Posted on 05/30/2021 2:19:07 PM PDT by EinNYC
Hey, all you FR woodworkers - I have a question for you. I have a 30 x 19 terrarium, which is temporarily empty. It is sitting on a 30 x 19" red oak table a friend of mine built a few years ago to hold it. The table is made of two 3/4" thick oak boards joined by a "biscuit", which lay atop 4 vertical oak legs 16" high, which are 2.5" wide x 3/4" thick. There is a 2.5" x 3/4" thick horizontal strut between the legs on 3 sides. This is so I can fit my gecko tank under this table, which sits atop a small oak dresser.
My question is this: The terrarium will soon be home to 3 adorable Eastern Spotted newts. I will have 6" of water and a few land areas of driftwood, maybe a rock or two, and some gravel, all of which will weigh about 150-155 lbs. I am concerned that the oak table will not be up to the task of holding this terrarium.
I have purchased some new 16" black square steel legs to substitute for the oak legs, which I will remove. These steel legs are 2" wide and are said to support 300 lbs. Do I need to further support the horizontal oak planks so that they can support the remodeled terrarium?
Thanks for the information. :)
Newt 
I wouldn’t do anything.
” all of which will weigh about 150-155 lbs.”
Double check that that is the total new load.
If so, sounds like you’ll be fine but I’m no expert.
I agree from afar.
One might suggest that OP utilize some sort of rubberized mat, etc, on top of the table to eliminate slidiness.
Consult with a local craftsman, perhaps an instructor at an artisan school, to be sure.
I like geckos. But I have a phobia about newts. You see, I was once turned into a newt by a witch. I got better...
Not just no, but hell, no! The whole assembly has no side to side stability. Looks like any sideways bump on either of the 19” ends, and it’s gone.
It is unstable with that much weight, without having stabilizing braces where the rear rail meets the legs and where the front legs meet the table top. I suggest triangle braces at each of leg connections.
The structure should have no problem supporting the weight. Just be careful to make sure the legs are attached in a way that stops the assembly from racking side to side or front and back.
Nice drift wood you got.
Hi.
May I suggest concrete and rebar?
5.56mm
Me too. When I lived in Oman two or three lived in my apartment. They ate the bad bugs. I was always amazed at their ability to crawl across a ceiling upside down and kill the bad but that could fly but was just resting.
The whole assembly has no side to side stability.
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Totally agree.... If the unit is against a wall, I would have dealt with the side to side problem (the 30” direction) with a piece on the back that strengthens ‘the box’... could be corner pieces or even a piece that goes completely from one side to the other. You say the front was left open so that you could slide the tank in. How much clearance is there from the top of the tank to the underside of the board above? You mentioned that three sides have a 2.5 x 0.75” board running horizontally... you sure that you can’t run one on the 4th side as well... and perhaps run one horizontally down the middle between the front and the back? Those 2.5 x 0.75” boards aren’t quite the best at stiffening up the connection between the legs and the top but it should work well enough if the connection to the vertical legs is done right. Also, a board running horizontally down the center below the two ‘planks’ on the top would give them some support from below they don’t have right now. Since that board in the center would tie in to the horizontal members between the legs, that joint too would improve the lateral stability.
One thing I always do is try to run a test to see just how far things need to be taken before going nuts on increasing stiffness and stability. If you were to butt the legs up against something so that it didn’t move (and had someone hold the other two legs down so that they wouldn’t lift off the floor) and then put some sideways force against the top, does it feel too flimsy? How much sideways force gives you how much movement? If 200 lbs of force only move it a 1/16”, that’s on thing... however if only 25 lbs move it 3/4”, that’s totally different and a problem that needs to be addressed.
Get a dog.
The only thing I would do is add a couple of triangular gussets to the corners to stiffen the legs. The table looks and sounds plenty strong enough for a 150-200 lb load, provided the legs are not allowed to “rack”.
I would say you need corner gussets on the leg connected to the top. For the front maybe you can take a coping saw and make some fancy salamander cutouts in the gussets.
according to this
there are several earthquate faults underneath nyc, and nyc seems overdue for a magnitude 5 earthquake.
a magnitude 5 earthquake can deliver a sizeable lateral jolt to the ground.
if you are replacing the legs anyway, you can make a quick patch by incorporating full triangles to convert three sides into trusses. just use flat steel from a hardware store, trim to fit with a hacksaw, drill for bolt holes, and bolt the flat steel onto the legs. on each side, use two flat pieces of steel, each running fully diagonal and crossing in the center. you can put bolt holes and a bolt in the center of each “X” in each truss.
while you are at it, as long as you are reinforcing, you could add two pieces of horizontal angle steel bracing under the table top, one in front and one in back (if you have access to and are handy with a welding machine, then you could also add angle steel bracing to the two sides). use the same bolt holes that you already drilled on the top of each leg. (a next step in my opinion would be to add with bolts a front to back horizontally running flat steel strap to prevent the angle steel pieces from twisting and failing under stress, as this is their favorite failure mode.)
overall, you probably want to apply an engineering fudge factor— build as if significantly more force than expected is applied. for example, if you know you need to resist a vertical load of 150 lbs, then design for a vertical load of 300 lbs, giving yourself a fudge factor of 300/150 = 2.
if and when going up over (say) about 6 feet, you probably want to use angle braces and wood screws to prevent falling over during an earthquake.
full disclosure, i am no expert but i have built cabinets up to 9’ tall with steel bracing, and custom study desks without any steel bracing. no accidents, no failures so far.
You haven’t gotten as good replies as I expected.
I think that’s because you’re in such safe territory that no one is “challenged”.
Add a lower board in the back to prevent racking, and maybe a board in the front too if you frequently have guests that enjoy adult beverages, and I think you’re over-prepared!
Yep…. I’m not impressed with the stability same as you. Needs bracing on all 4 sides. Gussets in the corners as well.
OP estimates that weight supported will be about 155 pounds. Heck, just have a 200+ pound butt sit on the table and see if it busts. Make sure the test butt does some serious wiggling to see if the thing collapses sideways.
Engineers do all sorts of calculations to size something to a certain strength plus a safety factor. For ultimate reliability though you apply a test load to verify the as constructed capability.
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