11. Pictures & Details

Riversong Truss Wall Section

This is my Riversong Truss wall, which is built with full-dimension rough-sawn lumber – 2×4 inner load-bearing wall and 2×3 outer skeleton. The two walls are tied together by 1×4 wood gussets 24″ oc.

It incorporates traditional platform framing for the second floor deck, though on the inner wall to eliminate the usual thermal bridging and air sealing issues, and a traditional balloon-framed ceiling/roof supported by let-in 1×4 ledgers. This allows full insulation depth at the eaves along with ventilation space and lets the ceiling joists become the rafter ties for triangulation of the roof as well as the soffit.

This is a detail of my shallow, frost-protected foundation with radiant slab and Riversong Truss wall. I always include a passive radon vent and good capillary break between foundation and framing (no PT sill).

Riversong Truss Section

Riversong Truss Section

This is the full envelope cross-section, showing exposed beam at 1st floor ceiling (braced and pegged to exposed posts), gangplank in attic for access from “hayloft” door above insulation level, and south solar overhangs for summer shading and weather protection, as well as soffit and ridge vents for a fully vented attic and gutters for rainwater control.

This version uses a more conventional double wall with CDX double top plate ties, with the inner wall bearing the floor decks and the outer wall carrying the roof load directly to the foundation.

The upper ceiling is thermally broken with XPS because the roof had to match the adjacent existing house to which this addition is connected by a two-storey conditioned entryway. The addition is angled 15° to the existing identically-sized house so that each has the same view of Vermont’s iconic Camel’s Hump.


This is a simplified double-wall system that I designed so that it can easily be built by others in NY state (perhaps an Amish crew). I used 16″ I-joists for the ceiling, not that it was needed structurally, but to simplify insulation depth with a walkable gangplank above.

The floor is a tinted radiant-heated slab that doubles as solar thermal mass, which is common to many of my designs. The foundation was designed to be either a frost-protected shallow grade beam or an insulated frost-wall.

This is the second (primary) floor of a walkout lake-front cottage built on a stepped ThermoMass foundation, that comprises two 4″ thick concrete walls enclosing a 4″ slab of XPS (tied together by hi-tensile fiberglass rods so that it acts like a monolithic structure).

The resulting 12″ thick foundation wall is the perfect match for my 12″ thick double-framed walls. On the left is the wall where it bears on the foundation, and on the right is the section where it bears on the stepped framed wall below.

ThermoMass Foundation

This is a concrete-XPS-concrete wall system that uses a matrix of 12″ oc fiberglass ties to structurally connect the inner and outer wythes of concrete for a wall with a thermal and capillary break midline that doesn’t require protection from fire, insects, UV or physical damage.

Slab-edge details allow continuity of thermal barrier. With 4″ of midline XPS and two 4″ wythes of concrete, this 12″ thick wall is perfect for a 12″ double wall frame, and offers load bearing support to both inner and outer structure.

My Riversong Truss wall system using full-dimension rough-sawn 2×4 inner load-bearing wall with metal T-bracing and 2×3 exoskeleton on shallow, frost-protected foundation.

Completed House

First Riversong Truss House – 1998, Charlemont MA

Completed Superinsulated Farm House

KD 2×4 double wall stepped framing on 12″ thick ThermoMass foundation. Floor assembly bears on inner wall, roof trusses bear on outer, plywood-sheathed wall.

Nearly Complete Lake Cottage

N-S Cross-Section

N-S Cross-Section

This is a hybrid single-wall insulated garage/workshop with a second storey double-wall superinsulated apartment topped with a roof truss. The foundation is a frost wall with exterior insulation on the top 2′ and both slab edge and subslab insulation for a radiant concrete floor. The two stories have to be separated by a 1-hour fire barrier and pneumatically isolated.

The first storey walls are framed with KD 2×8, 24″ on center, to both contain R-26 of cellulose and to support the inset I-joist floor assembly and the upper load-bearing outer 2×4 walls (with inner 2×4 walls bearing on the floor deck or the thickened wall in the stairwell).

West Elevation

West Elevation

Upstairs Apartment Plan

Upstairs Apartment Plan

Below is a “tiny house” or urban cottage for two designed for infill behind an existing house, for low initial cost and minimal operating cost with maximum comfort.

494 SF House for Two

494 SF House for Two

South Elevation

South Elevation

West Elevation

West Elevation



Below is a 1,000 SF small house for two with office/guest bedroom that is also designed for passive solar and superinsulation as well as ease of construction. The cross-section is the 1-storey schematic near the top of this page.

Small House Floor Plan

Small House Floor Plan

Next is a rather large and long homestead complex with a 2-storey main family house, a connecting utility area and an in-law apartment. The initial design was by homeowner, and I elaborated it into a functional and buildable superinsulated passive solar home.

1st Floor Full

Family Homestead with In-Law Apartment

Full South Elevation

Full South Elevation

Main House - South Elevation

Main House – South Elevation

This is an in-line KD double-stud envelope, sheathed with plywood, and a site-built stick-framed truss roof, with all framing on the same 24″ centers from foundation to roof. The gangplank in the attic is for “hayloft” access above the 18″ insulation depth. The base is a frost-protected, shallow foundation sandwiched with 2″ XPS.

North-South Cross-Section

North-South Cross-Section

Historical Flashback

In 1993-94, I was the project organizer, design committee chair, and construction supervisor for a community volunteer affordable building project called Building Our Swords Into Plowshares, which designed and erected a super-insulated duplex, built in the style of Habitat for Humanity, for a local Community Land Trust and Housing Coop in Greenfield MA. Ironically (or perhaps not), by the time we finished it after a full year of planning and design and two years of volunteer construction, both the land trust and the housing coop were financially strapped and unable to take possession of the duplex, so we arranged to transfer title to the local affiliate of Habitat for Humanity (which later built another duplex on the extra lot that came with it.

This project was the origin of the Riversong Truss (or modified Larsen Truss) wall system which became my hallmark since that time as well as my primary contribution to the field of superinsulated construction. Here are some of the details:

Plowshares 1Plowshares 2Plowshares 3Plowshares 4This was a far more complex project, as an attached duplex – on full basement with different roof heights and staggered walls – than the homes I have designed before and since. A well-earned lesson was that a double or truss wall system works best with a simple geometry (which also reduces cost, materials, construction time and heat loss).

Plowshares 2File0026Open House

[For more on this project: Constructive Program – Building on Our Ideals.]


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If you need project consultation or design services, contact me directly at

HouseWright (at) Ponds-Edge (dot) net.


by Robert Riversong: may be reproduced only with author attribution for non-commercial purposes and a link to this page

7 Responses to 11. Pictures & Details

  1. Mitch Neher says:

    Dear Sir,
    As regards your Riversong truss, are the first floor inner walls raised first; then the second floor platform is laid, followed by the raising of the second floor inner walls and then . . . well . . . Exactly when are the outer, “balloon” walls raised and gusseted to the inner, “platform” walls, anyhow? And what about those ceiling joists for the rafters (the ones that form the overhang)? Are they set up and nailed the wall trusses before the rafters are raised? If the questions belabor the obvious, please accept my apology. But I’m trying to picture the work as it goes along?

    • Riversong says:

      One of the advantages of this system over other double wall techniques is that it is built just like a conventional platform frame, with first storey walls, then second floor deck, then second storey walls, then ceiling joists and rafters. Once the roof is sheathed and papered so that the building is “weathered-in”, then the outer half of the wall trusses (with gussets) are attached after pre-fabrication in a site-built jig.

      The overhanging ceiling joists receive a temporary (or permanent) 2x sub-fascia, which acts as a stop for the rafter tails, making rafter placement easy and safe. The rafters in this system require only a plumb cut at each end (and a soffit cut at the tail), but no birds-mouth at the bearing wall, since they are supported by a beveled ledger let in to the inside of the structural studs.

  2. R Miller says:

    I just wanted to thank you for the time you have, do and will put into this website and the forums you’re on. I’ve gained a large amount of information from your words. Thanks and I wish you all the best.

  3. Rick says:

    This may be the single best page on high performance building on the internet. Thank you Mr Riversong!

  4. none says:

    Yep. One of best sites ever on passive design

  5. Kirk Ellis says:

    In earthquake country, structural sheathing is required. I am thinking of sheathing the inner 2×4 wall with 1/2″ cdx and then using short 6″ 2×4 pieces to connect those inner wall studs through the cdx to 2x4s on the flat outside. Putting 6″ thick roxul running horizontal in that gap and 1 1/2″ vertical between those 2x4s on the flat, then house wrap and stucco or other siding. Possibly using scrap strips of roxul to create a rainscreen gap between the siding and the house wrap. Similar to a Larson truss except using the structural studs instead of a separate 2×2 inner chord.

    • Riversong says:

      There are so many problems with what you propose that it’s difficult to offer a complete critique in a short reply. I suggest you get some construction or design training or hire a qualified consultant to walk you through the process.

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