I am an engineer. Sort of. I went to an excellent engineering school (University of Virginia) and I majored in Civil Engineering. I understand the concept of a free body diagram and how horizontal and vertical forces interact to make a structure sound. I took a whole mess of classes on this stuff...back in the 1990s. Then I graduated, went off to do some other stuff including being a C-130 pilot and filled my brain with tons of other technical stuff that had zero to do with civil engineering or building structures. So, as you can see, I'm an engineer. Sort of.
I thought long and hard about how I was going to accomplish the task of raising the floor of the workshop to accommodate the dust collection ducting and electrical system requirements of a several commercial grade woodworking machines and this is what I came up with: Floor joists supported by vertical blocks.
Sounds simple and in theory it is. This is a design I chose based on the situation at hand. Here are some of my thoughts:
1) The existing floor is concrete and therefore very strong. Using vertical wood supports directly on the concrete will therefore also be very strong.
2) Pocket hole joinery is good. It's strong, lasts a long time and is reversible. I can simply put the floor down and then open it up to install the ducting. If a duct interferes with a vertical support, I can just move the support. If this creates too large of a distance between supports, I can add another one to make up for it.
3) I want future flexibility and serviceability. As for the future flexibility, see number 2 above. I can move ducts and supports if I decide I want to move my machines. As for serviceability, I'm putting down 4x4 foot panels held in place by about 30 screws each. This allows me to remove the screws and pull up a panel whenever I need to get into the sub floor area.
4) I chose to double block each section of the floor. All edges of the floor panels will be screwed down into their very own 2x4. No sharing. This not only adds structural integrity, but also ensures that the deck screws holding the floor down have good purchase in the middle of their 2x4s. If I have to pull up a panel 5 or 6 times over the years, I'm not going to have splitting wood (this is what I hope).
5) Some of the machines I'm planning on putting on this floor are HEAVY. The jointer weighs in at just about 1000 lbs. I can easily beef up sections of the floor by adding cross bracing and additional vertical supports to keep everything structurally sound.
Now that I think about it. Perhaps I'm a floor over-engineer. There's very little chance this thing is going to sag.
It's all part of the vision.