Does my floor has sufficient support?

[Julius Chen]

I went in my crawl space to investigate if the structure down there can support my 120 gallon plus ~30 gallon sump setup. Do you think the floor as is had enough capacity to support my setup? Biggest concern is if the floor tilt/give in, the tank may slide over and may crush somebody nearby.

My tank footprint is 48"x24", and it is 24" tall. There is a sump of ~30 gallon in the stand below the tank. So total weight with water, glass, stand, substrate, rocks etc. proabably will be over 1,500 pounds, right?

First picture attached is a diagram, showing my tank in red rectangle. The main beams are one to the upper left and lower right. The main beams are 66" from each other. The cross support are those dotted lines. They are about 16~17 inches from each other, and they intersect the tank by 45 degrees. As shown in this diagram, the tank's footprint will intersect 3 cross beams no matter where I place it.

Second photo shows a support to one of the two main beams. It is made of concrete, supporting the horizontal main beams resting on its top. The supports for main beams are 80" apart on one of the two beams, and on the other one about 40" apart.

Third photo shows how the cross beams look like. I did not measure them, but remember they are probably 2"x4" wood. There appear to be plywood going up from the cross support to the hardwood floor above it.

 

[Dragonvale]

If I'm reading that correcting your tank would be going diagonal on two cross support beams. And those cross support beams are your 3rd picture posted? If so I'd go under there and add two 4x4's with jacks. That's what I did with a 250 with a 40 gallon sump. You would be able to give a light jump and you wouldn't see the surface of the tank move (I stopped all pumps and returns to test whether or not the floors flexed). Sorry if it seems like a pain which it is but better safe than sorry. I'm no contractor but that's what I did. Good luck.

 

[Julius Chen]

Dragonvale,

In worst case, the tank should be able to sit on 3 separate cross support beams, though the 3rd one will intersect with the tank foot print only ~10 inches (measured from both sides of the tank, so the beam itself underneath the tank should be about ~14 inches long).

The 4th cross beam (to the lower left corner of the tank) will be outside the tank's footprint, but very close to it.

I'd think this is more than just 2 support beams. But wonder if this means I have 2.5 cross beams or 3 cross beams supporting the setup.

 

[greengeco82]

Looks like your support beams are 4x4 and your cross beams are 2x4. I personally would be nervous putting all of the tank weight on the cross beams. I would also suggest more support.

 

[woodnaquanut]

That's a strong looking support system you have there. The post shown is 4x4 supporting a 4x6 (maybe 4x8) beam which supports engineered I beam joists. The joists only span 66 inches. Should be plenty strong.

If you feel you need more support to prevent any possible vibration while walking, you could put another 4x6 beam between the existing 4x6 beams. Proper support for the new beam would be a reinforced footing and either jacks or posts.

 

[Meshmez]

Looks like your support beams are 4x4 and your cross beams are 2x4. I personally would be nervous putting all of the tank weight on the cross beams. I would also suggest more support.

Its hard to tell what is going on in the pic, if we could get a better pic of the beams it might help. It looks to me like its 2x4's on either side of a OSB sheet vertically, making an I beam.
like this:

hard to tell if its that or if the osb is the sub floor. if the osb is sub floor and the cross beams are the support i would definitely add support. i doubt that would be to code though, so i kinda doubt thats the case.

 

[AHA]

I used mobile home piers to support the beams underneath my tank. They were made out of metal and adjustable, kind of looked like automotive jack stands.

 

[Julius Chen]

I will go down there in a week to take another look.

Most likely I will do something. Question is what are the options and products to choose from.

Options I can think of are:
1. Add a third main main beam in the middle between the two main beams in my photo;
2. Add a few (maybe 2) pillar on concrete base, or mobile home piers.
3. other?

The two options above both require foundation, as a stand sitting on dirty will sink over time. Do I dig a bigger hole and pour in concrete? That'd be too much work for me, esp. there is only 21 inches clearance in the crawl space.

Thanks!

 

[Meshmez]

I used these https://www.amazon.com/Akron-Produc...295917&sr=8-1-spons&keywords=floor+jack&psc=1 in the appropriate height. I attached the bottoms to the wide side of a 8 foot long 2x8 (or 2x10, i forget which) and then attached the top to a 4x6 which i pushed up to support the floor. I figure the 2x8 base should be plenty to prevent it from sinking. I did move the loose dirt out of the way so that the board is sitting more solid.

 

[Julius Chen]

So the bottom 2x8 just sits on top soil? Will it get wet and rot with ground moisture and/or rain in the winter?

Do you have to go back there from time to time to adjust the height, as this whole floor jack setup may sink?

Does the top 4x6 wood column contact the bottom of the cross beam shown in my photo, or it goes in parallel to the vertical OSB (those vertical plywood in my photo) and then reach the lower surface of the sub floor?

Thanks!

Wi

I used these https://www.amazon.com/Akron-Produc...295917&sr=8-1-spons&keywords=floor+jack&psc=1 in the appropriate height. I attached the bottoms to the wide side of a 8 foot long 2x8 (or 2x10, i forget which) and then attached the top to a 4x6 which i pushed up to support the floor. I figure the 2x8 base should be plenty to prevent it from sinking. I did move the loose dirt out of the way so that the board is sitting more solid.

 

[AHA]

The pier sit on a "pad", all that is a piece of treated lumber. Since it's treated you wouldn't have to worry about rot, and there shouldn't be any type of moisture under your house. unless a pipe breaks or something. The treated lumber should measure 2x12. Once you set it you shouldn't have to go and adjust it anymore. The piers come in different heights and can be adjusted 8-10 inches.

 

[Meshmez]

I would use pressure treated lumber for the 2x8 if i did it again, I unfortunately did not.

My crawlspace stays dry, even in the winter, so im not too worried about it. you could potentially put concrete pavers under it to separate it from the dirt.

The structure under my house is different from yours. i dont have the cross supports, just 2x6 t&g subfloor so i added my support between the 2 support beams, under the tank.

I will go back under periodically to check the height, but im not expecting a ton of change.

 

[Julius Chen]

I went down there again, and confirmed the cross support joists are exactly like the photo by Meshmez in post #6. And the subfloor sitting on top of this I-beam shaped cross joists is plywood.

Below are the dimensions of various beams/joists:

A. "I-beam" cross support joists:
i. the top and bottom wood are of same size 2"x1 3/8"
ii. the vertical piece is 1/2" in thickness, and 7" tall.

B. Main beams
i. one main beam (the upper left in the diagram in my original post) is 7.5"x5.5"
ii. The other main beam (lower right in my diagram): 9.5"x5.5"

As shown in the diagram in my first post, the upper left side of the tank is no more than 1" away from (or it may even be right on) the top of the main beam underneath it.

So love hear your comment as to how strong this support structure is.

I am thinking to provide two more support per the plan below. Love to hear any suggestions for revisions:

1. There will be 3 cross support joists going under the tank as seen in the diagram. I will add two jack stands, one each to the outside cross joist under the tank. There is a drain pipe below the middle joist, so I don't have access to the joist unless rerouting the pipe.

2. I will lay two pieces of 1' thick flagstones as foundation. Wonder if flagstone is strong enough for this purpose?

3. Purchase 2 of these https://www.amazon.com/Akron-Product...oor+jack&psc=1

4. Screw 2"x6" treated wood to the bottom plate of the jacks, and sit them over the flagstone.

5. Screw 4"x6" treated wood to the top plate of the jacks. One jack will support the left joist beam (out of the 3 joists running under the tank), and one jack will support the plywood subfloor near the right joist beam.

6. Turn the jack stands to raise the wood until in firm contact.

7. Revisit in a month to adjust further in case the new setup sinks into ground a bit.

 

[Meshmez]

im not a structural engineer, so take all this with that in mind.

Flagstone is probably not a good idea. if you're going to do something like that i would say use these.. http://www.homedepot.com/p/12-in-x-12-in-Pewter-Concrete-Step-Stone-71200/100333077

If you can use a 2x8 (or even wider) for the base its probably better, spreads the weight over more area so its less likely to sink in.

make sure you can get the boards under the house. I had to remove one of my foundation vent covers to be able to get the boards under there.

When i did mine, i laid the 4x6 out and laid the 2x8 on top. I centered and lined up the 2x8 and clamped it to the 4" side of the 4x6. I then used the jack bracket plate as a template to drill pilot holes for the lag bolts that hold the jack plates to the boards. i drilled through the 2x8 and into the 4x6 so that everything is lined up. then i mounted the jack plates to the boards. it was easy to do this out in the open, i didnt want to try to line everything up and do it under the house.

 

[Julius Chen]

is the 4x6 part of your existing joists, or just a piece of new wood to assist you drilling in?

I was thinking to use large screws to secure the treated wood to the metal plates. If you are to use lug bulks, wouldn't you have one end of the bolts sticking out and so the wood surface will not stay in contact with the joists on the top (or the concrete foundation at the bottom)?

im not a structural engineer, so take all this with that in mind.

Flagstone is probably not a good idea. if you're going to do something like that i would say use these.. http://www.homedepot.com/p/12-in-x-12-in-Pewter-Concrete-Step-Stone-71200/100333077

If you can use a 2x8 (or even wider) for the base its probably better, spreads the weight over more area so its less likely to sink in.

make sure you can get the boards under the house. I had to remove one of my foundation vent covers to be able to get the boards under there.

When i did mine, i laid the 4x6 out and laid the 2x8 on top. I centered and lined up the 2x8 and clamped it to the 4" side of the 4x6. I then used the jack bracket plate as a template to drill pilot holes for the lag bolts that hold the jack plates to the boards. i drilled through the 2x8 and into the 4x6 so that everything is lined up. then i mounted the jack plates to the boards. it was easy to do this out in the open, i didnt want to try to line everything up and do it under the house.

 

[Meshmez]

the 4x6 is what i have on top of the jacks, pushing up against the floor.

you just need the right length lag bolts so they dont go through

 

[Julius Chen]

I never used lag bolts before. Did some research just now - did you use nuts on the threaded side of the lag bolts? These nuts will be in the way for wood to wood contact/support, right?

If you don't use nuts, then the bolts grab the wood by its thread? In that case, wouldn't make more sense not to predrill, so you end up with more bite from the thread?

Someone suggests to simply use structure screws, because they are just as strong (if not more), and quicker to install. For my purpose, I think any types of screw of right length should work?

the 4x6 is what i have on top of the jacks, pushing up against the floor.

you just need the right length lag bolts so they dont go through

 

[Meshmez]

lag bolts are self tapping. I drilled a pilot hole to make it easier to thread. if you use too big of a bit then yes, the threads will have less to bite into.

in the end, yes. you can probably use any screw

 

[Julius Chen]

I went in and installed two jacks this afternoon. Mission accomplished.

Materials used:

1. Jacks: https://www.amazon.com/gp/product/B0052PLEOY/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

2. 2x8 treated wood

3. A few pieces of flat concrete pavers

4. Lag screws and washers.

I pained the wood with primer/sealer to help fight moisture over time. Also used marine grease over the thread of the jack's stems.

Photos attached. Now look forward to moving the tank setup to its final location!

 

[ThRoewer]

I have my tank (100 gal + 40 gal sump) on the second floor. I placed it next to a load bearing wall where underneath is also a walk-in closet which hopefully adds additional support. The thing that really scares me are the termites that are chewing everywhere on the house (the owner thinks it isn't a problem anytime soon).

One thing I really miss from Germany - solidly build houses with double walls of bricks and steel enforced concrete floors.