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Cornerstone Windows & Doors

Acoustic Ceiling Tiles - Install, Doors (Interior) - Install or Replace, Major Home Repair (General Contractor),

About us

Cornerstone Windows & Patio Doors is a full service replacement window company in business since 1999. Cornerstone installs quality window products from Simonton and Milgard. Cornerstone's sales approach is low key and realizes an informed consumer makes the best decisions for his or her home. Most installations take only one day and normally do not involve dry wall or stucco damage. All employees are fully bonded and insured. Cornerstone does not employ any subcontractors. Cornerstone takes meticulous pre-sight measurements to insure all installations fit correctly and some products come with a glass and screen breakage warranty. Cornerstone is a proud supporter of a number of local high and grade school teams and activities in the South Bay area of Los Angeles.

Business highlights

26 years of experience

Services we offer

French Doors & Entry Doors, Patio Doors, Replacement Windows

Amenities

Free Estimates

Yes

Reviews
4.736 Reviews
Number of StarsImage of DistributionNumber of Ratings
5
89%
4
3%
3
3%
2
3%
1
3%
Showing 1-25 of 36 reviews
Mike R.
Jul 2018
5.0
Yes, I recommend this pro
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. Mike Rounds and Nancy Miller

Edward N.
Jan 2018
5.0
Yes, I recommend this pro
From beginning to end the process was smooth and professional. Naturally it took a while for the manufacturer to make the windows and doors. Cornerstone did the job in the 1 1/2 days promised. The crew was great- did a lovely installation and cleaned up well.

Sandy R.
May 2017
5.0
Yes, I recommend this pro
I thought the process went amazingly smooth. We have three buildings that required multiple windows in each unit. They knocked it out so quickly and so professionally. Tony worked with me on EGRES requirements as wee coordinate with the city to ensure that we were properly permitted. The installers who worked with me were very conscientious, organized and did excellent work. I have had contractors here for large projects were it felt like a black crowd came over the properly until they left, but in all sincerity, I looked forward to seeing them each day. Communication was excellent, as was the workmanship. Very happy with the job, and would highly recommend especially for large projects.

Christine S.
Mar 2017
5.0
Yes, I recommend this pro
We had six bids on this project. Tony was great. No high pressure but knew his product well and how it could work for us. The installation process was great. He has an amazing crew that cleaned up every day and answered all of my (very picky) husband's questions. We love our new windows!

Arianna P.
Oct 2016
5.0
Yes, I recommend this pro
$13,000
Replacing the windows in your home isn't your typical run of the mill purchase. It's an investment, one that will add value to your home. We knew right away that replacing our windows was at the top of our list for home renovations, so we wanted to do the proper research before settling on a contractor. We also wanted to take it a step further and accompany new windows with shutters. Granted there are a lot of businesses who offer great deals and have proven to do an amazing job. Comparatively looking at Cornerstone (when it came to windows) we knew right away that Tony had both the experience and the competitive pricing that placed them at the top of our list. When we discovered that they also provide shutters (one of the few Windows contractors who do), and laid out pricing for BOTH, the combined pricing was in fact better on our pockets, and left us with the peace of mind knowing that we would be dealing with just one single contractor for both needs. Cornerstone was simply the best choice for us. Tony brought us through the entire process, offering excellent advice when comparing windows and shutters and helped us come up with a solution which worked best - based on whichever window line we decided on. Thankfully we made the right choice going with Simonton. His staff are some of the most professional we've ever dealt with. They were amazingly fast and care about the little details. Once they were done, we honestly couldn't tell that the crew had been working all day inside and outside of our home. The finished job looks stunning and added so much curb appeal to our home. All of our neighbors have commented and said how much they love the new windows. Owning an older home with 20+ year old windows can turn your home into an oven on hot days, which can be very uncomfortable considering we don't have central air. The quality of these windows have insulated our home so well, that we're reconsidering whether we even need central air. We couldn't recommend a better contractor for windows installation. If you're considering both windows AND shutters, then there is simply no better option considering our amazing experience with Tony and his team. We can't thank you enough!!!

Casey C.
Oct 2016
5.0
Yes, I recommend this pro
The job was outstanding, they were on time, fast, clean and did an excellent job. Tony and the boys were friendly and very professional,

Virginia D.
Oct 2015
5.0
Yes, I recommend this pro
$15,000
.

Sandra M.
Mar 2014
5.0
Yes, I recommend this pro
$3,000

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.



Beth M.
Jan 2014
5.0
Yes, I recommend this pro
$4,000
I would love to have wood, but those are very expensive.  I replaced 4 in the summer of 2012 first and was happy overall with the experience.  The only negative was that when they did the work the first time in 2012 they did not disclose that the vinyl windows leave no room for inside mounted shades, windows coverings, etc, only for outside mounts.  I really like inside mount and was upset, but they had been installed before I realized it.  The next order I asked about the inside mount and found that they can make an adjustment to accommodate inside mount but only if they know about it in advance.  So, the new four have inside mounted shades and the first four do not.  But they did a good job, were punctual, polite and clean.

Nan I.
Aug 2013
5.0
Yes, I recommend this pro
$3,551
.Excellent service, professionals all around.  It was a hassle free job from estimate to completed installation.  Windows were ordered and came early - job was completed a few weeks ahead of schedule.

Arnold L.
May 2013
1.0
$85,000
Horrible job.  Virtually every window and door that Cornerstone installed leaked starting with the first rainstorm of the season.  We suffered significant damage.  For a while, the owner, Tony Szik was apologetic and came out personally to work on the worst leaks.  When he realized that his "repairs" weren't solving the problem and that ALLof the windows were leaking, not just a few, he had a change of heart and began to ignore us.  We discovered later that he had improperly installed all the windows and ignored the manufacturer's specs and installation instructions.  In addition, we discovered that they had failed to even apply caulk around several windows.  We were told that the caulking used was not the recommended type and was destined to fail within a short period of time anyway. At great expense, we were forced to hire another contractor to remove and replace everything Cornerstone had installed.  it was during that process that we discovered that he had removed the flanges from some of the windows which voided our warranty.  It was a horrible experience.
Response from Cornerstone Windows & Doors
"This job consisted of 85 windows and 30 patio doors and our records show the project was completed in 2001-not 2006 as noted by reviewer. There were a couple of small leaks which were addressed immediately, as is standard company policy with all jobs, big or small. The caulking used was not only the proper one, but came with a 25 -year manufacturer's warranty. Cutting back the flanges on retrofit windows is a common practice. It is usually done if the window or door is in a corner, or, if it has a trim around it which won't allow the frame to lay flat to the stucco. This does not void the warranty, in fact, there are score lines on the back of each flange specifically for that purpose. The manufacturer's representative visited the job site after completion and deemed the job to be up to their standards. [member name removed] was given a 10-year written guarantee and warranty from the manufacturer after the project was completed."

Kenith J.
May 2013
5.0
Yes, I recommend this pro
From the start things were great with the estimate we received. Very prompt and professional. In a couple days the owner came and took exact measurements and everything was explained and we knew exactly what Cornerstone would do and what we needed to do.Cornerstone's office called us with regular updates, we always knew the status of our job. It took about a week to get the doors and the installation was scheduled. Cornerstone came exactly on time and they had enough workers and made the installation very professional. Everything fit and the doors are great! Cornerstone cleaned the site as if they had never been there. We could not have asked for any better service. AAA+++

John P.
Apr 2013
5.0
Yes, I recommend this pro
$8,000
Overall was very pleased with the outcome of the project. Windows and backdoor are great for the house. Good customer service and timely project, all removed and installed in one day.

Brian G.
Apr 2013
5.0
Yes, I recommend this pro
$12,000
I met with Tony.  He described the replacement process and measured the windows.  We then discussed many different options.  His price seemed fair, so we scheduled the job.  The crew arrived on time, did an excellent job, and were very neat.  It was a much easier process than I originally anticipated.

David D.
Jan 2013
5.0
Yes, I recommend this pro
$11,000
They lead us through the whole thing, the only thing I can say is DO go with Cornerstone.

Rudolph B.
Dec 2012
3.0
$4,000
Replaced all windows and sliding glass doors and two exterior doors.   All the window were replaced with Milguard brand replacement windows.  I did not  have any problems with the windows as they were all installed over two days and look very good.  I am well pleased with this end of the job.  The doors however, were a different matter.  I purchased two exterior replacement doors.  These were fiberglass insulated doors.  The doors were sold and installed in manufacturer's white color which of course did not match my home decor.  I thought I would receive some assistance with getting them finished but had to contract this out for myself.  The front double door had a small scratch/gouge in the finish metal work.   I requested that this be reordered and replaced.  The owner came out and decided that it only needed a touch up; so he used a magic marker and covered it up.  Additional calls to the office to rectify this matter went largely unheeded.  The fit on the doors was poorly done.  These are double opening doors and you can still see day light coming through and feel the wind through the cracks.  I don't think installing doors are their strong suit.   I have been living with this installation for 8 years now and I will have these replaced again but this time by a "Door Company" specializing in this installation.
The sliding glass doors came with different pull handles; one was gold finish and the other was white.  I asked that the white one be replaced with gold as well but was told that the sliding doors had been ordered that way and the handle could not be replaced (same manufacturer for both doors).  Again my call(s) were mostly not returned after payment had been tendered and after a while I just got tired and forgot about it (which I think was what the company was hoping for). 
I love the windows and sliding glass doors and they have made a big difference in our home.  My suggestion to others seeking this type of work with this company is to stick with windows only and hire someone else for doors who specialize in this type of work.  The issue here is not the quality of the product, but one of installation, service and follow-up.
I have several other homes to do but will go with Win/DOR this time.


Response from Cornerstone Windows & Doors
"Cornerstone Windows takes great pride in servicing all completed projects whenever necessary. Customer service is why hundreds of past clients refer Cornerstone to friends. Whatever the issue, the service department responds quickly to resolve the problem. Cornerstone also assists customers in regards to manufacturer product warranties. In reviewing the file on this project, we discovered no requests for any service issues. In regards to the staining of the doors, Cornerstone is not a painting or staining company. This is clearly stated on the contract that this service is not included. However, the customer did purchase 3 stain kits from Cornerstone which are offered by the door manufacturer knowing that he would have to hire a third party to apply the stain to the doors. We would also like to note that the customers home is located on a hillside. It is not uncommon for movement to occur in hillside homes. This is most likely the reason for the door movement (especially after 8 years). In regards to the door handles, The customer received the handles on the contract. The handles are removable and easy to change out. We would have been happy to sell him additional hardware. Finally, we're a little confused as to why someone would post a negative review 8 years after the job was completed."

Kenji O.
Aug 2012
5.0
Yes, I recommend this pro
$15,600
Scheduling an appointment with Cornerstone was very easy.  They were available to come as soon as the next day but for convenience, I had them come on a Saturday.  Marilynn arrived as scheduled, listented to what we wanted have done, made some suggestions and had a quote to us by the following Monday.  They were competitively priced to other quotes I had received (not the cheapest but in the same ballpark) and had knowledge of the workings of my homes association.  Based on their reviews on Angie's List, knowledge of my area codes and overall professionalism, I chose Cornerstone to replace my windows.  The windows took about 4 weeks to fabricate (the bay window was the timing item).
I had previously had other windows replaced using a retrofit design that I thought did not work well with the style of existing windows I had so I had Cornerstone completely rip out the old windows and install new ones.  This required installing new moulding and stucco work.  They installed all of the windows the first day of work; the sliding door, molding and initial stucco work the 2nd day and fnished up all of the windows on the 3rd day.  The Cornerstone crew managed by Antonio were great.  They arrived on time, cleaned up after themselves and did excellent quality work.  I was very happy with the final product which looked much nicer than a previous job done by a general contractor.  I would recommend them to others to use as well as use them again myself!          

Bill C.
May 2012
5.0
Yes, I recommend this pro
$6,500
They did a good job. They were cheaper than others.

Barbara P.
Mar 2012
5.0
Yes, I recommend this pro
$5,000
We have a 1949 bungalow in the middle of renovation.  The windows were original, down to the hardware; were in terrible shape, letting in the wind and rain.  I contacted Cornerstone and Marilyn came out the next day, listened and discussed what we needed and wanted, then measured, made some recommendations, gave us options on different materials and went back to her office.  We got her emailed quote less than 8 hours after she left our house. 

Being frugal, I called Marilyn the next day and thanked her but said I thought I needed to get a few more bids.  She said she understood and thanked me for letting her assist me.

I got 3 more bids over about 9 days - and since Cornerstone was still the best for materials and price, called Marilyn back and set up installation.  The windows were ready in 10 days.

Antonio and his crew (4 total) arrived at 10:00 and went straight to work.  6 hours of hard work later; we had all new windows with all new exterior trim and screens.  They sealed every surface outside neatly, cleaned the windows and swept the floors inside and the patio outside.  Antonio showed me how to operate all the windows (we got single and double panes) for cleaning, gave me all my paperwork and warranties and they were gone. 

All-in-all a great experience. 

 


Liz M.
Oct 2011
5.0
Yes, I recommend this pro
$2,700
From the initial estimate to completing the actual work, Cornerstone was great to work with! They keep the company's schedule on a board in the showroom, next to testimonials from happy clients. They have a showroom filled with windows and doors so that you can see and touch many of their products.  The owner, Tony Szik, called me to discuss the possibilities after he went to the house to take a look at the windows and write and estimate. This was an unusual situation in that three windows needed to be replaced in order to meet current city building codes and the existing windows needed to be retroactively permitted. Tony did everything he said he was going to do, when he said he'd do it. The new windows look beautiful and meet the current city code. Cornerstone did a great job cleaning up after the work was done. The support staff at Cornerstone was very helpful, and communication between Tony and his staff is good. Most of the time my phone calls were answered immediately, but the few times I left messages, my calls were promptly returned. I wholeheartedly recommend Cornerstone Windows and will call them again should I need their help!

Michael B.
Jul 2011
5.0
Yes, I recommend this pro
$2,200
Very well (see other comments).
Response from Cornerstone Windows & Doors
"There was absolutely no intention to deceive Member during the sales process. This was the first week of the Angies' List promotion and Member was the first respondent to the discount. Minor confusion. No deception. Cornerstone is happy to service all Angies' List customers and factor in the 5% discount into the final bid. We only request potential customers identify themselves as Angies' List members so we can apply the special 5% discount."

JACQUELYN M.
Jan 2011
5.0
Yes, I recommend this pro
Fit had to be "perfect" and it is! The installation team is the best. Prompt, polite, perfect! They work together like no others I've employed. They were a pleasure to have in my home. I wish Cornerstone could teach the world how to do business. Excellent in all categories and prices competitive.

Sam W.
Dec 2010
2.0
I was not satisfied with them. The installation itself was satisfactory. I wasn't satisfied with certain aspects of the attitude of the installer in getting things done. They also installed some retractable screens that are not sliding properly. The price was average. I didn't feel that they were professional.

MARY D.
Nov 2010
5.0
Yes, I recommend this pro
It was an okay experience. They were polite and were accurate about what they said that they would do. The house was power washed to get ready to rent and there ended up being leakage into the house. Part of the reason was that the house wasn't sealed correctly, but they didn't verbally mention to me that the windows should not be power washed. I can't blame them for this since the information was stated in their paperwork. Overall, they knew what they were doing and they did it well. The price wasn't the cheapest, but the quality was better.

Oscar B.
Oct 2010
5.0
Yes, I recommend this pro
$7,000
Four workers arrived slightly ahead of time and prepared for the work by laying down carpeting and tarps to protect the floors. They hauled away the old windows and thoroughly cleaned up afterward. All in all, everything was done smoothly, professionally, competently. I'm currently getting an estimate from them to have additional replacement windows installed.
Showing 1-25 of 36

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FAQ

Cornerstone Windows & Doors is currently rated 4.7 overall out of 5.

Yes, Cornerstone Windows & Doors offers free project estimates.

No, Cornerstone Windows & Doors does not offer eco-friendly accreditations.

No, Cornerstone Windows & Doors does not offer a senior discount.

No, Cornerstone Windows & Doors does not offer emergency services.

No, Cornerstone Windows & Doors does not offer warranties.