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Forum topic by newwoodbutcher posted 05-11-2018 08:43 PM 749 views 1 time favorited 16 replies Add to Favorites Watch
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newwoodbutcher

777 posts in 3047 days


05-11-2018 08:43 PM

A dear friend has asked me to make a headboard and night stands that float above the floor. In a modern sleek style. It’s an exciting project. Mahogany. My plan is to use French cleats to hold up the whole thing. Four boxes, two for the headboard and two nightstands. I’ve used French cleats several times but the “furniture” was always longer than it was deep, Because of the dimensions of the head board, I think I’m good with that one. I’m concerned about the night stands. The planned dimensions of the nightstands are 10” tall, 18” wide and 24” deep.. it’s the 24” dimentions I’m worried about. I’m confident that I can make the cleat connections to the wall and the nightstand strong enough but I’m worried that 24” is a bit far for a 10” back especially when one uses the nightstand as leverage to get out of bed. Any and all engineering and experience advice will be appreciated. I’m guessing there is a specific guideline on the relationship between these forces? I have some flexibility in dimentions, a few inches.

-- Ken


16 replies so far

View CaptainKlutz's profile

CaptainKlutz

596 posts in 1692 days


#1 posted 05-11-2018 09:52 PM

hmmm, 24” deep night stand?

Been there done that, got bruised once a week until I sold them.

16”-18” is ‘normal’ depth. Pillow only occupies 15-17” of top of bed, SO:
make sure to tell your friend they will OFTEN be hitting their shoulder on night stand when they roll out of bed!

Have no data, but a 4-5” tall 1” wide cleat attached to wall with 4 #12 wood screws will hold hundreds of pounds in cabinet. May still need to anchor the cabinet to wall to prevent lift and rotate out when not wanted.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View GrantA's profile

GrantA

672 posts in 1605 days


#2 posted 05-11-2018 09:54 PM

Sounds like a fun project! I would say, as far as your concerns on the night stands, just run a spacer across the bottom that’s the same thickness as the cleat. Then any downward pressure on the front edge of the piece would transfer against an 18” wide board bearing against the wall

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waho6o9

8516 posts in 2774 days


#3 posted 05-11-2018 09:59 PM

Use 2 cleats

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Jim Finn

2686 posts in 3119 days


#4 posted 05-11-2018 10:15 PM

I like to make, and use, metal cleats. Simple and strong.

-- No PHD just a DD214 Website> craftingcouple.com

View BFamous's profile

BFamous

185 posts in 318 days


#5 posted 05-11-2018 11:16 PM

I’d lean towards using metal brackets as well, just because I like to plan for the worst case scenario of someone dancing on them…

Though, as CaptainKlutz points out, cabinets hold lots of weight too. And if you have a spacer/filler strip at the bottom as GrantA points out, there wouldn’t be anywhere for the nightstand to go.

-- Brian Famous :: Charlotte, NC :: http://www.FamousArtisan.com

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clin

954 posts in 1193 days


#6 posted 05-11-2018 11:59 PM

The issue is the deeper the cabinet, the larger the moment (think torque) trying to pull the cleat AWAY from the wall. This also places an equal force pushing against the wall at the bottom.

And you are correct the the 10” height, makes these forces larger. You can take the weight of the cabinet and assume it is centered in the depth. So that is 12” from the wall. Let’s assume the cabinet and contents weight 75 lbs. So that’s 75×12 = 900 lb-in.

As mentioned, someone will put their weight on it. I don’t think 200 lbs all at the 24” front is out of the question. So that’s 24” x 200 lbs = 4,800 lb-in. So the total is 4,800 + 900 = 5,700 lb-in.

The cabinet is 10” tall, but the support for the cleat is not right at the top, it has to be down from the top. And similarly, all of the force at the bottom won’t be right at the bottom. But let’s assume those points are 8” apart. So the force pulling at the top and pushing at the bottom is:

5,700 lb-in / 8 in = 713 lbs

That’s the force trying to pulling out, not down, on the cleat at the top. And similarly pushing in towards the wall at the bottom.

I think it’s doable, but the cleat, which at most is 18” long, will have to span two studs. If it is an interior wall with 24” on center studs, I think you’d have to reinforce the wall. I’m not sure just how large the screws or lags bolts would need to be to support 700+ lbs in two studs. But it sounds doable to me.

Again, this is the force pulling straight out. The downward force would still just be the combined weight of the cab and load placed on it. A couple of hundred pounds is not an issue.

I agree that 24” sounds too deep and would make it harder to get in and out of the bed. If for example it was 18” deep, the same peak force would be 534 lbs. So still substantial, but significantly lower than 713 lbs.

I also think it would look odd being deeper than it is wide.

I don’t see that you mention the depth of the headboard. If this is one of those things where the headboard has depth with shelves in it, then I understand how the effective depth of the nightstand is less then 24”.

-- Clin

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newwoodbutcher

777 posts in 3047 days


#7 posted 05-12-2018 12:06 AM

Captainklutz, the headboard will be 12” wide so the table will go back to the wall leaving 12” sticking out from the headboard and head of the mattress.

-- Ken

View BlazerGator's profile

BlazerGator

25 posts in 1386 days


#8 posted 05-12-2018 01:41 AM

Perhaps your design would allow some way for the headboard to tie-in to the nightstands. It could take some of the weight and help out with the geometry a bit.

-- Blaze

View TungOil's profile

TungOil

1055 posts in 692 days


#9 posted 05-12-2018 01:49 AM

Skip the French cleat and screw it to the studs in several places. Use long screws like you would use for kitchen uppers. Not drywall screws.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

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newwoodbutcher

777 posts in 3047 days


#10 posted 05-12-2018 05:10 AM

Jim, can you show me what the metal cleats you make look like?

-- Ken

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newwoodbutcher

777 posts in 3047 days


#11 posted 05-12-2018 05:30 AM

Clin,
Thank you so much for your input. since I can’t hit two studs twice with 18” wide cabinets I’m thinking the cleat will span both nightstands and the headboard about 111”. Perhaps two cleats, upper and lower, 5-6” wide. You said you think it’s doable but the 713 number you calculated sounds astronomical . The headboard will be two cabinets 12” deep with two hinged lids, perhaps I could add another cleat (or attachment) to the side of he headboard as well but the force pulling away from the wall would’nt be reduced much if at all. How tall must a 24” deep cabinet be in your opinion to be sturdy enoug for years of use using 3” lag bolts and French Cleats. Do I need to consider a new design?

-- Ken

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newwoodbutcher

777 posts in 3047 days


#12 posted 05-12-2018 05:38 AM

Ting Oil, I’ve been thinking about making the boxes with 3/4” mahogany plywood. Which would allow me to screw a few rows through the back but I can’t hit two studs without a cleat running the full length of the four boxes. Would it help if the cleats were10” wide, essentially screwing the back from top to bottom to the cleats. Thank you for your advice. I need to sleep on this

-- Ken

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newwoodbutcher

777 posts in 3047 days


#13 posted 05-12-2018 05:40 AM

Blaze gator. Thanks for your idea. Think I’m going to make a plywood prototype and test a few ideas

-- Ken

View AlaskaGuy's profile

AlaskaGuy

4760 posts in 2506 days


#14 posted 05-12-2018 06:01 AM

View clin's profile

clin

954 posts in 1193 days


#15 posted 05-17-2018 12:06 AM



Clin,
Thank you so much for your input. since I can t hit two studs twice with 18” wide cabinets I m thinking the cleat will span both nightstands and the headboard about 111”. Perhaps two cleats, upper and lower, 5-6” wide. You said you think it s doable but the 713 number you calculated sounds astronomical . The headboard will be two cabinets 12” deep with two hinged lids, perhaps I could add another cleat (or attachment) to the side of he headboard as well but the force pulling away from the wall would nt be reduced much if at all. How tall must a 24” deep cabinet be in your opinion to be sturdy enoug for years of use using 3” lag bolts and French Cleats. Do I need to consider a new design?

- newwoodbutcher

Ken, sorry to take so long to respond, I was out of pocket for a while. While one long cleat can help address the issue of supporting the night stands, this is only good if there are studs near the ends of the cleats and these go near to the outsides edges of the floating night stands. Or the wall cleat is very strong (thick steel).

A lower clear is not needed. The problem is not that there is too much weight straight down trying to shear the cleat off the wall. So putting upper and lower cleats just makes it all harder and it’s really hard to make the cleats share the load. If you need more screw/bolt area, just make a single cleat taller so you can get 3 or 4 large screws in it.

But this won’t help the moment problem much. The most force is on the top edge of the cleat. And in fact the bottom of the cleat will be trying to push into the wall.

I’m no expert on selecting screws, but found this table:

http://www.siegefiles.outlands.org/Construction%20Plans/Tables,%20References%20and%20Best%20Practices/Fasteners/Lag%20Screw%20Withdrawal%20Strength%20(Doug%20Fir).pdf

According to this, a single 1/4 diameter lag bolt screwed in to a depth of 2” of wood will support up to 450 lbs for force trying to pull it out. Larger screws support more. I’m not sure how big you can go into a stud and not risk the screw being too big for the wood. 3/8” certainly isn’t an issue and maybe even 1/2” would be fine.

A 3/8” screw to 2” depth is good for 610 lbs. Now, I assume this table is a limit and therefore you should build in headroom. I’d go 2X. So I would consider the single 3/8” screw to a depth if 2” to be good for 300 lbs.

So this is why I think it is doable. But of course care is needed that the forces are shared among several screws.

Certainly it would make sense to use the 12” depth of the hardboard cabinet to help support the night stands. But this gets tricky.

Imagine the cleat system we’ve been discussing. Then put a single bolt between the night stand and the headboard cabinet, at say 10” from the wall. This will want to act like the pivot point of a tweeter tooter. If you put weight the front of the night stand, this will try to raise the back of the table and lift it off the cleat.

Of course the headboard is also supported by a cleat, so any force you apply from the night stand to the headboard, will still be there on the one big cleat. But it might ensure it spreads out better.

I’m not sure a cleat even makes sense in this application. As TungOil suggested bolting directly to the wall might be better. Though I understand your point about hitting studs. Just keep in mind that several of the reasons for using a cleat don’t apply here.

Cleats work great for hidden mounting when there’s no place to hide a screw. In your case screws would be easy to hide in the back of the cabinets.

Cleats are helpful for one-man installation. But unless you live on an island by yourself, that’s seldom that much help.

Cleats are helpful when for quick rearrangement of things, like in a shop. That doesn’t apply here.

Something else to consider would be to really tie the night stands to the headboard. Using something like 4 screws/bolts where these overlap. make the whole thing function like one big unit. Screwed to the wall (no cleat).

If the backs of the cabinets are 3/4” plywood as you said, I think that would be plenty strong enough even if there are not studs right at the ends. And with the night stands secured to the headboard, it certainly helps to spread any load that might be applied to the night stands. This is probably the way I would do it.

You could still do this where you mount the headboard section first, then attach the night stands to this and the wall.

Note: Even if attached directly to the wall, all those same forces apply. Because of that 24” depth, this is much different than bolting something like 12” deep kitchen cabinets to a wall. So you still want to use some good sized bolts, especially near the top of the cabinets. Also, try to get those as close to the top as possible.

As in my first post, if you could get the top screw higher so that the 8” became 9” the force drops form 713 lbs to 634 lbs. Bottom line, the higher up the top screw the better. This again would be better bolting directly rather than using a cleat. In fact, given the cabinet cleat has to be above the wall cleat, I’m not sure you could even get the 8” I proposed earlier.

-- Clin

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