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I paid someone else to build this basic shelf for me because i'm no carpenter, but i'm a little concerned about it's integrity because it will be holding aquariums. It's a frame of 2x4s with enough 2x4 braces running from front to back for the tanks to sit on, each brace is screwed in to the frame at the front and back with two screws. The problem is that half of the braces were short so there are 1/4th inch gaps instead of them fitting flush against the frame. Will they be able to hold 225 lb tanks like this? Or is there a way I could try to reinforce the braces? The mending plates were added when I pointed out that I was concerned about the gaps.

Edit: More pictures. One the top shelf all but the 2nd horizontal board from the left has the gap. He also added this scrap piece on here when I told him I wasn't comfortable with the corner of this tank floating.

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    It would be nice to see a picture of the whole frame assembly. To answer the question of whether or not you can trust it, we would need to see how many of those spacers are floating like that and how many are not, and where they are. That metal strap is the only thing carrying weight at that point, and the load is cantilevered because only one strap was used. Shoddy workmanship there, I'm afraid...
    – Jimmy Fix-it
    Jan 21, 2020 at 0:18
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    That joint is marginal at best.
    – batsplatsterson
    Jan 21, 2020 at 1:18
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    I might be overly cautious, but I'm not sure I'd trust the sheer strength of those screws with that much weight. I would prefer to see a joint with wood resting on top of wood taking the weight for something that heavy.
    – brhans
    Jan 21, 2020 at 1:21
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    Those butt joints and screwing into end grain would not be the way I would have done that. Also, those brackets should be removed. The wood will probably bend with the weight and close the gap. Then put the brackets back on. You could also shim those gaps. Hope you didn't pay too much for this.
    – JACK
    Jan 21, 2020 at 1:36
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    This is just bad design all around, and with that much weight at play you're headed for catastrophe. All the joints are weak, and there's almost no diagonal stability at all. You need post-and-beam support with lapped joint bonds, not this flimsy bracketing and butt-joint business. The question itself is flawed for that reason.
    – isherwood
    Jan 21, 2020 at 13:52

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I paid someone else to build this basic shelf for me because i'm no carpenter,

Unfortunately, I am afraid the person that built this isn't either.

There is a major weak point - the screws into the end grain of the cross pieces could just tear out of the wood. The gaps are not really the problem.

There are a lot of stronger options for the joint but most of them would involve starting from scratch, which would probably be best.

If you want to salvage this, you might find a bracket that makes it strong enough. I don't think it's ideal but the Simpson FBFZ for example might work:

Simpson FBFZ

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For how the shelf attaches to the uprights there should be a backup to the screws such that the self will rest on something even if the screws were to break. The simplest solution is to glue and screw a board just under where the shelf attaches. That will give greater surface area to the fastening than a few screws into endgrain. I can barely see some that serve that purpose fort he boards going front to back (which won't end up doing much of anything TBH) but they should also be present for the boards going side to side. The top shelf doesn't need this extra support because those members already rest on top of the upright.

The simplest way to reinforce the shelves themselves is to put a sheet of plywood (or similar) on top of it and fasten that down. That will spread the weight over all the members making up the shelf. You can drill holes in the sheet for cable/pipe routing if you need to.

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    Diagonal cross bracing would also add to the structural integrity and provide some resistance to side loads. Without cross bracing, all it might take is a sideways nudge to collapse the whole structure.
    – Phil Freedenberg
    Jan 21, 2020 at 15:29
  • Yeah, there are some members in the back to provide anti-racking support, but some extra bracing, (like corner braces) wouldn't go amiss.
    – ratchet freak
    Jan 21, 2020 at 16:02
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It should also be noted that for the unit to support any significant weight the 2x4 should be not be flat, they should be turned 90 degrees so they are vertical like floor joists.

I would also ad plywood decking to ad strength and make a solid shelf surface.

I found a web site that has a plan for some shelves. https://dadand.com/diy-2x4-shelving/

Since you are placing A LOT of weight on these i would add several cross beams on each shelf to support the plywood decking ( like floor joists and use 2x4 joist hangers to mount them).

I would replace the screws with 5 inch long 1/4" lag bolts and washers ( Pre drill your all holes for your lags ) and even L brackets on the bottom side of the supports on the sides of the unit.

Water weighs 8 pounds per gallon. if you are placing several aquariums on one shelf you may want to go with 2x6 framing.

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  • For that short of a span I think you can get away with them being flat. It would waste a lot of vertical space otherwise.
    – isherwood
    Jan 21, 2020 at 19:31
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    @isherwood Yes the span in the first photo is short, the second photo not so short. I was referring to the design i linked to not the less than optimal design that was used. I my opinion based on the need to support the weight in question, the OP should start over.
    – Alaska Man
    Jan 21, 2020 at 19:38

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