Floor joist opinions

[James77]

My plan at this point is to add a beam mid-span to support the joists from sagging.

I'm planning on making the beam out of 2 2x10 or 2x12s with 1/2" plywood pieces sandwiched in between every 2' or so. I'm going to support the beam on both ends with 2 or 3 2x6s, and the 2x6s will be notched so that the beam sits in the 2x6s.

I can screw the outer 2x6s (those closest to the wall) on each end to studs to help stabilize it. But, I'm not sure what I should do to attach the joists to the beam. I was thinking maybe some 'L' brackets to give it some added side-to-side stability. Or, is there a better bracket or way to do this?

These pics kind of show what I'm thinking about doing.

What you pictured will work fine.

I would not worry much at all about stabilizing the supports to the wall or the joists to the beam, unless you plan on bumping into them frequently . FWIW....I did a similar beam in my very old house on a 175g tank, although the tank was perpendicular to the joists. I used shims to fully support the beam to the joists, and after 2-3 years, there was zero settling from the tank as I could pull out the shims as easily as I could have years before.

 

[FuzzyZipperbaum]

armstrong makes some straps that will attach the beams to the posts...you can also run a 2x4 or 2x6 straight up the sides of the beams and lag them to the other posts...which is what I did....also I unless I mis read it.... I would use the 1/2 inch plywood as one piece between the 2x10's...makes it very strong....and GLUE the ^^&*$$ out of it.....

 

[Eud]

My floor was built with 2x8s joists under it and a 12.5 foot span from steel beam to wall. My petite wife walks across it and the books shake in the shelves, so the 75 gallon I'm putting in which will go parallel to those joists and right in the middle of the span will get LVLs sistered in on each of the two joists under the tank from beam to sill plate. I don't have the option to build a supporting wall to transfer the load to the floor of the basement because it's right in the middle of the finished room.

Given that yours is much heavier and that you are willing to do a wall underneath I guess I'd suggest a both-and approach of sistering some LVL beams and then putting a wall up to design a nice fish room underneath for the sump, reactors, skimmer, pumps, water change vessels, etc.

You get two for price of one, a robust support for the tank and a nice clean and quiet install upstairs.

 

[tufkab]

Like everyone else has said, get an engineer to look over it. The cost of the engineer is a drop in the bucket compared to what it could cost you if the proverbial feces were to impact the air circulation device.

That being said, I think you're over complicating things with that beam going across. You're trying to fix the sag in a large span by supporting it with another large span.

Pick the three joists that your tank will be on and sister each one of them, properly (glue, nails) with LVL and I will wager a week's pay that you won't even see a 1/16" of sag in that floor.

Again though, I'm not an engineer and neither is anybody that's responded so far (I think). But many of us have plenty of experience in construction and certain things will just make sense without any fancy math. It would be very prudent of you to get an engineer over and explain what you want to do and they ideas you are toying with.