Nails. How do you choose what size nail to use when building wall framing, rafters, etc?
There is a rule of thumb to choose the correct length of nail. To clarify descriptions first we'll define a couple of things. The member the nail is started in will be referred to as the attachment member or the "side" member. The "side" member is being attached or nailed to the "main" member, typically the thicker member. The nail must then be long enough to penetrate the side member and still have sufficient length to penetrate the main member far enough for the connection to reach design strength.
The normal recommended depth of penetration into the main member should be no less than 10x the diameter of the nail being used*. From the nail size chart below we see that a 10d common nail has a length of 3" and a diameter of 0.148"; 10 x 0.148" = 1.48". Therefore if we were nailing one 2x4 flat against another 2x4 (3.5" wide face to the other 3.5" face) we could use a 10d common nail and be within the penetration range recommended. A 10d box nail (3" x 0.128" dia.) would have sufficient penetration at 1.28" into the main member, but because of its reduced diameter it also has reduced strength.
*For lateral (shear) load, for nails inserted perpendicular to the grain. For nails driven parallel to the grain or toe-nailed, the lateral load should not be more than 2/3 of the tabulated values for lateral load. Lateral load varies with species ,the Specific Gravity or Density of the wood, as well as other factors.
A box nail may be as long as a common nail, and for some applications, non load carrying, like fence pickets the box nail may be better suited. However a nail with a smaller diameter can not be used, nail for nail, for applications where structural strength is paramount.
Rather than trust to the 16d, 10d, etc. name when selecting nails it is best to consider the actual dimensions; length and shank diameter in inches or wire gauge. For example, in Douglas Fir a 16d box nail has less than ¾ the lateral load capacity of a 16d common nail.
The AWC has a connection calculator available online.
It can be used for bolts, wood screws, lag screws and nails.
The IRC has charts that list the recommended minimum size nails for many typical construction joints and applications. Not only do they list the minimum size (both length and diameter) of the recommended nails, they list the number of nails.
Chapter 6, Wall Construction is a good place to start to find detailed joint by joint recommendations. Table R602.3(1) begins on PDF page 160 in the Minnesota online copy of the IRC (http://ftp.resource.org/codes.gov/mn_residential.pdf) and covers the use of common, box and deformed shank nails. Always read the footnotes.
Table R602.3(2) covers alternate fasteners such as staples. For sheathing panels the spacing of the fasteners around the perimeter (edges) of the panel is specified as is the spacing of the fasteners in the field or body of the panels.
Table 802.5.1(9) includes nailing information for rafter and ceiling joist heel joint connections. The information includes data for different snow loads, roof pitches, rafter spacing and rafter spans.
For example, a 5/12 pitch, 16" OC, 50 lb snow load, with a span of 12 feet calls for 4 – 16d common nails per heel joint. Note the specification is for "common" nails. That is a nail 3 ½" long with a shank diameter of 0.162" or #8 wire gauge.
Many nails sold for air nailers are of a lesser shank diameter. For example the big box stores near me sell mostly 0.131" diameter nails in the 3 ½" size. That is basically just a box nail. For a heel joint connection to have the proper strength the larger diameter 0.162" nail should be used. Equal strength can be achieved by using more of the "box" sized nails, assuming they can all be fit into the joint.
One reason I like my Senco nailers is the vast array of nails that are made for their guns. A proper 16d common sized nail is available for some of their units. Box equivalent nails are also available for applications where they are suitable. That may not be said for other brands or off brand tools and nails.
There is a document from the ICC that may be of further interest regarding fasteners. Document ICC-ES 1539, is an Evaluation Report on nails and Staples. A plethora of information is included. One of the features are tables that list substitutions for size and number of one type of nail for another for a variety of connections. This may be downloaded from... http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1539.pdf (http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1539.pdf)
This from Don_P.
An interesting little detective story. At the end, under the images, this can be downloaded in PDF form for anyone interestd.
had trouble attaching above ???
clicking the link below will download the file
Good stuff- Thanks! Is there any reason to use ring shanked nails, or any other high-hold nail? Does the code recognize a difference? The old timers used to say that hot-dipped galvanized nails hold a lot better. I'll be shooting a lot of nails soon, and I want the best bang for the buck, while keeping the inspector happy. I'm a big advocate of over-building, so I'll be exceeding code wherever it makes sense.
I especially like ring shank or spiral nails for applications where smooth shank nails have a tendency to back out; fence pickets come to mind, nailed decks as well. Here in the SW nearly every fence I've seen, built with smooth shank nails, have nails heads up to 1/4 to 1/2 proud of the surface after several years.
Some uses in the IRC nailing schedules do permit one size smaller nail for a deformed shank nail.
Personally I use deformed shank in places they likely are not needed. That's because rather than buy a carton of smooth shank and deformed shank nails (for my air nailers) in the same size, I buy the deformed shank whenever possible. Same reason why I usually have galvanized nails on hand. I would not likely do that if I was buying and using larger numbers of nails as if I was a contractor/carpenter making a living at pounding/shooting nails.
And you're right hot dipped galvanized nails have lumpy shanks and do hold better.
I also find that when using ring shank nails in particular it is easier to use a reciprocating saw with a metal cutting blade to cut the nails rather than trying to pull something apart when an error is made.
I might have jumped the gun with the dead chicken notes from Dr Woeste's class. There are two main ways a fastener gets loaded, in shear (laterally, or sideways), or in withdrawal. MtnDon began talking mostly about shear. A ceiling joist nailed alongside a rafter is a good example of a single shear connection with the ceiling joist being the side member and the rafter being the main member. Simpson hangers typically have nails in shear with a metal plate being the side member and the joist or wood part being the main member.
The dead chicken was dealing with withdrawal loading, which is a load direction to be avoided if you can somehow build the assembly so that the nails simply hold things in place or are in shear. The references give withdrawal and shear design values. For shear these mostly revolve around diameter of the fastener and the density of the wood after minimum penetration requirements are met. A bigger nail in a harder piece of wood is going to support more than a little nail in soft wood. For withdrawal add total penetration to the above variables, a longer nail is going to have more friction holding it from being pulled out than a shorter nail.
For withdrawal deformed shanks are the ticket, but keep the diameter up. For instance, I want the nail to keep the sheathing on the building so that it can perform its' function as a shear panel in the wind. Many times I want a nail capable of both high shear strength and good withdrawal resistance. I've attached a scan of the wet service table from the NDS. Notice nails in withdrawal in the lower part. Now look at built >19% and subsequently dried. That's a 75% strength hit. Now look below that at threaded hardened nails... no strength loss. Pallet manufacturers realized long ago that a nickle upgrade in fastener quality reaped huge dividends in durability.
Please note: As a result of poor communications (my fault) between myself and my friend PEte, today I made a few corrections to the language in the first message in this topic. Thanks for bearing with me.
A further contribution to the topic, from PEte...
Nails and their holding or strength values are dependent upon the following:
1. Wood species, more specifically the Specific Gravity "G" or Density of the wood.
2. Orientation to the grain with respect to the nail axis and applied loads.
3. Surface into which the nail is driven.
4. Depth of penetration.
5. Bending strength of steel the nail is made from.
6. The nail's length, surface finish, type of head, and most importantly its actual diameter.
7. All applicable adjustment factors (Table 10.3.1, pg. 58, NDS2001) should be applied to tabulated values. There is a wealth of important info. in the National Design Specification for Wood Construction (NDS), and I am referring to the NDS2001 here, not the latest ed. Also, there is much detailed info. on many construction materials and products at the ICC Evaluation Services, at www.icc-es.org (http://www.icc-es.org). Nails must generally meet the requirements of ASTM F1667.
Loading a nail in shear, which is the predominant way in which they are used is primarily a matter of the nail diameter (dia.), actually the projected bearing area between the nail and wood, per inch of penetration, that is (dia.)(length); and the Specific Gravity or Density of the wood which influences the wood bearing strengths.
Loading a nail in withdrawal is primarily a matter of the nail diameter (dia.), actually the circumferential area between the nail and wood, per inch of penetration, that is [(pi, π)(dia.)] [length]; and the Specific Gravity or Density of the wood which influences the holding and frictional values. Surface finish, nail head shape and size, and finally shank deformations influence pull-out values. Pull-out from end grain is verboten for any real strength capacity; and pull-out from side grain should be employed very judiciously, because of its inherent weakness.
Using nails in tension, withdrawal or pull-out, in significant structural joints, is just not recommended. The pull-out values in side grain (nail axis perpendicular to the wood fibers) are quite low and should be avoided when possible. Pull-out in end grain should never be counted on for strength (NDS2001, 18.104.22.168, pg.69). Still, nail pull-out is a common consideration in the attachment of roof or wall sheathing, siding and the like where significant negative wind pressures can occur, and must be considered. In these cases, ring shanked nails and the like are used to improve withdrawal values.
While toenailing is an acceptable practice in many cases, since it is the only alternative, it is an inferior means of nailing for several reasons. Splitting and edge and end distance, length of penetration are all questionable and so variable as to make this a relatively weak structural connection. Toenails should be driven at about 30 from the side member and be started about L/3, nail length/3, in on the side member.
Edge and end distance and nail spacing within a row of nails or btwn. rows of nails must all be considered when designing a nailed joint. If a nail near the end of a side piece in a joint splits the side piece, it is essentially ineffective, and the split may propagate further into the member.
The original structural meaning of pennyweight, 10d, 12d or 16d, etc., common nails or spikes related primarily to the shank diameter, and secondarily to the nail length, the primary dimensions required for calculating holding strength in a joint. Of course, steel strength was important too. With the introduction of nail guns, and the expansion of the world economy the primary meaning of pennyweight (the shank dia.) has gone out the window. To the layman a 16d nail means 3.5" long, and the steel quality, shank dia., and head size and shape can be almost anything the manufacturer wants to put in a box or on a stick or coil, as long as they don't jam in their guns and they sell a lot of them. In effect, this is profit to the nail manufacturer, he can make about 20% more 16d box nails, with clipped heads, than 16d common nails from a ton of steel. And, this says nothing about the steel quality which also became an issue some years ago. This really doesn't make much difference for some significant percentage of the nails driven around the world, but is a real nightmare for those of us who are called on the design and spec. structural wood joints, where shank dia., length, head size and steel bending strength are all important in the design process.
For most people here, Table R602.3(1), from IRC, will be about all you really need; if you spend the time to study the table, the footnotes, and the parts of the code that go with the table. Then having a good fundamental understanding of how the joint is loaded, and reacts to these loads, generally how the joint works and how the nails are loaded to make the joint work will stand you in pretty good stead. The document ICC-ES/ESR-1539.pdf, is also a good reference on the subject. Quite frankly, the codes have gotten so complicated on the issue of joint design, nail capacity for various loads, etc.; that a few basic capacity tables should be about all you need for light framing joints and will better serve the average builder. More important may be a basic understanding of how the joint actually works and how it is loaded, so you are not loading a joint or nails in tension, when there is no tension capacity present. I have seen this a number of times with loft joists, on joist hangers, acting as tension ties between the exterior bearing walls. The joist hangers at a ledger have very little tension capacity along the axis of the joist.
Because of the variability of lumber and of the nailing process it is generally true that more nails of a smaller diameter will produce a better performing joint assembly, assuming you get sufficient penetration into the second member and that you can physically get all the nails in the joint and prevent splitting, and comply with edge and end distances and spacing requirements.
A joint like the heel joint between a rafter and a ceiling joist (rafter tie) or the lap joint between two ceiling joists over an interior partition are basically lap joints, and the nails act in what we call single shear. That means there is a single plane (a faying surface) between the two members where the nail is acting in shear. But, the nail actually failing in a cleaving shear failure is unlikely in a nailed wood joint. As the members are loaded, the nail bears against the wood, the wood starts to yield or crush in bearing, and the joint starts to slip a bit. At the same time the nail starts to bend as the joint moves a bit and the wood yields in bearing, and if there is enough nail penetration into the member receiving the nail point, the nail in the two members will act a bit like a cantilevered beam out of/and btwn. each wood member; this nail bending (a point of contraflexure in the nail) tends to increase the wood yielding in bearing, thus bringing more of the nail length into play in bearing in each wood member. The bearing stress is at its max. in each wood member, right at the faying surface, and decreases with depth. Thus, the penetration of the point must be sufficient, so that its pull-out resistance is sufficient to allow the nail to act as this restrained cantilever as it deforms. The head of the nail actually adds a bit of effective penetration length at the side member, as does clinching the nail on the outside surface of the main member. At some point equilibrium is achieved between the sum of the nail capacities and the member loads; and then with some set tolerance for how much we are willing to let that joint slip in the process, in effect, this sets the nail capacity in lbs./nail for that type of joint.
You might expand on ring-shanked "P" nails and the code requirement(s) for them. "P" nails, or full-head pneumatic nails, are generally just a bit smaller in diameter than their common equivalent nail. When we built our facility, the inspector told me that on end-plates, code required one additional "p" nail, (3 instead of 2). Interestingly, you can increase the spacing on sheathing when using full head "p" nails as opposed to standard ring-shank sheathing nails as they are longer. You reference the Senco nails in your post. I didn't see anything about the extra nail. I never researched this personally; just took it on faith. Since nail guns and compressors are so cheap, they are not just for the pros anymore.
I used a couple of boxes of the Hitachi ring-shanked for our facility. They are tough to pull out when you make a mistake.
On our old house, I did a roof-over. Long story, but I built a new, taller roof right over the existing nearly flat roof. I used hurricane clips, as required, but the inspector said I didn't use enough nails. I put in the number required, which split the heck out of the trusses. The inspector said that that wouldn't hurt anything, and passed it. That still bugs me- make a prescribed nail count at the expense of the very thing you are securing! Now I would build it with straps that go over the truss, rather than being nailed to it.
If you're splitting wood something is wrong. This doesn't give the assumed holding strength and it stands a good chance of running the split up the board. If that is going on, stop and figure out another way, predrilling or another fastener choice or method. These charts and tables are assuming a good connection.
The pneumatic nails generally fall under the description "box" nails in the NDS tables and the connections calc. The codebook tables are often describing a "common" nail. A sheathing nail used to be an 8d common(.131x2.5") a gun 8 is often a .113x2.5". The shear capacity of the common in SPF through 7/16 ply is 60 lbs/fastener where with the gun nail it is only 46 lbs/nail. "Pull the trigger half again" is not far off most of the time.
Quoteexpand on ring-shanked "P" nails and the code requirement(s) for them. "P" nails,
I've never seen or heard of "P" nails as such. Full head yes; but just off hand can't point to the code reference. Maybe someone else can. No time for me right now as I'm loading some stuff up for the AM and have other things that must be attended to before leaving.
Quoteend-plates, code required one additional "p" nai
Not sure what is meant by end plate either. I think that inspector may have his own personal agenda... which is another topic altogether. Sometimes if a few extra nails will make the inspector happier it is worth it rather than try to get him to show you where it says so....
The point I was trying to make about Senco nails is that they do make nails for their nailers that are directly equivalent to "common" nail specifications. Same diameter and length. They also make reduced shank nails that are equivalent to "box" nails as the chart above indicates. Not all nails sold for nail gun use offer that. Some others must I would think, although I have noticed that some only come close. Some are maybe 1/4 inch short or a couple-three thou' shy of the code specification. There may be inspectors that would call the builder on that too.
I don't remember if I mentioned this... it is also very important when talking about nailing sheathing, NOT to overdrive the nails. Nail heads should be flush with the surface not below the surface as so often happens with air driven nails. Some of the better nailers come with or can be fitted with tips that prevent overdriving IIRC. People like me with older, but reliable, nailers turn down the air pressure and end up giving most of the nails a whack with a hammer to seat the nails properly. Over driving the nails effectively reduces the thickness of the panel at that point. The panel then no longer has the designed shear strength. (Thanks to PEte for that.
More later if I have time... or Monday - Tuesday
What actually split on my old house was the original rafters, not the new trusses. I cut the overhang off, laid a 2X flat on the old roof deck, and put the new trusses over the old, with hurricane clips holding them in place. I suppose I should have left the old rafters a bit longer, so I wasn't nailing so close to the edge, but I was following the instructions the county gave me to meet code. 4 hurricanes later, the roof is still there, so i guess it wasn't as compromised as I thought it would be.
Totally off topic- When I did the roof-over, the effect on cooling was amazing, since the old attic was now essentially conditioned space for the ductwork, unlike the typical 140 degrees most FL attics hit at middday. I vented the new roof, so it was basically shade over the old one. It amazes me that probably 95% of houses in our area have ductwork in a hot attic, including new construction.
Another bit of valuable info from PEte...
It seems that every problem we face has a primary and secondary, and then maybe third level failure mode and once #1 is satisfied, #2 may become critical, etc. etc. It would seem that every joint in the building might take a day to design, and for an engineer doing this design, it approaches that when every nail must be measured for length, and head size, and a micrometer used to check the shank dia. We didn't have these problems when all we had were spikes and common nails and we knew what that meant in head size, length and shank diameter You guys (DIY owner-builders) just have to be careful, there are warnings in Mnt.Don's post and in mine, or take your chances.
There are equivalency or strength comparison and substitution charts for various similar nails, but you must still know the joint forces and how the nail is loaded to use them. Regarding pull out strength of various nails: common nails rely on friction btwn. a fairly polished nail shank and the wood fibers, and various nail point shapes have some influence on this along with the wood Specific Gravity "G". Ring shank and other deformed shank nails, even hot dipped galvanized nails with a rougher shank surface actually bring a mechanical friction into play and thus have higher withdrawal values. But, changes in moisture content of the wood and shrinkage can significantly reduce the pull out values of some fasteners.