With the excavation, footing and foundation all complete, and the log-cabin materials all delivered to the site, work can get under way on building a floor system.
The first step is to install a metal termite shield (figure A) before the carpenters attach the first boards to the concrete foundation. For the termite shield, 10-foot lengths of galvanized sheet metal are used. Each sheet has a slight crimp along the length of the inside edge. This forms a metal barrier and overhang that will prevent termites from building their mud tunnels up the inside of the foundation and into the wooden walls.
The carpenters then attach the wooden sill-plates (figure B) to the concrete blocks using heavy-duty nuts and washers. These fasteners fit perfectly onto the bolts the block-masons had set earlier in the wet concrete. Since the sill plate is in direct contact with the foundation and with the metal termite shield, the building code requires that it be made with water-resistant, pressure-treated pine.
The six concrete-block columns that the masons constructed -- four in the middle and one at either end of the foundation -- will support the center beam that the carpenters build on-site (figure C). The carpenters use standard pine two-by-eights nailed together to form a six-inch by eight-inch bead. The center beam will support the floor joists and, ultimately, the floor itself.
The center beam rests on blocks of pressure-treated pine, which are also protects from termites using metal shields. The crew takes care to make sure that the joints between boards are located directly over the column and that the joints are staggered to avoid creating any weak spots in the beam.
With the beam completed, the carpenters immediately begin laying out the two-by-eight floor joists (figure D). The joists are spaced at 16 inches apart and are supported in the middle of the house by the center beam. On the outside, the joists rest on the sill plate and are secured by a double band of two-by-eights (figure E).
To prevent the floor joists from twisting, the carpenters nail short lengths of two-by-eights -- called bridging -- between each of them (figure F). Some kits come with metal bracing, but wooden bridging makes the floor more rigid, which means fewer squeaks.
With the bridging complete and the floor joists secured to the sill-plate and foundation, the crew begins dropping four-by -eight sheets of 3/4-inch particleboard in place to create the subfloor. Even before the first nail is driven, each sheet of particleboard is attached to the joists with a bead of construction adhesive on each joist. Using a combination of adhesive and nails makes for a stable floor.
The carpenter drives a stabilizing nail into each corner before quickly moving on to the next sheet. Once the first row of particleboard is secured, the crew switches to an air-powered nailer to speed up the process. Though some purists prefer the old-fashioned method of hammer and nail, the powered nailer drastically reduces the work time for this stage.
Installation of the last piece of sheeting marks the end of the first phase in this construction project. The foundation is complete and the crew has built us a solid floor system consisting of joists, bridging and the subfloor. The next step is construction of the exterior log walls the element that gives this project its defining look.
Constructing the Log Walls
The crew starts by carefully measuring and snapping a chalk line at the edge of the flooring to mark the locations of the inside of each log wall. With the line drawn, a bead of adhesive is laid down on the floor where the log will be positioned (figure G).
Starting at the front corner, the crew lays down the first log, lining it up with a chalk line (figure H) and making sure it makes contact with the bead of adhesive they've applied to the floor.
A carpenter then drills the first of several 1-1/2" countersunk holes, about 2" into the top of the log (figure I). Next, a 1/4" bit is used to drill a pilot hole all the way through the log for a 10" long bolt. The bolts are used to attach the log securely to the floor.
As each log in the first course is laid in place, it is aligned with the inside edge of the chalk line and bolted in place. With several people working together, the logs can be positioned and attached so as to compensate for any slight bowing that may have occurred in any of the logs.
At each corner and anywhere that two logs meet, a 1-1/8" hole is drilled completely through the two logs. The hole is filled with a latex sealant, and a 1" hardwood dowel is driven in (figure J). The dowel forces the sealant into the gaps between the two logs to help create a weatherproof seal at the corners and junctions between logs.
Two strips of self-adhesive foam weatherstripping are placed lengthwise along the top of the two ridges on each log (figure K). The weatherstripping will augment the tongue-and-groove design of the logs to help form a tight barrier between the logs.
It's vital that the first course of logs be installed accurately and securely since any mistakes will be magnified as the walls are erected, and any major problems with placement will be difficult or impossible to fix later.
RESOURCES :
Log Home Repair and Restoration Services
Log Home Repair and Restoration Services
Website: www.loghomerepair.com
Special Thanks for DIY Build a Log Cabin workshop
Blossman Gas
Website: www.blossmangas.com/
Inside Log Homes: The Art & Spirit of Home Planning and Decor
Model: 087905963X
Author: Cindy Teipner Thiede, et al
Gibbs Smith Publishing
Website: www.gibbs-smith.com
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