Walt:
One of the first of our tasks this spring involves applying siding to camping structure we built last fall. But before that work gets underway, there's one detail that needs doing to ensure the long-term welfare of the structure.
Fundamentally, the structure is an example of the type of building known as a "pole barn" in that its roof is supported, not by the walls as is the case in most modern "stick built" homes, but rather by treated poles rising up out of the ground. The weight of the roof, and the walls as well, are transfered to and borne by poles that sit on concrete pads set two feet below ground level (for larger pole barns, the pads are placed three feet down). The dirt packed around the poles goes a long way towards providing lateral stability for the building.
The floor and walls are attached to these vertical poles using construction screws, a fancy name for the over-size screws that have come to generally replace the nails that used to be used in this sort of application. The screws are handy in a variety of ways such as the ease with which they can be taken out when a board needs to be moved, or some design component needs to be changed‒for people who are learning as they go, they're very handy.
Since the construction screws are "self-drilling" in that they create their own pilot hole, the screws are also less likely to split the end of a board when compared to a standard screw or nail of the same diameter. Also when screwing into end-grain, they have considerably more holding power than a nail would (still not all that great, but good enough for certain applications).
The strength of these special screws comes from their hardness, but that hardness can be problematic in certain situations. For example, when put under enough lateral stress, they don't tend to pull out a little as a nail would; instead, they tend to sheer in half and fail completely. One of the first contstructions I did using these handy fasteners was an entrance deck. It was exposed to the weather, with the result that the wood it was constructed out of swelled with the wetness of winter, and shrank in the dryness of late summer.
One day, after a few years of this, it gave out a large ripping noise and fell apart rather spectacularly. It started out with one screw snapping, which put more stress on the next screw, which then snapped and so on creating a cascade of snapping fasteners. It was one of those moments that's both very funny and very frustrating.
The solution was to reassemble the deck using more consuction screws, and once it was back in place, to reenforce those screws with through bolts and lag bolts large enough to contain the seasonal stresses. In time, we scrapped out that deck, but while its gone physically, the memory of that failure influences how we build today.
Here's a pic of a couple of 3/8" lag bolts holding one of the Adirondack's deck support beams in place. If you look closely, you can see the heads of the two construction screws (one above and to the left of the top lag, and another below and to the right of the bottom lag) that initially held the board in place before the final installation of the lag bolts.
To ensure that our humid winters and dry summers don't cause the structure to pull itself apart, each of the main 2x6's needed to be reenforced with a lag bolt, but unlike the lags shown above standing "proud" of the board, these needed to be recessessed so that their heads didn't get in the way of the siding that be attached to those 2x6's.
One of the key principles in sustainable construction is to find something similar to what you want, something that has stood the test of time, and copy as much as you can. Another way this princple is expressed is that if you do something new in an old way, you have a fair chance of succeeding. If you do something old in a new way, you have a slight change of succeding. But if you intentionally undertake to do something new in a new way, thereby rejecting the valuable legacy bequeathed by those who've gone before, well then you have almost no chance of succeeding the first time.
There will be times when you find that you have no choice but to do something new in a new way, but if that's the case, be prepared for a long and frustrating struggle with the Law of Unintended Consequences.
When situations arise in which one has to do new things in new ways, one's best hope is to focus really, really intently on the task at hand. Fortunately, that's rarely necessary since those who's primary goal is to understand the art and craft of sustainable design have a wealth of past practice to study and learn from.
As Windward evolves, we are steadily learning about techniques that meet our long term needs, lessons often learned amidst the frustration of rebuilding something, like that deck, that didn't work out well enough. The structures that did perform as hoped point the way towards success in building similar structures, thereby serving as learning resources for future Windwardians who take the time to look at and copy the work already done and the lessons learned along the way.
But there often are details that aren't obvious to the observer, which is why I'm taking the time to offer this "word to the wise" article. I take it that by having searched out this article, and by your being willing to invest the time needed to read this far into it, you've demonstrated that you're one of the wise ones, and so I'm pleased to reach out to you and share some tricks of the trade.
Because the siding will be attached to the face of the 2x6, the first thing that needs doing is that we need to drill a hole into the 2x6 to accept both the head of the lag screw and the washer that enables the lag to get a grip on the 2x6. Without the washer, the head of the lag would just dig into the wood instead of compressing it, thereby greatly lessening the strength of the bond between the 2x6 and the 4x4.
In this case, we're using 1/4" lag bolts to secure the 2x6's, and a 15/16" flat drill is a handy size for the larger hole needed to seat the washer.
One thing to notice is that the hole isn't drilled to line up with the center of the 4x4 that we'll be securing the 2x6 to; rather, it's set an inch in from the inside edge. The point of that is that we want to move away from the end of the 2x6 so that it has more "relish." That's a term from timber framing used to describe the amount of wood remaining on the outside of a mortise, i.e. the amount of wood that secures the timber in the joint. If the timber, or in this case the 2x6, splits, then almost all of its strength is lost; the more relish, the less likely the wood is to split.
A flat-blade drill leaves a nice tapered hole in the center of the hollowed out space, and that hole would make a nice starting hole for a lag bolt. Unfortunately, given the length of the lag screw we're needing to use, the amount of force needed to screw it all the way into the 4x4 would be such that the lag would be likely to fail.
So, we'll use a 1/4" drill bit to ease the passage through the 2x6 and into the 4x4. If you pay attention, you'll be able to feel when the drill passes through the 2x6 and starts to bite into the 4x4. It's okay to drill a 1/4" or so into the 4x4 to make it easier to get the lag started, but you don't want to go deeper because that would lessen the holding power of the lag.
Tapping the lag screw soundly with a hammer helps to get it started into the wood.
Here's a pic of the washered lag snug in it's hole.
There are a few more details that I want to call your attention to. This sort of work offers a good deal of satisfaction but it can be quite frustrating to over torque a bolt and have it snap off. Given a big enough wrench, this can happen with any diameter bolt, but it's a common problem when using 1/4" hardware in that the commonly used ratchets are large enough that it's easy to apply too much force.
Here's a pic showing a bolt (on the right) that sheared off at the weak part where the threads start.
When doing a couple of bolts, there's no problem with just using a small wrench to ensure that one's mind doesn't wander and let habit‒and muscle memorty‒take over. A moment of inattention, and then comes that sinking feeling as the ratchet starts to spin without resistance because you've applied too much force. Snapping off a bolt in something like an engine block is such a pain that mechanics often use different ratchets depending on whether they're taking something apart, or putting something back together again.
On a job like this, there are a couple of tricks that will help prevent the aggravation of having bolts shear away. One trick is to hold the ratchet around the head, using your wrist to rotate it instead of using your arm to pull down on the handle.
Another trick when using a large ratchet to drive a small bolt is to only use a couple of fingers on the handle instead of a full grip.
Another trick is to use a ratchet that's no larger than the diameter of the lag you're driving. In this example, I'm using a 1/4" drive ratchet on a 1/4" lag.
Even being very careful, sometimes the lag will snap anyway. One situation in which this can happen is when one is unknowingly trying to screw a lag into a knot that's being hidden by the 2x6. Here's a pic showing such a knot, only this one happens to be visible.
When that happens, and it will, one option is to just drill another hole and try again. The result won't look very pretty, but it will serve the need, and in this case it's going to be covered by the siding and won't show anyway.
