Large Bookcase Commission Job- Is Glue Optional in a Dado?

craftbeerguy

Craft Beer Guy
User
Hey Guys,

I've secured a contract for 11' of wall-to-wall faced frame bookcases that are 101" tall. These will be divided in (4) 8' sections that will sit on a ladder base approx 5" tall. No special breaks or pilasters will be incorporated as the customer has asked for function before style. A bottom deck, top and (5) shelves will be let in with full dados .25" deep. The fronts will be nosed with 1.25" Hard Maple between stiles - all of which passes the Sagulator test. The rear of the shelves will be screwed in from the .5" backs for additional support.

I was exploring assembly options for the 8' tall sections as gluing up 7 shelves into tight dados could pose a problem. I asked the question on a long-trusted "professional" site. One of the long-time retired contributors said that I could dry fit the shelves into the dados and screw through the case sides into the shelves. Who wouldn't love this idea? I could not find any research in testing this method but it made me ask what contribution the glue has in a tight joint. Shear force is about the only consideration here.

Your thoughts and thanks.........
 

bobby g

Bob
Corporate Member
I routinely just insert the shelves into tight dados and drive screws to hold them in place when it’s a built-in and they’ll never show.
 

chris_goris

Chris
Senior User
whats the issue with the glue? I would definitely screw them from the sides, as an assembly aid if nothing else. Are you attaching your shelves to your back panel as well?. A couple screws would suffice here.
 

demondeacon

Dave
Senior User
Given the size of the case and the weight of it with and without books, I would not chintz on the glue, particularly for the lower half. Books are quite heavy when crammed in.
 

JohnnyR

John
Corporate Member
Firstly, I can't imagine such a large bookcase without adjustable shelves. I built 5 sections of 3' x7' cases with only the top and bottom glued. Also have 1.25 maple on the front and back of each shelf held up by shelf pins. Makes sense to glue the middle shelf for support but remember that each section will support the others and is probably not needed. It's held up perfectly for the last 15 years.
 

mkepke

Mark
Senior User
I too would do adjustable not fixed shelves but that aside, screws should be plenty unless the shelves themselves are expected to deflect significantly under the load.

Most people don’t want sagging shelves so if you build those properly all the weight is being carried to the floor by the dados (and the back if you attach it to the shelves). Screws/glue/etc just serve to keep the shelf from shifting.

-Mark
 

craftbeerguy

Craft Beer Guy
User
Hey Chris, thanks for your input. Here's my take with an analogy... Recently, I had perfect fitting mortise and tenon joints on a table I made, when it was dry-fitted. When glue was applied, I presume the expansion from the moisture swelled the mating joints with a fit so tight, I had to beat it together.

Using this same scenario gluing up awkward 8ft case sides w/ 7 tight dados seems a bit risky with $100/sheet Maple if they don't set right the first time. My original question is if the glue adds anything substantial enough to warrant it's use. There's a cost benefit to consider. And yes, there will be screws coming in from the back.
whats the issue with the glue? I would definitely screw them from the sides, as an assembly aid if nothing else. Are you attaching your shelves to your back panel as well?. A couple screws would suffice here.
 

craftbeerguy

Craft Beer Guy
User
Given the size of the case and the weight of it with and without books, I would not chintz on the glue, particularly for the lower half. Books are quite heavy when crammed in.
Hey Dave, I'm questioning what the glue adds. I don't disagree that it adds something.
 

craftbeerguy

Craft Beer Guy
User
Firstly, I can't imagine such a large bookcase without adjustable shelves. I built 5 sections of 3' x7' cases with only the top and bottom glued. Also have 1.25 maple on the front and back of each shelf held up by shelf pins. Makes sense to glue the middle shelf for support but remember that each section will support the others and is probably not needed. It's held up perfectly for the last 15 years.
Johnny, in the past I found shelves are usually adjusted once. I prefer and sold the engineering strength of the fixed shelves specifically for a load of books at 40lbs per foot. Given the customer knows their library, to determine heights was easy. Though I do like the idea of gluing up the middle section.
 

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