Mother's $10-per-Square-Foot (or Less!) Earth-sheltered House: Part II

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REAR ROOF

The northern section of roof has a 1-in-3 pitch, and all the rafters have the same bird's-mouth angles. Of course, the inner ends of three of them-the east, north, and west—are square—cut at an 18-1/2° angle, but the remainder intersect cross rafters in the same fashion as did those on the front roof. The first beam to install is the north-south peak rafter, which needs to be almost 23 Feet long. By this stage of construction, though, we'd run out of salvaged 2 X 10 X 24' boards, so we built the beam in two sections . . . and supported the adjoining ends on a post in the 2 X 6 plumbing wall between the bathroom and the bedroom closets. It would be preferable to run a continuous rafter here. Nonetheless, the support post should be retained, since this one rafter carries considerable load distributed from the other rafters that join it by way of the two cross rafters.

The remaining beams were cut and installed in much the same fashion as were those in the southwest rafter section . . . with a single cross rafter installed first, the jack rafters set in place (without a ledger, which is not needed on such a steep pitch) and end-nailed, and then the remaining layers of cross rafter backed against the first. There was even some duplication of cross rafter intersection cuts, since the angle of each northeast rafter matches that of one on the northwest.

Once the main rafters were up, we installed the bridging, leaving a 2" fire clearance where the chimney would penetrate the roof. And before sheathing the back roof section, we went ahead and laid up the chimney block (16" X 21" concrete units with 8" tile liners), so that the woodstove flue could be flashed properly when we installed the roofing.

The clerestory formed by the junction of the 1-in-3 rear roof pitch with the 1-in-12 front allows plenty of daylight to reach the bedrooms and bathroom. But to protect against summertime overheating, we decided to add an overhang (or eyelid, as we've anthropomorphically dubbed it). This projection consists of 2 X 10's angling out from the east and west rafters to form a point overhanging the center post.

Sheathing and sealing the rear roof went much the same as did that job on the front, except that—because of the steeper pitch—we had to maintain only a 12" overlap on the roll roofing. Still, we used plastic roofing cement liberally under the joints.

The partitions between the bathroom and the two bedrooms were fitted against the underside of the rafters, and each stud had to be cut to length and forced into place against its top plate to push that board up against the rafters. Because the top plates had to both bend and twist, it was important that the studs be cut to the right lengths and angles to insure a solid fit. This bit of framing turned out to be the trickiest—or at least most frustrating —part of the entire construction. It could have been made much simpler by running all interior walls on a radius of the circle . . . but unfortunately, the resulting rooms wouldn't work well with conventional rectilinear fixtures, such as a bathtub, washer-dryer, and so on.

As you can see, "drying in" this building required some creative construction techniques . . . but the resultant savings in materials were probably the essence of the building's low cost. In the next installment of this series we'll be able to detail the waterproofing and insulation measures, and move right along to some of the elegant finishing touches that you've seen in the pictures in this and the last issue of MOTHER. Be sure to be on hand for Part III . . . when you'll find out about our experimental waterproofing techniques.

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