# What screws to use for floating vanity frame?



## Lkvinson

This may not be the right forum, and I am new to the site and the world of woodworking, so forgive me.

I am building a floating shelf vanity measuring 50" x 24". My intention is to create a simple frame using 2×4s that the edge-glued panel countertop sits on, and the 2×4S will of course be attached to the studs in the three walls around the vanity. I am not sure how best to join the frame to the studs- the last thing I want is for the sink to be too heavy and everything come crashing down. I Have (#8) 2 1/2" screws but am concerned they will not be strong enough, even if I use two screws per stud (there are 4 studs in the wall behind the vanity and one student on either side). Should I use lag bolts?

Thanks all!


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## UpstateNYdude

I'd make a french cleat set it in and then lag into the studs. I'd also add some bracing underneath 24" is fairly wide to be unsupported.


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## CampD

2 1/2" screws are enough. Build the frame, screw it in place predrilling holes, than attach the top with screws from underneath. You could even make a false bottom with just a few screws holding it in place.

Good luck!


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## MrFid

Welcome to the site!

I also think 24" of hang is probably too much for even a lag bolt, especially considering you're dropping a sink into the coutertop. No matter how strong your connection is between the counter/frame and the wall, it will feel wobbly if it's not supported further out. Which is not a feeling someone wants when they're washing their hands or leaning on the counter. You can probably find fairly non-obtrusive shelving brackets at a home center that will suit your purposes. Or, if you know how to weld (or know a local welder) they could easily fabricate something that would provide much more support underneath the shelf.

Let us know if you need more help with your project. There are lots of smart people on here that I've learned a lot from. We look forward to seeing what you come up with. Again, welcome to Lumberjocks!


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## Lkvinson

Thank you both! Doug, I was doing some more thinking last night - Would it be better to use 3 1/2" screws? I've got to go through 1 1/2" of 2×4 and 3/4" of drywall before I even hit the studs.


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## Lkvinson

Great idea with the shelving brackets! That's one of those, "oh, duh! " moments.


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## jonah

Welcome to LJs!

If I'm understanding correctly, this floating vanity has walls on three sides around it.

If that's the case, screwing it into the framing on all three sides will be plenty to support a 24" front, so long as the whole assembly is sufficiently stiff. Having a strong frame and cross bracing will help there, but brackets in the corners couldn't hurt either.

Your instinct is right that you need 3.5-4" screws. Personally, I'd use beefy 1/4" lag bolts rather than wood screws. Be sure to pre-drill the holes to avoid splitting the wood.


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## jerkylips

I missed the part about "3 walls" at first, as I suspect some others did too based on the responses. If the shelf is supported on 3 sides - back and each side - I would do a cleat into each wall, and fasten the counter top to the cleat from below. This picture shows 2 of the 3 sides. I would use 4" lag bolts into the stud - be sure to pre-drill.


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## JBrow

Kate,

I doubt the vanity top plus even a cast iron sink will exceed the strength of standard 3" construction screws. By my calculation, the combined weight of a cast iron sink (about 30 pounds) plus a hard maple 2" thick vanity top (about 65 pounds) plus miscellaneous dead load will probably weigh no more than 150 pounds. I think 12 (2 screws per stud) 3" construction screws would be more than sufficient to carry this load (about 13 pounds of load per screw).

An alternative to construction screws and fasteners already suggested that would be stronger are structural screws or sometimes called timber screws. My understanding is that these specialty screws offer greater shear strength than drywall or construction screws and lag screws. Structural screws can be found with various heads and differing sizes, some of which are low-profile heads. Although some manufacturers may state that predrilling is unnecessary, I would predrill as added insurance against introducing a split in the framing studs.

Here are some examples of structural screws…

https://www.lowes.com/pd/FastenMaster-50-Count-0-to-x-6-in-Ecoat-Spider-Drive-Structural-Wood-Screw/3295080

https://www.menards.com/main/tools-hardware/fasteners-fastener-accessories/screws/wood-screws/fastenmaster-reg-headlok-reg-3-x-2-7-8-spider-drive-black-flat-head-wood-screw-1-count/p-1446588768376.htm

As to screw length, I think a 2-1/2" long screw is not long enough when using 1-1/2" true thickness material as cleats to support the vanity top. Assuming the 2×4 cleats are screwed over ½" thick drywall, a 2-1/2" long screw would only extend ½" into the framing. I would prefer 1" of the screw in the framing. That then would require a 3" long screw for a 2×4 cleat. On the other hand, keeping the amount of the screw buried into the framing no more than 1" could reduce the chances of inadvertently drilling into an electrical cable that is run through the center of the framing studs while providing plenty of support for the cleats.


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## TheFridge

A dozen screws 1" into the stud will hold up just about anything. I usually use spax screws or #10 screws for jobs like this.


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## clin

Since it is supported on three sides, the loads are pretty small at any point. Your worst case load is the 300 lb guy that will sit on it.

The cleat that jerry shows is the way to go. You don't need a 2×4 frame up against the wall. 1×2 would be enough. The front end, of the two side cleats, are where the greatest load will be and two screws there is not a bad idea. Though one good size screw like a #14 should be plenty.

Elsewhere, one in each stud is certainly enough. As for screw length, you will probably have 1/2" drywall and then the thickness of the frame/cleat.

Assuming a 1" thick frame/cleat, + 1/2" drywall, + 1" screw into stud, as TheFridge suggested, you need screws 2.5" long. If you use 2×4 or similar frame/cleat, then you need another 1/2" so 3" long. A bit longer doesn't hurt, but unless you know for sure there isn't wiring running through the studs, you don't want to just run 2" deep into the stud.

#8 screws are probably plenty big, for all but the front end of the frame. You won't break (shear off) the #8, but they could bend. The bigger the screw, the less they will bend and the more wood the forces are spread over. So maybe just go with #14 or similar fro those front ones. You'll want to pre-drill for those to make sure you don't split the frame/cleat or stud. I'd pre-drill the frame/cleat no matter what, makes it easier to pre-load the screws when mounting. For #8 screws in the stud, you don't need to drill the stud.

You didn't describe how the shelf was constructed. At 50" long, you will need some strength along that front edge. If the top is something like 1.5" hardwood, then that's likely plenty. But if the top is laminate covered particle board or similar, then you need to support that.

This of course may be why you have described a frame. And certainly a 2×4 frame going around all 4 sides is more than enough. Smaller would still be okay, even for the 300 lb guy who will sit on it. You just want the shelf to not bend too much under an extreme load. And of course not bend or sag at all under it's own weight and the weight of the sink.

Often a smaller frame is desired for looks. If so, you could consider a steel tube long the front.


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## MrRon

You have to realize the weight of the sink is equally distributed around the lip of the sink, which is closer to the walls. The shelf itself won't sag, as the weight is not concentrated at the center of the shelf. Besides, 2" thick maple is pretty stiff all by itself. I would recommend 4" star drive deck screws, 2 per stud is adequate. Anymore and it is overkill. Just make sure the supports are screwed tightly against the wall. You want as much tension applied to the screw to reduce the shear on the screw. You do not want to introduce bending in the screw.

PS; *Don't *use stainless steel screws. 1/4" lag bolts are also OK


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## clin

Shelves stills sag with evenly distributed loads. just not as much as if the same total load is in the center. Also, I don't think the OP said anything about a 2" thick maple top. That was someone else's example used in a weight calculation.

Though I agree that if it were a 2" thick maple top, that alone would be plenty stiff enough.

While I see no big advantage to stainless screws, why NOT use them? Is there some reason they wouldn't work as well?


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## jonah

There's no reason I can think of why stainless steel screws wouldn't work perfectly fine.


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## JBrow

clin and jonah,

The only reason to avoid stainless steel screws is that the heads of ones I have used strip easily. But if the hole is predrilled to the correct size and care is used when driving the screw, I would think stainless would hold weight like a construction screw in this application with no problem. But then since I am not a metallurgist, the loading capacity of stainless compared to other metals is a guess.


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## Lkvinson

Thank you for all the responses. This forum is a wealth of knowledge and I appreciate you all taking the time to respond and explain!

You had me sold on using cleats instead of a frame, but I've run into a new problem. When I went to measure out 24 inches from the back wall, I discovered that the stud on one side started at about 23 3/4" from the wall…I wouldn't be able to screw the front of one cleat to a stud. After much swearing and head scratching, I figured I could either: 
1. Use heavy duty toggle bolts to attach that end of the cleat to the drywall
2. Support the countertop on that side with a bracket ( as suggested above). I know Lowe's carries a 22" bracket with 500lb capacity, and I figure I could attach it to the stud along the back wall.

Thoughts?


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## 000

I would use 1×3 cleats instead of 2×4

On the wall with no stud, I would use 3 or 4 EZ anchors and some panel adhesive.
I would use any #6×2 1/2 - 3" screws with the EZ anchors.

No reason to pay extra for stainless steel screws. 
I've used plain old drywall screws with no problem. Even though a lot of people don't like them, they will work fine.

No need for the bracket either.


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## JBrow

Kate,

I suspect that the stud finder may have failed to detect the stud on the one end wall where the nearest found stud measures 23-3/4" from the inside corner. If standard framing practices were followed where studs are located 16" center to center apart, there should be a missed stud somewhere within the 23-3/4" span.

My guess is the near edge of missing stud is about 14-1/2" from the edge of the stud located 23-3/4" from the inside corner. Alternatively the missing stud could be somewhere around 16" from the inside corner of the drywall.

There are several ways to check whether an unfound stud exists that does not rely on a stud finder. The pros seem to prefer the knocking method, which I have never perfected. Lightly knocking along the span with your knuckle will produce a sound. A hollow sound reveals no stud while a solid sound indicates proximity to a stud.

If there is base board installed and you can see where the base board was nailed to the drywall, the location of the nails in the base board could identify the location of the stud. If no baseboard was installed and you intend to install base board, some small holes that will be covered by the base board could be created and the stud bay probed with a stiff wire. The probing holes would have to be at least 1-1/2" above the floor assuming a single bottom plate in the wall framing.

Sometimes there are telltale signs of a stud on the surface of the drywall. These could be nail pops or slight dimples. A flash light held oblique to the surface of the wall can help highlight imperfections on the surface.

If wall was framed with a stud that is bowed in, the drywall at that stud will be pulled into the stud leaving a depression in the drywall. If the stud is bowed out, the drywall may belly out. If either condition exists, a straightedge held against the wall and parallel to the floor can reveal the center of the depression or the belly and the likely approximate location of the stud.

My last thought would require drilling some small diameter holes in the area where you plan to install cleats to the wall until the drill bit hits the stud. The cleat would cover these holes.

But if in fact there is no stud, I personally would like to ensure there is some solid framing to which the cleat could be installed. This could require opening the wall, installing some blocking, and then repairing the drywall.

jbay's idea of using the wall EZ anchors and adhesive may be enough. However drywall is not all that strong or structural. If his approach were followed, I would wonder whether that particular cleat would eventually detach from the wall requiring a repair down the road. But then opening the wall to install blocking guarantees repair work; it just an easier repair now. If the countertop and sink are especially heavy, installing blocking would be best. But if the entire assembly is not so heavy, plenty of EZ anchors and adhesive could be enough.


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## 000

> Kate,
> 
> jbay's idea of using the wall EZ anchors and adhesive may be enough. However drywall is not all that strong or structural. If his approach were followed, *I would wonder whether that particular cleat would eventually detach from the wall requiring a repair down the road.*
> 
> - JBrow


NEVER! (I don't wonder) Your talking shear forces, nothing pulling the cleat off the wall.
I've made a living doing this for over 30 years, I can't count how many times I have done just the same, 
I've never had a drywall failure.


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## jonah

It's very possible that her framing is 24" on center. My house (mid 90s construction) was built with 24" on center metal studs. If that's the case, I would use the construction adhesive and anchors jbay recommended.


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## Tony_S

> I would use 1×3 cleats instead of 2×4
> 
> On the wall with no stud, I would use 3 or 4 EZ anchors and some panel adhesive.
> I would use any #6×2 1/2 - 3" screws with the EZ anchors.
> 
> No reason to pay extra for stainless steel screws.
> I ve used plain old drywall screws with no problem. Even though a lot of people don t like them, they will work fine.
> 
> No need for the bracket either.
> 
> - jbay


+10


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## MrRon

> There s no reason I can think of why stainless steel screws wouldn t work perfectly fine.
> 
> - jonah


Stainless steel screws are not as strong as steel screws. They will break if you drive them too tightly. I built 2 decks. I used SS screws on the first and had around 30 screws shear. With the 2nd deck, I used steel screws and didn't shear a one. I drove around 800 3" star drive screws through construction grade lumber.


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## MrRon

If the wall supports give you concern, I don't see why you couldn't add a vertical floor support at each side of the vanity at the front. It wouldn't need to be much bigger than a 1×3. Put it against the wall between the floor and the bottom of the 2×4 frame.


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## AlaskaGuy

> I would use 1×3 cleats instead of 2×4
> 
> On the wall with no stud, I would use 3 or 4 EZ anchors and some panel adhesive.
> I would use any #6×2 1/2 - 3" screws with the EZ anchors.
> 
> No reason to pay extra for stainless steel screws.
> I ve used plain old drywall screws with no problem. Even though a lot of people don t like them, they will work fine.
> 
> No need for the bracket either.
> 
> - jbay
> 
> +10
> 
> - Tony_S


What they said would be fine.


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## MadMark

My rule of thumb for screw length is its twice as long as the thickness to the wall. 1 for the cleat and 1/2 for the rock is 1-1/2 doubled yeilds a 3" screw. Ymmv

M


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## Lkvinson

Thank you to everyone for your input! I finished the vanity this week and couldn't be more pleased. I used 1×3 cleats, attached to the studs and with EZ anchors as suggested. I also took the depth of the vanity down to 22" for purely aesthetic reasons. It feels extremely sturdy and was a great first project for practicing basic skills like scribing wall and staining/sealing. It also gave me an excuse to buy a table saw!


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## John Smith_inFL

*wow - looks AWESOME !!*

good luck in your future builds


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## Tony_S

Looks like a pro did it….You're a natural!


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## AlaskaGuy

Fits like a glove


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