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Forum topic by zombolina posted 03-29-2017 12:47 AM 532 views 0 times favorited 11 replies Add to Favorites Watch
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zombolina

25 posts in 1838 days


03-29-2017 12:47 AM

Topic tags/keywords: question help book cabinets mdf weight

Hi, cabinet newbie here. I am building 13.5” h x 10.5” d bookshelves that will span two adjoining walls at ceiling level. I will be building them in units, hanging them separately, and applying a face frame.

The boxes are 3/4” veneer MDF with glued and pinned butt joints, with a 1/4” melamine back in a 1/4” groove that is placed 1/2” from the back edge. I’m adding a full length nailer of 1/2” ply, 3” wide, glued and pinned on the upper back.

I built the first corner unit, and now I’m guessing that I should have nailed through the sides into the top and bottom instead of the other way around. See photos. FYI the joinery in the center 45 is glue and dominos.

Question is, do we think this construction will be strong enough to hold books? I plan on using 3 1/2” torx screws through the nailers into the wall studs, as well as blocks up into the ceiling joists. And there will be a horizontal cleat mounted to the wall running underneath all of the units. And applied solid wood face framing.

Each wall is about 9 feet long, each leg of the corner unit is 30” wide, and each straight unit will be no more than 30” wide.

Whatchall think?

-- Success is the ability to go from one failure to another with no loss of enthusiasm. -Winston Churchill


11 replies so far

View papadan's profile

papadan

3584 posts in 3209 days


#1 posted 03-29-2017 02:05 AM

Is that laminate on the MDF plastic? Glue wont do any good on plastic laminate. The ends need to be made the other way with the sides screwed into the top and bottom. 3 1/2” screws is overkill on the mounting, you have 1 1/4 thickness so 2 1/2 is plenty

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zombolina

25 posts in 1838 days


#2 posted 03-29-2017 02:16 AM

No, it’s wood veneer over MDF. The back panel is melamine but it just floats in the groove.

So if I reverse the joinery, glue and 18g pins are enough?

thanks!

-- Success is the ability to go from one failure to another with no loss of enthusiasm. -Winston Churchill

View SawduztJunky's profile

SawduztJunky

71 posts in 998 days


#3 posted 03-29-2017 02:27 AM

I hate MDF. I hope you’re not planning on putting much weight on the shelves. It will sag soon and split later. It’s so heavy on its own.

-- I don't think I'm ever more "aware" than I am right after I hit my thumb with a hammer. Questions about solid surface? Just ask. http://www.swiiitch.portfoliobox.net

View jerryminer's profile

jerryminer

812 posts in 1282 days


#4 posted 03-29-2017 07:03 AM

I think your bottom shelf-to-side connection is weak. Imagine a load being placed on the front of the shelf. You will be relying on the glue-and-pin joint to resist the load.

A better construction method, IMHO, would have the sides supporting the shelves, something like this:

-- Jerry, making sawdust professionally since 1976

View zombolina's profile

zombolina

25 posts in 1838 days


#5 posted 03-29-2017 01:54 PM

Thanks Jerryminer,
Is that about 1,5” left from the bottom of the dado to the edge of the sideboard?

-- Success is the ability to go from one failure to another with no loss of enthusiasm. -Winston Churchill

View Loren's profile

Loren

9643 posts in 3488 days


#6 posted 03-29-2017 03:32 PM

I think you’ll be ok but you might consider
running some countersunk screws in from
the bottom. You can get covers for the holes.

Confirmats are really the right kind of screw
but drilling the holes properly requires
special equipment.

Miller dowels would work as well. I’ve never
used them but they appear real strong to me.

View clin's profile

clin

754 posts in 836 days


#7 posted 03-29-2017 05:52 PM

I’d also have the sides cover the ends of the top and bottom boards. It would look better and is more conventional. And the dado, as Jerry showed, would be the way to go. The face frame will go a long way towards supporting the shelf and avoiding sag.

However, I have concerns at the bottom miter. Is there going to be a vertical face frame there, tying the top to the bottom? If not, then there is nothing supporting that end of the shelf. That’s a weak spot that would put a lot of force on that miter joint. Though if you joined the two face frame piece securely at that inside corner, it will help.

I also don’t understand how your face frame would fit on. Normally it would be like Jerry’s box, and the face frame would be flush with the bottom shelf and extend down to the bottom of the side panel. That 1/5” you mentioned.

As you’ve shown in your photo, where does the face frame go? Does it go up above the shelf, creating a lip?

Another option to using a dado, is to put a cleat on the side panel that supports the shelf. The shelf can then rest on this, much like it would in a dado. The face frame would cover the cleat from the front. The cleat of course would be made of something more substantial than MDF. So there would be no risk it would fail.

The weakness is the shelf itself. With just about any kind of fastener going into the end of MDF, there’s quite a risk of the shelf just giving out. That’s the big advantage of the dado or a cleat. It supports the entire edge of the shelf, and over the full thickness of the shelf.

-- Clin

View zombolina's profile

zombolina

25 posts in 1838 days


#8 posted 04-10-2017 05:26 AM

Thanks everyone!

Here’s how I plan to apply the face frame after installation of the boxes.

Since I’ve now put a dado in the side for the bottom, I decided to cover the ends of the sides with .25 finished ply. This also would hide some metal bracing that I can put into strengthen that miter in the corner.

The next hurdle is to install these on walls and ceiling that are not straight! Here’s a shot of the corner of the room. Thinking about installing .25” above the window casing so that the applied .25” sheeting will rest on the molding. I’ll put up a hardwood cleat level with the casing to give the others something to rest on.

Any advice on how to do this alone? I’ve seen the jacks that are used to help hold wall cabinets up during installation, but they are not tall enough as I am putting these up 7 feet.

Thanks !!!

-- Success is the ability to go from one failure to another with no loss of enthusiasm. -Winston Churchill

View jerryminer's profile

jerryminer

812 posts in 1282 days


#9 posted 04-10-2017 07:16 AM

Get a helper

-- Jerry, making sawdust professionally since 1976

View zombolina's profile

zombolina

25 posts in 1838 days


#10 posted 04-15-2017 12:29 AM

Tada!

I got a short helper and these went in quickly. 3 more then the face frame and replace the ply ledger with a walnut one. Plan on sheeting the bottoms with .25 walnut ply.

Thanks so much for all of your help!

-- Success is the ability to go from one failure to another with no loss of enthusiasm. -Winston Churchill

View pontic's profile

pontic

505 posts in 449 days


#11 posted 04-15-2017 12:36 AM

You are cooking now. Should hold a few books.

-- Illigitimii non carburundum sum

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