A philosophy of outbuildings: first worked example

In late 2019 I wrote a post called A Philosophy of Outbuildings, attempting to capture the lessons from 40 years of making and using utility structures ranging from outhouses to the awesome barn my parents built that we’ve been making cider in. One of the fundamental principles was that small outbuildings should be portable, so they can be moved to a more useful spot (or to get them out of the way of some other project). Since then I’ve built a couple examples of this, and thought I’d capture the results in case they are of any use to the greater internet community.

The purpose of the first was simple: to shelter a small diesel tractor that came to us from Five Islands. The tractor gets used for bushhogging, harvesting firewood, and moving mulch/gravel around the yard, and sits idle through the winter; it is approximately as old as I am and would deteriorate rapidly if left in the sun/rain, so it needed some protection. My model was the very successful open-front pole-barn that my father and grandfather built in the early 1980s that we used to keep the cider operation out of the rain in Cider Year Five, but I didn’t have firm plans for the land where I built it, so I wanted to be able to move the shed later if I needed to.

Expanding slightly on the dimensions of a single bay of that pole barn, I settled on a footprint 10′ wide and 14′ long, with about four feet of overhang on the open west end. The building would be floorless, open on one end, and sit on two 16′ 6×6 PT skids with chamfered ends, blocked up level on pads of coarse crushed stone. The closed back end of the building is built on a 4×4 cross-beam set on top of the skids and lagged down. The walls are framed with rough-sawed 2x4s from Five Islands, and diagonally sheathed with Hammond Lumber shiplap. I used a chevron pattern for the sheathing on the side walls, in hopes of providing the long 6×6 skids some structural support to prevent sagging. I did the project in a hurry with the winter of 2019-2020 closing in, so I don’t have great construction pictures; here’s the walls framed up at the end of the first long day:

Rafters were cut from 2x6x8′ rough-sawn, with something like a 6-pitch. Collars were likewise 2×6; 2×4 would do but I had thoughts of hanging a boat from them. The roof is strapped with 1x and dried in with dark green five-rib steel sheet. The overhang on the open end is supported by 4×4 diagonal braces, and the roof structure is tied together by a 20′ PT 2×8 ridgebeam. It got dark inside, so I used a large piece of salvaged plexiglass on the closed gable end up high to let in a bit of light. Here’s the ‘finished’ shed, with happy tractor inside:

The most obvious miss was that I should have extended the diagonal siding to tie in with the 4×4 brace poles that hold up the overhang; this was not obvious because I built the wall sections before fully thinking through the overhangs, but it would have made the structure stouter and also helped to keep weather out. The gable end of the overhang could also be sheathed to keep rain/leaves out, at the cost of some light.

At least until I further perfect the art of portable buildings, this was as large as I was prepared to go on a floorless open structure that I would hope to move with come-a-longs, pulleys, and small tractors/vehicles. My biggest concern was wracking/distortion, both from natural ground settling and also during any future move. To prevent in-plane wracking of the open end I added a pair of a-frame type diagonal braces that can be seen in the photo above, to tie the side walls and end collar tie to the ridgebeam; not sure how well they will work, but they look cool. There is also some small chance of a tornado or derecho-type event picking it up and blowing it over; it’s surrounded by mature trees so it feels fairly protected, but at some point when I put the last few boards on the gable end I should probably also cable it down to the bases of a couple trees for extra security.

In order to skid the building I would plan to temporarily add structure to tie together the skids at the open end, and also temporary internal cross-bracing or cabling to keep the footprint square. With just 5″ of undercarriage clearance, it would be interesting to see what it can skid over; I have a feeling that I should have done something to elevate the bottom of the back wall more – e.g. bandsaw an arch into the underside of a 4×8.

From an ecological perspective, other than the steel roofing (approximately 2lb/CO2 per square foot as calculated in the post linked above) and a handful of pieces of PT trucked up from the Southeast, the building is made from untreated locally milled lumber. The overhangs are decent, the skids sit on crushed stone and/or blocks, and the site is reasonably airy for being in the woods, so I am optimistic it will hold up well over time.

The next building in the series is smaller but more exotic – a kinematically-correct portable solar chicken coop.