How to calculate appropriate beam size for load bearing?

[TheMilly]

 

 

After waiting for a spot in our contractors chaotic schedule we realised it wasn’t going to happen in the time frame we wanted. The timber that was ordered is  F14 cypress 150x200mm in a 3.3m length, held up by 2 f14 150x150 posts.
mas per the picture we are replacing 3 studs to take out a half wall.
Can we be confident this beam is sufficient? There are piers below the house. 
picture is pre asbestos wall removal, with the 2 panels being wall to remove.

 

[EricL]

Hello @TheMilly 

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thanks for sharing your question about your load bearing beam.

Only your contractor can answer your question in regards to the suitability of your load bearing beam. If this is what your contractor suggested odds are they have already done the calculations to account for the weight and the dynamic forces that will be applied to the beam. You can refer to a span table, but that would not be enough as there are forces acting on your beam that are unique to your home. I suggest contacting your contractor so that they can verify that the beam you have installed is the correct one.

If you need further assistance, please let us know.

Eric

[TheMilly]

I think our contractor knew less than he should.  I’m guessing that’s why he’s put this off. So I’m looking to independently verify! Is there a way to calculate load? 

[JacobZ]

Hi @TheMilly,

Unless your contractor is a licenced engineer, then they are not typically capable of making determinations on this kind of work.

A structural change to your property, like the one you are planning, should always be run by your local council who will likely require submissions for building approval which will require an engineer.

I'd suggest you contact an engineer for assistance with this. They will be able to assess the roof and ensure that the beam is capable of supporting the load from above.

Let me know if you have any further questions.

Jacob

[TheMilly]

Hi @JacobZ, this question was more to learn about engineering in carpentry and I was hopeful for an an interesting informative look at structural complexities, which might well be outside the scope and expertise of this community. I appreciate the add to my post and see this would be the most legally defensive reply, but I’m told (by council) not necessary in this particular project, cheers. 

[MitchellMc · Accepted solution]

Hi @TheMilly,

I see you’re trying to get a better understanding of the engineering behind your beam installation, and it’s great to see that you’re eager to learn more about the complexities involved.

While span tables can provide some guidance, they only go so far in determining the appropriate size for a load-bearing beam. It’s essential to remember that a beam isn’t just about its size or the material used; it’s about how it interacts with the entire structure and how the load is distributed across the system.

Engineers consider many factors, such as:

1. Load Distribution: They assess the weight of what’s above and how that load is distributed across the beam. This includes everything from the roof load to the weight of the walls and any other structural elements.

2. Supporting Structure: They need to evaluate how the beam is supported at its ends, as well as how the posts and piers below the house will be interacting with the load. It’s not just about whether the beam itself is strong enough—it’s about the entire load path from the top to the foundation.

3. Deflection: Engineers also calculate how much the beam might bend or deflect under load. Excessive deflection can lead to structural problems, even if the beam is strong enough to carry the load.

4. Building Codes & Regulations: There may be specific requirements set by your local council or building code that govern the size and type of beam needed for your particular situation, based on the expected loads and the structure’s design. An engineer will be familiar with these codes and can ensure everything meets the necessary standards.

5. Material Properties: F14 cypress, while a strong timber, has certain characteristics, such as its grade and strength, that need to be factored into the design. An engineer will calculate how these materials perform under the specific conditions of your home.

6. Connection Design: An important aspect that often gets overlooked is how the beam is attached to other structural elements. Engineers are responsible for designing the connections and mountings for the beam, whether that's through bolts, fixings, support plates, or other methods. These connections are important because they determine how effectively the beam transfers loads to other parts of the structure. Poorly designed connections could compromise the entire system, so it's vital to have them engineered for optimal strength and durability.

Why an Engineer is Needed
A licensed engineer has the expertise to analyze all of these factors and more. They’ll assess the structural integrity of your entire system, not just the beam itself, to ensure safety and durability. In fact, most building projects requiring a structural change will need an engineer’s calculations to ensure compliance with safety standards and building codes.

Even if council approval isn’t strictly necessary for your project, an engineer’s input will give you peace of mind that your beam and the rest of your structure can safely bear the loads they are meant to carry.

So, while I completely understand your interest in the practical side of things, this is one of those situations where a professional assessment is important to ensure everything is up to standard. I’d recommend reaching out to a licensed structural engineer to verify that your beam is suitable for the job.

Please let me know if you have any questions.

Mitchell

[TheMilly]

Thanks @MitchellMc for putting this together. These are precisely the kind of references I was after, and not knowing technical terms was the first hurdle. I may have been ambitious in my expectations, as my curiosity and desire to crunch numbers was looking for more technical details (which in all fairness is why engineers charge $5k) but knowing the technical terms will point me in the right direction on Google so much appreciated.

The “ask a professional” appears to be the mandatory disclaimers which I appreciate in an online forum of potential accountability. 

[TheMilly]

I found this resource online which breaks down the calculations, for anyone else interested! 

https://www.timbertrading.com.au