Jason Rhoads November 3, 2014 Share November 3, 2014 I have an interesting project for which I need some input. I want to build a storage area of sorts to fill in a space where my tank currently resides. The tank will sit on top of the storage area under which I will move my 55g refugium and my 30g sump. My question is about the strength of the frame I have built to support the tank. The span I need to cover is right at 9 feet in length and 3 feet in width but my tank is only 5 feet in length and 2 feet deep. Thus, the tank, being centered on top of the box, will not sit directly on the outside supports of the frame. At this point, I have a top frame (on which the tank will rest) constructed out of 2x4s with two 2x6s joined together running down the center of the box (the 2x6 beam only has vertical supports at either end, while the 2x4 spans have vertical support at the ends and in the center). The 2x6s span the entire length (9ft) and the 2x4s span 4ft sections (having vertical supports at their center). I have the top frame resting on a total of 8 groups of (2) 2x4s joined together to form my vertical supports. Additionally, I plan to skin the top of the frame with 1/2" plywood which will help distribute the load between the 2x6 beam and the 2x4 spans on the outside of the frame. Here are some pictures to help: My question is: Do I need to add a center vertical support to the 2x6 beam, or will this design hold a 100g tank as is without too much deflection? Thanks! Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 Jason, I am not an engineer, I usually pay them to make sure things work out and I am not liable if they don't! So don't take anything I say seriously....now that we have that out of the way...... I tend to over build everything, the things I don't like when I look at your stand are the lack of any diagonal bracing in the corners, and you don't have any hangers to support the short horizontal joists that run front to back. Those are then tied into the center pair of 2 x 6's that have no support under them in the middle (which I believe is your question). 9' is too long a span IMO and I would use use a center post with diagonal bracing in both directions at all corners. Link to comment Share on other sites More sharing options...
DCReefer1964 November 3, 2014 Share November 3, 2014 Jason, I am not an engineer, I usually pay them to make sure things work out and I am not liable if they don't! So don't take anything I say seriously....now that we have that out of the way...... I tend to over build everything, the things I don't like when I look at your stand are the lack of any diagonal bracing in the corners, and you don't have any hangers to support the short horizontal joists that run front to back. Those are then tied into the center pair of 2 x 6's that have no support under them in the middle (which I believe is your question). 9' is too long a span IMO and I would use use a center post with diagonal bracing in both directions at all corners. Jason you have been TANKED!!!! +1 on Duffy's recommendation. Link to comment Share on other sites More sharing options...
AlanM November 3, 2014 Share November 3, 2014 I have an interesting project for which I need some input. I want to build a storage area of sorts to fill in a space where my tank currently resides. The tank will sit on top of the storage area under which I will move my 55g refugium and my 30g sump. My question is about the strength of the frame I have built to support the tank. The span I need to cover is right at 9 feet in length and 3 feet in width but my tank is only 5 feet in length and 2 feet deep. Thus, the tank, being centered on top of the box, will not sit directly on the outside supports of the frame. At this point, I have a top frame (on which the tank will rest) constructed out of 2x4s with two 2x6s joined together running down the center of the box (the 2x6 beam only has vertical supports at either end, while the 2x4 spans have vertical support at the ends and in the center). The 2x6s span the entire length (9ft) and the 2x4s span 4ft sections (having vertical supports at their center). I have the top frame resting on a total of 8 groups of (2) 2x4s joined together to form my vertical supports. Additionally, I plan to skin the top of the frame with 1/2" plywood which will help distribute the load between the 2x6 beam and the 2x4 spans on the outside of the frame. Here are some pictures to help: My question is: Do I need to add a center vertical support to the 2x6 beam, or will this design hold a 100g tank as is without too much deflection? Thanks! Get a granite top on the whole thing that can spread the weight over to the edges and hold the eight border legs in compression and you'd be good. 8) If your tank was sitting on the outsides of that frame you'd be fine, but putting it in the middle, I agree with Duffy, it would be nice to do more to transfer the load to the edge boards and down to the floor. If those horizontal runners were sitting on a 2x4 that went to the ground instead of just hanging on to the edge with screws I also think you'd be good. As it is, you're depending on the screws not to shear off, which they do. Especially if someone is pouring saltwater on them by accident from time to time. Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 LOL @ DC. I did think that diagonal braces at the corners would be a good idea. Honestly, I ran out of 2x4's long enough to make that brace. I am going to head to home depot this evening and buy a few more. Just so I ma clear, you mean putting a board running diagonally from bottom to top on each short side, correct? I didn't add any bracing to the short horizontal joists, because I couldn't think of how to do so without sacrificing storage space under the tank, and I figured that they were mainly there to help tie the center beam in with the 2x4's making the same span. The plywood will help tie the top together as well. Link to comment Share on other sites More sharing options...
BowieReefer84 November 3, 2014 Share November 3, 2014 If you skin outside of stand with 1/2" material you won't need diagonal braces. I agree to support the middle beam with vertical supports on each end and in the middle. 9' is long... I'm not an engineer. Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 If your tank was sitting on the outsides of that frame you'd be fine, but putting it in the middle, I agree with Duffy, it would be nice to do more to transfer the load to the edge boards and down to the floor. If those horizontal runners were sitting on a 2x4 that went to the ground instead of just hanging on to the edge with screws I also think you'd be good. As it is, you're depending on the screws not to shear off, which they do. Especially if someone is pouring saltwater on them by accident from time to time. Interesting point. I was thinking that the load would be mainly borne by the 2x6 beam. I can add some more vertical legs to the outer frame and run 2x4's under the 2x6 beam right at where the sides of the tank would be situated. Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 If you skin outside of stand with 1/2" material you won't need diagonal braces. I agree to support the middle beam with vertical supports on each end and in the middle. 9' is long... I'm not an engineer. I wish I could put skin on the outside, but I built it to take up the space it is going into. I can skin the front, top and back, but not the sides (which is where it is needed I think). Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 LOL @ DC. I did think that diagonal braces at the corners would be a good idea. Honestly, I ran out of 2x4's long enough to make that brace. I am going to head to home depot this evening and buy a few more. Just so I ma clear, you mean putting a board running diagonally from bottom to top on each short side, correct? I didn't add any bracing to the short horizontal joists, because I couldn't think of how to do so without sacrificing storage space under the tank, and I figured that they were mainly there to help tie the center beam in with the 2x4's making the same span. The plywood will help tie the top together as well. The diagonals don't need to be run from the bottom to the top, just 6" to1' long pieces that are put in the upper and lower corners so that load can't shift diagonally. So you would need 8 on the top, and 8 on the bottom. If you screwed a solid piece to cover the ends and the back it would also do the same thing. Usually is just cheaper. Part of the problem is your center span. Some one may say it will be fine, and if they can give you calculations- great. If not, I just would not want to take the chance if it was my tank. Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 To give you an idea, Fairfax County's deck code is 8' o.c. for posts supporting beams. Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 The diagonals don't need to be run from the bottom to the top, just 6" to1' long pieces that are put in the upper and lower corners so that load can't shift diagonally. So you would need 8 on the top, and 8 on the bottom. If you screwed a solid piece to cover the ends and the back it would also do the same thing. Usually is just cheaper. Part of the problem is your center span. Some one may say it will be fine, and if they can give you calculations- great. If not, I just would not want to take the chance if it was my tank. As much as I hate to cut into the glorious space this affords, I think that adding the center vertical brace is a good idea. Link to comment Share on other sites More sharing options...
Origami November 3, 2014 Share November 3, 2014 Ignoring the fact that you've got a tricky balancing situation on your hands with this design, I ran a quick beam deflection calculation for the 9-foot doubled-up 2x6 span using a point load equal to 1780 pounds (a conservative figure for water, rock and tank). The calculation failed, projecting a beam deflection of about 1/6 of an inch. This, coupled with unequal deflection across the sides, would put a large stress on the seams and may lead to premature tank failure. Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 As much as I hate to cut into the glorious space this affords, I think that adding the center vertical brace is a good idea. That glorious space won't be so good with a hundred gallons of salt water on what ever is in it, along with the sand, rock, and splintered stand....just sayin' Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 Ignoring the fact that you've got a tricky balancing situation on your hands with this design, I ran a quick beam deflection calculation for the 9-foot doubled-up 2x6 span using a point load equal to 1780 pounds (a conservative figure for water, rock and tank). The calculation failed, projecting a beam deflection of about 1/6 of an inch. This, coupled with unequal deflection across the sides, would put a large stress on the seams and may lead to premature tank failure. Yea what he said! :laugh: That is why Tom gets the big bucks. Link to comment Share on other sites More sharing options...
Origami November 3, 2014 Share November 3, 2014 By the way, the analysis does not take into account that you're shifting some of the load out to the 2x4 beams, but I'd be concerned that you'll see a lot of uneven deflection the way you have it in your pictures. There's nothing particularly wrong with large open spans - my tank sits over a 6' span with a couple of 2x8's, but you've got a really large span going there with little support under the critical areas (the perimeter of the tank where the seams are located). Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 Also based on the pics, you will have to add 2 x 4's on the sides of all four corners to have a flush surface if you are going to skin it with plywood on the sides. I think you are going to remove your old stand and tuck this one in the alcove where that stand is. If so, you can also screw the stand to the wall studs for extra support. Link to comment Share on other sites More sharing options...
AlanM November 3, 2014 Share November 3, 2014 Some one may say it will be fine, and if they can give you calculations- great. If not, I just would not want to take the chance if it was my tank. You can get yer own numbers here: http://www.johnbridge.com/vbulletin/deflecto.pl The Deflectolator. Tells you how much bow you'll get in the center of a joist span if you put in your joist width and thickness and how far apart they are. I put in 9 feet and 2x6 joists that are 3" wide (since you have two of them), and I get a deflection of .174 inches assuming a 50psf load. Not sure if that helps or what. Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 By the way, the analysis does not take into account that you're shifting some of the load out to the 2x4 beams, but I'd be concerned that you'll see a lot of uneven deflection the way you have it in your pictures. There's nothing particularly wrong with large open spans - my tank sits over a 6' span with a couple of 2x8's, but you've got a really large span going there with little support under the critical areas (the perimeter of the tank where the seams are located). I love open spaces under the stand. mine is 8' x 3' of wide open space, but I also built it with PSL lumber and planned on the span, weight, and me crawling all over the top of the stand. Link to comment Share on other sites More sharing options...
Origami November 3, 2014 Share November 3, 2014 Another point of reference: The beam deflection calculator that I'm using says that you can safely span the 9-foot gap with two 2x8's supported at either end with five inches of post material (2 each 2x4's stapled together at a right angle) under the end of each beam. If each beam runs under the tank edge, you'll see something on the order of 1/20" to 1/14" deflection. Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 Would it be easier to scrap this design and use (4) 2x8's running across the top with two under the long seams (front glass and back glass) of the tank? Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 Another point of reference: The beam deflection calculator that I'm using says that you can safely span the 9-foot gap with two 2x8's supported at either end with five inches of post material (2 each 2x4's stapled together at a right angle) under the end of each beam. If each beam runs under the tank edge, you'll see something on the order of 1/20" to 1/14" deflection. Thanks Tom, your post hit just as I was typing my above comment. I am going to look into this design. Link to comment Share on other sites More sharing options...
Origami November 3, 2014 Share November 3, 2014 Would it be easier to scrap this design and use (4) 2x8's running across the top with two under the long seams (front glass and back glass) of the tank? Yes. But be sure that you support the beams with posts at the end. This is most critical for your load-bearing beams. Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 Here is how mine looks. Yes it is over built, but I am not worried in the slightest. Based on what Tom said you would be better off with 3 sets of two 2x8's built the way you have it, and could get rid of the center post. You still would need beefier corner posts, and some diagonal support. If you can secure it to the wall studs that might do it. I would also use hangers 18" o.c. +/- for the same size material (2x 8's) for the joists. Using 3/4" plywood would also help. Link to comment Share on other sites More sharing options...
Jason Rhoads November 3, 2014 Author Share November 3, 2014 Wow, am I glad I stopped here before I started filling it up! I am going to knock out the little supports running perpendicular to the 2x6 beam and add two 2x8 beams (one on each side) to the current design. I am also going to work on the diagonal bracing Ken mentions and screw it into the wall studs when I get to the point of moving the old stand out of the way. Thanks a lot all! Link to comment Share on other sites More sharing options...
DuffyGeos November 3, 2014 Share November 3, 2014 You don't want that thing falling when your son uses it as a fort! Link to comment Share on other sites More sharing options...
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