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Help With Plywood Joints

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Forum topic by Curryfire posted 10-26-2016 10:26 AM 806 views 0 times favorited 18 replies Add to Favorites Watch
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Curryfire

3 posts in 413 days


10-26-2016 10:26 AM

Hey Guys,

Been a long time lurker on this fantasic forum. I’ve been charged with my wife to start a new project for the kids and need some help from you guys. We’ve been searching for a bunkbed for our kids for the last few weeks and have not been able to find anything locally that we liked. A while ago, my wife found one that she really liked, but had sticker shock when she saw the price ($8K). This bed is basically made out of 3/4” baltic birch and looks like something you would find in Ikea. I was able to find the assembly directions, and it looked very doable with my simple shop. However, I’m puzzled with one thing. For the top bunk, they have 3/4” ply for for the two front and back walls, and they have two 3/4” plys that they use cross dowell hardware to make the basic box. For the bed, it looks like they have a 1”x2” rail that goes around the bottom perimeter and they place a sheet of 3/4” ply the size of the mattress on top of it. What do you guys think they did to attach the rails to the 3/4” walls? All i could think of was maybe a shouldered dado with glue. I’ve attached a drawing below to show you what I’m talking about. Do you think this would be strong enough to support the mattress and the kid?

https://www.flickr.com/photos/144410192@N02/shares/Sc3U2H

Thanks,
Curryfire


18 replies so far

View rwe2156's profile

rwe2156

2710 posts in 1315 days


#1 posted 10-26-2016 12:31 PM

I would NEVER build a bed – especially a bunk bed – out of plywood.

Use 2X solid wood.

-- Everything is a prototype thats why its one of a kind!!

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dhazelton

2608 posts in 2131 days


#2 posted 10-26-2016 12:46 PM

I don’t know why you can’t build a child’s bunkbed out of plywood – if the platform the mattress sits on is a solid sheet nothing will rack on you. I would think those cleats are held on with glue and 1 inch screws.

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Curryfire

3 posts in 413 days


#3 posted 10-26-2016 12:54 PM

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Ripper70

608 posts in 743 days


#4 posted 10-26-2016 12:54 PM

Have you been able to see this bed up close and personal or have you ben going off photos from online? Hard to believe that little strip of wood will support the weight of the plywood bottom, the mattress and the kid. Suffice to say, if it was me, I’ll take the top bunk!

If you want to build your own find it in a store and take plenty of pictures and measurements to use as your plans. Then save yourselves a boatload of money by building it yourself.

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

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Ripper70

608 posts in 743 days


#5 posted 10-26-2016 01:15 PM



This is what we are modeling our project after.

http://www.casakids.com/blog/2015/2/23/ohh5eyd909kp5l01g2uwo7367oaq6f#canvas

- Curryfire

Haha! I used to live a few doors down from this place. I remember seeing miniature model displays of their work in a local storefront window. Their stuff was very expensive but well crafted and they were a popular local business with a strong neighborhood following.

Assuming they ship these units out and require self assembly you’d have to guess they use those cam lock nuts to make it easy to put the thing together. I think it’s a great looking piece and would figure that if you have the tools and some skills you could DIY and come up with your own method of making it secure.

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

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dhazelton

2608 posts in 2131 days


#6 posted 10-27-2016 12:48 PM

Now that I see it I’ll bet they use the prefinished ply and the whole thing is assembled with screws only. Probably a lot of pocket screw joinery going on.

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firefighterontheside

16910 posts in 1691 days


#7 posted 10-27-2016 01:03 PM

The ledge would be plenty strong to support all. It’s essentially how my kids bunk beds are now. In fact, mine only has the ledge on the sides and not one at the ends. That is how they came, but I think I will be adding ledges on ththe ends before the kids get much bigger. Baltic birch will work nicely for your bed. I wouldn’t use any other plywood in this way though.

-- Bill M. "People change, walnut doesn't" by Gene.

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rwe2156

2710 posts in 1315 days


#8 posted 10-27-2016 01:14 PM

After seeing the picture, I will probably work, but I would still use dimensional 2x lumber for the long spans or laminate 2 layers of 3/4 ply.

I envision 2 kids in a bed practicing latest wrestling moves, or jumping up and down trying to touch the ceiling, etc etc. I had 3 boys all within 4 years of each other so I know what I’m talking about. ;-)

I think joinery is going to be the issue. I also envision lots of screws holding this think together.

It needs to be dismantled to move and assemble so I would be looking at mortise/tenon with bolts (IOW don’t glue) for the long stretchers.

-- Everything is a prototype thats why its one of a kind!!

View jerryminer's profile

jerryminer

800 posts in 1276 days


#9 posted 10-28-2016 05:30 AM

Screws alone would be plenty to hold that ledger on (although I would glue and screw). A single #8 wood screw penetrating 1/2” into plywood has a shear strength of over 400 lbs. (according to the American Plywood Association)

A screwed-on ledger is SOP for beds. Done all the time.

-- Jerry, making sawdust professionally since 1976

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Cooler

299 posts in 678 days


#10 posted 10-28-2016 01:21 PM

My queen size bed, which I bought from Scandanavian Furniture about 25 years ago has required some refastening of the joints. The bed looked wonderful when purchased (and expensive) but turned out to be teak veneer over particle board with metal fasteners for quick assembly (It arrived assembled).

Over the years I have refastened the corners using glue blocks (2” x 2” hardwood ripped to make triangles for gluing). That has been more than sufficient for that purpose.

The slats similarly failed and I replaced them with two sheets of 1/2” ply. There is a center divider so each piece is about 5 feet x 3½ feet, going full width of the bed and one for the headboard end and one for the foot board end. That too has been more than up to the task. The plywood rests on a 3/4” square strip screwed to the sideboards. There is a center board that supports the middle running from the head to the foot.

I would do something similar for the child’s bed. The center support will prevent the plywood from bowing and slipping off the support cleats.

If this (final) construction has stood up to my nighttime gymnastics it should do fine for a child’s bed.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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BinghamtonEd

2286 posts in 2204 days


#11 posted 10-28-2016 02:22 PM

Perhaps the 1×2 frame that supports the mattress is registered in a dado on the sides, top, and bottom. This would allow for it to be broken down later on. You can see two cam screws (I assume that’s what they are) above where that support frame would be. If you put the frame in the dados, and locked the cams, that would hold the frame in. And, the dado shoulder would provide plenty of support for the frame, even without glue/screws.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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Curryfire

3 posts in 413 days


#12 posted 10-28-2016 02:30 PM

Thanks everyone for your advice! I’m modeling it using sketchup and post pics when I start cutting.

-curryfire

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Cooler

299 posts in 678 days


#13 posted 10-28-2016 02:33 PM



Perhaps the 1×2 frame that supports the mattress is registered in a dado on the sides, top, and bottom. This would allow for it to be broken down later on. You can see two cam screws (I assume that s what they are) above where that support frame would be. If you put the frame in the dados, and locked the cams, that would hold the frame in. And, the dado shoulder would provide plenty of support for the frame, even without glue/screws.

- BinghamtonEd

On my bed, the 3/4×3/4 strip is just screwed into the sides with short screws on about 1 foot centers. My bed had the cam locks (which failed) and I added the glue blocks (which did not fail).

This is not fine furniture. Pocket screws plus glue blocks in the corners will be more than sufficient for the purpose. The glue blocks are going to be hidden and that makes for a lot of flexibility on construction.

The bed has to last for about 6 years for a child, and then gets handed down. So this is a 12 to 18 year piece of furniture. Plywood will work fine for this.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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BinghamtonEd

2286 posts in 2204 days


#14 posted 10-28-2016 03:32 PM


Perhaps the 1×2 frame that supports the mattress is registered in a dado on the sides, top, and bottom. This would allow for it to be broken down later on. You can see two cam screws (I assume that s what they are) above where that support frame would be. If you put the frame in the dados, and locked the cams, that would hold the frame in. And, the dado shoulder would provide plenty of support for the frame, even without glue/screws.

- BinghamtonEd

On my bed, the 3/4×3/4 strip is just screwed into the sides with short screws on about 1 foot centers. My bed had the cam locks (which failed) and I added the glue blocks (which did not fail).

This is not fine furniture. Pocket screws plus glue blocks in the corners will be more than sufficient for the purpose. The glue blocks are going to be hidden and that makes for a lot of flexibility on construction.

The bed has to last for about 6 years for a child, and then gets handed down. So this is a 12 to 18 year piece of furniture. Plywood will work fine for this.

- Cooler

On the bed I built for my daughter, I used a scrap hardwood strip glued and screwed to the side with furring strips as mattress supports. It’s held myself, my wife, my daughter and my son all at the same time without issue. Many ways to solve the problem, but not what the thread was asking for.

My answer to the question was not in response as to what is required joinery for a bed. It is in response to the actual question that was asked. The OP stated that the design in question uses 1×2 to support the mattress, not glue bocks, not pocket screws, and whether that design was strong enough, and how it was attached to the walls of the box.

Based on your previous comment, and your response to mine, it appears that you did not thoroughly read the original post, or you chose to ignore the actual question at hand. Don’t give me the “this is not fine furniture” line because you chose not to read. Based on the fact that the OP has the assembly instructions in hand, I think we can safely assume that they don’t include “pocket screws plus glue blocks”.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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Cooler

299 posts in 678 days


#15 posted 10-28-2016 03:46 PM

Perhaps the 1×2 frame that supports the mattress is registered in a dado on the sides, top, and bottom. This would allow for it to be broken down later on. You can see two cam screws (I assume that s what they are) above where that support frame would be. If you put the frame in the dados, and locked the cams, that would hold the frame in. And, the dado shoulder would provide plenty of support for the frame, even without glue/screws.

- BinghamtonEd

On my bed, the 3/4×3/4 strip is just screwed into the sides with short screws on about 1 foot centers. My bed had the cam locks (which failed) and I added the glue blocks (which did not fail).

This is not fine furniture. Pocket screws plus glue blocks in the corners will be more than sufficient for the purpose. The glue blocks are going to be hidden and that makes for a lot of flexibility on construction.

The bed has to last for about 6 years for a child, and then gets handed down. So this is a 12 to 18 year piece of furniture. Plywood will work fine for this.

- Cooler

On the bed I built for my daughter, I used a scrap hardwood strip glued and screwed to the side with furring strips as mattress supports. It s held myself, my wife, my daughter and my son all at the same time without issue. Many ways to solve the problem, but not what the thread was asking for.

My answer to the question was not in response as to what is required joinery for a bed. It is in response to the actual question that was asked. The OP stated that the design in question uses 1×2 to support the mattress, not glue bocks, not pocket screws, and whether that design was strong enough, and how it was attached to the walls of the box.

Based on your previous comment, and your response to mine, it appears that you did not thoroughly read the original post, or you chose to ignore the actual question at hand. Don t give me the “this is not fine furniture” line because you chose not to read. Based on the fact that the OP has the assembly instructions in hand, I think we can safely assume that they don t include “pocket screws plus glue blocks”.

- BinghamtonEd

He was asking about the “rails” to which I answered that the “rails” on my bed were simply screwed in place. Those never failed.

I supplied additional information that indicated that the take down feature of the original furniture was inadequate and it seemed that the item he was buying used that same hardware. I suggested ways to overcome that design inadequacy.

As for the pocket screws, in general if this is not going to be shipped and knocked down, pocket screws are preferred in my opinion to the take down hardware.

So I answered the question and supplied additional information based upon my experience. I don’t see why you would choose to criticize my response.

Also the title for this thread “Help for plywood joints” would invite discourse on plywood joinery.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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