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Height to depth ratio for bookcase?

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Forum topic by JonC123 posted 07-21-2019 03:04 PM 240 views 0 times favorited 5 replies Add to Favorites Watch
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JonC123

12 posts in 482 days


07-21-2019 03:04 PM

Topic tags/keywords: design

I just finished building a simple bookcase and noticed it’s not very sturdy. I’m guess it’s because of the dimensions. 60”h x 36”w x 7 1/4”d

I’ve read about the golden ratio for rectangles but the articles I’ve read only mention HxW and not depth.

I’ll end up anchoring it to the wall so not a big deal but would like to understand the design part a little better.

Thanks
Jon


5 replies so far

View bilyo's profile

bilyo

774 posts in 1550 days


#1 posted 07-21-2019 03:15 PM

Do you mean “sturdy” or “stable”. A book case can be sturdily built and not be very stable. By their very nature, usually tall and relatively shallow, they tend to tip easily; especially when loaded. Of course, changing the depth to give it a larger footprint will make it more stable but, that may not be practical. Just anchor it to the wall and be done with it.
If sturdiness is the real issue, then we need some more information about how you have it constructed to help you fix it. Usually if you have a top and base with sturdy joints and then put a back on it, it will be pretty sturdy.

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JonC123

12 posts in 482 days


#2 posted 07-21-2019 04:03 PM

I meant stable then, it can tip easily. I’m going to anchor it to the wall, just curious if there’s some ratio to follow if you wanted to make it stable on its own.

For example I’ve read about large shelving units in warehouses make this calculation to determine its safety rating.

Don’t know if these a best practice for woodworking or not.

Thanks

View Delete's profile

Delete

439 posts in 820 days


#3 posted 07-21-2019 04:35 PM

For a free standing bookcase that is only 7 1/4” deep I wouldn’t go any higher than 3’, and even then I would add a decorative molded base around the bottom to increase you depth and greatly decrease its tendency to tip. For taller bookcases 10 or even 12” depth, is much safer, adding base moldings (like baseboards) even more so. Off course they can always be built in or screwed to the wall. Unless you are careful with book placement they can get top heavy and unsafe.

View bondogaposis's profile

bondogaposis

5487 posts in 2799 days


#4 posted 07-21-2019 05:12 PM

One thing you can do is to add a separate base and increase the foot print somewhat.

-- Bondo Gaposis

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Rich

4677 posts in 1037 days


#5 posted 07-22-2019 12:16 AM

The golden ratio is for visual aesthetics, not structural integrity. If 7-1/4” is the depth that was appropriate for the books or whatever you plan on putting on the shelves, then there’s nothing wrong with that. Just anchor it to the wall like you plan to, and you’ll be in good shape.

Your height to width ratio is close to the golden ratio, so you got that part right.

The stability of any upright piece is dependent on the location of the center of gravity (COG). If the height of the center of gravity is less than the distance from the COG to the front (or whatever direction it might tip around) then it will be most stable since it will have to defy gravity to tip. As the COG height increases, it will still require some force to tip it, however the distance it needs to tilt before falling becomes less.

-- My grandfather always said that when one door closes, another one opens. He was a wonderful man, but a lousy cabinet maker

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