mounting screws

      July 24, 2005

What size screw are you using to install uppers? A friend says heís been using drywall screws without any problem for years. Iíve been using 1/4 inch bolts and washers for years without problems. Are there any Liquid Nails stories out there?

Forum Responses
(Cabinetmaking and Millwork Installation Forum)
From contributor A:
Drywall screws were never designed for the assembly or installation of cabinets. The price of good #8 wood screws isn't that high compared to the risk of problems associated with using an inadequate fastener. Iím sure you will get some responses saying they are fine, but I don't see the value in the risk of a failure. The first major failure I dealt with was a peninsula upper which was hung from the soffit, which dropped into the arms of a woman as she was stocking the cabinet with clean dishes. The drywall screws either broke under the load of the dishes, or broke when the screws were torqued too tight during installation. I had to build a new cabinet to match, and replace the laminate top as a result of the cabinet corner landing on it. She had to replace her dishes!

From contributor B:
Type Cabinet Installation Screws into internet search and you will find them. I use them - truss head, #3 Phillips or square drive. They do not break. I use QuikScrews and there is a website. They are not cheap but save time, and you really only need to predrill the cabinet.

From contributor C:
First, let me say I don't install cabs for a living. But, having built and installed lots of things, I can tell you that sheetrock screws should suffice in most cases when attaching cabinets to a wall. I must add that it also depends on how many you use. What you're mainly concerned with is shearing strength. If memory serves me correctly, an average 16 penny nail will need approx. 600lbs to shear it off. Of course, we're not talking about using one nail to hold 600lbs. Not the same thing. Example: I have personally used 6 drywall screws to hold a CD/DVD shelf that, when filled, probably weighed somewhere near 250lbs (4 x 8 box). Having said that, I'm sure there are dozens of the right screws for the job out there that are tried and tested, made of titanium, kryptonite etc.. I'm just saying that drywall screws will work.

From contributor D:
What is the shear strength of a drywall screw?

From contributor E:
Drywall screws are brittle and they will snap before they bend. The screws that I use will bend 90 degrees and still not break. Drywall screws are just that - for drywall. They may work but why take the risk? To answer the original question, I use 2-1/2 #17 auger point, square drive screws with trim washers.

From contributor C:
I got curious and did a search for proper fastening of cabs. I have cut and pasted the section below.

Installing Wall (Upper) Cabinets
Starting in the corner, set the first unit in place and snug it up to the wall. Use a level to make sure that it's plumb up and down both sides and front. Shim as needed to hold it plumb. To secure the first cabinet, pre-drill and drive a couple screws (2-1/2" drywall screws are usually fine) through the top and bottom nailing strips in the back of the cabinet.

Here is some proof that drywall screws are fine. I will note that I found (through other article) that shearing strength of drywall screws is not close to other screws. They are considered brittle and will snap easier. However, again, it's how many you use for the job. Even though I've used them lots of times, I guess if I installed for a living I'd use stronger screws. Like someone said, why chance it?

From contributor A:
To contributor E: I am a proponent of overkill, but a #17 screw? Is that a typo or some metric size? Based on my Architectural Graphics Standards manual a # 17 screw would be around .28" in diameter.

Also, in reference to contributor Cís statement on the strength of a 16D nail, the 16D nail has a designed safe working strength of 128# in lateral shear (Architectural Graphic Standards). Where it actually shears, I don't know, but if a mild steel nail at .164" in diameter has a safe load of 128#, then I would expect a drywall screw to have substantially less since its strength would be based on its root diameter and not the thread diameter. And the root diameter of a drywall screw is easily half that, if not less than a framing nail.

From contributor F:
Contributor Cís last line said it all. Why chance it? I do install cabinets for a living. I have an expensive liability insurance policy, and I do think about stuff like little old ladies or kids being crushed by one of my installs failing. It's just as serious and important an issue as electricians getting those screws good and tight. People might die, or get hurt, or suffer loss of valuables. You can defend drywall screws all day long, but you are wrong. I started using them in the seventies too, because everything else was the pits. Thankfully, the manufacturers caught on and have really filled the void with easily available high quality fasteners. They are now in every decent hardware store anywhere. Considering the overall costs of cabinets, an investment in five bucks worth of screws seems miniscule. Drywall screws often snap just as you finish driving them up and the head grabs, and you won't know it or won't want to ugly up that spot with another screw right beside it. Put the drywall screws away, and do it right.

Now, as to the original question, so far the talk applies only to hanging where wood framing is used. No, you don't need adhesive if the fasteners are right. Then there's drywall on steel studs, without blocking. I use #10 x 3" sheet metal screws and drill the cabinet. The screws will punch their own custom fit hole in the steel when you drive them in. If looks matter, you can counter bore a shallow 3/8" diameter hole before drilling and peel-n-stick caps will hide it. If it's a really big one or will be loaded, I do glue these to the drywall with construction adhesive.

On masonry, the cabinet gets drilled, and then the wall is drilled with a hammerdrill. Then use KwikTap screws, and sometimes glue. Tapcons are more expensive, and KwikTaps seem to hold their thread edges better. One more thing about concrete block - try to do the fastening in the webs (the solid area at the ends and center) not just for a better grip, but many times water, gas, and electric lines are run inside the voids and drilling through them is messy.

From contributor E:
To contributor A: The #17 is in reference to the point type I believe. The actual screw size is #8.

From contributor A:
To contributor E: thanks for clearing that up for me on the screw tip. I missed contributor Bís earlier mention of this! I have not changed brands or design of flathead screw since I first setup shop 20 years ago and never heard of a #17 screw tip.

From contributor G:
For what it is worth, I have quite a bit of cabinet installation experience. I have used just about every fastener there is working at different shops. I would say I have screwed well over 100,000 cabinets to the wall in my installation career. The vast majority of these used nothing more then a 3" drywall screw. I have never seen this screw actually fail. The only problem I had once was installing a 24" deep upper, which was about 36" tall, with multiple fixed 3/4" thick dividers/dividers. You could say it was the mother of all back breakers. It was to go above a refrigerator in a nook by itself. I had it on the wall with one screw, and man was that cabinet heavy. I removed the prop sticks I had in place to get another screw in easily. The cabinet was so heavy that the head of the screw pulled right through the back and the nailer and the cabinet fell. Damage was minimal and I was able to repair it and rehung it after removing the intact screw from the wall. I am particular about my screws, however. I never predrill or countersink before running them, so twisting the heads off is always an issue. I will take a few and run them into studs all the way and make sure the heads do not break off. I do the same for the 1-1/4" screws also.

Remember to use a fine tread screw if you are going into steel studs, as the coarse thread ones do not hold. I am sure these other fasteners mentioned are great products and superior. Sometimes you have to use them, beauty washers, and other things, as the job requires. Just think about sleeping under it with it fully loaded. Never hang a cabinet and walk away unless you will have no problem sleeping under it.

An additional note, for what it is worth - I live in Southern California. The Northridge earthquake hit where I live very hard. The majority of my installations have been within a 20-mile radius of the epicenter. Nothing fell that I installed. As they say, "The proof is in the pudding". Furthermore, I did some work after the earthquake for a general contractor. I would say it was about 6 months worth of damage review of homes, buildings and apartments. I reviewed and reordered the damage for about 4 places a day for 6 months straight. I saw some serious stuff in that time, but I never saw a cabinet that had fallen off the wall. Whether it was drywall screws or just nailed on, although some of the nailed on ones did loosen up, nothing fell. All of the builders out here now require cabinets to be screwed, and not nailed, to the wall. It had been that way for about 4-6 years before the earthquake. Before that it was nail and go.

From contributor B:
To contributor A: A #17 auger tip screw looks like someone cut a groove into the tip of a screw with a Dremel type cutting wheel, and a #17 has 2 such grooves into it. They are self-drilling screws for wood. They are not threaded to the head as a sheet metal screw is. They have an unthreaded shank that is strait, not tapered, the same diameter as the threads. This way you are only threading into the stud, not the cabinet, so it will pull tight. Wood assembly screws are the same way.

From contributor I:
I wonder if this discussion is going on because everyone is talking about different things. I used to buy drywall screws at times - they were a small shank, shallow thread screw. I use a lot of #9 particle board screws. These are much thicker shank with deeper threads and a steeper thread angle than regular wood screws. My regular supplier closed so I've looked for another local source. While in one of the home supply places I checked out their supply. They have boxes of the same screws labeled as drywall screws. They bend rather than break and the heads are much harder to twist off than drywall screws. To me, a drywall screw has a thin shank, shallow threads and the head is easy to twist off while driving them in.

From contributor J:
I've been installing high end cabinets for about 20 years using 3" #8 drywall screws without a problem. I am particular about how the screw looks inside the cabinet and always try and sink it flush with the back of the cabinet. Having said that, I agree with everything that has been said about the drywall screw not being the ideal fastener, for all the reasons given. I guess the reason I've used drywall screws all these years is because they're readily available at Menards or any big box store. I have been looking for another screw that looks good and would be readily available. The perfect screw would be one that would stay on the driver tip, and perhaps be a flat head that I could countersink. Also, maybe silver in color so I could use the excuse of they're the same color as the hinges and not have to put those stupid sticky dots on them. What do you think?

From contributor K:
If you use enough 3 in. screws youíre going to hit electrical wires or plumbing unless youíre always installing on 2x6 walls.

From contributor L:
Hereís a little footnote about drywall screws. Many years ago, I made a simple sign with a 24" x 24" piece of 3/4 melamine screwed to a 2 x 2 post using 4 drywall screws. I brought it outside, found a soft place in the ground, steadied the sign, raised my 2 lb mallet, and took my first and only blow on the top of the post. The drywall screws sheared clean off from the shock and the sign fell to the ground. I still clutched the post in my hand, dumbfounded. Needless to say, that was the day I saw the light and never used another drywall screw on one of my cabinets.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor H:
Well, I use to heat treat tons of drywall screws and let me tell you not every drywall screw gets heat treated to spec! Now I bet that'll surprise everyone.

Some screws will snap easier than others simply due to the heat treat process not being uniformly applied. That happens when we push the production limits and some go through the furnace in a thicker pile than others. Some get more case than others and sometimes the same screws donít get tempered back correctly - resulting in screws that snap easily. They are supposed to have some bend in them. In fact, we use to test for this. This results in not all screws getting the same treatment. It also explains why all of you are getting the results you are getting. I'll guarantee you every screw is not exactly the same hardness, nor brittleness (yes, there is a difference). I used to wonder at some of the stuff we sent out that never came back for rework - now I know where they went.

A drywall screw will have a shear capacity of about 190 lbs - use 3 of them and that's near 600 lbs.! That's a lot of dishes! Of course, a thicker screw will obviously have more shear capacity. But, a properly heat treated drywall screw should suffice, as some out here have demonstrated. Here's a thought: what if person A uses a number 8 lousy-heat treated screw (thinking it has more shear strength) than person B who uses a properly heat treated drywall screw? Between the two, there is no doubt in my mind I'd use the drywall screw because I know a screw not properly hardened will fail for sure. All screws are heat treated, but don't ever assume they all get the same treatment. Hope that explains why sometimes they break, strip and why sometimes they don't.

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