
  • Dear Tony,

    I want to thank you for helping us on the installation at the third home you have worked on for us. It has been such a stressful time as the move date has come and gone serveral times. Also every service provider has changed their schedule or prices, thus causing frustration and anxiety. You have 100% always delivered what you say and when you say it will occur.

    My trust in your company is so great that I’m leaving the condo unlocked and the check under the doormat just to make life easier. Trust like that is unheard of unless you’re good friends or close family.

    On the subject of family, I had the pleasure of meeting your son when the team were installing at a neighbor’s home. He was as dedicated as you have always been and was proud of his work. All employees are content and feel respected, as that team obviously did that day, they feel ownership over their work. What a great way to run a company.

    Take care!

    Cara B., Hermosa Beach

  • Cornerstone Windows’ customer, Lisa G. talks about how the staff made her feel very confident through the entire sales and installation process.

    Lisa G.

  • Another satisfied customer!

    Sherri, Redondo Beach, CA

Angie’s List

“Cornerstone made it simple and easy to get all of our windows replaced. They had a full crew, arrived on time, spread protective covers over everything, and handled the entire window replacement process (including sliders and screens) in a quick and professional manner. We had investigated several other firms and took the recommendations of our complex’s maintenance manager and went with Cornerstone. Based on results, it was one of the best recommendations we have ever received for any kind of home maintenance, upgrade and repair work.”  -Angieslist.com, Mike R. of Rancho Palos Verdes

“From our initial visit in the showroom to the consultation and measuring in our home and then the installation, the products, staff, professionalism and the experience was outstanding.” – Angieslist.com,  Ed B.  of Rancho Palos Verdes

“Excellent!!! extremely pleased with installation of 17 windows. The crew were friendly and very clean. I will be sure to have referals, and my business again” –  Angieslist.com, Diamond S. of Los Angeles.

“I am writing this review because I broke the handle on my sliding door today and went to their shop to inquire about a replacement. They immediately brought me the replacement handle and off I went. No hassles. Cornerstone was awesome when they did the install several years ago. Punctual. Professional. No surprises. My two experiences with Cornerstone have been great and I would recommend them to anyone looking to replace windows or doors. ” -Angieslist.com, Sandra M. of Redondo Beach


“We love our new windows!!! Tony was awesome and answered all our questions. The installers did a fantastic job! Everyone we dealt with was very professional and courteous. They were also very reasonably priced. We would definitely recommend them and will use them again. Thanks guys! :)” – Yelp review, Jaime E. of Lakewood.

“Good price, good quality and professional installation with a great warranty. They were always on time for appointments. I would definitely do business with them again and refer them to family and friends or anyone looking for replacement windows.” – Yelp review from Chris M. of Palos Verdes.

“The windows themselves (Milgard) are perfect! I couldn’t have wished for a better design. They are a very close replica of what we had originally. I am really happy with them, really happy with Cornerstone & I would highly recommend them.” – Yelp review from Rebecca P. of Hermosa Beach.


“A pure pleasure to work with this company. Cornerstone should be very proud of their employees. The fellas that installed my windows were timely, courteous and well mannered. I would recommend them in a heartbeat.” – Yahoo review, Annie.

“Cornerstone Windows met all if its deadlines as promised, performed quality workmanship and had the best price in town. I would highly recommend Cornerstone for any remodeling or construction job relative to windows and doors. From the owner to the sales & office staff to their excellent installation team, I couldn’t have asked for more excellent service.” – Yahoo review, satisfied customer.

We Exceed Expectations

Cornerstone is dedicated to surpassing your expectations for window and door installations.

Contact our window replacement experts now at 310-325-4700 for a free in-home estimate.

Tony Szik's Cornerstone Doors & Windows, Inc., Door Installation, Torrance, CA

Cornerstone Windows is A+ rated from the Better Business Bureau since 2002