Heading tags (H1 through H6) are HTML elements that define the structure of a page. Search engines use them to understand the topic and organisation of your content. They also improve accessibility, as screen readers use headings to help users navigate a page.
Every page on your AEC firm website should have exactly one H1 tag — the main topic of the page. For a project page, this would be the project name. For a service page, it would be the service being described. The H1 should include your primary keyword naturally.
H2 tags are used for major subsections, H3 for sub-subsections, and so on. A common mistake on architecture and engineering firm websites is using heading tags purely for visual styling rather than content structure — for example, marking up a caption as an H2 simply because the desired font size is large. This confuses search engines and undermines the page structure.
Proper heading hierarchy also makes your content easier to scan for human visitors, which can improve time on page and reduce bounce rates — both signals that can indirectly influence rankings.