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Excerpt from The EcoNest Home: Matrix Framework

The following excerpt is an example of a technical section of "The EcoNest Home."

Matrix Framework

The matrix is the framework that creates the structure for the LSC wall system. The EcoNest matrix system uses modified Larsen Trusses[1], each made with a pair of 2x4s joined with plywood gussets. When used in conjunction with a load bearing timber frame, trusses may be placed at 32” intervals. When used as the load bearing wall the Larsen Trusses must be spaced at a maximum of 24” intervals.

The matrix has the following features:

·        Creates straight and stable deep wall trusses saving on wood use.

·        Reduces infiltration and thermal bridging.

·        Provides for uninterrupted wall insulation of light  straw clay

·        Streamlines door and window installation in thick walls

·        Facilitates the attachment of temporary formwork

·        Supports horizontal stabilizing bars for settlement reduction

·        Defines inside and outside corners

·        Creates wall cavities that are easily loaded and tamped.

·        Provides for efficient electrical installation

·        Provides support for cabinetry and shelving attachment

·        Is readily accepted by framers, electricians and plumbers who already have familiarity with conventional framing

Larsen Truss Fabrication

Efficient, uniform, professional results can be achieved even by novice carpenters, by using the following tried and true step-by-step procedure.

Straight Larsen Truss Construction:

Straight Larsen trusses are the primary matrix component. To achieve consistency and efficiency we first build a jig.

Constructing standard Larsen Truss jig:

1.      1. Create the base screwing two layers of ¾” plywood together measuring 12” wide x height of desired truss. We typically make the jigs 96” tall.

2.      2. To this base attach a spine consisting of 2-layers of ¾” x 5” plywood (or other stable sheetgoods) down the center of the base for its entire length. This serves as a spacer for the two studs.

3.      3. Screw gusset stops to the spine, per diagram below for accurate placement of plywood gussets. Note the bottom gusset stop is placed so that the bottom of the first gusset is located 1” from the bottom of the studs. This allows space for electrical wiring to pass under this gusset. Electricians love this thoughtful detail which eliminates the work of drilling passageways for wiring.

4.      4. Screw a plywood foot to the bottom end of the jig per diagram below for accurate bottom alignment of studs.

Illustration 8-2  Straight Larsen Truss Jig

Constructing Straight Larsen Trusses:

1.      1. Precut all 2x4 studs to length and 3/8”  plywood gussets to a size of 3”tall x 11-7/8” wide

2.      2. Set Larsen jig on work table to a comfortable working height typically 32-36” above floor/ground

3.      3. For maximum efficiency a pneumatic staple gun is used for fastening the gussets to studs.

4.      4. Load jig with two studs aligned with bottom foot.

5.      5. Fasten the gussets with 3 staples/fasteners per connection.

6.      6. Label the top gusset to ensure that Larsen trusses are installed right side up.

Student fabricating a Larsen truss in the jig.

Illustration 8-3 Straight Larsen Truss



[1] The Larsen truss was created by John Larsen, a builder in Edmonton Alberta in 1981. It uses small dimension framing members joined with plywood gussets to build thick insulated walls for the purpose of energy efficiency.