CraigFL

travelover

I've got a degree in mechanical engineering, too, so I understand the physics involved. I remember working out these formulas long hand pre-calculator.

But realistically, the OP only wanted to slap down another layer on the top side. Sistering is not ideal from an efficiency standpoint but if you are trying to keep the same ceiling height, it is a cheap, low tech way to reinforce the floor. Ditto with blocking or diagonal braces between joints.

And yes, the length of the joists is more important than the depth, but I didn't think the OP was gonna make the room smaller, and I didn't see a willingness to add posts underneath.

Nestor_Kelebay

I took engineering years ago, but I still remember and understand the basics of beam design, just as others in here do.

I just figured I'd bring out the point about strengthening the joists themselves. I always hear about people sistering joists, and there's no doubt that sistering joists will result in a stronger joist system. But, it's also true that there are other options available that may work better that haven't been presented to the homeowner.

When I have suggested these options on other Q&A forums I've posted on, I've gotten a lot of resistance. Most of the time the arguments against it went as follows "I've been doing this kinda work for 600 years, and I've never ever heard of anything so stupid in my life until you opened your mouth. Do you realize that I had to grit my teeth to stop myself from laughing out loud at what you said! That's cuz it was so mind-bogglingly stupid. Do you hear me?"

So, what do I do with criticism like that? I can explain the equations, and why adding wood should work, but I can't change prejudice, and this guy has already decided it's a stupid idea before he's even taken the time to think it through. So, I just throw the idea out there with the formulas to show why it should work, take the criticism on the chin and carry on. What else would anyone do?

I just thought I'd explain the basics so that people in here can see for themselves that there are alternatives to sistering joists that they might want to explore. If they do, then I'd recommend they proceed with the assistance of a consulting engineering firm or architectural firm to ensure that what's done is structurally sound and approved for insurance purposes. Your house is your biggest investment, and you should proceed with structural changes only with an engineering or architectural firm on side to approve the changes just to cover your A$$.

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Adk

Great piece of advise!!!

Nestor_Kelebay

PS:

I think I still have a post I wrote up years ago that explains these beam equations in more detail. I don't want to hijack this thread, but am willing to post it here or in a new thread if anyone wants to read it.

__________________
New Mexico; the only state in the union where "he needed killin" is a legitimate defense in court.