What type of log joinery works and why?
Our goal with this page is to educate everyone on the proper way to build a log home. There are many questions surrounding this industry; Do I want a handcrafted home or milled?, Should I used kiln dried logs or fresh cut logs?, How should the logs be joined together?, What type or size of log should I use? These are all very important questions that must be answered before you make your decision. I bet that when you first decided you would like to have a log home you never realized how many different ways there are to join logs. It doesn't matter if you've never worked with wood before or if you are a seasoned veteran, everyone will come away with an abundance of fresh knowledge after reading this article. If you do all the research just as we have you will find that what you read here today is all true.
Every log ever cut will check (crack) in the same place when it dries and that location is always the closest point to the pith (center). If you kiln dry or air dry a log it will check in random locations closest to the pith and now you have pre-existing checks. The problem with this is that when you get around to joining the logs together a lot of those pre-existing checks are pointed upwards which if not filled will collect rain water. This is why it is best to use fresh cut (green) logs with no pre-existing checks. By using green logs we can actually cut them in a way (described later) in which we program them to check internally so you don't get those large outer checks. It is the same principal behind why you make a stress cut (expansion joint) in cement. You program the cement to expand and contract at that point and not crack somewhere else. This cannot be achieved with any milled log or by a handcrafter that still uses the outdated swedish cope lateral groove and round notch. The biggest problem with milled logs is that you cannot control what the log is going to do. I like to compare them to a freshly milled and kiln dried pile of 2x4's. They come out of the machines perfect but then whamo, most of them warp and twist every which way and end up as firewood. Obviously we are handcrafters and believe every log home should be left in it's natural state. It makes us cringe evertime we think of a big beautiful tree getting sent through a molding machine. Just think of all the pollution caused by milling and kiln drying a log when it's a better building product left as is. As you read and learn about the science of wood and fibre saturation of their cells you will understand that we do what we do because it's just common sense.
What we have set out to do is to create an informational page for people who are interested in the constructions methods used by log builders today. We hope that by reading this you can understand a bit about what we do, and hopefully see why it is we employ the saddle notch or shrink fit saddle notch in conjunction with the double scribe lateral groove to create our homes.
Types of Joinery
North Country Log Homes, Inc. prides themselves on using the most advanced forms of log joinery known to exist today. Here at NCLH, Inc. we use the saddle notch and the shrink-fit saddle notch in conjunction with the double-scribe lateral groove. This however is only one way in which we build our houses and below we will briefly describe the other forms in which we use that are available to our customers.
figure 1
Let's start with the notch as this is the corner stone of any log structure. The most basic corner notch used is the round notch. A round notch is made by simply cutting the exact contour of the log below into the bottom of the log going above it (see fig. 1). It is the oldest and by far the most unstable notch. The round notch is typically unused in the construction of handcrafted log homes due to its instability, but is the primary notch used in the construction of manufactured homes as it is the only notch that can be made by a machine. The problem with this notch is that it will never stay tight. Even if the logs are kiln dried they are still going to shrink and the corners of your home will need to be caulked.
figure 2
The second and most commonly used notch by handcrafters is the Saddle Notch (see fig.2). This notch is cut to fit a reshaped log where the vertical sides have been carved back to create two sloped planes at approx. 45 deg. These sloped planes are referred to as saddles. This notch was developed to cure the problems caused by the round notch. This is done by allowing thelogs to slide down the flat saddle as the logs shrink and compress keeping the corners locked tightly. Under most circumstances the saddle notch is suffice, although it has been found that during a long winter heating season the inside notches of a log home will open up slightly because of the low humidity and excess drying that occurs with the inner half of the logs.
figure 3
This annoyance led to the invention of the Shrink-Fit Saddle Notch (see fig.3) From the outside the shrink-fit saddle notch appears the same as the traditional saddle notch. The difference is that there is a wedge shaped surface left on the interior side of the saddle. When the notch wants to shrink it is forced to climb that wedge on the saddle and in turn keeps the corners tight year round. This is the most advanced notch at the present time, and when used in conjunction with the double-scribed lateral groove (explained later) is the only combination that can provide you an air tight caulk free building.
figure 4
figure 5
figure 6
figure 7
figure 8
Next we have the Norwegian or Diamond Notch (fig.4). This is a purely aesthetic notch that performs just like a saddle notch. The only difference is there are saddles cut into the top and bottom of each log to form a diamond shape.
In Fig. 5 you will notice that we have gotten rid of the corner notch completely and have incorporated a Sliding Dovetail Joint with a Corner Post. This is becoming increasingly more popular due to it's sleak and more contemporary look. Due to having posts for corners this form of construction also tends to require less maintenance than if there were notched corners with exposed end grain.
If you would like to get the full historic rustic appeal from your home than I suggest going with a Chinked Log Wall System (see Fig.6). Here we eliminate the cutting of the lateral grooves but retain the notched corner. After your home is set up the gaps left between the logs are filled with foam backer rods and then sealed using a colored rubberized caulk known as "chink" (no more oakum and mortar like in the old days).
Lateral Grooves
Lets move onto the lateral grooves, which are the grooves that follow the length of the log seaming them together. There are only two basic types employed by hancrafters: The Swedish cope or Scandinavian full-scribe (see fig.7) and the Double-Scribe (see fig.8).
The Swedish Cope (see Fig. 7) is made by making a series of cuts into the bottom side of the log forming a U shaped channel. This style is most commonly used because of it‘s simplicity. The problem with this style is that you are removing all the wood from the bottom of the log and this makes the log unstable, even with kiln dried logs. When you remove too much wood from the bottom of the log you are almost guaranteeing yourself to get a check out the bottom. This check causes the log to split making it rise off the log below causing an unstable condition and a spot for air and water to infiltrate. No matter if it is cut by man or machine it still does not perform as well as the double-scribe lateral.
The Double-Scribe Lateral Groove (see Fig. 8), which North Country Log Homes, Inc. uses, is the best choice of lateral grooves. By removing small amounts of wood from both the top and bottom of the log and making a kerf (relief cut) into the top 1/3 of the log you can localize the major checking inside the log where it is not visible. This internal checking causes the top of the log to spread open, not the bottom like the swedish cope, tightening itself against the bottom of the log above. This chain reaction continues up the wall and the joinery continues to get tighter as the logs shrink and compress onto one another. This is the only groove that can provide a chink-less union between logs and minimize checking along it's outer surfaces.
We here at North Country Log Homes, Inc. hope that by reading this article you have gained a little more insight into the art of log crafting. There are many forms of joinery and we want to make sure everyone is aware of the differences between them. We hope that you will use this information when deciding on a new North Country Log Home.