Why We’re Different

All we do is replace windows & doors!

Cornerstone Windows Front Door Entry Door
Cornerstone Windows Front Door Entry Door

Installing high-quality replacement windows, patio doors, and Entry Doors improves your home’s beauty, minimize outside noise, and reduces heating and air conditioning bills.

Here’s why Cornerstone is different:

  • Serving the South Bay since 1999 – 25 years in business!
  • Owner, Tony Szik, has over 44 years of contracting experience
  • Fully licensed, bonded, and insured
  • NO subcontractors – only Cornerstone employees
  • Products are purchased directly from the manufacturer – no middlemen
  • All windows & doors are custom manufactured to fit your home

We offer a large selection of high-performance products in the following categories:

  • Vinyl Windows
  • Fiberglass Windows
  • Garden Windows
  • Patio Doors – swinging, sliding & folding
  • Entry Doors
  • French Doors

Our Commitment

Our commitment spans from everything to the value of our products to the craftsmanship of installation

Our commitment to supplying customers with the finest windows and doors is backed by our dedication to customer satisfaction. Contact us for a free estimate at (310) 325-4700 and start enhancing your home’s beauty and value today.

Transform your home with new windows & Doors!
Contact us today for a FREE estimate

Cornerstone Windows & Patio Doors

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