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Shelf w/ no underneath support -- screw directly into studs

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Forum topic by ZMonet posted 12-18-2013 05:52 PM 2388 views 0 times favorited 63 replies Add to Favorites Watch
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ZMonet

26 posts in 1085 days


12-18-2013 05:52 PM

In my numerous Google searches, I kept getting directly here because apparently you guys store quite a lot of heavy wood in your garages and need shelving. I was hoping I might take advantage of some of your expertise since I have a shelf I would like to build to support heavy weight, in this case a fish tank.

Basically, I want to make my best effort to support a shelf in my family room so that it can hold a fish tank, total weight around 500 pounds. I have one of those wall nooks where someone once thought a TV would go, but is now largely useless. I want to put a fish tank there. The dimensions are 52” wide x 30.5” high x 26” depth. I removed the 1/4” plywood shelf to reveal 2×4 frame screwed (3” screws) to studs on three sides. The 2×4 frame does not have anything supporting it from underneath (in the pics below, that is some cement board about 7/8” down to insulate from the fireplace). There are 2×4 studs running on 3 sides, but obviously not the front side.

The fish tanks dimensions are 48” wide by 13” deep, so basically it will sit across the entirely of the width, but will only go half-way back. Unfortunately I want to place the fish tank towards the front.

MY QUESTION: What is the best way to shore this up so that it will support the 500 pounds of weight? I was planning on using Simpson Strong-Ties to strengthen the framing. I was also going to add some 2×4 cross sections. I would think the point of potential failure though is connecting the frame to the studs. I was planning on using 3/8” lag screws and washers (pre-drill the holes to avoid splitting) everywhere I can to better attach the framing to the existing studs.

Anything else I can do? Everything inside the nook will be obscured when I am done (plan on putting picture molding around the entire thing, with a board for access too). Thanks in advance for any help.


63 replies so far

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Rick M

7921 posts in 1844 days


#1 posted 12-18-2013 07:14 PM

It seems you have thought it out fairly well. Take the total weight and divide by the number of studs and it will give you an idea of how much each fastener will have to support (don’t use cheap lag bolts). You could skin the 2×4 frame top and bottom with plywood effectively creating a torsion box to better distribute the weight and strengthen the frame. Seems safe assuming you have enough studs so that each lag screw isn’t overburdened. Tank maintenance might be a pain in the rear.

-- http://thewoodknack.blogspot.com/

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ZMonet

26 posts in 1085 days


#2 posted 12-18-2013 07:17 PM

Thanks Rick! Do you think 3/4” maple plywood on top would work? One other question, does doubling up the 2×4s (side to side) help at all?

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Richforever

754 posts in 3184 days


#3 posted 12-18-2013 08:11 PM

If there is nothing under the 2×4 frame to support it, can you stick a vertical pipe or 2×4 underneath the 2×4 frame to give it support? If the fireplace is underneath, you should be able to shim under the 2×4 frame to give it support above the cement board.

Good luck.

-- Rich, Seattle, WA

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CharlesA

3022 posts in 1262 days


#4 posted 12-18-2013 08:30 PM

I have no major suggestions, but attaching 2×4’s with pocket holes/screws is remarkably strong.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

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ZMonet

26 posts in 1085 days


#5 posted 12-18-2013 08:57 PM

Thanks Rich. So it isn’t a major foul to have the cement board partially supporting? I wouldn’t see why not, but just wasn’t sure why the builders set the 2×4s just off the cement board when it seems like it would have been easier to have it rest on it.

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WibblyPig

168 posts in 2739 days


#6 posted 12-18-2013 09:49 PM

What kind of tank – freshwater? A few thoughts off the top of my head:

While you have everything open, I would move that outlet to the top so you can use it for your lights and filter. Also, take out all the drywall and replace it with cement board because it is going to get MOIST in there and even greenboard will mold. Paint the cement board black and you won’t have to worry about the background.

As long as you’re moving the outlet, add a second outlet so you’ll be covered for lights, heater, filter. If it’s a FOWLR you can also add a powerhead to give you more current.

Use nails and not screws – screws are great for holding things but don’t have the shear strength to support that kind of weight. If you lag into each stud and throw in a couple of nails it should be plenty of support. Use a piece of 3/4” B/C plywood over the 2×4s and spar varnish or shellac it to keep water from getting to the plywood. (Yes, shellac works fine – I had a 65 gallon reef and all the oak around it was shellaced – I spilled gallons of water on it over the years with no problems).

I assume you’ll have a hinged door at the top for access. Either seal everything REALLY well inside there, put a little computer fan in for circulation or put a glass cover over the top (which will affect your PAR but isn’t an issue if you’re not doing a planted tank or a reef).

I wouldn’t count on using the cement board for support – you don’t know what it’s attached to or how – it’s probably just a few screws holding it in and it’s acting as fireproofing.

-- Steve, Webster Groves, MO "A society grows great when old men plant trees whose shade they know they shall never sit in."

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Rick M

7921 posts in 1844 days


#7 posted 12-18-2013 10:35 PM

I suspect the cement board and 2×4s being separated is a code issue since it is a fireplace, I would keep them separate.

-- http://thewoodknack.blogspot.com/

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ZMonet

26 posts in 1085 days


#8 posted 12-18-2013 11:51 PM

Thanks WibblyPig! I hadn’t even thought about the moisture but that is a great point. Would moisture be a problem even with a cover on the tank? I’ve already changed over the outlet to GFCI, but raising it would not be a problem if I’m ripping out the drywall anyway. And yes, I do plan to have a door on a hinge. The tank is a 55 gallon and I plan on having fresh water fish, no live plants. The depth of the tank is only 13”. I’d probably go bigger, but I want to be somewhat reasonable about weight, especially since it is over a fireplace.

My biggest concern is that the heavy weight will be on the front half (front 13” of 26” depth) of the side not supported by studs.

Is there any value to doubling up the studs? I will certainly add more front to back support but I was wondering if there is anything else I should be doing.

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jumbojack

1667 posts in 2088 days


#9 posted 12-19-2013 12:41 AM

Do you use the fireplace? Do you like boiled fish?

-- Made in America, with American made tools....Shopsmith

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ZMonet

26 posts in 1085 days


#10 posted 12-19-2013 01:43 AM

The fire place gets used, but sparingly. Regardless, I’ve put a digital temp. gauge above the fire place and let the fireplace run for a couple of hours (the most it ever runs) and the temp. only went up a couple of degrees.

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Rick M

7921 posts in 1844 days


#11 posted 12-19-2013 02:44 AM

Bumping up to 2×6’s would benefit because it will allow more fasteners but I don’t believe putting a 2nd board inside the first will help much if at all.

-- http://thewoodknack.blogspot.com/

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WibblyPig

168 posts in 2739 days


#12 posted 12-19-2013 02:47 AM

If you have the space, I would probably take out all of the 2×4s and replace them with 2×6s. Put a double header on the front nailed and glued with a piece of plywood between the two 2x’s. Then use joist hangers to hold everything in place.

You’ll be fine with single 2×6s around the 3 walls. Adding “studs” every 16” o.c. isn’t really necessary but it won’t hurt. Lag and nail as stated above and you should be fine. The load is distributed evenly around the perimeter – look at the frame of the tank – all of the load is on the plastic rim around the perimeter, not the glass. As long as you’re securely anchored at the corners, the tank won’t be going anyplace. Don’t forget the plywood – on second thought instead of B/C use CDX though I’d still seal it. Put down some 1/4” foam to absorb any ridges in the plywood and you’ll be golden.

-- Steve, Webster Groves, MO "A society grows great when old men plant trees whose shade they know they shall never sit in."

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ZMonet

26 posts in 1085 days


#13 posted 12-20-2013 01:44 AM

OK, on the advice here (thanks WibblyPig), I’ve ripped out the 2×4 frame and will build a similar frame out of 2×6s. If this thing fails, I want to know I did the best I could do short of ripping out the entire thing. I will double up the front of the 2×6s. I’ll do it, but what is the purpose of the plywood in between the double-uped 2×6s? Does it give it a better bond?

I may just backer board the ceiling unless you think humidity is going to get that high in there even with a cover on the tank. If I do backerboard, can I put the backerboard right over the drywall, or do I have to remove the drywall first?

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Rick M

7921 posts in 1844 days


#14 posted 12-20-2013 08:50 AM

I’m pretty sure he meant put the plywood atop the 2×6’s, to set the tank on.

-- http://thewoodknack.blogspot.com/

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MT_Stringer

2853 posts in 2695 days


#15 posted 12-20-2013 09:51 AM

Put 1/2 inch plywood between the two 2×6s and plenty of glue and nails. The result will bea laminated beam just like those used to span openings in rooms to support the load above it. Plenty strong.

-- Handcrafted by Mike Henderson - Channelview, Texas

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