Will this countertop base bend? 2x12’s

OmegaBravo7

OmegaBravo7

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Wondering if anyone has an engineering background, or can speak just from experience...

The objective is to build a 9ft x 11inch bar countertop fixed at both ends (no legs or support anywhere between between the two ends).


Using two 2x12’s stacked (to gain super strength to prevent flex), 9ft long and 11in deep.

The countertop will be quartz with 4” edge

Will this bar countertop hold steady without any bend/flex? I don’t want to endanger anyone nor do I want to crack the stone.
 
OmegaBravo7 said:
Wondering if anyone has an engineering background, or can speak just from experience...

The objective is to build a 9ft x 11inch bar countertop fixed at both ends (no legs or support anywhere between between the two ends).


Using two 2x12’s stacked (to gain super strength to prevent flex), 9ft long and 11in deep.

The countertop will be quartz with 4” edge

Will this bar countertop hold steady without any bend/flex? I don’t want to endanger anyone nor do I want to crack the stone.
Click to expand...

please clairify "stacked"

laid flat or on edge? Maybe a little picture,?
 
OmegaBravo7 said:
Wondering if anyone has an engineering background, or can speak just from experience...

The objective is to build a 9ft x 11inch bar countertop fixed at both ends (no legs or support anywhere between between the two ends).


Using two 2x12’s stacked (to gain super strength to prevent flex), 9ft long and 11in deep.

The countertop will be quartz with 4” edge

Will this bar countertop hold steady without any bend/flex? I don’t want to endanger anyone nor do I want to crack the stone.
Click to expand...

To help you the person will need to know dimensions of counter top including the thickness. Plus the weight of the counter top
 
gondar1 said:
please clairify "stacked"

laid flat or on edge? Maybe a little picture,?
Click to expand...

Two 2x12’s on top of each-other (screwed together), laid flat. That will give me a flat surface for the stone to sit on. They will be 42inches off the ground, and supported on each both ends using 1.5” steel legs. The middle will be all open to fit as many stools as I can
 
Taureau said:
To help you the person will need to know dimensions of counter top including the thickness. Plus the weight of the counter top
Click to expand...

That is the countertop base: made out of two 2x12’s. It’s a bar countertop so the middle will be open for stools. Will only be fixed on the ends.
 
Something like this, I found on google as an example. Except I’m making the base for the stone countertop using two 2x12’s and the length will be 9ft across
 

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I am by no means a engineeer so take what I say with a grain of salt, but I used to work as a carpenter and I would be shocked if you can get 9 foot of two 2x12s screwed together to bend. Like at all. Any idea how heavy the countertop will be?

things to look for when picking your 2x12s: make sure they are dead nuts straight and not warped, look for any hairline cracks/splits and dont buy anything with knots in it. Dont buy anything that has been exposed to the elements.
 
OK, I am not an engineer but I have built some stuff, so here is what I'd do -
2- 2x4's x 9' on edge like a joist, spaced 11 inches ( or however wide is needed to fit under the slab) with 1/2 inch plywood screwed to the top .

maybe use 2 x 6's, or 3 - 2x4's if your worried, either way it'll be much lighter, and much cheaper, and easier yo move if needed .@ addy is right, two 2x12's laminated together won't hardly ever budge at all over that short span but lumber on edge is strong and you didn't say the weight but I'd guess max is not over 250 lbs.
(viewed from the end)

bar.png -
 
Its not a very long span, so you shouldn't need too much as long as no one is sitting on this thing. The 4" edge should be lots of girth.

-2x4s on the edge would be stronger than anything on the flat. Wood on the flat has a tendency to bend and warp, its not often laid that way. Wood is very strong when it wants to bend it does. I'd be careful in you wood selection to make sure its dry.
-Consider engineered boards like plam or timberstrand that wont bend or warp. Or, making it yourself with plywood laminated together. (again, on edge, never flat)
-someone mentioned support it with metal L or tubing, you can use a product called PL premium to glue the metal right onto the counter. Haven't seen the project but feel this is the direction I would go in myself.

Hope that helps.
 
Twoskinny said:
I would use steel. Possibly 2x4 box steel 1/8” thick x 2 with plywood between the counter top metal structure
Click to expand...


I agree with the metal, you could park a car on that tho.. I honestly don't think you'd need much more than some 1 1/2-2" angle iron. x 2
That said, use square tubing if you want to be safe. There should be load support data online for all of this.
 
I am an architectural engineer but to be brutally honest I’m not the best to ask about this. I could calculate the shit out of it and give exact load and calculations but it would all get way too complicated. This isn’t a structure that needs to pass safety codes like beam and column structures.


I would actually try and go with 3/4” plywood on top and 3 2x6 under to simulate a T beam. It would likely make your counter about 6” thick but I believe that would be much more rigid than a couple 2x12’s. Glue it in with PL and and screw it down really well. It shouldn’t have much flex
 
Thanks for the replies bros.
To answer all in a nutshell...

The quartz countertop will weigh approx 160lbs.

I can’t add anymore height (Thicknes) to the edge, we are keeping the stone countertop edge between 3-3.5” max. So 2x4’s and 2x6’s sideways won’t be possible.

can’t add addition upright support in the middle because it’s a window directly in front of it, we want to maximize stool/seat spacing, and looks better open.

A good point was brought up, you might get someone drunk to decide to sit or stand on the counter, or just students goofing around. I only considered a couple of people leaning on it while eating and pushing against the counter to get out of their stool.

I also did not consider the 2x12’s warping. When I googled it it’s certainly a possibility we’d want to not risk.

I’ll shell out the extra cash and have the base constructed out of welded steel square tubes (painted), But damn it’s expensive lol

Base: Three 2x2 steel square tubes with 1/4” thick walls. 1/2” plywood laid and screwed on top (stone will crack if laid directly over steel).

Legs: 1.5” steel square tubes 3/16” walls.

Will that prevent any and all bending?
I use the deflection calculators online but every fucking site gives me different answers with the exact same numbers punched in
 
This
I would buy 1 inch steel angle iron at the length you need. Run it on the outer edges, then attach them at the ends with another piece of angle iron with screws. This way it wont be too thick.
Attach it to 3/4" plywood. Run screws in it every 12" Set your top on that after laying down a bead of silicone.

I pretty much did the exact same thing I suggested to you on a platform I use to hold thousands of pounds of meat. I actually suspended it off a rail line on the ceiling with threaded rod so legs like you just going up instead of down. I used 1" plywood but didn't have a slab of stone on the top,.
Seriously I put at least 2500 lbs on that and it held no issues.
 
Sorbate said:
This
I would buy 1 inch steel angle iron at the length you need. Run it on the outer edges, then attach them at the ends with another piece of angle iron with screws. This way it wont be too thick.
Attach it to 3/4" plywood. Run screws in it every 12" Set your top on that after laying down a bead of silicone.

I pretty much did the exact same thing I suggested to you on a platform I use to hold thousands of pounds of meat. I actually suspended it off a rail line on the ceiling with threaded rod so legs like you just going up instead of down. I used 1" plywood but didn't have a slab of stone on the top,.
Seriously I put at least 2500 lbs on that and it held no issues.
Click to expand...

Would the perimeter 1” angle irons actually be stronger the three 2x2 steel tubes?
I don’t doubt your base holding thousands of lbs, its the slight bend it gives while holding that weight that worries me. I don’t even want 0.0625” bend anywhere if someone stood on it
 
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