Floor Support Questions

[ReefDoberman]

After countless hours on google with no answer, I figured I would post here to get feedback based on experienced large tank owners. I am setting up a 265 gallon reef in my living room which is on the main floor of my house (above the basement) and I wondered if anyone knew how much floor support would be needed to avoid any issues?

The tank will be going against a wall that is an "outside" wall for the house however the support beams under the floor run parallel to the aquarium with one, maybe two beneath it. I am no structural engineer but this doesn't seem like it will be adequate?

Can anyone provide guidance with regard to what may be required if the floor isn't enough? I'd like to avoid having to use those portable I beams since I will be finishing the basement and this will take up a considerable amount of space. I'd rather find a way to run new beems under the floor/in the ceiling of the basement if possible.

Not sure if this matters but it is a newer house, built in 2007.

Your help is appreciated.

 

[sonnus]

Your best bet is to find a local structural engineer to calc it out for you. It shouldn't cost more than a few hundred dollars for the peace of mind. If you have trouble finding an engineer then just call up a local architect or general contractor and ask for a referral.

After that disclaimer, I think if you just double-up the existing floor joists you'll be fine. If you're not sure you can triple them up too, this is done on new construction all the time. You would not loose any space in your basement because you're just adding material in the floor space. Just make sure the new joist has good bearing on the top plate on both sides and nail the new joist 8-12" on center with 16d framing nails to the existing joist. You might have to trim/rip the new joist a little to get it in, then just use wood shims to get it up tight to the sub-floor. Sometimes jacks are needed to get the joist into place too.

 

[sonnus]

Here is a cross-section to illustrate what I am talking about. Again, call a local engineer to make sure this will work.

 

[Hal]

What Sonnus said is a good start, but probably not enough. I just installed a 240g (72x28x30) into my house. My tank is in the corner against 2 exterior (load bearing) walls, and the span of the joists is about 7-8 feet from foundation wall onto a steel I-beam. I had doubled up one joist already for my old 150g tank, but after doing the math decided that I needed more for my new 240g tank. By my calculations, if I added a steel I-beam running parallel with the existing joists near the front edge of the tank I would be fine. The I-beam only came in 16 ft lengths, though, so I had them cut it in half and installed 2 i-beams spaced apart by 24 inches or so. My I-beams were only 6 inches tall, so they rested on vertical 2x4's which then sat on top of the foundation/existing I-beam.

If your basement ceiling is exposed then I would add additional joists or I-beams.Personaly I'd add joists between the 16" on center joists. Unless the feet of your stand are directly over a joist, you're going to have a bending moment in the plywood that is proportional to the cube (square?)of the distance from the joist. That's why it's critical to minimize the distance that the feet of the stand will be from the joist. If you know where the feet will be, put a joist directly underneath that spot. Joists are cheap, and easy to install if you have an exposed ceiling in your basement.

If you can find the smaller (in height) I-beams, they would work too, and be even stronger than the joists.

I have a CAD drawing of my floor layout, but it's in a .doc format. I'll try to upload it later.

 

[Rploaded]

Seek an engineer. Just imagine building your beautiful tank and the floor settles or gives enough to crack it.... 500-2000$ dollars up front for peace of mind is nothing compared to what you will have in it...

Good luck...

 

[Hal]

I am an engineer. Trust me, this is basic math and loading spec's. It's not rocket science.

Oh, when you said you wanted to avoid "portable I-beams" I assume you meant floor-jacks/columns?

Lastly, I've discovered that the town building inspector will often look at this type of thing and provide advice free of charge.

 

[gbru316]

I am an engineer. Trust me, this is basic math and loading spec's. It's not rocket science.

Oh, when you said you wanted to avoid "portable I-beams" I assume you meant floor-jacks/columns?

Lastly, I've discovered that the town building inspector will often look at this type of thing and provide advice free of charge.

Sure, but are you willing to assume liability without ever taking a look at the structure?

I'd hire a local engineer as well, if for nothing else than peace of mind. We did this before removing a wall, cost $125 for the visit, and we received a document saying that it was inspected, and that engineer assumed liability if removal of the wall hurt the structural integrity of the house.

 

[Hal]

Sure, but are you willing to assume liability without ever taking a look at the structure?

Heck no.

I only meant this to suggest that with a little common sense and math, the risks are pretty low. For sure you get even more peace of mind if an expert inspects it (and will guarantee their opinion, but IME that doesn't usually happen). If the screw-up factor were high I'd definitely spend the money, but that's not the case here.

Crud, just put joists every 4 inches and you don't even need to do the math.

Disclaimer: we still need to know what the span of the joists are.

 

[gbru316]

Heck no.

I only meant this to suggest that with a little common sense and math, the risks are pretty low. For sure you get even more peace of mind if an expert inspects it (and will guarantee their opinion, but IME that doesn't usually happen). If the screw-up factor were high I'd definitely spend the money, but that's not the case here.

Crud, just put joists every 4 inches and you don't even need to do the math.

Disclaimer: we still need to know what the span of the joists are.

Meh, just remove the floor under the tank and pour a slab from the second floor to foundation, reinforced with rebar

 

[Loktai]

meh, just remove the floor under the tank and pour a slab from the second floor to foundation, reinforced with rebar

+1

 

[ReefDoberman]

Thanks for all the great feedback here. Double up on the floor joists and adding additional "doubles" in-between the current joists sounds like it would do the trick. In the end getting an engineer to the house to confirm will be the route I go.

 

[Hal]

Thanks for all the great feedback here. Double up on the floor joists and adding additional "doubles" in-between the current joists sounds like it would do the trick. In the end getting an engineer to the house to confirm will be the route I go.

The key is to have a joist (or a double) directly under the feet of your stand. Then all the load is transferred directly to that joist and you don't need to worry about bending your flooring.

 

[Hal]

Ok, got my drawings. Here's what I started with. I doubled up on one joist when the house was built. It was just a guess, and served me fine for my old 150g tank. Not quite enough though for my 240g.

Here's the addition of the two I-beams:

Unfortunately, I didn't plan ahead quite well enough. As you can see, the feet of my stand don't sit directly on top of a beam/joist. The math says it's close enough though.

The pic also doesn't show the 2x4 wood blocks that are under the I-beams that transfer the load onto the foundation wall and onto a second I-beam cross piece (also not shown in the 2nd pic).