Wednesday, June 3, 2020

Cabin #6 Phase 1 complete

PHASE 1 - Log Work

The log work for the cabin walls is complete! Eleven rounds of logs for an 8 foot cabin ceiling height. Window and door openings rough framed. Loft floor and opening for stairs roughed in.

A temporary floor has been put in place to make a work surface for the next phase.

Just how many phases are there to building this hand hewed log cabin you ask? Lets see...

Phase 1 - The log work, building the walls. - Getting the logs, racking, pealing, hewing, notching.

Phase 2 - The roof framing.  - Top plates, ridge beam, rafters and porch framing.

Phase 3 - Cabin site work. - Driveway, leveling, gravel, concrete slab, electric and gas service lines.

Phase 4 - Move Cabin to site. - Dis-assembly, transport, finish coatings, re-assemble, stairs, floor and
                loft railing.
Phase 5 - Roof - finish roof boards, install, insulation and roof tin.

Phase 6 - Electrical and gas lines inside cabin. - Wall and ceiling outlets.

Phase 7 - Trim out cabin. - Install door, windows, floor insulation and finish floor. Gas fireplace.

Phase 8 - Chink logs. - Inside and outside after one year of log drying time.

So on and off for the next year I will be posting my work and progress on Phases 2 thru 8. Let's get started.

PHASE 2 - The Roof Framing

Building with "green" timber requires some consideration for the fact that wood shrinks as it dries out. Wood has a grain and the wood shrinks along the width and thickness. For round logs we look at the diameter. For example, in the green (wet) state the log may be 12" in diameter. After the log has air dried (3 to 6 months) it will shrink. If the new dry diameter is now  11 and 3/4" that's 1/4" per foot shrinkage. You can calculate that an 8 foot tall stack of "green" cabin wall logs is going to shrink down 2" when they are dry. It must be noted that wood does not shrink lengthwise (an 8 foot long log will forever be 8 foot long wet or dry).  Knowing all this, allowances must be made for this shrinkage or all kinds of nasty problems will visit your work (window and door frames with vertical pieces) in the future. Crushed windows and doors that will not open!

The roof framing (in blue) for this cabin will be sitting on a 10 foot tall stack of green logs (in yellow) that will be shrinking down to somewhere around 9' - 9" when dry in a year or so. The roof frame is being made from dry 6x6 timbers so there will be little or no shrinkage. But what the roof frame sits on WILL SHRINK! Now this would not be a problem if there was no porch because the tail end of the roof rafters (in red) would just end up 3" closer to the ground when the cabin logs dried. However there will be a porch (in orange) on Cabin #6 and it will have to be adjustable to allow for the 3" movement of the roof rafter tails downward. One solution might be to wait and build the porch after the cabin has dried. Something to consider, but either way a method of adjustment will be needed. Either to lower or raise the porch framing to meet the tail ends (in red) of the roof rafters. I am going to build the porch now and adjust it downward as the cabin log wall shrink.

The sketch above shows the framing design I have chosen. Ten  6x6 rafters (four shown in red 12' - 6" long in the front and 14' - 3" long in the back) spaced 48" O.C. They will sit on a 16' long 6x6 top plate in front over the door and 20' - 8" long 6x6 top plate on the back side. The back top plate is longer to provide a 30" overhang on the rake ends of the cabin. This will help protect the bottom logs from the weather.

The height adjustable porch will also be built from dried 6 x 6's. It will be fastened to the cabin wall with screws using a slotted 2 x 6. The screws will go through the slots into the cabin logs. As the cabin wall logs shrink the slots will allow the screws to slide down. The front posts holding up the 6 x  6 porch beam will have adjuster screws at the bottoms. As the wall shrinks the screws will be adjusted to lower the top beam.  

One of my concerns is the span I am making with the 6 x 6 rafters on the back side (about 11 feet from ridge to top plate) expecting them to support the roof load. HEY, it just dawned on me that the span will not be 16 feet as I was thinking. This is good news. The span of the ridge will be another issue. So I will get some test data to work with. Here goes...

So I took an 18 foot long 6 x 6 and spaced it at 16 feet with 2 x 4's over another 6 x 6. Then I marked the center at 8 feet. I stretched a line from end to end.

I placed a screw at the 16 foot midpoint on the bottom side of the string.

Then I loaded'er up. At 700 pounds the gap was 1". At 878 pounds as shown here the gap was 1 and 1/2 ". If I get some time on my hands I could set this up and test for a span of just 11 feet.

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