What size concrete pillars and beams should I use for a 3-story addition with floor trusses to carry load to exterior walls?
Asked by Jeremy Schmidt 
2 months ago
Last Updated: October 27, 2024
I’m thinking about adding a big extension to my place. The plan is to have it three stories tall and 32 feet by 52 feet in size. The floor trusses will support the weight and transfer it to the outer walls. I’m considering a pier and beam foundation, but I could use some advice on how big the concrete pillars and beams should be. Any tips or suggestions would be really helpful.
If you’re unsure about this, it might be best to seek help. Consider hiring an architect to design and a framer to assist you. I’ve seen even experienced framers make mistakes that put a house in danger.
While I’m experienced in construction, foundations are not my specialty. I’m planning to hire an engineer beforehand to make sure I have everything I need. The foundation is the only part of the project that I haven’t quite figured out yet. It’s still about two years away, but I want to lay the groundwork next year so it can settle over winter before the full construction begins.
They’ll outline the specific requirements for the load in your area. I wouldn’t rely solely on advice from others here for your foundation needs.
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Mr Worre
It seems like you should prioritize getting engineered plans instead of relying on social media advice.
Miller here, just trying to get a general idea of where I stand before investing in an engineer since they can be expensive
Having an engineer is essential in this situation.
Remember, free engineering advice is often not the best. Building your own addition is possible, but it’s crucial to involve the right professionals, such as an engineering and architectural firm.
As many others have mentioned before, having an engineer is crucial. As a carpenter with 25 years of experience, I know better than to do those calculations myself. I might have an idea of what could work, but one mistake could lead to a disaster. Your safety is worth more than saving a few thousand dollars to hire an engineer.
The building permits office will likely ask for an engineer or architecture blueprint for approval.
Foundations alone are insufficient. Apart from vertical loads, you must address lateral loads with shear walls and likely holddowns to withstand earthquakes and/or wind. It’s best not to pour a foundation until the structural design, including finalized floor plans and elevations, is ready.
Consider hiring an architect. It’s a worthwhile investment. A stamped plan will be necessary for a permit regardless.
It’s advisable to consult an engineer, conduct a soil test, and obtain a PE stamped design. While it may seem costly, engaging with planning and zoning for your local area at the outset of the permit process will simplify your life. Prior to commencing work, arrange for a pre-construction inspection/meeting with your local building inspector. Many inspectors offer this service to ensure you are aware of the verification requirements. Architects concentrate on aesthetics, while engineers focus on the structural aspects and how they integrate with the installation site. Engineers also possess knowledge of the AHJ (authority having jurisdiction – local code) under which you will build and tailor the structure to meet specific criteria. This is an area where cutting costs is not recommended.