nails vs screws?

rocking23nf · August 05, 2009, 09:56:12 AM

Hi all, just wondoring everyone opinions on nails vs screws? Im good with a drill but not so good with a hammer. So I tend to use screws alot more then nails. So far on my cabin I used nails for my joist hangers, and screws for the plywood subfloor. Now on to the walls, for the plywood I was going to use screws again, but for the studs does it have to be nails? I watched a holmes on holmes last night and they were using screws on the wall studs, but I couldnt tell if it was a load bearing wall or not.

Squirl · August 05, 2009, 10:27:38 AM

I love Holmes on homes too. He is a big fan of using screws, but when he comes to the states he uses nails. He has had a few diatribes about that too. The reason being they are not to code. That is one of the few things I always thought was screwy about the show. He goes on yelling for an hour that nothing is built to code, yet he doesn't like to nails.

August 05, 2009, 11:13:57 AM

Here is the situation. Unless you use the old fashion type screws with the solid clear shank part way down before the threads start, you don't have enough shear strength. The typical screws that you use that have thread the whole length,
will break under the loads that are designed for inyour house.

There may be some that are specifically designed to handle the same shear strength as nails but I don't know if they
exist or not. I would prefer to use screws, but PEG has always warned against it due to the lack of shear strength.

The screws with the shanks would work, but you have to drill/countersink first and then screw. Don't forget to allow for root thickness when you predrill or you will split the wood.

Bruce

zion-diy · August 05, 2009, 03:38:13 PM

we built our entire house with screws. the only nails were a few finish nails, and the roof shingles.
been 3 yrs now, no pulled boards, withstood the super tuesday f-4 tornado that came within 800 yds of the house. this year, we added on to our south facing wall. unscrewed the siding, the wall studs, and nary a broken screw. used the siding boards on the addition.
there may be lots of opinions, but my answer is real world experience.
Alex

JRR · August 05, 2009, 06:24:09 PM

Thanks for sharing your experience, Alex. I also "believe in" screws for structures ... but have limited, though satisfying, experience with them. We must remember restrictive/protective codes must be adhered to in most areas of our "democracy-country". Luckily I have some property in a non-coded area, that allows me to experiment.

If a screw is only half as strong as a nail .... then use two screws.

August 06, 2009, 07:46:07 AM

Shhhhhhhh... [cool]we too live in an unrestricted area. outside of perking land for septic, it's build what you want, where you want, how you want. What a concept. A little common sense can go a long way.

MountainDon · August 06, 2009, 05:07:07 PM

As mentioned if you are in a code enforcement area nails are required for framing and general construction work. We have no choice in the matter.

Many screws are more brittle than common nails that are hand driven or the stick nails that are air gun driven. The screws I mean are the "deck" type screws whether they are the bright gold zinc or any of the coated ones that are suitable with ACQ treated wood. I love those screws too; fast to drive with a battery operated drill/driver, easier to remove, they can clamp two pieces together...

Let's pick a 3" deck screw. Screw it into a 2x4 or 4x4 until about 1 1/2" is still showing. Now drive a 3 to 3 1/2 inch nail in about the same distance. Give the screw and the nail each a sideways whack across the grain with the hammer. More than likely the screw will shear off while the nail will bend.

Nails will bend under shear loads. I have never seen a nail break, although I have seen a few bend. I have seen screws sheared off.

I use deck screws on decks. I have used some on sheet subflooring, although I prefer ring shank nails with the air nailer for that. Screws are also great for drywall; better than nails in that use.

Screws cost more than nails for an equivalent quantity. That's also one reason I avoid them for much general work.

Some of the reasons for methods and materials demanded by building codes make sense. Some are more difficult to figure out. Some do seem to be blatant attempts to force the builder to use a manufactured product. Some may be due to inertia in the "system". Whatever the reason I still preder to frame with nails and save the screws for the specialty jobs. I will admit that owning three different air nailers, plus a stapler does make much of my nailing faster and easier than hand nailing with a hammer.

Squirl · August 07, 2009, 09:08:57 AM

I have started to prefer a hammer myself. Fits in my belt, lightweight, doesn't lose power, I can drop it from a roof. I got two of those thumb savers from Lehman's for $10. They are fantastic. I can extend my reach and I stopped losing my fingernails.

MountainDon · August 07, 2009, 10:04:49 AM

http://www.lehmans.com/store/Outdoors___Gardening___Composting_and_Cleanup___Thumb_Saver___1085495?Args=

August 07, 2009, 12:14:42 PM

Close to 30 years ago when I was driving a couple of hundred pounds of nails a week the biggest problem with the cheap keg nails was the heads popping off when you set them. They still held some side load but obviously had little pull strength. When I worked in a trailer factory (Manufactured housing

) we used screw guns and staple guns mostly and I noticed that even when we twisted the heads off the screws they still held pretty good, Much better than the headless nails did. In the most recent years I use screws about 60% more than nails but I ain't throwing away my hammer yet. For speed and cost it's hard to beat a nail

rocking23nf · August 07, 2009, 01:11:09 PM

In my cabin, the prevoius owner covered in the loft with a simple floor on joist hangers, and the ledger board was screwed in with 3 1/2 or 3 inch screws. It was impossible to get it off, I tried prying with crowbars, the thing was as solid as concrete. I had to scrap all the paint off all the screws and then unscrew them to get the board off.

This was a 12 foot board with about 50 screws in it. The wall holding it up would have come down before this came down.

MountainDon · August 07, 2009, 02:00:25 PM

Screwa have great pull strength; nearly impossible to pull them out. It is the shear strength that is questionable with some screws.

JRR · August 07, 2009, 02:36:09 PM

Quote from: Squirl on August 07, 2009, 09:08:57 AM
I .... prefer a hammer myself. .... doesn't lose power....

Mine does.

archangel · August 07, 2009, 09:36:22 PM

Not only the shear issue, but they are less likely to flex and give a little.

For example.

Back in the earth quake prone areas of California, an earthquake will cause some nails to pull out a little and let things slide back and forth a little but the screws hold so tight, they will pop, snap and shear or the little grip the screw threads have will pull apart causing a catastrophic failure!

However, if you want to prevent that creaking caused by settling, you could just add a few screws as you nail and if an earth quake or tornado spins by the screws could fail and the nails will still be there.

August 07, 2009, 10:11:23 PM

Most of this stuff does have some reasoning behind it, the bending/shear strength answers are spot on. The code referenced NDS, Nat'l Design Specification for wood construction has tables for wood screws in shear BUT read the footnotes;
"Design values are for rolled thread wood screws inserted into side grain with axis perpendicular to wood fibers, minimum penetration into main member 10D; and screw bending yield strength = 100,000 psi for .099"-.142"D. 90,000psi for .142-.177"D. 80,000 psi for .177-.236"D. 70,000psi for .236-.273"D"

Remember that a lag is a screw as well, by the time you get up to a 3/8" and larger lag the minimum bending yield strength is 45,000 psi. The AWC connections calc has all that info in it, those are the folks who put out the NDS.

So they are allowed, short of the SDS and Fastenmasters I don't know of any that state they are approved for structural use. An inquiry to the manufacturers asking what they have that is NDS compatible might prove me wrong. What the code doesn't want is brittle failure. We want buildings to bend, deform and scream in ductile failure before collapse. Brittle failure is WHUMP, no warning. I've seen screws shear so I don't trust them for structural use unless they are specifically designed for it.

I love screws for non structural applications and they have great tensile properties. I screw things like log siding and heavy trim from the backside all the time. Hides the fastener and holds up better too.

If we have anyone at VT, Brooks Labs does fastener testing there, I've toured and been given a demonstration but don't know if they have published results for the public. Most screws snap well below the numbers called for above. One thing the professor did note is that we use better nails in pallets than in houses, kind of eye opening. The pallet industry realized that 5 cents added to the cost of the fasteners in a pallet increased its durability manyfold. I kinda think a lot of these problems are less code problems and more our society's immediate bottom line orientation.

cordwood · August 11, 2009, 01:39:59 AM

Quote from: Don_P on August 07, 2009, 10:11:23 PM
Most of this stuff does have some reasoning behind it, the bending/shear strength answers are spot on. The code referenced NDS, Nat'l Design Specification for wood construction has tables for wood screws in shear BUT read the footnotes;
"Design values are for rolled thread wood screws inserted into side grain with axis perpendicular to wood fibers, minimum penetration into main member 10D; and screw bending yield strength = 100,000 psi for .099"-.142"D. 90,000psi for .142-.177"D. 80,000 psi for .177-.236"D. 70,000psi for .236-.273"D"

Remember that a lag is a screw as well, by the time you get up to a 3/8" and larger lag the minimum bending yield strength is 45,000 psi. The AWC connections calc has all that info in it, those are the folks who put out the NDS.

So they are allowed, short of the SDS and Fastenmasters I don't know of any that state they are approved for structural use. An inquiry to the manufacturers asking what they have that is NDS compatible might prove me wrong. What the code doesn't want is brittle failure. We want buildings to bend, deform and scream in ductile failure before collapse. Brittle failure is WHUMP, no warning. I've seen screws shear so I don't trust them for structural use unless they are specifically designed for it.

I love screws for non structural applications and they have great tensile properties. I screw things like log siding and heavy trim from the backside all the time. Hides the fastener and holds up better too.

If we have anyone at VT, Brooks Labs does fastener testing there, I've toured and been given a demonstration but don't know if they have published results for the public. Most screws snap well below the numbers called for above. One thing the professor did note is that we use better nails in pallets than in houses, kind of eye opening. The pallet industry realized that 5 cents added to the cost of the fasteners in a pallet increased its durability manyfold. I kinda think a lot of these problems are less code problems and more our society's immediate bottom line orientation.

Kinda like what I said above but with numbers. The funny thing is when I used to build pallets I hated those stupid curly nails because they would bend when you just look at'em

They (the SMART ONES) used to tell us we couldn't use 32 oz hammers because they tore the wood fibers, Then they said we couldn't use nail guns for the same reason,...Apperently Senco had more money than Vaghan because super driven nails are more OK than very hard driven nails

Any time you rely on a fastener such as a nail or screw for structural integrity you are asking for trouble. Any and all designs should take into acount the limitations of the fastener to be used and adjust the design accordingly (or the fastener)
You can bet when I get the wife to agree on the "Love Swing" from Adam & Eve I wont just nail it to the ceiling joists

I am going to screw that puppy up!

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She just handed me the coffee pot and said " When the Genie pops out ask him how to hang it",........Wonder what she meant by that?

Don_P · August 11, 2009, 05:47:12 AM

The tables and the AWC calculator give allowable loads for fasteners for two situations, shear, what you call side load, and withdrawal, pull out strength. A screw is superior in withdrawal. The best design is to use the fastener to simply hold parts on each other and let the wood take the load whenever possible. We worked for one newlywed couple, she insisted on a beam that something or other could be hooked over

Whoops, I'm daydreaming and smell burning bacon.

builderboy · August 25, 2009, 02:13:33 PM

I screw everything (keep your minds outta the gutter fella's)... but just to tack it together. I find it easy when building alone- you can back out screws and move things a little if you need to (I do). After I'm fixed where I want to be I nail to get shear strength. If I were a real builder instead of an accountant i probable wouldn't need to do this.

MikeT · August 26, 2009, 08:38:22 AM

On my project, I used nails (both hand driven and air driven), air driven staples, a screws. What I used where depended on the situation. I did find that the Simpson strong drive screws were great if I needed to get a strong connection between pieces of wood and I couldn't hammer or staple.

My structural engineer inspected it and commented that in an earthquake, the house should still be intact--it may slide to the bottom of the hill, but it will still be standing!