I live in a 2800 ft2 log home that I designed and contracted myself 15 years ago. It came as a custom CAD/CAM kit from Model Log Homes (no longer in business). The logs are Doug Fir from Montana, 10" dia., cut live, check groove cut to heart, air dried in pole barn for 19 months to a moisture content also of 19%, tripple tongue and groove milled top and bottom, with saddle notches. The thermal mass is equivalent to R19 insulation. Butts in the same course were toenailed with large nails (I think about 4 penny). We put 3/4" dia. 4' long steel drift pins throughout the walls as the courses were stacked. Threaded rod goes from foundation to roof through the saddle notches on the corners.
Though I contracted it, I hired a contractor who had built about a dozen houses from the same manufacturer to be my building foreman. He and his partner did most of the construction themselves, working time and material. My wife and I did some of the work (cleanup, staining, and I put on 85% of the roof) and we subbed out excavation, drywall, insulation, gutters, cabinet manufacture, manufacture and installation of custom cultured marble bathroom lavs and shower, and masonry on the fireplaces (cultured stone). The only time we had more than the two main workers was when the logs arrived in 2 semi trucks. We hired a dozen guys from an employment agency to work half a day and unload the trucks, and about 3 who stayed the rest of the first and also for a second day. The log dealer was there with a blueprint and called out specs for logs of specific code numbers to go to specific locations. The logs were up and in place in two days. The reason I was the contractor and the other guy the foreman was that he had gone bankrupt during the recession in the early 90s. I had the startup capital and he didn't. I proved to the bank that I was an outstanding financial manager (long story) and they agreed for me to handle all the money while he did the construction. I secured all bids for all the materials, did the ordering and payments, got bids from, hired and paid the subs, and made the payments to the two main builders.
Logs do take a lot of maintenance. I have to restain the southern and western exposures almost every year. As others have said, big overhangs are highly recommended. If you can orient the house to the south, I'd put a covered porch on the south side and at least 3' overhangs everywhere else. If you don't take care of the logs, they will turn into the compost that Eddie talks about. You absolutely should familiarize yourself with the product line of a company called Perm-A-Chink. Some logs have a propensity to develop numerous or sizeable "checks" or cracks which need to be filled. Due to expansion and contraction, a flexible filler is needed. Placing a foam backer is necessary because if the latex caulk fills the full depth of the check, it can extrude too much when it expands from summer heat. On the other hand, log homes properly maintained can last a long time. I have been to a village in Switzerland where several log houses over 500 y.o. have been relocated to a log house museum. Such houses in Switzerland can have an astounding rustic beauty. The variety of rooves is amazing, from slate, to thatch, to sod filled with alpine wildflowers.
There are lots of Log Home magazines, but many deal with furnishings; you can think about that later. One that used to deal with design and construction considerations was Muir's Original Log Home Guide for Builders and Buyers. Log Homes Magazine did an annual Construction and Finance Guidebook as well as Buyer's Guide. The Construction and Finance Guidebook was most helpful to me.
Log homes can be uniquely custom crafted or milled. Custom crafted are built on a lot, disassembled, shipped, and reassembled. The trees can be cut dead or harvested live. If the tree is already dead, something killed it-fire, insects, something, but it may have had years while standing to air dry well. If harvested live, you know it was likely healthy wood (do you prefer to eat food that was found already dead or food that was slaughtered healthy and processed immediately?) but the downside is that it is wet and needs to either air dry for awhile or be kiln dried (better but more $). Swedish coped logs can be latex caulked and tongue and groove logs can be weatherstripped. Custom crafted logs need to have the gaps filled. The terminology has changed since the pioneer days. Frequently, back then, many logs were not coped or butted at the joints; they just passed over each other. Large gaps would be left between the courses. These were filled with long wedges from split rails. This was called the "chinking" and the mud which filled the spaces between the logs and chinks was called "daubing". Today, the caulk that is used in the small gaps between courses is referred to as the "chinking". Logs can be milled round, D-shaped, or square, though square should actually have the outer surface angled like clapboards are done so a drip edge takes rain away from the joint between courses. Log siding does not have the visual 3-dimensional depth of full logs, however they have the advantages of drying with fewer checks and of the ability to be placed on the sides of insulated walls. Artificial sculptured cultured concrete log walls are becoming more popular. The Wilderness Lodge at DisneyWorld uses this material. Courses that alternate at joints may end with a saddle notch or dovetail. Perpendicular courses built at the same level usually end in butt and pass joints, but can simply butt or miter.
Cabins or houses built from logs must take settling into account. Our logs settled 4.5" after being stacked. The logs still rise about 1/8" every winter (cold, wet, and humid here) and fall that much in summer (very hot and very arid). To deal with this, cabinets were screwed to plywood backerboard. Vertical slots were routered into the plywood, and lagbolts used to lag through the slots into the walls. We used exterior wall to exterior wall trusses, so the interior stud walls are non-loadbearing. The caps of these walls stop 3" shy of the trusses. A parallel 2x4 is nailed to the trusses and then 1x4 trim tacked to that. The trim is secured to the trusses and overlaps the interior wall. As the exterior log walls rise and fall, so do the roof trusses and the trim. That trim, which is attached to the trusses, sildes up and down against the top of the interior stud wall. Windows are secured with an extra frame with slots and lags into the end of log sections. Half-log headers have gaps between the top of the window and the header. The gap is stuffed with fiberglass batting and covered by wide trim. In places where log trusses sit above the headers to a doorway, we routered a big slot and inserted very beefy steel T-bar inside the half log header.
Placing Romex also takes pre-planning. We stacked two courses, stopped and drilled vertically through the 2 logs and sill plate into the joist cavity, then chipped out the top inner edge of the log. When wiring later, we snaked the Romex through this hole and the foreman built nice little pine boxes that scribed into the cope between the logs with the outlets. I have also seen a technique on other houses with round logs in which the Romex is simply run in the cope between the first and second courses and covered with a long piece of trim.
I love my log home. It is decorated with a lot of southwest and native American art. Our 1100 ft2 great room has big log trusses and 2x6 tongue and groove ceiling, and solid oak flooring. My wife calls it our temple to wood. I have a cedar canoe in those trusses and wrought iron chandeliers with hand hammered copper trees, elk, moose, bear, etc. A totem pole tells the story of our daughter's adoption. We have paintings of mountains and mountain men, an Indian war shirt, wooden skis, a wooden snow sled, snowshoes, Indian bow and arrow, spears, tomahawk, peace pipe, papoose, and all other kinds of rustic decor on the walls. It is really a dream home for us, but it also really does take endless maintenance. Besides the staining, dust settles on the log copes and the tops of all the members of the log trusses. Still, I wouldn't trade it for anything, or won't until I am too old to take care of it. (We also work endlessly in the almost 2 acre woodland garden we have developed-got to keep that Kubota busy somehow). We call the house Woodhaven and the woodland garden The Haven Wood. When I can't take care of it all anymore, I guess I'll move to the Oregon coast where I think I'll contract a nice little cottage built out of rocks, something like the kind of thing you see in a Thomas Kinkade painting, surrounded by big trees and lots of blooming Rhododendron. No maintenance on those rocks in my old age retirement. Hmmm, got to find the time to start some sketches; also got to plan a modest but big enough woodland garden to justify talking the wife into letting me take the "Bota with us when we move.