Sarah Buchner: Carpenter Turned AI Leader in Construction

The Beginnings of Sarah Buchner in Construction

Sarah Buchner, before becoming the founder of Trunk Tools, a startup specializing in artificial intelligence for the construction sector, spent over ten years working in this field. Originally from Austria, she grew up in a modest environment where her father worked as a carpenter. To support the family, he took his children to job sites, which allowed Sarah to start working in construction as a teenager.

She describes herself as coming from a working-class background, a heritage that has profoundly influenced her professional journey. Although she climbed the ranks to become a general contractor, overseeing large-scale construction projects in Europe, a tragic event marked a turning point in her career: the death of a worker on one of her job sites.

This incident profoundly changed her perception of her work. "When you realize that lives are at stake under your responsibility, it changes your perspective," she confided. This awareness drove her to develop an application dedicated to the health and safety of construction workers. Although distinct from Trunk Tools, this initiative introduced her to the world of software development and encouraged her to pursue a PhD in data science applied to construction and artificial intelligence.

During her research, she discovered a major problem: although construction companies generate a massive amount of data, it is often scattered and difficult to utilize. "The data exists," she noted, but it is "so messy and unstructured" that traditional analysis methods quickly reach their limits.

The Birth of Trunk Tools

Seeing an opportunity to make this data more accessible and useful, Buchner decided to found Trunk Tools in the United States rather than in Europe. In 2019, she moved to California to join the Stanford Graduate School of Business. It was in 2021, while she was still a student, that she founded Trunk Tools, graduating the following year. Like many startups, the early days were chaotic, and it wasn't until 2023 that the company found its first significant product and market.

At that time, advancements in large language models began to make it more practical to process large amounts of unstructured data, a major asset for the construction sector. According to Buchner, an average job site can generate between 3 and 4 million pages of documentation, scattered across numerous systems. Trunk Tools integrates with these systems, adding an analytical layer that allows for the exploitation of this information for various tasks.

The company primarily targets general contractors and subcontractors, while also beginning to collaborate with some project owners. Trunk Tools' AI agents can analyze contracts and construction plans, identify inconsistencies, and assist in managing specifications, bids, and tenders, thus facilitating communication between different workflows. For example, an agent can detect an issue in a plan and relay this information to another agent to assess the next steps and the potential impact on other aspects of the project.

This ability to connect information is crucial due to the inherent complexity of construction projects, as Buchner highlighted: "For a human brain, it is impossible to calculate the secondary and tertiary effects of changes due to the complexity and interconnections."

In one concrete case, a project owner requested a change that the construction company would normally have implemented without hesitation. Trunk Tools calculated that this change would add nearly $4 million to a project of about $100 million. Informed of the cost, the owner decided not to proceed.

In another example, an incident on a job site involved a worker exposed to chemicals. A Trunk Tools agent was used to obtain detailed instructions on how to respond to this exposure, underscoring the importance of quick action in such situations.

Expansion and Growth of Trunk Tools

Based in New York, Trunk Tools now employs over 100 people. Sarah Buchner, as the sole founder, believes that her PhD provided her with the technical skills necessary to not require a technical co-founder. However, she recruited experienced AI engineers from the start and has since built a strong technical leadership team.

The startup has also diversified its product offerings. About a year ago, Trunk Tools had two operational AI agents; today, it has more than ten. The pace of development is such that the company sometimes struggles to train its sales and customer success teams on new products as quickly as they are launched.

Trunk Tools has raised approximately $70 million from investors such as Insight Partners, Redpoint, and Innovation Endeavors. Revenues quadrupled last year and are expected to grow by 3.5 times this year, according to Buchner. The latest funding round, a $40 million Series B in 2025, valued the company at $325 million.

An Unconventional Founder

The funding journey was tougher at the beginning, partly because Buchner did not fit the typical profile of tech startup founders. "I think it was difficult at first because I may not look like the traditional tech founder," she said.

However, once Trunk Tools began to scale, Buchner's experience in the industry became an asset. Having spent years doing the same job as her clients, she could accurately answer investors' questions about construction.

"When I walk into a room full of investors, I know that... I’m probably the most informed person about my industry," she asserted.

AI in an Industry Reluctant to Technology

Traditionally, the construction sector has been slower to adopt new technologies compared to other sectors like finance or legal services. One reason, according to Buchner, is the often significant distance between those who purchase the products and those who actually use them.

Purchasing decisions are often made by executives in offices, while end users work on-site, under pressure to meet project deadlines. Additionally, profit margins in construction are generally low, meaning a poor purchasing decision can have significant financial consequences.

However, Buchner observes that AI is being adopted more quickly than other technologies in the construction sector. Trunk Tools has also understood that simply selling the software is not always enough. The company now offers training and change management services to help clients integrate AI into their large organizations.

Buchner's industry experience plays a key role here. Rather than following a conventional software business model, she focuses on the real needs of construction companies.

"I’m just focused on solving a problem," she stated.

In retrospect, Buchner always envisioned starting a business one day. For a long time, she thought it would be her own construction company. Ultimately, the carpenter turned entrepreneur founded a software company for the industry where she had already spent a significant part of her career.