# What Length Screws To Reinforce Plywood Cabinet Joints



## JIMMIEM (Feb 5, 2016)

I'm making a hanging wall cabinet out of 3/4" cabinet grade red oak plywood with red oak face frame. The cabinet will be 36 " tall X 36" wide X 12" deep. The shelves will be adjustable. I will hang it via a French Cleat. I plan to attach the top and bottom to the sides with biscuits and reinforce these joints with SPAX or GRK screws driven through the sides. Instead of plugging or filling the screw holes I will apply 1/4" plywood panels to the sides to hide the screws.
What length screws would you recommend that I use?
Thank You


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## Loren (May 30, 2008)

1-5/8" screws are fine imo. Probably overkill even but when I use biscuits for cabinets that's the size I use.


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## CWWoodworking (Nov 28, 2017)

I use #6×2" zip-r from Hafele. Lately I just pocket hole cabinet boxes. IMO it's easier.


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## 1thumb (Jun 30, 2012)

I first heard french cleats referred to as dutch hangars. Years later i watched an episode of this old house filmed somewhere in europe. wherever it was, when you moved, you took the kitchen cabinets with you. ie, dutch hangars


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## JIMMIEM (Feb 5, 2016)

> I first heard french cleats referred to as dutch hangars. Years later i watched an episode of this old house filmed somewhere in europe. wherever it was, when you moved, you took the kitchen cabinets with you. ie, dutch hangars
> 
> - 1thumb


The next time I move it will be to a nursing home or boot hill. I'm using French Cleats because they will make it easier to hang the cabinet by myself.


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## Sark (May 31, 2017)

I always used #8 1 1/2" screws for cabinet assembly. Never a fan of Spax or Grx for that matter, I settled on square drive from McFeely. My favorites are ProMaster. Like Spax in that they have a wavey thread that cuts its way through, nibs to make it self tapping. Where they are vastly superior is grip. The square drive gives so much better grip than star driver. Sharper than the competition too…and I've done lots and lots of cabinets with them.


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## JIMMIEM (Feb 5, 2016)

> I always used #8 1 1/2" screws for cabinet assembly. Never a fan of Spax or Grx for that matter, I settled on square drive from McFeely. My favorites are ProMaster. Like Spax in that they have a wavey thread that cuts its way through, nibs to make it self tapping. Where they are vastly superior is grip. The square drive gives so much better grip than star driver. Sharper than the competition too…and I've done lots and lots of cabinets with them.
> 
> - Sark


Because I will be putting the screws into the end grain of the top and bottom boards I will pre-drill. In this application I figure the screws will be under shear load. GRK gets good reviews for attaching kitchen cabinets to wall studs.


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## CWWoodworking (Nov 28, 2017)

With #6 you don't have to predrill. Don't worry about shear strength. The wood will fail before you break 6 or 8.


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## JIMMIEM (Feb 5, 2016)

> With #6 you don't have to predrill. Don't worry about shear strength. The wood will fail before you break 6 or 8.
> 
> - CWWoodworking


In that case if the top and bottom of the cabinet are 13 inches wide and I use 5 #20 biscuits to secure them to the cabinet sides do you think the screws are overkill?


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## CWWoodworking (Nov 28, 2017)

If your using biscuits, I'd screw it. Just because you wouldn't have to leave it clamped.

Honestly 4 screws per corner for a 13" cabinet is plenty strong. Once it's on the wall it will never fail.

The only thing I'd be concerned with on a 36" cabinet would be shelf sagging. I'd probably use a hardwood stiffener.


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## JIMMIEM (Feb 5, 2016)

> If your using biscuits, I'd screw it. Just because you wouldn't have to leave it clamped.
> 
> Honestly 4 screws per corner for a 13" cabinet is plenty strong. Once it's on the wall it will never fail.
> 
> ...


I may go with just the biscuits and see what happens. I can always add screws and end panels later. I'll leave the face frame a little wide so if I have to add end panels I'll be able to flush trim then.
I checked Sagulator and will add solid edging or thicken the shelves. I have a tendency to overbuild…..probably due to lack of experience.
I don't mind having to leave it clamped for a while….no rush…..this has been in the planning stage forever.


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## JackDuren (Oct 10, 2015)

> 1-5/8" screws are fine imo. Probably overkill even but when I use biscuits for cabinets that s the size I use.
> 
> - Loren


+1. That's all we used in commercial cabinetry..


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## JIMMIEM (Feb 5, 2016)

Am I overthinking this? If the top and bottom of the cabinet are 13 inches wide and I use 3 #20 biscuits on the end of each piece can I skip the screws? The French cleat will abutt the top of the cabinet and have a biscuit into the cabinet sides. The cabinet back panel will be 1/4" ply and dadoed into the cabinet sides, top, and bottom.


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## Sark (May 31, 2017)

I don't know why you want to skip the screws. I'd skip the biscuits if I were making the cabinet. Our process was to pin nail the pieces to hold them in place. Then pre-drill when needed. Then screw. Simple and fast and strong.

Are screws stronger than biscuits? My guess is that they are just as strong for this purpose if not stronger. We avoided glue whenever possible, and in cabinet-box making its usually possible.

How are you going to attach the French Cleat to the cabinet? That's maybe a more important consideration than screws vs. biscuits. Run a 4" wide nailer at the top inside of the cabinet. Then screw through the sides into the nailer, and add a couple of screws into the top, and you'll have an strong support to attach the French cleat on the back.


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## JIMMIEM (Feb 5, 2016)

> I don't know why you want to skip the screws. I'd skip the biscuits if I were making the cabinet. Our process was to pin nail the pieces to hold them in place. Then pre-drill when needed. Then screw. Simple and fast and strong.
> 
> Are screws stronger than biscuits? My guess is that they are just as strong for this purpose if not stronger. We avoided glue whenever possible, and in cabinet-box making its usually possible.
> 
> ...


I'll use the screws. I'll attach the French cleat with screws through the box sides. The cleat will be up against the box top too.
Thank you. I appreciate you taking the time to respond.


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## Sark (May 31, 2017)

Another advantage of the screw-it-together method, is that if you need or want to change/fix/alter the cabinet, you can easily take it apart and put it back together. Which I've done more times than I can count…


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## JIMMIEM (Feb 5, 2016)

> Another advantage of the screw-it-together method, is that if you need or want to change/fix/alter the cabinet, you can easily take it apart and put it back together. Which I've done more times than I can count…
> 
> - Sark


OK. Screws and pins (23 gauge?). Also, I saw some articles on making nicer end panels than just a flat panel. The end panel design was the same as the doors. When I make the rail and stile overlay doors I can make a couple more sized to cover the sides of the cabinet. Doing these end panels means no reason not to use the screws.


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## Sark (May 31, 2017)

I only used 23 gauge on trim…I use the 18 gauge on the cabinets…they are easier to get out than the 23 gauge when you need to redo. But the 23 should work fine, its only for alignment and to hold things together while you get the screws in place.

And yes, if the side panels are exposed then you have the option of using the same style as the door. More dressed up look at a higher cost.


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## waho6o9 (May 6, 2011)

I like to install the French cleat on the wall and notch my panels to slide them in place. Works for me.

15/8" screws work well. Spax or GRXs are the preferred brands.


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## JIMMIEM (Feb 5, 2016)

> I only used 23 gauge on trim…I use the 18 gauge on the cabinets…they are easier to get out than the 23 gauge when you need to redo. But the 23 should work fine, its only for alignment and to hold things together while you get the screws in place.
> 
> And yes, if the side panels are exposed then you have the option of using the same style as the door. More dressed up look at a higher cost.
> 
> - Sark


I have an 18 gauge nailer so I'm good to go.
I bought extra plywood and solid oak so I've got plenty of stock. The 3/4" red oak plywood actually measured 3/4". Can't remember the last time I saw that.


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