Shelf Plan sanity check please - Woodworking Talk - Woodworkers Forum
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post #1 of 13 Old 08-08-2020, 02:42 PM Thread Starter
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Shelf Plan sanity check please

Hi So I'm planning to make a bookcase to support some heavy albums for my father. Like 25-30lbs per book. I whipped up some quick cad drawings for the carcass using 1X12 (.75" x 11.5") northern wight pine.

I ran the numbers on how much it can support and it seems way stronger than I anticipated. Using this calculator I got a sag of 1/20th of an inch per shelf at 375lbs or 1875lbs for the entire unit which is well below the 43,200 lbs I calculate for the compression strength of the unit.

Does that seem in the correct zipcode to anyone else. And if not what would be the correct way to calculate the capacity.

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post #2 of 13 Old 08-08-2020, 02:56 PM
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I have no clue about your design or capabilities.
but, I would really like to see some photos of those 30 pound books !!

.
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there is no educational alternative to having a front row seat in the School of Hard Knocks.
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post #3 of 13 Old 08-08-2020, 03:08 PM Thread Starter
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I unfortunately don't have pictures but they are heavy duty stamp albums. Several thousand 8.5x11 pages.
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post #4 of 13 Old 08-08-2020, 03:55 PM
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The Sagulator WoodBin

This is a good site to calculate shelf spans for given weights. You'll need to weigh the books and how many would be on each shelf, after that just plug in the numbers. How the shelves are attached is important, a dado with screws would be good, sitting on adjustable pins not so good. Adding a 1.5 inch strip across the front edge would stiffen it up, as would driving screws through the cabinet back into each shelf. I like eastern white pine, but at 3/4" and a 31 inch span my gut would say that noticeable sag is likely after a few years without edging, could be wrong. Also, you can buy 5/4 x 12 which is one inch thick and might give you more piece of mind

Best of luck
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post #5 of 13 Old 08-08-2020, 07:53 PM
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Quote:
Originally Posted by Lucek View Post
I unfortunately don't have pictures but they are heavy duty stamp albums. Several thousand 8.5x11 pages.

How thick is each book? I have never seen a stamp album over about 4" thick.


George
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post #6 of 13 Old 08-08-2020, 08:26 PM Thread Starter
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The plan was to glue and screw the shelves into the sides.

Also when I plug in the variables into Sagulator I get,
Quote:
The Sagulator helps you design shelves by calculating shelf sag (deflection) given type of shelf material, shelf load, load distribution, dimensions, and method of attachment. You can also specify an edging strip to further stiffen the shelf. See the notes below for usage tips.

Shelf Characteristics
Shelf Material
Pine, Eastern white
Shelf attachment Fixed (attached to sides) Floating (not attached)
Shelf load
375
per foot (305 mm) total
Load units lbs kgs
Load distribution Uniform load Center load
Shelf span
30
in cm mm
Depth (front to back)
12
Thickness
.75
[Optional] Edging Strip (see note #10)
Material
None
Width (vertical plane)
Thickness
0.05 in total

0.020 in per foot
ACCEPTABLE
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post #7 of 13 Old 08-18-2020, 07:06 PM
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Based on experience building conference room book shelves in law offices....3/4" shelves longer than around 24" without some type of vertical reinforcing will sag over time. We've used 1-1/2" vertical hardwood "nosing" on the plywood shelf faces that seemed to be good up to around a 36" long shelf.
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post #8 of 13 Old 08-19-2020, 09:52 AM
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Sagulator or not, I can't imagine 3/4" material supporting that kind of weight without sagging unless the unit is a foot wide.

Attaching a bullnose strip front and back will help, but my suggestion is do yourself a favor and go with 2X material. If that isn't available you can laminate (glue) 2 x 3/4" material.

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post #9 of 13 Old 08-19-2020, 11:04 AM
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Before you go too far with this, another thing to think about is the placement of this 1875 pound bookcase. The footprint is small for such a heavy weight. I would not put it on a second floor or a raised foundation floor unless you are certain that there is sufficient structural support for it.

I faced a similar issue with a special file cabinet that weighs nearly 900 pounds empty. I consulted with an engineer, who advised me not to put it in our house, which has a raised foundation. It lives on the concrete slab in our garage.
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post #10 of 13 Old 08-21-2020, 09:42 AM
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Quote:
I faced a similar issue with a special file cabinet that weighs nearly 900 pounds empty.
That's a good point. I had a piano which had to weigh at least 500lbs, I kept it near a load-bearing wall.


I made some shelves 2 years ago to hold a bunch of vinyls, those things weigh a lot more than they look! The span was close to 6' however, so I opted for 2x12 douglas fir. Lighter than pine but stronger from what I've read. Appearance is a personal taste, but I like the thicker looking shelves.
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post #11 of 13 Old 08-21-2020, 12:00 PM
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Quote:
Originally Posted by GCTony View Post
Based on experience building conference room book shelves in law offices....3/4" shelves longer than around 24" without some type of vertical reinforcing will sag over time. We've used 1-1/2" vertical hardwood "nosing" on the plywood shelf faces that seemed to be good up to around a 36" long shelf.
Quote:
Originally Posted by DrRobert View Post
Sagulator or not, I can't imagine 3/4" material supporting that kind of weight without sagging unless the unit is a foot wide.

Attaching a bullnose strip front and back will help, but my suggestion is do yourself a favor and go with 2X material. If that isn't available you can laminate (glue) 2 x 3/4" material.
as drawn i agree with these two. a 30 shelf without support will sag. a 1/4" plywood back and 1.5" face frame will make for a sturdy book case



you might want to read this post over on lumberjocks

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post #12 of 13 Old 08-21-2020, 12:38 PM
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Originally Posted by phaelax View Post
That's a good point. I had a piano which had to weigh at least 500lbs, I kept it near a load-bearing wall. [...]
My upright piano weighs 550 pounds which rests on four built-in casters. Grand pianos can weigh up to 1000 pounds, sometimes more, and they rest on three casters.

Our neighbor had two grand pianos back-to-back on a raised platform that dominated her living room. One was a 6'2" Steinway. The other was a 9'3" Bechstein concert grand. I had not thought about it until now, but the combined weight was nearly 2000 pounds. All of that weight rested on six casters, and I'm guessing that each one had less than a square inch of contact surface.

I could have put carbon paper under the Bechstein and made diamonds. :-)
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post #13 of 13 Old 08-21-2020, 03:59 PM
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I've heard of people renovating homes and putting cast iron tubs on second floors with some bad results. Those tubs can be 300-500lbs and without double up the joists under it, the floor won't support it full of water and a person. Or two if you're lucky
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