Architectural plans and structural plans are two very different things, yet we see people use them interchangeably all the time.
That confusion can cost you both money and time.
Understanding what each set of plans actually does (and doesn’t do) is one of the most important things you can figure out before breaking ground on your project.
We will use our almost three decades of engineering experience, where we’ve worked with clients including Adidas, the U.S. Army and the U.S. Air Force, to discuss the differences between architectural plans vs. structural plans, and why it matters.
What Are Architectural Plans?
Architectural plans define how a structure looks and allow everyone involved to get a clear visual interpretation of the new structure before a single board gets cut. You can think of them as the pretty pictures depicting your future space.
Architectural plans include:
- The layout.
- The flow.
- The visual interpretation of how a home or building comes together.
Here’s an example, courtesy of The House Designers:
Architectural plans do not require a stamp from a state-licensed engineer, and engineering will not stamp or modify them in any way when used for a residence. When the structure is larger and commercial, a licensed architect may very well be required.
They do need to be accurate to scale, though, because engineers extract AutoCAD files from them to use as the wireframe model that starts the structural engineering process. If that AutoCAD is off, the whole process hits a wall before it starts.
What Are Structural Plans?
Structural plans are the set of drawings and math that tell builders how to construct a home so that it is code-compliant and built safely.
Think of it like this: architectural plans define space. Structural plans prove that the space can hold up to the wind, snow and seismic loads that will affect the site where the home will be built.
The predominant purpose of structural plans is to ensure that the structure, when built according to the engineering plans, is safe for its intended use. This is why all engineering plans carry a state-licensed engineer’s stamp.
Structural plans include:
- Analysis of wind, seismic, and gravity forces according to building code.
- Drawings covering the foundation plan, floor framing, roof framing, and structural systems specific to that home.
- A calculations book that proves, mathematically, that the engineering is sound and the structure is safe.
- Details for gravity, wind, and seismic loads (which may not be to scale).
Here’s an example, courtesy of Ekwueme Philip Osondu on Medium:
One thing that sets structural plans apart from architectural ones is that every set is specific to a single address.
The snow, wind, and seismic loads applied to a structure are determined by its exact location. The same set of plans cannot be reused for a different site, even one nearby.
How Architectural and Structural Plans Work Together
Ideally, architectural and structural plans should be in sync with each other.
Architectural typically comes first, and structural is built with direct consultation of the architectural plans. They are not interchangeable. If the architectural plans are off, then the engineering will likely be off too.
Take a two-story home, for example. The load-bearing walls on the upper floor need to align with the load-bearing walls on the lower floor.
A PSE architectural rendering showing a two-story home design. The structural engineering process starts once plans like these are accurate and to scale.
If the architectural plans aren’t accurate and those walls don’t line up, the load paths are gone.
This can lead to delays in the project. Engineers are usually managing multiple projects at once, and delays aren’t easy to absorb.
When an inaccurate architectural AutoCAD causes a problem, the project doesn’t just pause mid-process and wait. It can go back to the end of the line until more information is available, or corrections have been made.
Once the engineer moves to the next project in the queue, there’s no guarantee of how quickly things can pick back up.
Sometimes delays are unavoidable. For example, a missing geotech report (the analysis of local soil and its load-bearing capabilities) can stop a foundation design.
But errors that arise when architectural and structural plans don’t align are entirely avoidable.
We can tell you from our experience as a structural engineering firm that it’s worth spending the time to get both plans right initially, so you don’t have to endure lengthy mid-project delays.
Can You Build a Home With Architectural Plans Alone?
Although architectural and structural plans are vastly different, you can’t have one without the other.
We’ve seen and heard of many people who are building a home go out and buy architectural plans, thinking that’s all they need.
The truth is, what they’ve bought is a set of pretty pictures and an AutoCAD file.
Building departments in communities that are managing how their neighborhoods look may accept the architectural plans for aesthetic review.
For the structure to actually get permitted and built safely, though, you need structural engineering.
No one actually needs a license to design a home. To engineer one, though, you need a license in the state where the work is being done.
That requirement exists because structural plans are what stand between a building that holds up and is safe to occupy – and one that doesn’t. They’re what get reviewed, stamped, submitted, and ultimately approved for a building permit.
Here’s an example of a stamped and sealed structural engineering plan, courtesy of MT Solar:
Also, changes to architectural plans that could affect engineering have to be made by the person who created them.
Like any outright-owned artwork, engineering firms are not permitted to adjust the architectural designs of others. It’s a copyright issue, and a legally binding one.
If the original designer isn’t available, a signed release is required before any changes can be made. It’s one more reason the architectural plans need to be right before it ever reaches the engineer.
It’s also why keeping both architectural and structural under the same roof is easier for most property owners (more on this in the next section).
Should the Same Company Handle Your Architectural and Structural Plans?
When architectural design and structural engineering are handled by separate firms, it can complicate communication efforts and extend timelines.
Here are scenarios to demonstrate this:
- Choosing multiple engineering firms: Say the structural engineer is mid-project and finds an issue that traces back to the architectural plans. That problem has to go back to the architect, who is running their own workload and timeline. Depending on how responsive they are, you might not hear anything for two or three weeks.
- Choosing one engineering firm: When architectural design and structural engineering are handled in-house, that same problem gets resolved in a conversation. There’s no email chain, no waiting on a separate firm’s schedule, no project sitting idle.
Choosing one engineering firm can also lighten your cost commitment. For residential projects, a home designer can handle the architectural side, and the cost difference compared to hiring a licensed architect is significant.
The structural work gets done to the same standard, because building code requirements don’t change based on who drew the floor plan.
If possible, choosing the same engineering firm to handle both of your architectural and structural needs can improve communication and significantly lower costs when compared to using an architect.
Why? Because a Home Designer at PSE works strictly to expedite the engineering process, not to inflate the cost of designing a home.
Need Help With Your Next Project Plans?
We covered a lot in this post, so let’s quickly recap what was covered:
- Architectural plans define the look and layout of a structure (remember: pretty pictures). Structural plans prove it can be built safely and are what you need to get a building permit.
- The two plans work in sequence. Architectural comes first, and structural engineering is built on top of it. If the architectural is off, the engineering will be too.
- Working with one firm for both can reduce delays and will absolutely lower your development cost.
If you’re still working out whether your project needs home design, structural engineering, or both, reach out here, and our experts can help you figure out what your project actually requires before anything else.