Here's how to build a log shelter. This project was a re-reconstruction of a building originally built by the Civilian Conservation Corps in the early 1940's.
We used locally harvested Sitka spruce logs purchased from a local mill. The fireplace was made of local stone but since that was contracted out this will primarily cover how the log structure was built.
Most of this Instructable will focus on the technique used to cut and build the roof trusses. Ample resources are available on log construction. Putting on a roof is also well documented. But we had a hard time with some of the roof truss planning so came up with a few tricks to pass on...
Step 1: Prior shelter condition
Here's why we decided to rebuild the shelter. Unfortunately, the roof on the log structure wasn't large enough. In our temperate rainforest, the 100 or so inches of precipitation a year quickly caused the exposed logs to rot. So we knew we needed a larger roof.
Also, the logs on the inside, next to the fireplace, were being ignited when large fires were built. Some of the original stonework had begun to fail so we knew we needed to rebuild the fireplace and build it so that the logs would be less exposed.
Finally, we got some grant money to do it!
Step 2: Materials and equipment
We had access to an amazing amount of equipment. Not all is necessary though. Much of this work was done by just one person. Rarely were more than two people involved. So equipment like a Bobcat loader with forks, an overhead lift, a generator, and other major equipment were used.
Smaller tools included
a chainsaw with associated tools and protective equipment
a few large drills, bore bits, and other accessories
levels, string levels and laser levels
angle grinder and flap wheel sanding discs
a huge vice
tape measures and squares
extension cords galore
hammers, sledge hammers
wheelbarrow and shovel
reinforcing rod - 1 inch
threaded rod, washers and nuts
lag bolts, washers and nuts
nails and screws
rock and mortar
3/4 inch thick plate steel
Step 3: Building the walls
In the 1970's the walls of the shelter were rebuilt. The chimney and floor remained original. In that reconstruction they replaced the lower logs with concrete which helped eliminate the rotting of the lowest logs.
Aside from that the shelter was disassembled. Parts of the roof were saved for another project. Some of the logs were used for constructing sills to work on the new logs. The chimney was initially left in place and worked around. The initial plan was to apply for additional grant funding for reconstruction of the chimney. However, by doing this job "in-house" we had significant savings and were able to contract that out later.
Start out with the largest diameter logs on the bottom. Alternate the butt ends and the top ends.
The first course of logs were planed off to sit level on the lowest level of concrete footing. A notch was cut to saddle the second tier of concrete. Having a freshly sharpened chain and an adequately powered chainsaw will help a lot with the milling.
Line up a log, sit it on top of where it will be and then level it as best you can. In our case, using a machine with forks and the log chained in place worked very well. Measure the distance that the log is above where you want it to be. Se the scribing tool to that length. Then keeping the scribing tool level and perpendicular to the existing log, trace the contour for the cut onto the top log. Do this on both sides.
Roll the log over. With a chainsaw and a partner to spot the far side, cut a series of parallel cuts to the depth marked by the scribing tool. Use an axe or adz to remove the material and then chisels or the chainsaw to clean the cut. Roll it into place again and check it. Mark areas to be cut if you need to.
The bottom course of logs needs to be drilled from the bottom to receive the metal posts. Successive layers should have the bottom of the log marked lengthwise and have a groove cut the entire length.
Using a long auger bit and a powerful drill, drill through two logs that are stacked and then drive in a piece of 1 inch rebar or pipe. You might want to mark where these are so you don't drill into them when doing higher logs.
As I said, many volumes have been written on different ways to build a log structure. But here's a way to make roof trusses...
Step 4: Roof truss design
We had six roof trusses to build for out shelter. The logs we had to work with varied in diameter from 18 inches to about 8.
We knew we needed the trusses to span about 20 feet. We decided to have an additional 2 feet on either end for some overhang (see the reason we had for this replacement). So we needed a minimum of 24 foot long "tie beams". We also decided to have the roof peak at 5 feet above the tie beam.
We needed a "king post" in the center. And two rafters that connected the king post to the ends of the tie beam. And finally, we wanted smaller "struts" to connect about the mid-point of the rafter to the tie beam. (See the notes in the photo.)
But with all the different sizes of logs we knew we needed a few constants...
Ideally, the outer edge of the rafters should be consistent. We planned on spiking in 4x4 s for the plywood sheathing. Avoiding having to notch or shim these would make the roof much more level of a surface. In order to achieve that, we knew the length of the apex and the length of the tie beam span. It was just some trig and we knew the length for the rafters.
But we couldn't just cut the rafters to length. We needed them to be notched. And with the variable diameter of the king posts, tie beams and rafters no calculations were going to hold true from one truss to the next.
So we made a full-size template...
Step 5: Log truss template
We purchased a number of 1/4 inch sheets of plywood and tacked them together covering a large enough area to actually sketch out each truss using the logs we had available.
We marked a center line for the tie log and a center line for the king post. We also marked where the rafter was to intersect the tie beam as well as the point where the rafter would project to connect with the other rafter on the top.
Each log was checked to see how it would be used on the site - checking for bow or sweep (although our logs were in really good shape because they were selected for this purpose).
Once we knew which side was "up" we marked the ends of the log with markings to show the "center" of it. Note that the center does not necessarily end up in the center of the grain.
Using half of the butt diameter we marked on our template one half of the height on either side of our center line. Repeat for the top end of the log.
We then snapped chalk lines to show, in general, where the log surface would fall.
Repeating that for the king post was the next step.
Now we had a full-size sketch of the intersection of the king post and the tie beam. We chose to make a 3 inch deep notch in the tie beam for the king post to sit in.
The fourth photo shows in red the cuts necessary for both the king post base and for the center top of the tie beam. We could now use our template and measure from the center of the king post index line to the outside to determine the width of the cut on the tie beam and how much to notch on the king post.
Step 6: Sketching the rafter intersections
Using the same ideas for the king post and tie beam calculations we applied to the rafters. However, we wanted to make sure the top side of the rafters was the index point instead of the center. If the rafter log was 12 inches in diameter or 8 inches in diameter we wanted the top surface to be equal on each side and from truss to truss.
We drew a line up from our connection point on the tie beam. Snapping a line between that point and the apex gave us the outside line. Then using the measurements of the diameter of the rafter log at the butt and top we marked that on our template. Snap another line... Repeat for the other rafter.
Now we marked a 3 inch deep cut on the tie beam at the point that the rafter met the tie beam. Draw a line from that depth to the point where the underside of the rafter meets the tie beam and you have the measurements necessary for the cuts on the tie beam.
Add a line perpendicular to the rafter lines and you get the measurement for the pieces to cut out of the rafter so that it fits into the notch of the tie beam.
Repeating similar lines on the top end of the king post and rafter intersection gives the measurements for the king post notches and the cut-aways from the rafter.
Use the same method for measuring and marking the struts if you decide to use them. We had a mark for the intersection point of the struts on both the rafter and the tie beam. A 3 inch deep center cut and the corresponding angles were easy calculations after doing so many of these!
Step 7: Marking the truss pieces for cutting
With the measurements the template gives us we can go back to the logs for marking and cutting. Marking the 3 inch deep cuts are relatively easy. (Look at the last of this set of photos for how i did it.)
But marking from the depth of these cuts to the end of the taper is a little trickier. Projecting a laser line from a level attached to a tripod works quite well though. Check out the photos.
The level needs to be positioned in-line with the log for this to work well. I had considered figuring out how to attach the level to the log parallel to the center line and projecting back toward the log... but when you're dealing with chainsaw carpentry you'll accept a certain deviation from measurements.
Step 8: Put up the front posts
Meanwhile... back at the shelter... poured concrete inside culvert tubes were positioned for the front posts. Rebar was left sticking out of the top.
The shelter posts were drilled out to accept the rebar and then lifted using a set of chains and straps and a forklift. Then the front sill for the tie beams was lifted into place after notches were cut to connect the two logs. Ample bracing (from the old shelter) was used to keep the set stable until the tie beams were put into place.
Step 9: Position and notch the tie beams
Once you magically put the tie beams on top of the shelter and have positioned them in their location...
We used heavy machinery instead of magic.
But once in place we used ample string lines and long tape measures to make sure we were square. Then we determined how deep we needed to notch the ends of the tie beam to nest onto the top row of logs in the back and the beam across the front of the shelter.
Use the scribing tool to notch the logs, cut away as you did with the logs for the walls and then roll them over into place.
We pounded rebar through the tie beams and onto the lower logs so they wouldn't move and hopefully so the roof doesn't blow off!
Step 10: Assemble the roof trusses
Using the large forklift we carefully positioned the pieces of the roof trusses. Unfortunately there were only two of us working on this and we were so involved that we didn't get photos taken of the process.
We put up a king post and then braced it to the adjacent tie beam and to its own tie beam. Then lowered rafters into place and placed the struts in by hand.
We drilled out and lagged or through-bolted the pieces where possible. Not just for strength, but also because people had knocked out some of the struts on the old shelter for use as firewood!
Step 11: Add the roof and fireplace and you're done
Attaching the 4x4 treated purlins along the rafters was easy - we drilled them out and drove large spikes into them at 2 foot intervals, Then we sheathed the roof and finally added metal roofing.
The fireplace construction was done by a contractor so there isn't too much I can add to it here.
But there are a few tricks we had during construction...
We rented a heated and lit warehouse with a massive lift. This was incredibly useful when building the trusses. We were out of the weather, able to work at almost any hour, and we could lift up the logs to move them around quite easily. Definitely cheating.
Big machines. We also rented a large forklift with an extending boom. Although we had access to a boom truck, this was definitely the right took for the job. It can articulate from side to side... so reaching over the shelter and positioning a rafter in place was really helpful.