When do you need an engineer’s stamp?

A stamp (or seal) is the mark a licensed professional engineer puts on drawings and calculations they prepared or directly supervised. By sealing them, the engineer takes professional responsibility that the design meets the applicable codes and standards.

A few things are worth knowing:

• Licenses are issued by each state. The engineer generally needs a license in the state where the project is.
• A stamp covers the engineer’s scope, not your whole project. An engineer might design and stamp one beam, a foundation or a retaining wall, while you draw the rest.
• The discipline matters. Structural or civil engineers handle structure and foundations. Electrical engineers handle electrical design when it’s required.
• A stamp doesn’t guarantee a permit. The building department still reviews the plans and can ask for changes.

The residential building code includes prescriptive rules: span tables for joists and rafters, header sizes, wall bracing, footing sizes and more. If your house or outbuilding is conventional light-frame construction and stays within those tables and their limits, you can often design it yourself by following them, with no engineer.

When part of your design falls outside those limits, that part has to be engineered: designed with calculations by a licensed professional. Long spans, tall walls, heavy point loads, unusual shapes, large openings in braced walls and steep or unstable sites are common examples.

That’s why the question is rarely “does my project need an engineer?” It’s usually “does any part of my project go beyond what the code lets me build without one?”

This varies by jurisdiction, but these situations often need engineering:

• High wind, snow or seismic areas where the loads exceed the limits of the code’s prescriptive tables
• Retaining walls above a certain height (often around 4 feet), or ones that hold up a driveway, a slope or a building
• Beams, headers and girders that fall outside the span tables, including many engineered lumber and steel beams
• Engineered foundations on expansive or weak soils, steep slopes, or piers and posts outside the standard details
• Roof-mounted solar, where some jurisdictions want a structural letter confirming the roof can carry the array
• Post-frame buildings and trusses, which are commonly engineered by the supplier or truss manufacturer
• Removing or changing load-bearing walls in an existing house
• Larger or non-residential buildings, which usually fall under the commercial code and require a licensed design professional

Some states also require a licensed architect or engineer for buildings over a certain size or for certain uses, whoever builds them.

The building official in your jurisdiction decides whether a design needs engineering, based on the adopted code, local amendments and state law. Two neighboring counties can answer the same question differently.

Ask early, ideally before you finish your drawings. Many departments offer pre-application meetings or will answer questions by phone or email. Bring a simple sketch and describe what you’re building, where, and anything unusual about it. Ask what design values apply at your site, such as wind speed, snow load and seismic category, and write down the answer.

If you do need an engineer, clear drawings save time and money. Before you reach out:

1. Draw what you can. A dimensioned floor plan, elevations, a section and a site plan tell the engineer exactly what you’re building.
2. Gather site information. The design values from your building department, a soils report if you have one, and photos of existing conditions.
3. Define the scope. Say exactly what you need engineered: one beam, the foundation, the whole structure, or a letter about the roof.
4. Get the scope and fee in writing before work starts.
5. Put their work into your set. Show the engineer’s sizes and details on your plans, and include their stamped calculations or letter with your submittal.

AI CAD PRO is free software for drawing the plans: floor plans, site plans, electrical and solar sheets, elevations, sections and one-line diagrams, with an AI assistant that draws and revises them with you. Clear, organized plans make an engineer’s review easier.

It doesn’t supply complete structural, mechanical, plumbing or other engineering calculations, and its drafting checks aren’t a code-compliance review. It doesn’t replace an engineer’s stamp where one is required.

We’re building an optional program that will connect you with licensed engineers who can review your plans, send comments you can work through in the app, and seal the final set when they approve it. It isn’t open yet, and the free software doesn’t depend on it. Licensed engineers can learn about the reviewer network.