I want to make sure my house is strong. I have heard that using screws is the strongest possible construction method, but no one builds a house from screws.
Am I wrong in wanting to use screws?
Screws don't have nearly the shear strength as nails. Also, they usually fail with a sudden snap, where nails will bend and/or pull out slowly. Much better to see a leaning wall and have time to get out from underneath than have it suddenly fall on you. ;)
Screws have there place when it comes to resisting pull-out, and can sometimes be used effectively along with nails, but not many people bother with the extra time. It takes two seconds to shoot a couple nails at opposing angles next to each other, and as a pair they will resist pull-out quite well.
I second the Honorable Mr Bass. However John did have an article on earthquake screw nails on the CountryPlans Site. I have not noticed it as of late you might drop him an e-mail and see if it is still available. Very interesting article.
use the recomended amount of nails and then add some extra screws. thats how i do it anyways
Gentlemen, my thanks. It certainly gives me something to think about. I was not aware that the sheer point of screws was lower than nails. But, I know that screws pull the pieces of wood tighter together than nails can. So, I think I'm leaning toward...CjAl's idea.
Great summary and explanation by Earnest T. Bass.
Because of those reasons, the building code requires nails. Many building inspectors will fail framing if it does not have the required nailing.
I would only favor screws where I needed a lot of pull strength and it wasn't structurally dependent such as siding and roofing.
Screws won't make a house stronger, just stiffer. Compare an oak branch to a reed grass in a wind storm---which is more likely to break? Nails are more ductile--like others have pointed out, they flex a bit. A house that can move a little can withstand more freeze/thaw, wind, earthquake, etc.
For any given nail, I suspect a stronger screw can be found. If screws are inherently weaker ... why the sudden popularity of timber-screws? There are lag-bolts used in wooden bridge construction, nails or spikes could be used...but could the framework endure the pounding required to insert the spikes? That's a big advantage for screws, they are installed with less impact on the structure.
Does anyone use nails for decks? Nails are easier to manufacture than screws ... especially strong screws. I believe screws have a future in home construction .... especially when the latest wind resistive codes adopted by the state of Florida show screws, or nails, used to attach sheathing to framing. (Or I misread it!)
The reason screws are used for decks goes back to what was said about pull strength vs. sheer.
There's no sheer stress on decking, only pull. Consequently, screws are ideal for that application.
I'm guessing that if FL adopted a wind code that requires screws, it's probably in addition to nails, and is in the planes that are susceptible to a direct "pull" from wind...
Otherwise, nails are better in most applications because as mentioned, they have some flex whereas screws just snap.
For any given nail, I suspect a stronger screw can be found.
LLikely you are right, just need to go bigger..so the operative word here is same size.
If screws are inherently weaker ... why the sudden popularity of timber-screws?
Uhh...there are a lot of thing that have sudden popularity that are not popular because better. So I guess the operative word here is popular with whom.
There are lag-bolts used in wooden bridge construction, nails or spikes could be used...but could the framework endure the pounding required to insert the spikes?
You are right again, but as is admitted by all but the moat rabid nail fanatic...there are certainly some users that screws are better for. Does not make them better for other things, such as framing.
That's a big advantage for screws, they are installed with less impact on the structure.
You are kidding, right? If you building cannot take the pounding of a nail that is proportionate in size to the building, you are in big trouble that even screws cannot help
Does anyone use nails for decks?
Yes and works fine. Why not? Just because you have a power driver does not meant you have to use it.
Sheer is a curtain, shear is the lateral force that snaps a brittle screw :-\.
There are structural screws, these will have an ESR number or approval on each box, fastenmaster, grk, simpson sds. These are the new timber screws, they replace lag screws which are ductile fasteners listed in the NDS with tables of strength, etc. The timber screws do not require pilot and lead holes and are often cheaper, definitely so if labor is paid for. I keep a box or two on the job, ran a few today. I do use deck screws in withdrawal only situations or to tighten up framing but they are not load carrying. I've replaced deck screws on decks that snapped under the shear force of drying wood, and not just a few. The old soft wood screws that stripped out under the driver and led to the hardened screws... they are fine, they're ductile. They'll earn you a failed inspection most likely and you'll cuss the entire time. Deck and drywall screws are the brittle ones but you really don't know much about the steel in an unlisted screw.
Substituting a larger brittle screw doesn't get you there, we want a building groaning ductile failure that screams "Get Out!" not a brittle failure that simply goes Whump!
Home demonstration, drive a nail and a screw side by side into a board and strike each back and forth sideways hard, count the number of licks each can take.
Please post the cite to the Florida sheathing requirement, read the footnotes, I'm betting that was a misread. Sheathing is a shear brace and a non rated screw would be the wrong thing to use. Deformed nails, ring or screw shank would be fine, it's the steel.
In large timber construction like bridges you see the lag or bolt (A35 steel), what you don't see is the spiked shear plate or split ring shear connector that the lag or bolt is tightly sandwiching inside the joint. A nail or spike cannot reliably hold the joint together through moisture cycling enough to keep those shear developers in place to do the real work. This is akin to folks seeing a piling buried 30' deep, burying theirs 3' deep and thinking they have done the same thing.
Is anyone interested in further reading on connections?
If screws are inherently weaker ... why the sudden popularity of timber-screws?
Uhh...there are a lot of thing that have sudden popularity that are not popular because better. So I guess the operative word here is popular with whom.
Assuming this is a question: I don't know who they are popular with ... unless I could answer with, "customers". I don't remember seeing them in local big box building supply stores, say, five years ago. If I wanted some, they were a special order item. But today the local (Atlanta) HD, Ace, and Lowes have them in several lengths on the shelves along with other fasteners. Since they have recently appeared in numbers, I assumed they were now "popular" ... perhaps a careless conclusion. And with what population sub-set? I don't know. Perhaps: Folks who want them.
I love 'em. I first got them with log home kits as an alternative to lags. It turned a tedious operation that took about a minute per lag to one that took seconds per screw. We still kept a few hundred lags on hand to pull down pesky logs but they do a good job. They next found a place as an alternative to lags or bolts for fastening deck ledgers. It takes 2-3 times as many but is still faster. If I'm lagging a porch roof ledger to studs I never was keen on a big honking lag, the much smaller ledgerlocks are a great choice there. Screwing Sips to a timberframe with the big flathead sdws's or purlins to a built up roof, we used to beat in 12" 80d ring shanks by hand, talk about sore arms. Every fastener has its' place :).
QuoteSheer is a curtain, shear is the lateral force that snaps a brittle screw
Doh! I hate it when I miss those!
Timberlok (I think that's the brand name I'm thinking of) screws
are increasingly popular. They're specifically marketing toward deck construction, for those who haven't seen them. Supposed to replace lag bolts. They advertise in magazines like Journal of Light Construction and Fine Homebuilding and if I'm thinking of the right thing, they've even shown the numbers that show why they're as good as lag bolts.
However, that's a very specific product, not just a standard screw, and I'm going to take a guess that they ain't cheap...
It's one of those words I've seen interchanged a whole lot lately, I guess the school marm came out in me c*.
1/2" lags and bolts can get pretty spendy too. This months Fine Homebuilding has a cost breakdown but I think they are a bit high on the lags. I've got pt on Thursday and need to go to Lowes to pick up what I forgot today d*, I'll try to remember to check prices. Course if I could remember anything I wouldn't be needing to go back. Back in the day I was buying lags by the thousand and that got it down but that is a lifetime supply for most folks. Hmm, CP co-op?
Quote from: Don_P on July 09, 2012, 11:17:22 PM
Timberlok (I think that's the brand name I'm thinking of) screws are increasingly popular. They're specifically marketing toward deck construction, for those who haven't seen them. Supposed to replace lag bolts. They advertise in magazines like Journal of Light Construction and Fine Homebuilding and if I'm thinking of the right thing, they've even shown the numbers that show why they're as good as lag bolts.
However, that's a very specific product, not just a standard screw, and I'm going to take a guess that they ain't cheap...
1/2" lags and bolts can get pretty spendy too. This months Fine Homebuilding has a cost breakdown but I think they are a bit high on the lags. I've got pt on Thursday and need to go to Lowes to pick up what I forgot today d*, I'll try to remember to check prices. Course if I could remember anything I wouldn't be needing to go back. Back in the day I was buying lags by the thousand and that got it down but that is a lifetime supply for most folks. Hmm, CP co-op?
The Log Home Store has Oly Log Screws that appear to be the same as the Timberloks. They also carry Log Hog screws which have a larger diameter. Price isn't too bad if you buy the boxes of 250. I used a lot of these in 4" - 16" lengths on my cabin. I used the long ones to help hold my log walls together, but used the shorter ones as a lag-bolt replacement. Used a Chinese Hole Hawg copy to screw them in, a very powerful drill, and I think I only broke one log screw out of the 700+ log screws I used. They are very strong.
http://www.loghomestore.com/1746-oly-log-screws.php (http://www.loghomestore.com/1746-oly-log-screws.php)
In many cases, screws will never replace nails. I started my build using lots of screws and by the end of my build a few years later I was using far more nails than screws.
Not all screws or nails are created equal. There are malleable screws, and there are brittle nails. The key is to look at what they are approved for. Simpson makes connector screws, for example, which can be used in the place of nails, but they ain't cheap.
Quote from: Don_P on July 09, 2012, 05:41:34 PM
Is anyone interested in further reading on connections?
You know I do.
More info is always good.
When I was building I did a fair amount of research on nails as i had to bring them in from the States and figured I may as well bring in the best. Also was using green lumber and had some unknown qualities so i though best nails would be best.
I ended up with ring shank or spiral for all but a few uses. HDG. Mostly hardened. The cost differential is small or such an important component.
In looking I found an amazing about of difference in shear values in 16d nails...like 5x. True, the manufacturer values are only part of the shear equation, but it does count. Was hard info to get from some. my main supplier was MAZE nails..great stuff. GripRite never answered any emails.
Another good test (instead of whacking it with a hammer) is build a square out of 2x4's with each side being a few feet. Do two diagonally opposite corners with screws and the other two in nails. Set it on a corner and push down, see which corners fail first.
It's true, though, there ar places you want the stiffness---like in some places for shear transfer. Deckboards, too, since flex at that point isn't important and nails (if driven in straight) will work their way out.
If the only reason you're choosing a screw is the issue of a nail backing out, driving a nail in at an angle helps keep that from happening
In fixing old broken stuff I can't recall coming across nails that had failed, but I can think of quite a few screws that had. I also think nails are kinder to wood fibers than sharp screw threads are. Buildings are always moving, expanding, contracting, and vibrating.
Our house is built entirely with screws. The only nails were a few finishing nails, and the roof nails holding the shingles. It's been up since 2005 now and has survived an f4 tornado passing 800 yards away with only a few shingles taken off. (knew I should have screwed the shingles down) It has survived all kinds of winds, snow, and everything else nature has thrown at it.
Put me down as one who believes in screws.
(https://i991.photobucket.com/albums/af36/zion-dyi/Als%20race%20cars/house%20pics/pool.jpg)
Quote from: zion-diy on July 10, 2012, 02:13:51 PM
.... f4 tornado passing 800 yards away with only a few shingles taken off. (knew I should have screwed the shingles down) ....
What were you THINKING!
I also have an all glued-and-screwed cabin that has impressed us in high winds. Rock solid so far. .... and my shingles (corrugated metal) are/is screwed down.
BTW, that is very nice looking digs!
For want of a nail the shoe was lost.
For want of a shoe the horse was lost.
For want of a horse the rider was lost.
For want of a rider the message was lost.
For want of a message the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a horseshoe nail.
Don't lose you kingdom...use good nails.
If you are worried about nails pulling out, use ring shanks.
I don't worry about nails pulling out ... ain't got any nails!
Years ago, I used to wear shoes that had nails. Most everybody did. Nails held the soles to the rest of the shoe. Once I had one of those nails protrude upward, I hardly noticed until I could hardly walk. It was in my only footwear, my motorcycle boots ... and i was on a several state tour ...with no time to stop and buy new footware. By the time I got back home, I had a severe heel problem. What does this story have to do with anything? Not much.
Except it is a happy curiousity that most footwear, today, is generally more serviceable, more comfortable .... and usually is manufactured without nails.
.... so there is hope for homebuilding!
There is a good online course on connections at apawood.org
Click on the "wood university" tab bottom right of the home page, sign in and take a look at course 201. For some of you this will have a lot of review information, but worthwhile, I'm going through it again now.
The connections calc at awc.org is good, it is under the "codes and standards" tab > software.
It contains the same info that is in the NDS connections tables.
Go ahead and set up a wood screw example (yes, wood screws are allowed) hit the calc button... now read the first footnote, there is the problem with deck and drywall screws. Email the manufacturer and ask for the bending yield strength information and file it.
The problem is with the mode of failure, drywall and deck screws fail suddenly. A ductile failure is what is desired. This graphic from the course above does a good job of explaining;
(https://i180.photobucket.com/albums/x109/windyhilll/fastenerductility.jpg)
SO, JRR---is your home sewn together? That would sure provide plenty of flex
Quote from: flyingvan on July 11, 2012, 09:20:51 AM
SO, JRR---is your home sewn together? That would sure provide plenty of flex
Now, now!
It's glued ... just like my sneakers!
Glued and screwed! So stiff, if it ever breaks ... it will be in a thousand pieces!
I think I have a pair of sneakers like that :)
I bumped into this while searching for something else. This is another e course on connections;
http://www.awc.org/HelpOutreach/eCourses/DES110/DES110eCourseV02-2011.pdf
(>6 MB, I'm gonna go change the oil while it tries)
The American Wood Council library of e courses is here;
http://www.awc.org/HelpOutreach/eCourses/index.html
I did check lags and ledgerlocks at Lowes the other day, lags were $2.49 ea singly. Ledgerlocks were ~$38/25 (OK, I wrote it all down in the store but apparently the dog ate it) The ledgerlocks (that particular screw) had higher shear numbers than the equivalent 1/2" lag ???. The timberlocks were a bit cheaper but have lower shear numbers. I think for many applications the different structural screws are definitely in the running.
Don_P,
Thanks for the links. I have read thru the first one ... all many pages! It is a good read. But it puzzles me why folks who put such effort in making such an elaborate presentation ... refuse to use spell check. Example: "stringer" on page 132/133. ... also, did they really mean to have the green check on page 113?
But I was most puzzled by the article on "wood bolts" on page 142/142. Are the bolts made of steel ... or wood? Are they "wooden bolts"? I thought surely they must be steel until I read "The wood bolts were actually a laminated beech product"
?? Not much info on an interesting concept.
They could stand a good proofreader. I think I saw a sheer /shear mixup in there as well ;D.
I googled the trestle, they had very specific needs to use the wood bolts, pretty neat;
http://www.ece.unm.edu/summa/notes/trestle.html
Neat, indeed!
Thanks Don! That was really something!
Bruce
I, like others am a big screw fan. ;D Due to shear strength, there are places where nails and only nails should be used. However, screws can pull a joint tight, and create a compression strength in a way that a nail can not acheive. A screw can pull or align a joint, and, toe screwing from opposite directions creates an incredible joint. I suspect that a stud wall toe screwed together can pull the base plate and top plate together in a way, that reduces the shear risk of using screws. If your structure is subject to a catastrophic forces that bring into play shear strength, then perhaps the far greater pulling resistance of screws can come into play. That beng understood, I can understand, from a seismic perspective (earthquake), why code doesn't allow screws. For us as amateurs and hobbyists, screws have an unbeatable attraction. They can be undone, and, redone. If I had $1 for everytime I had unscrewed something and rescrewed it back successfully, why....drinks are on me! It is slower than a bunch of wood monkeys firing away with nailers, but with impact drivers and screw guns firing collated screws, the gap narrows. I like to think I understand when to use nails. But given a choice, I will always screw!
Mtn Don has an interesting line in his signature :
"Just because something has been done and has not failed, doesn't mean it is good design."
If something has not failed, it is only proof that it has not failed yet. I'm going to stick with code recommended practices as much as possible. The proper use of nails is to keep two things from sliding apart.
Keeping things from sliding apart is the basis for all home construction. Everything should be built to resist shear forces, seems like gravity should be the only thing providing compressive force (which is why building perfectly plumb is important).
There are screws that can pass code inspections. They may not be listed directly in the IRC, but GRK, Fastenal and others do have screws that have passed testing. There are charts with shear values for these. Armed with that a person may be able to get their local inspector to pass the structure. All too often though when somebody says they will be or have used screws, the screws end up being the more common and cheaper "deck" screw. Those can be dangerous to use as they are brittle and shear easily. The structural screws are great but also expensive compared to a common nail.
I vote for screws...hands down. I remember as a kid building forts how many nails it would take for me to build something .. I would just keep pounding them in...15 or 20 lol. All my projects seemed to suck.
Fast forward to modernish day jeff. Fist project when I got a cordless impact driver..i was sold. I told my dad...if I used this back in the day my forts would have been much better.
The advantages of screws are just so numerous.
Maybe a bit more costly..but when I am redoing something it takes me two seconds and by not wrecking the boards I save that back easy. Imagine if we built using screws instead of demoing houses we could easily dis-assemble them and re purpose that wood with out wrecking the building.
People new to building will instantly be able to build solidly without wrecking wood and banging thumbs. The learning curve for newbies is much better with screws.
This shear strength argument Im not sure I follow. Your going to tell me that a movement will have the same impact as a hammer. A hammer wont break a deck screw( based on my experience anyway). If that much stress was present in a building by shifting ( It seems unlikley to me anyway) I would think it would tear out of the wood first. Heck i
ve used sheetrock screws framing our cabin. The door is sticky now so its shifted a bit due to shallow piers (whatever). So there is obviously stress on the building...you know what ..its solid..this is with 3" DRYWALL screws!! It.just seems like a minor point compared to all the advantages. But i guess that says something that its the biggest item against screws.
As far as being brittle..even deck screws do bend...I've bent them. They dont just instantly snap when given the least bit of shear pressure. What is more shear pressure then slamming a hammer against them? This is also not as simple as my last sentence, b/c your not slamming a hammer against them. Your slamming malleable wood. Its a relationship thing. The wood absorbs some shear it does not all get transferred to the screw. Based on my experience the wood is what will take the stresses. Or if there was insane amounts of stress the screw stays put and the wood will pull out leaving the screw. I would like to see someone break a screw by bending two pieces of wood with a screw at the joint. The more I think about it the le3ss relevant the hammer against a screw example is. What we are trying to do is the classic example of science. Attempted to learn by isolation. Its not like that though...everything is in context of its environment. There is no hammer being slammed into the screw in your house... its not relevant.
I think this has more to do with what people are comfortable with. If you got good at hammering then you probably prefer that. I on the other hand think its a no brainer. Whatever cost increase easily is made up by being able to re-use the screws and the wood. This being said i hve used a combination in our build..but have over time gravitated toward a good screw..( sorry, had to do it!)
I will simply say that decades ago when we first moved to NM and I was looking for some sort of work I liked, I filled in the time with doing handyman repairs. I saw a numbers of projects from fences to utility sheds that a DIY'er had built using the very common gold colored zinc plated deck screw. I can not remember how many times I'd go to remove those screws and find them broken off between the head and where the threads started. Innumerable. I'm sure that some of those took a good few years before failure.
Then a personal project note. We have a wood walkway around a portion of the back yard. 2x sections screwed down to 4x beams. It is low to the ground, on ground in places, and the wood moves a lot with seasonal changes from dry to wet. The screws (the coated ones suitable for PT wood as well as the gold zinc) also snap off from time to time in the same fashion.
I have personally seen deck screws shear off when used for temporary bracing, as when lifting and standing an assembled wall. I now use either GRK structural screws or scaffolding nails.
We're all free to do as we choose; I just believe that deck screws in particular are not at all useful as a substitute for common nails when structural strength is important. There are screws that are suitable for structural use, but they cost even more. However, they come with a pedigree, there are charts that list their strength. Can't find that information for a deck screw. If anyone does, let's see it.
I'm a little confused. ??? (so what else is new) :-\ When someone is framing a house or cabin, what part of the framing is in shear? I always thought that studs were mounted in compression. Same with floor joists, when they're mounted on top of sill plates. It seems to me that these parts are the most important piece of the puzzle. So, what am I missing?
You're not wrong. The main force taken by studs IS a compressive force. In a perfect world you wouldn't even need a nail. You could just dry stack everything.....However--
Did you know when you walk across your floor your weight makes the walls bow in towards you ever so slightly? Have you noticed a stud left lying around awhile starts bending and twisting, while the ones in your wall pretty much stay put? That connection between a stud and plate endures side loads from wind, slamming doors, earthquakes, unpermitted additions, ledgers, etc.....So, those nails take quite a bit of force from many directions. When a tractor bumps into that wall in 60 years whoever's on the other side will appreciate good construction practices
Ok, that explains a lot to me. thank you.
I have two tool box's at home - 1 large with tools and 1 smaller with small bits or stuff to build things with
there's two drawers of fixings plus various bolt divided box's
roughly 5 drawers 36" w by 24 deep
The only nails I stock in my collection are 1" panel pins
every other timber fixing is a screw...............
Mind you I have'nt built a house yet !
But if you took a look a for example a 48" wide shear wall built to code and used screws instead, I be very interested in what fell apart first.
every thing I ever built with nails- panel and frame if you pushed it hard enough on the diagonal the nails pulled out of the sheeting and then the frame collapses
The ones with screws I'd have to undu.
Ref the heads popping of deck screws- yep bent a few and poped a couple of heads- decks etc deal with expansion and contracting every day, where as framing is a dry relatively mild climate behind the siding
but I think I've bent more nails and had more pull out of what their meant to be keeping togther, than I've ever had with screws