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Long Bookcase: Wood Movement + Leg Supports?

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Forum topic by Dagobah posted 01-20-2020 03:55 PM 536 views 0 times favorited 15 replies Add to Favorites Watch
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Dagobah

80 posts in 1548 days


01-20-2020 03:55 PM

Thinking about building this 7’ long bookcase out of 3/4” rift sawn walnut. Two questions:

1. Am I crazy to do this out of solid wood instead of ply? The 2 vertical dividers would be dadoed into the top/bottom. The side panels would be doweled into the top/bottom. Is wood movement going to cause issues?

2. With the 7’ length, I’m also concerned about having enough leg support for a case full of books. What’s the best way to add center support?

Both these questions have me wondering if this isn’t why I’ve seen hardwood bookcases built shorter. For example in this video Frank Howarth makes multiples here instead of longer runs. Am I better off going with two 3.5’ cases (esp if I want to stick with hardwood)?

7’ Long
12” Deep
30” Tall
4” Legs
Overall Height 34”


15 replies so far

View Phil32's profile

Phil32

1146 posts in 788 days


#1 posted 01-20-2020 04:23 PM

I built a similar bookcase nine feet long for my wife’s cookbooks. Loaded with books, you should have no problems of wood movement – sagging, maybe. Why do you need the legs? It just creates a difficult to clean space under the lower shelf. Why not enclosing the base with kickpanels that rest on the floor?

I also have some experience with solid walnut used for bookshelves. My brother-in-law built one fifty years ago. It was given to me when the household was changed more recently. There had been no wood movement over those many years.

Walnut is expensive. I doubt any reaches the market that is not processed (dried) very carefully. Did you mill the walnut trees yourself?

-- Phil Allin - There are mountain climbers and people who talk about climbing mountains. The climbers have "selfies" at the summit!

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sansoo22

1178 posts in 539 days


#2 posted 01-20-2020 05:45 PM

You’ve got something close to a mid century modern design. With the feet spaced so far out you will most likely run into sagging issues. It might not be for a few years but im pretty sure it will happen. If you google mid century modern bookcases you will see quite a few examples of long and low cases that have the feet pulled in slightly from the ends. In your case that would most likely be something like a 5’ base with the 7’ case on top. I think that would give you less chance of sagging.

As far as hardwoods are concerned i wouldnt worry about it. The same MCM design period used to make a lot of long and low furniture pieces out of redwood, teak, cherry, etc. Many of those are still around today and still holding boo

View LesB's profile

LesB

2626 posts in 4328 days


#3 posted 01-20-2020 06:04 PM

I second Phil’s response.

Unless you have an inexpensive source of Walnut I would go with Walnut veneered plywood and even then you are looking at over $200+ for the plywood. You can cover the plywood end grain with thin veneer strips or solid wood strips. Or, use a solid wood face frame to cover the edges on the case and wider wood strips on the shelves to make them look thicker, over hang on the bottom edge a little. This also stiffens the shelves.

In the drawing looks like you have stretchers on the bottom between the legs. That will probably support the center but again I agree with Phil in using a box toe kick. The house keeper will appreciate it.

It is hard to read the dimensions in the drawing but it looks like the cabinet is 36” tall. Do you really want 16”+ shelf space. I usually make my shelves adjustable but then you will need a couple more shelf boards.

-- Les B, Oregon

View Dagobah's profile

Dagobah

80 posts in 1548 days


#4 posted 01-20-2020 06:49 PM

My initial thought was ply but I’m unsure how to deal with the exposed edges on the top and bottom (left and right side) of the case – as I don’t want to have mess with miters on that long of a piece.


I second Phil s response.

Unless you have an inexpensive source of Walnut I would go with Walnut veneered plywood and even then you are looking at over $200+ for the plywood. You can cover the plywood end grain with thin veneer strips or solid wood strips. Or, use a solid wood face frame to cover the edges on the case and wider wood strips on the shelves to make them look thicker, over hang on the bottom edge a little. This also stiffens the shelves.

In the drawing looks like you have stretchers on the bottom between the legs. That will probably support the center but again I agree with Phil in using a box toe kick. The house keeper will appreciate it.

It is hard to read the dimensions in the drawing but it looks like the cabinet is 36” tall. Do you really want 16”+ shelf space. I usually make my shelves adjustable but then you will need a couple more shelf boards.

- LesB


View bondogaposis's profile

bondogaposis

5873 posts in 3236 days


#5 posted 01-20-2020 07:00 PM

Wood movement is not going to be a problem, because it will all move in unison. I think sag will be the issue. That is too long of a span to be supported only on 4 legs. Books are heavy. You need to either increase the width of the bottom stretchers, add two more legs or set it on a plinth.

-- Bondo Gaposis

View LeeRoyMan's profile

LeeRoyMan

1422 posts in 612 days


#6 posted 01-20-2020 07:30 PM

I like the look of it with the legs. Looks more like a piece of furniture instead of a cabinet.
I think if you’re putting a back on it there wouldn’t be the sagging. I would make the legs a little taller so that you could make a taller stretcher under the shelf.

View Woodknack's profile

Woodknack

13503 posts in 3265 days


#7 posted 01-20-2020 09:37 PM

Solid wood is a lot stronger and more rigid than plywood. Sagulator says acceptable but that doesn’t include the back which will add a lot of rigidity.

https://www.woodbin.com/calcs/sagulator/

-- Rick M, http://thewoodknack.blogspot.com/

View LesB's profile

LesB

2626 posts in 4328 days


#8 posted 01-21-2020 12:40 AM

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-- Les B, Oregon

View Ripper70's profile

Ripper70

1378 posts in 1793 days


#9 posted 01-21-2020 05:07 AM



Why do you need the legs? It just creates a difficult to clean space under the lower shelf. Why not enclosing the base with kickpanels that rest on the floor?

- Phil32

+1

-- "You know, I'm such a great driver, it's incomprehensible that they took my license away." --Vince Ricardo

View pontic's profile

pontic

801 posts in 1493 days


#10 posted 01-21-2020 10:51 AM

Plywood, trim and kick panels.

-- Illigitimii non carburundum sum

View Peteybadboy's profile

Peteybadboy

2330 posts in 2834 days


#11 posted 01-21-2020 11:38 AM

I agree with Pontic.

-- Petey

View Lazyman's profile

Lazyman

5864 posts in 2272 days


#12 posted 01-21-2020 02:41 PM

Personally, I like the look with the legs, though I might make them slightly taller so that you can get some sort of vacuum or broom underneath it to clean.

I agree with Rick. I plugged the numbers into the sagulator too. It doesn’t have an input for the supports underneath but if you include a 2” edge strip, a single 7’ shelf with 30 lbs per foot load will only sag .21” over the entire span. Increase to 2.5” and it goes down to .14” so 2 of them should be even better. Assuming that you make the carcass nice and strong with a well attached back, it will basically be like a truss bridge. I don’t think you will have much sag at all.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Madmark2's profile

Madmark2

1722 posts in 1473 days


#13 posted 01-21-2020 03:00 PM

Last time I made a heavy weight bookcase I put a tongue on the back edge of the shelves and made the back out of pieces of 1/4” hardwood ply. This made full width stiffeners for all the shelves.

On the front edge of the shelves I biscuited on a trim 1×2 with a couple of reeds routed on the face and the corners rounded. This added even more stiffness to the shelves. I told the client that they could put their anvil collection on it. LOL

I used a couple of lengths of half-rope trim to cover the ends of the shelf dados.

The case was 12” deep and I put two 15” flat 1×3 feet on at either end. The 3” toe extension was beveled to reduce toe stubbing and helps move the center of gravity back to make the case less tippy when the kids climb on it.

The client’s daughters were tots when the case was built. Last I heard the girls were married getting ready for kids of their own. The client still uses it and said that with all the use it never tipped.

Making a large, one piece, unit may limit its placement options if you move.

Nothing gives me more pride than to see a piece I made give long (decades) and sturdy service.

M

-- The hump with the stump and the pump!

View jmartel's profile

jmartel

9075 posts in 3035 days


#14 posted 01-21-2020 04:43 PM

With a back the whole thing acts as one rigid beam. You should be fine with sagging. If you are worried, make the bottom stretcher between the legs deeper. Go to say 6” on that and it will support a lot of weight.

Worst case scenario, make the bottom supports removable from the case itself, and you can add center legs later if needed.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View pontic's profile

pontic

801 posts in 1493 days


#15 posted 01-22-2020 01:31 AM


Last time I made a heavy weight bookcase I put a tongue on the back edge of the shelves and made the back out of pieces of 1/4” hardwood ply. This made full width stiffeners for all the shelves.

On the front edge of the shelves I biscuited on a trim 1×2 with a couple of reeds routed on the face and the corners rounded. This added even more stiffness to the shelves. I told the client that they could put their anvil collection on it. LOL

I used a couple of lengths of half-rope trim to cover the ends of the shelf dados.

The case was 12” deep and I put two 15” flat 1×3 feet on at either end. The 3” toe extension was beveled to reduce toe stubbing and helps move the center of gravity back to make the case less tippy when the kids climb on it.

The client s daughters were tots when the case was built. Last I heard the girls were married getting ready for kids of their own. The client still uses it and said that with all the use it never tipped.

Making a large, one piece, unit may limit its placement options if you move.

Nothing gives me more pride than to see a piece I made give long (decades) and sturdy service.

M

- Madmark2

Now that sounds like a stout piece! Sounds nice looking too. Most likely will be around when we are long gone.

-- Illigitimii non carburundum sum

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