Best way to reinforce the floor for a 210-250 gallon tank

[208reef]

Good Afternoon,

When I built my house 8 years ago I took lots of pictures of the guts of the house as it was built in case I ever wanted to put a large aquarium in it. From these pictures could anyone recommend how to best reinforce my floor for a 210-250 gallon reef tank?

From the pictures you can see the current structure under the tank would be 5 perpendicular floor joists, 1 perpendicular exterior wall, and 1 parallel interior load bearing wall with a 2x4 pony wall sitting on footings.

I was thinking to use these Tiger Jack posts and to set them on 12"x12" concrete pavers. Then I'm assuming I'd need to put some kind of beam(s) parallel to where the tank (perpendicular to the direction of the floor joists). Assuming this is even the best method, how many jack posts should I use, where should I position them, and what dimension of beam should I use above the floor jacks?

 

[BeanAnimal]

The load would likely be fine without, being so close to the bearing wall. However, the added support will add reassurance and prevent floor bounce.

Is the floor dirt or stone?

Pavers can be rather brittle with point loads but will likely work. You can use a bit of sand to ensure good flat contact. If you feel like a little extra work you can pour some 2’ x 2’ pads with a piece or two of rebar in them. Formed with 2x4s. Would only take a 80# bags of concrete. 2 jacks would be fine with a simple beam 4x4 lumber (kiln dried), or easier just a short hunk of 4” h beam would be inexpensive. Overkill, but no floor bounce.

Snugged up, but don’t try to jack the floor.

 

[BeanAnimal]

Also, looking at that drawing, space appears to be tight. Not sure how jacks will fit if the backfill is graded to the top edge of the footing as shown in the drawing. If that is the case, the floor could be cribbed up with 4x4 or 6x6 cribs and wedges to get it tight

 

[redfishbluefish]

Disclaimer....I don't know what I'm talking about so take what I say with a grain of salt.

Here's what I'd do....you have engineered joists also commonly referred to as I-joists. It appears your pony wall simply supports a very long span of the joists. Instead of using jack posts, I'd build yet another "pony wall" since your in a crawl space that's never going to be finished. I believe you have an unfinished (gravel) floor in the crawl space and so I'd begin by putting in some kind of footing...and not just 12 x 12 pavers...more like mucho concrete. Because you have I joist, also make sure you install crush blocks at the load point...where this new pony wall meets the I joists. You should have these crush blocks where your current pony meets the joists. The last thing I'd do is strap the joist together in a number of places. Maybe one line of strapping between the two pony walls and then another line or two past the new pony wall. Strapping I joists greatly increase the load transfer to adjoining joists.

 

[BeanAnimal]

Instead of using jack posts, I'd build yet another "pony wall"....

...and not just 12 x 12 pavers...more like mucho concrete.

That is in essence what that jacks or cribs become. The difference being that that the pony walls sit on full footers, given the load they are rated to carry.

In this case there is only a small amount of load that will be transferred to the new support structure. The overall load of the tank is around 2,000 pounds. The existing joists and footers are going to carry the bulk of that load to the ground.

Even if we say that the new support will take 50% of that load, it is only 1000 pounds. On two 12x12 pads, that is 500 pounds each at 500 pounds per square foot. If we make those pads 24x24 that is 125 pounds per square foot. No need for mucho concrete or now"footers".

Because you have I joist, also make sure you install crush blocks at the load point...where this new pony wall meets the I joists.

Squash blocks are not need and will not work here, as there is no bearing wall above transferring load to the bearing below the joists (the new pony wall, cribs, or jack and beam).

The last thing I'd do is strap the joist together in a number of places. Maybe one line of strapping between the two pony walls and then another line or two past the new pony wall. Strapping I joists greatly increase the load transfer to adjoining joists.

Again, for the load in question, this really is not needed. The joists already likely have blocking to prevent twisting. The two supporting structures (the existing bearing wall and the new support) are so close together that strapping really does nothing.

The existing bearing will likely take 90% of this load with little or no floor deflection. The "new" support is peace of mind for this size tank and may help prevent floor bounce.

Not trying to be argumentative... just trying to be helpful.

 

[redfishbluefish]

Not trying to be argumentative... just trying to be helpful.

Best of luck either using a beam and jack posts, or cribbing or a short pony wall and now putting a ton or two above that creating a point load and expecting 3/8 inches of OSB not getting crushed. It's been a couple years but when I was swinging a hammer, crush blocks on a point load were a code requirement in the United States. These could be as simple as scrap 2x4's cut to fit.

Pony walls used to simply extend very long I joists (which I believe that is what is being done) have a tendency to be the cause of ....vibrational something or other....I can't remember the full name, but it's when the beam slightly twists when loaded....ie walk across it. You stop this by strapping (easier than blocking) the joists with 1x3's, within 8 feet of each strapping. This also greatly increases load transfer to adjoining joists....and again, an aging brain, but 40% load transfer sticks in my brain.

As far as a footing, for some reason your builder spec'ed 16" x 8" minimum footing for the pony wall. Josh or golly, I wonder if that was a code requirement. Don't know if I'd go that deep for whatever added support you use, but it would still be a good amount of concrete.

 

[BeanAnimal]

Not trying to be argumentative... just trying to be helpful.

Best of luck either using a beam and jack posts, or cribbing or a short pony wall and now putting a ton or two above that creating a point load and expecting 3/8 inches of OSB not getting crushed.

The weight is a load distributed over 5 joists and two bearing points separated by roughly 2 feet. We can dig deeper and do the math if needed. The force on the webbing is a very tiny fraction of its crush rating. Maybe 1% at most.

It's been a couple years but when I was swinging a hammer, crush blocks on a point load were a code requirement in the United States. These could be as simple as scrap 2x4's cut to fit.

They are called squash blocks and are meant to carry the load from the upper linear bearing surface to the lower, bypassing the joist. This is a live load over top of a joist, there is no upper bearing surface to transfer the load from. Squash blocks would simply point load spots on the subfloor (or stand!), exactly what you don’t want.

Pony walls used to simply extend very long I joists

They are no different than any other load bearing member, be it beam or footer. They are carrying the load from the bearing wall above, in this particular case. In some cases they may be less substantial and meant to only prevent span deflection.

(You stop this by strapping (easier than blocking) the joists with 1x3's, within 8 feet of each strapping. This also greatly increases load transfer to adjoining joists....and again, an aging brain, but 40% load transfer sticks in my brain.

The joists will already be blocked and the pony wall and new cribbing or beam will act as straps. There is no need to add more.

As far as a footing, for some reason your builder spec'ed 16" x 8" minimum footing for the pony wall. Josh or golly, I wonder if that was a code requirement.

No need to be flippant. In fact, as a staff member I am absolutely dumbfounded at your tone!

They are load bearing footers and spec’d as such. Look at the drawing, they are carrying the load bearing walls. So from the roof down to the soil. All the OP is doing is putting a rather small aquarium flush to a load bearing member and adding a bit of support to prevent floor bounce. If it were a 2000 gallon tank, then yes new footer and means to prevent piling and maybe I joist deformation (maybe, but even then squash blocks still would not be applicable). This tank is 2,000 pounds not 20,000.

Don't know if I'd go that deep for whatever added support you use, but it would still be a good amount of concrete.

No, it wouldn’t. The load to distribute is minimal to begin with. You are severely overthinking this for the amount of weight given.

If you honestly want to get into the math and engineering we can. You swing hammers (your words, not mine) I do too, but also do engineering and physics.

 

[Reefering1]

 

[redfishbluefish]

I believe they call that theory versus practical experience. I'm out of here....best of luck.

 

[Reefering1]

 

[BeanAnimal]

I will get you started with some of the engineering.

Typical TJI has a web design to between 100 and 400 PSI. For crush strength. The bearing wall per plan is squash blocked. Meaning the web currently carries the dead load and design live load and not the bearing load from above.

Let’s go big on current load to cover all the base worst case.
15 psd dead
40 psi live
They never carry the bearing load, that is what the squash blocks are for.
That means the TJIs have a web load of less than 1 PSI before the tank goes in, assuming a furnished home and 6” TJIs even less for taller.

Tank is about 12 square feet and fully decked out around 2000 pounds. So 166 pounds per square foot. It spans 5 joists but being next to a load bearing structure and due to subfloor 7 or more joists handle the load, but let’s call it 5.

The tank is 2 feet front to back, but the top and bottom chords of the TJI distribute the load down the length of the TJI but lets ignore that and pretend the entire load is only carried over the 2 foot span of each of the 5 joists. That is 10 feet total or 120 inches. The web is 5 inches tall, let’s ignore the chord. That is 600 square inches carrying 2000 pounds. That is 3.3 PSI for a web rated at 100 to 400 PSI. And real world a fraction of that 3.3 PSI because we made crazy assumptions to increase the load.

We can do the rest of the math if you wish for the entire floor system and support.

Disclaimer....I don't know what I'm talking about so take what I say with a grain of salt…
….I believe they call that theory versus practical .
I’m outa here… Best of luck.

You openly give a disclaimer with the first statement. No problem there, you are trying to offer help.

The issue is the second part contradicts the first and the fact that even though you admit you may be out of your depth, you want to argue with somebody who is not out of theirs. In fact, your behavior is rather childish for being a member of R2R staff and sets a pretty crappy example of how to engage in friendly conversation.

Respectfully, this is not a practical experience issue. I have practical experience (yes I have built homes from soil up) as well as a pretty deep understanding of the engineering. Instead of being combative (for absolutely no reason), why not honestly gain some knowledge to help with the practical experience part and set a better example for others?

 

[Reefering1]

 

[208reef]

The load would likely be fine without, being so close to the bearing wall. However, the added support will add reassurance and prevent floor bounce.

Is the floor dirt or stone?

Pavers can be rather brittle with point loads but will likely work. You can use a bit of sand to ensure good flat contact. If you feel like a little extra work you can pour some 2’ x 2’ pads with a piece or two of rebar in them. Formed with 2x4s. Would only take a 80# bags of concrete. 2 jacks would be fine with a simple beam 4x4 lumber (kiln dried), or easier just a short hunk of 4” h beam would be inexpensive. Overkill, but no floor bounce.

Snugged up, but don’t try to jack the floor.

Thanks for your response. The floor is dirt.

I will get you started.

Typical TJI has a web design to between 100 and 400 PSI. For crush strength. The bearing wall per plan is squash blocked. Meaning the web currently carries the dead load and design live load and not the bearing load from above.

Let’s go big on current load.
15 psd dead
40 psi live
They never carry the bearing load, that is what the squash blocks are for.
That means the TJIs have a web load of less than 1 PSI before the tank goes in, assuming a furnished home and 6” TJIs even less for taller.

Tank is about 12 square feet and fully decked out around 2000 pounds. So 166 pounds per square foot. It spans 5 joists but being next to a load bearing structure and due to subfloor 7 or more joists handle the load, but let’s call it 5.

The tank is 2 feet front to back, but the top and bottom chords of the TJI distribute the load down the length of the TJI but lets ignore that and pretend the entire load is only carried over the 2 foot span of each of the 5 joists. That is 10 feet total or 120 inches. The web is 5 inches tall, let’s ignore the chord. That is 600 square inches carrying 2000 pounds. That is 3.3 PSI for a web rated at 100 to 400 PSI. And real world a fraction of that 3.3 PSI because we made crazy assumptions to increase the load.

We can do the rest of the math if you wish for the entire floor system and support.



I think you hit the nail on the head with the first statement. No problem there, you are trying to offer help. The issue is the second part contradicts the first and the fact that even though you admit you may be out of your depth, you want to argue with somebody who is not out of theirs. Respectfully, this is not a practical experience issue. I have practical experience as well as a pretty deep understanding of the engineering. Instead of being combative, why not honestly gain some knowledge to help with the practical experience part?

Lots of great information in all your replies to this thread. I really appreciate the time you've taken to share so much detail.

 

[208reef]

The load would likely be fine without, being so close to the bearing wall. However, the added support will add reassurance and prevent floor bounce.

Is the floor dirt or stone?

Pavers can be rather brittle with point loads but will likely work. You can use a bit of sand to ensure good flat contact. If you feel like a little extra work you can pour some 2’ x 2’ pads with a piece or two of rebar in them. Formed with 2x4s. Would only take a 80# bags of concrete. 2 jacks would be fine with a simple beam 4x4 lumber (kiln dried), or easier just a short hunk of 4” h beam would be inexpensive. Overkill, but no floor bounce.

Snugged up, but don’t try to jack the floor.

Would 3000 psi concrete deck blocks work better than pavers if I want to avoid messing with concrete? Based on your feedback I was thinking of something like this just for peace of mind like you said. The floor in the crawl space is dirt, but it is very heavily compacted because they found old farmhouse septic material under my lot, so had to dig up everything, put rubber liners down and then compact dirt back in to be stable enough to pour a foundation on.

 

[BeanAnimal]

I don’t think that a jack right on the paver would fail (point load and crack the paver or pile it into the ground). There really is not going to be that much load. 1 beam and 3 jacks and pavers, even if the entire tank was resting on them would be 650 pounds per paver. Real world it will be a fraction of that even with a room full of guests. Take into account the existing load bearing structure, the joists distributing part of the load etc., and there is just not a lot of weight going to be on those added supports as long as you don’t jack them up to become the primary load bearing members. They are just there to carry any extra load.

Compacted soil has varying bearing capacities before piling (material being pushed into it or plastically deforming it ) but even on the low end (expansive clay) you are looking at 1500-2000 psf. Increase the pavers from 12x12 to 24x24 and you are at most a hundred or so psf per paver being transferred to the soil.

Those deck blocks would be fine with regard to strength. Sitting them on 24x24 pavers would further distribute the load, as they less than a square foot each alone. I just don’t think that they are needed (at all).

If the soil is not perfectly flat you can use an inch or so of paver base, level it and compact it it perfectly flat (use a screed). Or compact it (not worry about perfect) and add 1/2” of concrete (not play) sand on top of the paver base and screed it flat. This will give the pavers a good base and prevent them from being only partly supported. If you were going overboard you could place geotextile fabric down before the paver base. Just like you would for setting a paver patio or walkway. This is done to prevent the paver base from migrating into the soil, but it is a dry area and not needed.

Nope that all makes sense.

 

[208reef]

I don’t think that a jack right on the paver would fail (point load and crack the paver or pile it into the ground). There really is not going to be that much load. 1 beam and 3 jacks and pavers, even if the entire tank was resting on them would be 650 pounds per paver. Real world it will be a fraction of that even with a room full of guests. Take into account the existing load bearing structure, the joists distributing part of the load etc., and there is just not a lot of weight going to be on those added supports as long as you don’t jack them up to become the primary load bearing members. They are just there to carry any extra load.

Compacted soil has varying bearing capacities before piling (material being pushed into it or plastically deforming it ) but even on the low end (expansive clay) you are looking at 1500-2000 psf. Increase the pavers from 12x12 to 24x24 and you are at most a hundred or so psf per paver being transferred to the soil.

Those deck blocks would be fine with regard to strength. Sitting them on 24x24 pavers would further distribute the load, as they less than a square foot each alone. I just don’t think that they are needed (at all).

If the soil is not perfectly flat you can use an inch or so of paver base, level it and compact it it perfectly flat (use a screed). Or compact it (not worry about perfect) and add 1/2” of concrete (not play) sand on top of the paver base and screed it flat. This will give the pavers a good base and prevent them from being only partly supported. If you were going overboard you could place geotextile fabric down before the paver base. Just like you would for setting a paver patio or walkway. This is done to prevent the paver base from migrating into the soil, but I a dry area it is not needed.

Nope that all makes sense.

Yes, makes complete sense. I'll see what I can find at the hardware store tomorrow. Thanks!

 

[BeanAnimal]

Yes, makes complete sense. I'll see what I can find at the hardware store

Good luck. Let us know how things progress.