How much weight can a wall support (mounting a cabinet on a wall)

[todd]

I wouldn't be that concerned at this point. My beef with drywall screws (like Charlie, it sounds), is that they seem to twist off the head during installation rather easily.

todd

[Charlie Self]

Mark Jerde asks:

Half a ton? Books are heavy, but that's still a lot of books. If the screws haven't sheared off by now, I'd forget it. I think. Then again, I might run in some other type of steel screws just to be safe.

Hope you're not in earthquake country.

Charlie Self "I hope our wisdom will grow with our power, and teach us, that the less we use our power the greater it will be." Thomas Jefferson

[Silvan]

Wish I had remembered how hard they are. I used some to screw a jig together. The points were sticking out a trifle at the bottom, so I whipped out my handy dandy X-Acto razor saw.

Such a pity. I used that stupid thing all the time for cutting everything, but now it's ruined unless I find some reallllly tiny needle files to put new points on it.

[Swingman]

What part of the world are you in? Makes a big difference on the answer to your question.

You did build your cabinet, destined for wall use, with built-in screw strips, didn't you?

I build both wall and base units, which must be attached to a wall, with at least an upper and lower 3/4" thick screw strip that sits flush between the back panel and back edge of the cabinet sides.

TIP: If you bevel the bottom part of the TOP screw strip, it will also do double duty it as the top half of a "French cleat'.

Here in the US, where most construction is wooden frame, I use deck or drywall screws for the LOWER screw strips of my cabinets, screwed into studs or blocking.

BUT, I _always_ screw at least two 3 1/2" lag bolts, using the TOP screw strip of the cabinet, the number depending upon the width of the cabinet, into at least two studs, or the blocking between the studs.

On a 48" wide cabinet, I would use 3 lag bolts on the TOP screw strip, one in the middle and the other two evenly spaced toward the sides.

Fastened thusly at the TOP screw strip, you can use just about any type of screw, drywall or otherwise in the lower screw strips and the cabinet will handle all the weight for which it was designed.

I recently started using "French cleats", but I still like the lag bolts in the top screw strip for peace of mind, particularly when I do work for someone besides myself ... not to mention possible liability issues.

[Juergen Hannappel]

[...]

[...]

What is the use of the lower screw strip? The upper one bears the weight, keeps the cabinit from falling. The lower would just keep it from lifting off the wall, which it would have to do against gravity; Most wall-hanging cabinets from furniture shops come with only the upper mounting option...

[Swingman]

Around here, mainly to keep the leveling wedges from falling out, and lets you get away with actually using all those drywall screws you have on hand from another project. ;>)

IME, using the bottom screw strips helps in pulling the cabinet tightly against the wall, helps with rigidity of the unit, and aids in leveling a line of cabinets when part of a wall of cabinets fastened together.

[Mark & Juanita]

But that's a torsional force, not shear force.

[Jon Endres, PE]

Look up "french cleat".

you attach the lower portion of the cleat to the wall studs with lag bolts or large screws (2 or more per stud) and then use additional short screws to simply secure the bottom of the cabinet to the wall, you should be able to hang a couple hundred pounds.

As an example - I built a simple bookshelf for my office - birch ply and a face frame, dadoed and rabbeted and glued. I used a french cleat with four screws, two per stud, and used two more screws (#10 x 3) to secure the bottom. To test, I did a couple of chinups on the shelf. I weigh almost

290 lb. It held. Do it this way and you won't have to worry about any normal amount of weight.

Jon E

[Jon Endres, PE]

No, but the *slightest* bit of bending during maximum shear load will cause failure. There's only one thing drywall screws are good for, and that's hanging drywall. If an in-duh-vidual is too cheap to spring for a box of decent screws to support some weight, the in-duh-vidual deserves to have their project fall apart.

Jon E

- just say (tmPL) I took a ingineering class once....

[Rico]

Whack the protruding ends with a hammer and they snap right off. I learned that from a guy that built stage sets for acting groups. Works like a champ.

As Billy Gates would say regarding their brittleness, "It's not a bug, it's a feature."

Dick

[Rico]

Shear occurs in torsion too.

Dick

[todd]

Lots of armchair engineers in the audience lately. The primary failure mode of a circular member in torsion is by shear stress. There's a difference in a shear force and a shear stress.

todd

[Larry Kraus]

How do you join this screw strip to the cabinet? I've looked through many cabinetry books and articles without finding many details on this connection. Looking at most manufactured kitchen wall cabinets, it appears that the strip just fits between the end panels and squeezes the back panel to the wall. Since the back panel is usually just a stapled-on piece of eighth inch ply or hardboard, I'm unable to see where the strength is.

"Sw>I build both wall and base units, which must be attached to a wall, with at

[The Other James]

The top screw strip should be attached to the top of the cabinet and also at the ends, to each side panel. The bottom one should be attached to the bottom and the sides.

[Swingman]

Properly done, the screw strip is itself screwed into the cabinet top and sides, and to the bottom and sides ... it becomes an integral part of the cabinet construction and _very_ strong.

For additional strength in a cabinet that must hold a lot of weight, I also glue it to the back panel when I install it.

Keep in mind that the back panel in a cabinet made this way is contained in a rabbet that is cut 3/4" from the back edge of the two cabinet sides. If you use a 3/4" thick screw strip, generally about 4 1/2" wide, it fits flush with the back edges of the cabinet.

I'll mention again that if you bevel the bottom edge of the top screw strips before installing it, the strip itself can also be used as the top half of a "French Cleat.

When doing this, I often use a double French cleat and put an additional screw strip in the middle of the back of the cabinet. There is a picture of this double cleat used to install a wall cabinet on my website: one of the journal pages (writing desk).

[Tim Douglass]

Earthquake would be my biggest worry. The additional jarring might easily start a chain reaction of breaking screws. I've used drywall screws to hold cabinet parts together then later torn them apart. You can easily tell the difference in strength between the drywall screws and "regular" screws. Even the cheap deck screws from the Borg have much better shear strength than good drywall screws.

Oh, half a ton of books isn't much. Get out a scale and start figuring. A set of encyclopedias can easily run 150-200 lbs.

Tim Douglass

[Tim Douglass]

What amazes me, Jon, is not that the shelf held 290 lbs, but that you, weighing 290 lbs, are able to do a couple of chin ups. I'm only 275 and anything involving lifting my body weight has been out of the question for years.

Tim Douglass

[Jon Endres, PE]

Two or three is about all I'm capable of. Always been a big boy, but I've kept myself in marginally good enough shape to do what needs to be done. :) One thing I have worried about, as a volunteer firefighter, is getting into trouble and having my fellow FF's not be able to get me out. Full air pack and gear I tip the scales at almost 340 lbs.

J

[Rico]

Yeah, but he has a degree in PE.

Dick

[B a r r y B u r k e J r .]

Hey!

I'm 250 and bicycle 4000 miles a year (on and off road), play roller hockey in the summer and ice hockey in the winter.

I regularily leave mere 170 pounders in the dust on my bikes.

It's a number...

Barry