The phrase "original builder" refers to the person or organization who constructed or created something first. They are the ones responsible for designing, making, or establishing something from the beginning. Full definition
We are purchasing a house from the 60s with original builder - basic white laminate countertops and I'm wondering if underneath ours will be the same. (rainonatinroof.com)
The homeowner wanted Chaulk — who was not the original builder — to referee. (canadianbusiness.com)
The workmanship of the 17th century portico is absolutely beautiful and really shows the respect and love of the original builders for their deity. (religion.blogs.cnn.com)