Please help me determine if I need to reinforce my floor (pics/info)

[magicstix]

I'm planning out my next aquarium build. I'm pretty sure I can get away with a 180 gallon no problem, but I want to go big, much bigger, say 240 gallons or more bigger. The only problem is that my den isn't exactly on concrete, and I'm trying to determine if I need to reinforce the floor.

"Just do it! It's safer than sorry." Isn't a particularly helpful answer, as it's not as simple as just throwing a couple of jackposts in the crawlspace. The crawlspace floor is covered in gravel, which covers uneven bedrock, so I'm not sure I can get a level base for the jackposts. If I can put the concrete bases on top of the gravel and have no problems, so be it, but I don't know if that's safe or not.

So here's the situation. I'm looking at an 8 foot long tank, which means a minimum of 240 gallons, so a minimum weight of around 3200 pounds when water, stand and rocks are included. Obviously going up in gallonage will increase the weight footprint, but if I can fit a 240 without reinforcing, I'd do that over a 300 gallon with reinforcing.

The area where it's going is as follows: I have a den, 12 x 11 feet, over a 4 foot crawlspace. On 3 sides of the den I have concrete foundation walls (one of which is the concrete slab of the garage). The tank would be perpendicular to the floor joists, which are 2x6s 12 feet long (I think). Joists are spaced 16 inches apart. Each end of the joist appears to rest on top of a 2x6 on its side, which in turn sits on the garage concrete slab at one end, and the concrete foundation wall at the other. The "floor" of the crawlspace is gravel varying in depth over uneven bedrock (but has been leveled flat on top). It basically looks like they dug up the area when building the house and said "screw it, this rock's too big" and covered it over with gravel. The house was built in 1984.

Here are a couple of pictures from below (looking into the crawl space; the tank would be on the other side of the ceiling almost exactly over the AC duct on the left):

And here's a closeup showing the end of the floor joists resting on the 2x6 on the concrete slab:

Here is a mockup of everything in blender, with the 8-foot tank blocked out against the wall:

The tank will span at least 5 joists, and could be positioned across 6 (top down view):

My thinking is that this is perfect, because the tank will be up against the wall that's on the side with the garage concrete slab, and that the load will almost immediately be transferred into the concrete slab, meaning I *won't* need to reinforce the floor.

Here's what I mean (front ortho view, similar viewpoint to the real photos):

Now, I'm not entirely opposed to the idea of reinforcing the floor. I do, in fact, have all of the parts required (a 12 foot 4x4, 2 appropriate sized jack posts, and concrete blocks used for foundations of decks), but because of the gravel floor, I'm not sure I can do it safely or correctly.

These are the concrete base blocks I'm talking about:

Would these be OK on top of leveled gravel, or would they need something more sturdy under them?

If I can't reinforce the floor correctly, I would prefer to not to have to at all. 240 gallons seems to be my sweet spot in terms of budget and space, but if I *have* to reinforce the floor, and I can't do it easily, I'll be forced downsize my plans to 180 G.


So, what are everyone's opinions? Do I need to reinforce the floor for 240G or higher, or am I alright given the situation? Do my loading expectations (i.e. the fact that the tank is very close to the garage concrete slab means most of the load will go into the slab and not the joist) make sense?

 

[Flippers4pups]

Quick answer from me, I would sister the floor joists in the length of the tank. Add 4x4 or 6x6 that length under the front of the tank and add floor jacks under each side. If possible I would dig where each jack would stand, down to bedrock and set the jacks on it. If not to bedrock, dig for piers and pour concrete in the holes and once set, place the jacks on the pier.

I sistered my joists under my 125 and did the 4x4 under the front of my tank and placed jacks under each end. I did this mostly to keep the tank from "rocking" on my living room floor.

 

[redfishbluefish]

I tend to be anal when it comes to load. I sistered 2 x 10 joists for the 90 gallon tank I installed and also threw in a perpendicular 2x6 by three beam to support all adjoining joists......with blocking as well.

You might be alright, but unfortunately load isn't a simple calculation. Here's what I'd do so that I could sleep comfortably at night.....I'd begin by adding blocking to all adjoining joists in this room....maybe centered to the room or if a long span, every third. This blocking adds tremendous strength to the load capacity of a floor by transfering load.

The second thing I'd do is to throw out that 4x4....they are useless unless your putting up a fence. Make a double or ideally a triple beam out of 2 x 8's and glue and screw this beam (code requires bolts, but that's overkill), every minimally 18 inches. Make footing....if pouring your own, I like 2 x 2 x 2 foot footing.....but the precast you show would work as well. Now here's where you could use that 4 x 4.....With at least three footings, support that beam to the the footings....with that beam running parallel to the existing joists.....and close to the outer edge of where the tank will sit. You should need a hammer to hit these 4x4's into position to support this new beam.

I hope I've explained sufficiently. I don't have the great pictures you've posted to show what I'm talking about.

 

[bif24701]

Quick answer from me, I would sister the floor joists in the length of the tank. Add 4x4 or 6x6 that length under the front of the tank and add floor jacks under each side. If possible I would dig where each jack would stand, down to bedrock and set the jacks on it. If not to bedrock, dig for piers and pour concrete in the holes and once set, place the jacks on the pier.

I sistered my joists under my 125 and did the 4x4 under the front of my tank and placed jacks under each end. I did this mostly to keep the tank from "rocking" on my living room floor.

This is a good idea and will help keep the tank and floor stable. Good thing it sits right there buy suppor. It can keep your tank from bouncing or vibrations when you walk by it.

I would not do 4x4 or 6x6. This is what I would do. Measure out 3' from the supporting wall or find exactly where the front of the tank will sit. Use two 2x8" and make a beam running perpendicular to each joists the tank will sit on. Adhesive and screws to secure the two together. Use block to support the 2x8's on each end, just get the soil below level and packed before stacking blocks like in the picture below. This will be far more stiff than using 4x4 or even 6x6. Besure to attach each joist to the beam with the prober clips. Do this and your floor won't budge!

 

[Idoc]

If you don't support the floor, at least take initial sag measurements of the floor before you place the aquarium. Then, while filling the tank, take additional measurements...if it shows significant sag initially, it's probably only going to get worse. Then at least you know you need to drain the tank and put the effort into reinforcing the floor. Personally, I wouldn't even consider that large of an aquarium weight without reinforcing since not placing directly onto a concrete slab. Shoot...I'm nervous that a 75g tank was going to be too much for my floors...decided to put the tank in the finished basement for piece-of-mind.

 

[miyags]

Around here min spec for floor joist is 2x10's, and most beef them up for 220 or larger tank.

 

[bif24701]

I tend to be anal when it comes to load. I sistered 2 x 10 joists for the 90 gallon tank I installed and also threw in a perpendicular 2x6 by three beam to support all adjoining joists......with blocking as well.

You might be alright, but unfortunately load isn't a simple calculation. Here's what I'd do so that I could sleep comfortably at night.....I'd begin by adding blocking to all adjoining joists in this room....maybe centered to the room or if a long span, every third. This blocking adds tremendous strength to the load capacity of a floor by transfering load.

The second thing I'd do is to throw out that 4x4....they are useless unless your putting up a fence. Make a double or ideally a triple beam out of 2 x 8's and glue and screw this beam (code requires bolts, but that's overkill), every minimally 18 inches. Make footing....if pouring your own, I like 2 x 2 x 2 foot footing.....but the precast you show would work as well. Now here's where you could use that 4 x 4.....With at least three footings, support that beam to the the footings....with that beam running parallel to the existing joists.....and close to the outer edge of where the tank will sit. You should need a hammer to hit these 4x4's into position to support this new beam.

I hope I've explained sufficiently. I don't have the great pictures you've posted to show what I'm talking about.

Dang! Do great minds think alike or what!

 

[ReeferMaddness843]

Don't ask me. I'm the guy in a second floor apartment that had a 90 gallon. Lol. Have an 80 shallow and feel much better now.
In all seriousness though, great advice here!

 

[redfishbluefish]

Dang! Do great minds think alike or what!

No! It's just anal folks think alike.

 

[Idoc]

Don't ask me. I'm the guy in a second floor apartment that had a 90 gallon. Lol. Have an 80 shallow and feel much better now.
In all seriousness though, great advice here!

That's hilarious...just think, that poor family on the first floor never knew that they could have received a "bath" at any moment, lol.

 

[magicstix]

That's hilarious...just think, that poor family on the first floor never knew that they could have received a "bath" at any moment, lol.

We had a 90 gallon on the 2nd floor loft at my parents' house when I was in high school. No one ever gave it a second thought...

 

[Carlos Danger]

I would use your "deck concrete blocks" and stack them on top of the heavier much more capable house concrete blocks. I used a glue lamb to span the length and in-between used the 4x4's. Here's what I did.

 

[magicstix]

I would use your "deck concrete blocks" and stack them on top of the heavier much more capable house concrete blocks. I used a glue lamb to span the length and in-between used the 4x4's. Here's what I did.

The big problem I see is that I have the gravel floor. I'm not sure how deep the gravel is on the side of the space where I would need to put the jackposts, but I know the gravel sits on uneven bedrock. No matter how sturdy the concrete base, it doesn't matter if I can't get a stable floor to put it on...

 

[Carlos Danger]

I also doubled up all the bearing wall or pony wall 2x4's, doubled up all floor joists, and filled the floor joists and packed the TJI floor joists to the I beams. It Definitely makes it stronger.

 

[Carlos Danger]

I'm sorry about that. It also would help out if you blocked out the floor with 2x10 or 12"s not sure what that is you have and block the floor joists every 18" to 24". That will really help to disperse the load. It would look like a tic tac to board when finished. You can see my blocking in this picture.

 

[magicstix]

I also doubled up all the bearing wall or pony wall 2x4's, doubled up all floor joists, and filled the floor joists and packed the TJI floor joists to the I beams. It Definitely makes it stronger.

I could fill that whole crawlspace with concrete too. That'd guarantee I wouldn't have a problem, but it also wouldn't be good engineering.

I have to trade off the amount of cost/work in shoring up the floor vs. the size of the tank it gets me.

At this point, I think I'm still OK with reinforcing the floor so long as I can avoid having to pour concrete, but if it gets too difficult I'll have to downsize my plans.

 

[ReeferMaddness843]

That's hilarious...just think, that poor family on the first floor never knew that they could have received a "bath" at any moment, lol.

Lol! I'm running it backed up to a load bearing wall and across multiple joists. Not a drop of sweat that it's not supported well for its weight.

 

[JoshH]

If you want to avoid pouring concrete which you realistically should only do if you're willing to dig down to bed rock and pour directly onto it with drilled rebar to secure the footing's to the rock as that gravel is more than likely far too unstable to just put deck post support's on or even semi bury. I would just triple up the 2x6 joists that run under the tank, probably the cheapest and most effective solution, even if you quadrupled up the joists it would still cost significantly less and be far less effort than dealing with concrete. Don't get me wrong if it was me I'd be going the footing route but that's more of me being anal than anything else. Sistering up the joists in all reality should be more than enough. If you really want to go all out sister them up with LVL beams. Definitely the most expensive route but as far as support the only thing better would be a concrete floor. And I'm willing to bet that sill plate ( what your 2x6 joists are sitting on) at the garage end is really on a footing at the end of your garage slab and not on the actual slab as a garage floor is not structural by any means. If you do sister up the floor joists also make sure there's one under each end of your tank and cross block along where the front of the tank will be.