Framers and Structural Engineers Required!

Hello, looking to see if anybody on here has advice or feedback on a stand design that I'm looking into when planning my 700g plywood tank.

The black lines will be 2x4's
The brown blocks will be 2x6's

My main issue right now is designing the stand to make enough space for the sump system that I want to keep underneath. I wanted to try and get it made out of steal, but it was much too expensive for making sure my better half doesn't lose her mind when she sees the size of this tank.

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Thanks in advance for any feedback or suggestions.

I think there's a metal fab shop new castle ice. They might be able to bang it out pretty cheap. If I knew how to weld...I'd be right over!!!

*near

Thanks for the info Denizaari! I've contacted RTC to see if their welding students could make the stand, but I'm not entirely sure on the price. Right now I'm looking at around 100 board feet of 2x6 which isnt cheap, and that's not even counting the 2x4s

Do you need an extra hand? I can bring myself and sweat a little. Call me if you want me to. I'm down to come over soon and work through the night too. Anything to help out.

Cool, thanks for the help. Once I get everything set up I'll definitely need a hand. Not sure how much this monster is gonna weigh, but I'm sure I'll need a hand just moving the stand.

So, I'm a mechanical engr by degree but not necessarily by practice, and I'm in grad school for my MS in Civil and Env Engineering. Not a structural engineer, but my sense is that this stand is over built. The tank is going to weigh something like 5000 pounds, but most structural wood is rated for over 350 psi, so in a 2 x 6 (actually 1.5 x 5.5) you get 8 square inches, and about 2500 pounds of load before it buckles. Technically you could hold up your tank with 2 2x6's. I also think all the cross 2x4's are perhaps unnecessary. I could see one or two in order to increase the stiffness of the wood top, but you don't need so many for that, and the rest are just overkill.

Totally oversimplified, I know, but it's enough that I would seek out someone more qualified before I bought all that board feet of lumber, and before I built a stand that I could barely move, especially since you're struggling to fit the sump underneath. I think you could thin out the supports by at least one.

Metal would be the way to go for such a big tank stand, I'd think. Sorry not more helpful, but I could look into it more if you don't find a better qualified professional.

What are the dimensions of the tank? Looks like way overkill. Proper joinery is just as important as using the proper lumber. You don't want your cross members supported by screws alone.

Do you really mean board feet, or lineal feet? 1 board foot = 12 sq inches x 1 inch thick.
An 8 ft 2x6 = 5.5 bf

hose91 wrote:So, I'm a mechanical engr by degree but not necessarily by practice, and I'm in grad school for my MS in Civil and Env Engineering.  Not a structural engineer, but my sense is that this stand is over built.  The tank is going to weigh something like 5000 pounds, but most structural wood is rated for over 350 psi, so in a 2 x 6 (actually 1.5 x 5.5) you get 8 square inches, and about 2500 pounds of load before it buckles.  Technically you could hold up your tank with 2 2x6's.  I also think all the cross 2x4's are perhaps unnecessary.  I could see one or two in order to increase the stiffness of the wood top, but you don't need so many for that, and the rest are just overkill.  

Totally oversimplified, I know, but it's enough that I would seek out someone more qualified before I bought all that board feet of lumber, and before I built a stand that I could barely move, especially since you're struggling to fit the sump underneath.  I think you could thin out the supports by at least one.  

Metal would be the way to go for such a big tank stand, I'd think.  Sorry not more helpful, but I could look into it more if you don't find a better qualified professional.  

Thanks for the info, hose91. I wasn't sure the breaking strength of a 2x6, but knew it was pretty high. The 2x4's are really just going to be the frame work holding the 2x6's together, and shouldn't really provide any support for the tank. All of the weight of the tank will be resting completely on the 2x6's, and because the tank will be almost 6000lbs of water alone...Overkill will help me sleep at night.

I can adjust the placement of the outside 2x6's to provide more room for the sump, or design a sump system on the side of the tank that would allow pothos and peace lily's to grow out of the sump and provide additional bio filtration.

Metal is my first choice, but the stand by itself was quoted at $1200. If I can build a stand from 2x6's that'll hold up a full size pickup truck for $240, then the rest of the money can go towards the tank and filtration.

plaamoo wrote:What are the dimensions of the tank? Looks like way overkill. Proper joinery is just as important as using the proper lumber. You don't want your cross members supported by screws alone.

Do you really mean board feet, or lineal feet? 1 board foot = 12 sq inches x 1 inch thick.
An 8 ft 2x6 = 5.5 bf

The tank is going to be 8' x 4' x 3' - 719g

The weight of the tank will be supported by the 2x6's, and the 2x4's will only be there to be a frame for the supporting structure.

Its been 15 years since I worked construction, so I think its lineal feet I meant. Just the length of each board divided by the number of cuts to make the 2x6 support structure.

Is there any structure on the bottom of the tank other than the perimeter? How do you plan to join the cross members to the posts?

Im not sure if you have looked at MFK under the DIY section, but tons of big builds there. Might give you some inspiration.
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plaamoo wrote:Is there any structure on the bottom of the tank other than the perimeter? How do you plan to join the cross members to the posts?

There will be a 4' x 8' plywood sheet on the top and possibly on the bottom of the stand. This will be done to help spread the load of the tank. Once the stand is completed, it might get the fancy treatment with outer layers of stained oak but that will only be if its going to be brought into the house later on.

The cross members will be screwed and glued. 3 and 4" wood screws...lots of them. I was contemplating lag bolts to go all the way through each 2x6 - 2x4 - 2x6 but that's an enormous amount of drilling, and may truly be overkilling the overkill. Although, lag bolts may definitely be used with the tank is built.

DMD123 wrote:Im not sure if you have looked at MFK under the DIY section, but tons of big builds there. Might give you some inspiration.
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I'm a total MFK DIY stalker...I think I've read every big build on that website several times! Its like a really bad addiction seeing all those big tanks!

Its what makes me stay up at night thinking of ways to build tanks from my bucket list.

CMooreCichlids wrote:

DMD123 wrote:Im not sure if you have looked at MFK under the DIY section, but tons of big builds there. Might give you some inspiration.
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I'm a total MFK DIY stalker...I think I've read every big build on that website several times! Its like a really bad addiction seeing all those big tanks!

Its what makes me stay up at night thinking of ways to build tanks from my bucket list.

LOL, that site has given me all types of ideas. I have to really limit my time there or else I get the bigger tank twitch.

DMD123 wrote:

CMooreCichlids wrote:

DMD123 wrote:Im not sure if you have looked at MFK under the DIY section, but tons of big builds there. Might give you some inspiration.
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I'm a total MFK DIY stalker...I think I've read every big build on that website several times! Its like a really bad addiction seeing all those big tanks!

Its what makes me stay up at night thinking of ways to build tanks from my bucket list.

LOL, that site has given me all types of ideas. I have to really limit my time there or else I get the bigger tank twitch.

Yes its a very bad influence. This tank that I'm planning will hold pbass, altifrons and red hooks...but my next tank will be a 12' planted altum tank. I just need to sacrifice a 125g tank for the front and back panels.

I was asking about the tank itself. Are there braces of any sort other than the perimeter frame? If you're going with that design I'd consider through bolts. You won't need half of those posts IMO.

plaamoo wrote:I was asking about the tank itself. Are there braces of any sort other than the perimeter frame? If you're going with that design I'd consider through bolts. You won't need half of those posts IMO.

I havent decided 100% on the tank itself, although I will be using lag bolts to secure the frame to the base of the tank.

I'll be framing it much like a house, with metal brackets for added support and fiberglass covered in Pond Armor. I've seen it work with lag bolts only, and no other framing.

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This is one of the nicest tanks I've seen, and my inspiration for getting a large tank built.

I scanned through this thread. Pretty sure this wasn't mentioned. With your current design above you will have about 20 inches between each support. This is very little clearance to slide large equipment in such as a sump, be able to maneuver it around into position, then you will have to wiggle yourself in there for the plumbing and what not. I would either use pine 4X4's or double up 2X4's for the 4 corners and then use them in the middle @ the 4 foot mark. One in the back, front and one right in the middle. I then would frame around the posts using 2X4s. After it's framed corner to corner I would use 2X4's on the bottom front to back. This is what I would also use to support the middle support. Then lay in a sheet of ply wood for the floor of the stand. Then stain and seal the floor and anywhere else that's going to be tough to get to before continuing. You will notice after the flooring is in the structure will be solid (don't forget to square everything up before laying the floor).
Also, all the 2X4's need to be installed with crown up. The weight of the tank and water will lay the structure flat. For the top you could mimic the floor framing design. Then choose to either slap ply wood on the top or just leave it open.
For a nice finish you can choose to use finished ply wood and 1X4's for the skin. This is what I did on my 7' stand. Then finish up with any type of stain/sealant you want.
You may have to add supports for doors if you are going to hang them, or you can choose removable panels for the front using industrial clips or magnets.

This design will allow you access to slide a much larger sump in or multi sumps in if you wish.

No pine, Doug fir! Select boards without a crown. It will be well worth your while to buy quality lumber. The top needs to be flat. If it's not you'll need to run a planer over it.

plaamoo wrote:No pine, Doug fir! Select boards without a crown. It will be well worth your while to buy quality lumber. The top needs to be flat. If it's not you'll need to run a planer over it.

  I agree.

I did this too, digging through piles of lumber picking out the straightest pieces. When I was done with mine it was off no more than 1/16 measured from every angle.  I was proud of myself

fishNAbowl wrote:I scanned through this thread. Pretty sure this wasn't mentioned. With your current design above you will have about 20 inches between each support. This is very little clearance to slide large equipment in such as a sump, be able to maneuver it around into position, then you will have to wiggle yourself in there for the plumbing and what not. I would either use pine 4X4's or double up 2X4's for the 4 corners and then use them in the middle @ the 4 foot mark. One in the back, front and one right in the middle. I then would frame around the posts using 2X4s. After it's framed corner to corner I would use 2X4's on the bottom front to back. This is what I would also use to support the middle support. Then lay in a sheet of ply wood for the floor of the stand. Then stain and seal the floor and anywhere else that's going to be tough to get to before continuing. You will notice after the flooring is in the structure will be solid (don't forget to square everything up before laying the floor).
Also, all the 2X4's need to be installed with crown up. The weight of the tank and water will lay the structure flat. For the top you could mimic the floor framing design. Then choose to either slap ply wood on the top or just leave it open.
For a nice finish you can choose to use finished ply wood and 1X4's for the skin. This is what I did on my 7' stand. Then finish up with any type of stain/sealant you want.
You may have to add supports for doors if you are going to hang them, or you can choose removable panels for the front using industrial clips or magnets.

This design will allow you access to slide a much larger sump in or multi sumps in if you wish.

And I may be kidnapping you soon fishNAbowl.   

I will need to rework the plans for this stand, and see about replacing the 2x6's with doubled up 2x4's. I know it may be overkill to have so many structural supports, but I want to be able to park my wife's SUV on this thing without it budging.

fishNAbowl wrote:

plaamoo wrote:No pine, Doug fir! Select boards without a crown. It will be well worth your while to buy quality lumber. The top needs to be flat. If it's not you'll need to run a planer over it.

  I agree.

I did this too, digging through piles of lumber picking out the straightest pieces. When I was done with mine it was off no more than 1/16 measured from every angle.  I was proud of myself

This is a big issue...Its damn near impossible to find all of the lumber needed for a job like this when none of the pieces are straight. I'll have to spend half a day in a lumber yard just to get a handful of straight pieces.

Umm,  I'm a licensed structural engineer and this is (kind of) overbuilt.  I say (kind of) because I'd frame it differently, but the way that you've drawn it, you don't actually have a lot more wood in there than you need.  The bending capacity of frame is proportional to the square of the depth, so you will get a lot farther going with frame members that are deeper than 2x4s.  i.e. if you used 2x6s, you could almost remove all of the interior columns:  the allowable stress for No. 1 grade doug fir under wet use with permanent loads is 918 psi, if you space your joists at 16" they would be at 931 psi, so if you went with 12" spacing, you'd be good to go.  That being said, deflection could be a problem (I calculate it at about 1/16" under that load).  For peace of mind I'd probably go with select structural grade 4x6s or, even better, 2x8s.

This isn't really that much load when it comes down to it, because it's distributed across a large area, even being very conservative, I'd say your load might be 220 pounds per square foot (psf), the water alone is 187 psf; this is similar to the loading for a commercial storage (filing) room or library.  Most of the heavy industrial structures I work with are designed for 600-1000 psf.

You need to make sure to pay attention to the lumber grade.  There is a HUGE difference in the load carrying capacity of the framing depending on the lumber - 'stud' grade lumber is barely over half the capacity of No. 1 grade.   I wouldn't even consider building something like this with less than No. 1 grade lumber, select structural would be better.  A lot of standard lumber yards don't have anything better than 'stud' grade in 2x4 and sometimes 2x6, but even Lowes or Home Depot usually carry 'No. 1 & Better' for 2x8's or larger.

There are additional reductions in the capacity if you have notches cut in the framing or use incised (pressure treated) lumber.  An additional benefit of this is that usually the higher grade stuff is straighter.

-Justin

jrygel wrote:Umm,  I'm a licensed structural engineer and this is (kind of) overbuilt.  I say (kind of) because I'd frame it differently, but the way that you've drawn it, you don't actually have a lot more wood in there than you need.  The bending capacity of frame is proportional to the square of the depth, so you will get a lot farther going with frame members that are deeper than 2x4s.  i.e. if you used 2x6s, you could almost remove all of the interior columns:  the allowable stress for No. 1 grade doug fir under wet use with permanent loads is 918 psi, if you space your joists at 16" they would be at 931 psi, so if you went with 12" spacing, you'd be good to go.  That being said, deflection could be a problem (I calculate it at about 1/16" under that load).  For peace of mind I'd probably go with select structural grade 4x6s or, even better, 2x8s.

This isn't really that much load when it comes down to it, because it's distributed across a large area, even being very conservative, I'd say your load might be 220 pounds per square foot (psf), the water alone is 187 psf; this is similar to the loading for a commercial storage (filing) room or library.  Most of the heavy industrial structures I work with are designed for 600-1000 psf.

You need to make sure to pay attention to the lumber grade.  There is a HUGE difference in the load carrying capacity of the framing depending on the lumber - 'stud' grade lumber is barely over half the capacity of No. 1 grade.   I wouldn't even consider building something like this with less than No. 1 grade lumber, select structural would be better.  A lot of standard lumber yards don't have anything better than 'stud' grade in 2x4 and sometimes 2x6, but even Lowes or Home Depot usually carry 'No. 1 & Better' for 2x8's or larger.

There are additional reductions in the capacity if you have notches cut in the framing or use incised (pressure treated) lumber.  An additional benefit of this is that usually the higher grade stuff is straighter.

-Justin

Ahh man, I shouldnt have tried reading this after work. Now I'm gonna have to read this like six more times before I understand half of it!

Thanks for the info, Justin. I'm gonna have to chew on this for a while before making changes to the plans.

Here's some snap shots of the stand I built. It probably won't help with structural integrity questions since this tank is only 140 gallons. But it may help on 'how to finish' . I have no degrees in engineering. I just looked how others made their stands, a bit of internet reading and went to town.

This stand is 7 feet long and about 20 inches wide.

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2 2X4's where used on each corner. The middle part in the front is 10inches. I used framing 2X4's 10" apart and the skin of the stand is finished 1" paneling.

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This thing ended up being stout. The way the floor is attached and interlocked into the frame, and the way I interlocked the skin this design is completely solid.  The front middle support was installed mainly for the doors I never installed. I also used a router and rounded all the corners of the wood paneling skin.

If you decide to put a skin on your stand this can be counted for in structural strength. 4X4's on the corners, and an outside skin on the ends using 3/4 or 1" solid wood paneling , or even a quality plywood is going to beast up the strength quite considerably.   Same for a middle piece like my stand. If I was going to make a stand for a 8' tank. I would make a middle section 20" - 24" wide using 4X4's or doubled up 2X4's then cover them with a 3/4 -1" skin of solid wood or a quality plywood. Or you could go with a 3 door design, placing 4X4's or doubled up 2X4's every 2 1/2 feet (roughly). 24" should be more than enough opening to slide 1 or 2 fat sumps underneath.

At the time when I was putting the skin on my stand I constantly measured for trueness. A skin will make the design completely solid..

I see the steel idea is somewhat dead, yet being a machinist I must advocate for the sweet stuff! You could end up using a lot less material and get a stand that is twice as stout and with the right finish coating could outlast the tank. Sure, you will probably spend a little more on material. I also happen to weld for a hobby!   

Addicted2CAs wrote:I see the steel idea is somewhat dead, yet being a machinist I must advocate for the sweet stuff! You could end up using a lot less material and get a stand that is twice as stout and with the right finish coating could outlast the tank. Sure, you will probably spend a little more on material. I also happen to weld for a hobby!   

I really would prefer a steel stand, but having been quoted $1200 for the stand its kinda out of my reach right now.

I was even looking into getting the material separately, and ordering enough 2" tube steel is still going to cost twice as much (or more) as the lumber and materials. This isn't even taking into account the finish coating materials.

Addicted2CAs, if you got a sweet hook up to help with a steel stand I'd be more than willing to entertain the idea of getting some metal working done. I'm still toiling over the design of the wood stand, and whether I can reach the height I'm wanting for the sump system, or if I'll need to make a short stand with the sump system on the side of the tank.

I too am a strong sump and wet/dry guy and it makes ever wood stand I make tough to design around this. Cool part about a steel stand is that a lot less material is used, making way for more design ideas to hold and position your sumps. If you really want to go all in, I'd consider a ball bearing sled that your sumps sit on, so come maintenance time you could open the side door of the stand and slide the whole deal out. Just a thought! This is my favorite part about the hobby! I too am a strong sump and wet/dry guy and it makes ever wood stand I make tough to design around this.