Usonia House
AN OFF GRID HOMESTEAD, DESIGNED TO GROW

The Shell Loft

Plan No. UA-204 · Version 1 · Construction set issued
Inquire for Pricing or a Custom Variant
The Shell Loft from the drive, a dark steel arch with a covered porch along one side.
The Shell Loft from the drive. Dark metal over the arch, deep green on the end wall, and the covered porch running along one side.

THE SHELL LOFT is a spec home built on the oldest Usonian idea there is, that a small house drawn carefully is not a compromise. One 24 foot arch does the structure, the roof and the weather skin in a single move. There is no truss package to buy and no gable to frame. What that saves goes straight into the things you actually live with: a heated floor, a wall of glass, and a covered patio you will use from April to November.

Why the Shell Loft.

The name arrived after the drawings did, from looking at what the building actually does. Outside it is rigid, pointed and self contained, a hard back turned to the weather. Inside it is soft, warm and smooth, all curve and wood and a heated floor underfoot. That is exactly the relationship a shell has with the thing it protects. And a shell is never only armour. In nature it is a structure other life grows on and into, part of a system rather than a wall against one. This house is meant to work the same way, sheltering a family and giving everything that comes after it, the porch, the pergola, the garden, the next building, something to attach to.

The Shell.

The shell is a 24 foot steel arch, 18 feet 8 inches to the ridge, framed in ribs at 24 inches on centre and skinned in 26 gauge steel panel. It arrives as a kit and goes up in days rather than weeks. The curve is not a style decision. It is the least expensive honest way to enclose that much volume, and it happens to be beautiful.

Every Square Foot Working.

768 square feet on the main floor, with a 270 square foot loft bedroom tucked up under the curve. Bath, laundry, pantry and mechanical stack tight against one end, which frees the opposite end to open completely to glass and the covered patio beyond it. Nothing in the plan is left over.

Heat and Power Off the Grid.

In floor radiant heat runs off a wood boiler, so the fuel can come off your own land. The slab is insulated and poured with the tubing in it, which is the quietest and most even heat there is. Every appliance is electric, and the service is laid out to accept solar whenever you are ready for it.

Built to Be Added To.

The covered porch and the pergola are not options on a list. They are the first two attachments, and the structure is drawn to keep taking them, out along the arch and up. This is meant to be the first building on a homestead, not the last one.

Where the First One Is Going.

Usonia House is building the first Shell Loft as the Jimmer Loft, in central Wisconsin. Same plan, same arch, real dirt. Everything that build teaches us comes back into version two.

What the Design Service Includes.

Complete construction drawing set; foundation and slab plan; main floor and loft plans; roof plan; exterior elevations; building and wall sections; assembly isometrics; exterior and interior renderings; site adaptation for your lot and jurisdiction.

Specifications.

TypeSpec home, off grid homestead dwelling
Structure24 ft steel arch shell, ribs at 24 in. on centre
Main floor768 sq. ft.
Loft270 sq. ft.
Total conditionedApprox. 1,038 sq. ft.
Rooms1 bedroom in the loft, 1 bath, kitchen, pantry, laundry, mechanical
Height18 ft. 8 in. to the ridge
FoundationInsulated heated slab on grade
HeatingIn floor radiant from a wood boiler
PowerAll electric appliances, solar ready
AttachmentsCovered porch and pergola, drawn to expand
StatusVersion 1, construction set issued
PrototypeFirst build in central Wisconsin as the Jimmer Loft

Figures are for version 1 as drawn. Every commission is adapted to your lot, your climate zone and your jurisdiction. Snow load, base anchoring and the insulation assembly are confirmed by a licensed engineer for your site before construction.

THE DRAWINGS
Shell studies. Curved side profile, horizontal striping, and the rigid outside against the warm interior gradient.
Where it started. Shell studies from the sketchbook, the curved profile and horizontal striping on one page, and the rigid outside against the warm interior gradient on the other.
Main floor plan of the Shell Loft.
Main floor. Services against one end, the whole opposite wall in glass, and the covered patio past it.
Cross section through the arch, showing span, ridge height and the loft deck.
Cross section. Twenty four feet of span, eighteen feet eight to the ridge, and the loft deck set where the curve still gives headroom.
Hand drawn 24 foot arch profile with clear widths at two foot intervals.
The arch profile, drawn by hand. Clear width at every two feet of height, which is what decides where the loft can go.
Front elevation of the Shell Loft.
Front elevation. Two loft windows in the curve above the porch roof, three openings below it.
Rear elevation of the Shell Loft.
Rear elevation. The glass end, with the pergola line running off to the side.
HOW IT GOES TOGETHER

This is the part that makes the price work. The shell is a manufactured steel arch kit, so the structure, the roof and the weather skin arrive as one system and go up in days. Everything we design happens inside it and off the end of it.

Exploded assembly diagram of the Shell Loft shell showing base plates, ribs, ridge beam, insulation layers and steel roof panels.
The shell, taken apart. Base plates and pre-welded stublets, steel ribs at 24 inches on centre, the ridge beam, two layers of insulation, then 26 gauge PBR panels. Seven parts and no truss package.
Cutaway isometric of the Shell Loft with the covered patio and pergola.
Cut through the length. The loft sits over the service end, the living volume runs the full height of the arch, and the patio and pergola attach at the glass end. Every future addition works the same way.
INSIDE THE ARCH
Living room of the Shell Loft looking out to the covered patio.
Looking out. The end wall is glass from the slab to the loft line, with clerestory windows above it in the curve.
Interior of the Shell Loft looking back toward the loft and stair.
Looking back. The service end carries the loft above it, and the arch keeps going overhead.
The Shell Loft glass end under the pergola.
The glass end under the pergola. The patio is the room the house borrows in summer.
The Shell Loft from the side, showing the full length of the arch and the garden.
From the side. The arch runs the full length, and the garden runs right up to it.

Obtainable

One arch does the structure, the roof and the weather skin at once. That is why the money can go into the heated slab and the wall of glass instead of into framing you never see again.

Livable

A warm floor under bare feet, a bedroom in the curve of the roof, and a covered patio wide enough to eat on. Small does not have to feel small.

Unforgettable

Eighteen feet of clear volume over a room you can cross in ten steps. Nobody walks in and forgets it.

Ask About the Shell Loft

See how we work on the Working With Us page, or head back to the Catalog of Designs.

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