Quick Definition

Exterior walls give shape to a home, provide structural support and protect the home from outside elements. Exterior walls are an essential factor in insulating the home and keeping out moisture, mold and more.

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In Depth

Typically, exterior walls have one face to outside the home (exterior elements) and one face inside the home (conditioned space). Not all exterior walls are load bearing, but in most cases they will serve some structural function like supporting the roof.

Exterior walls come in different types (like wood, SIPs [Structural Insulated Panels] and modular) and are assembled using various construction methods:

Wooden Stud – This exterior wall type is probably the most commonly used wall system and can be constructed on site or in a factory (i.e. modular). This wall type is comprised of several components:

  • A single 2x sole plateSole plate (also sill or bottom plate) is the horizontal 2x material at the bottom of a wall system that is fastened to the foundation.A sole plate holds the vertical studs in alignment and attaches them to the foundation. is attached to the sub-floor or foundation to which wooden studs are attached by toe-nailingAn angled nailing method used to join two pieces of lumber that meet perpendicularly to each other.
  •  Wooden 2x studs, attached to the sole plate are spaced 16” on center (standard framing), or 24” on center (advanced framing).
  • On top of the studs a double or single 2x top plateHorizontal 2x material at the top of a wall system that is fastened to the foundation. It holds the vertical studs in alignment and creates space for drop ceiling members or second floor joists to rest. ties the studs together
  • The exterior side of the wall typically is a multilayered system comprising of:
    1. A layer of either plywood or OSBOriented Strand Board is an engineered wood product formed by layering strands (flakes) of wood in specific orientations. Has a rough and variegated surface with the individual strips (2.5 x 15 cm / 1 x 6 inch) lying unevenly across each other. which acts as bracing and helps resist moisture moving into the house
    2. A layer of House WrapA thin membrane applied to the exterior sheathing of a home and acts as a moisture barrier, keeping exterior moisture out of the home and allowing moisture inside the home to escape. House wrap is installed before siding. which acts a protective moisture barrier to the house
    3. A layer of exterior finish material which can be a wide range of materials like wood, cementitious fiberboard, vinyl sidingVinyl – Polyvinyl Chloride, also known as PVC, is a man-made plastic. Vinyl siding is widely used because of its cheap cost, ease of installation, and low maintenance. Dioxins, plasticizers and known carcinogens are found in vinyl siding and, for this reason, Make It Right does not recommend this material., metal siding, stucco, etc.
  • The cavity of an exterior wooden stud wall is typically insulated with batt insulationStrips of insulation, usually fiberglass, that fit between studs or other framing., blown inAn insulation product composed of loose fibers or fiber pellets that are blown into wall cavities or attics using special pneumatic equipment., or spray foam insulation.
  • The interior side of the wall typically is sheathed with gypsum boardA type of drywall made from a non-combustible gypsum core, held in place by a paper backing., but it also can be sheathed with plywood, or OSB before the layer of gypsum is applied.

Metal Stud – This exterior wall type uses an extruded steel channel shaped stud in the place of wooden studs. The main difference between wooden stud walls and steel stud walls, other than the material, is the Sole PlateSole plate (also sill or bottom plate) is the horizontal 2x material at the bottom of a wall system that is fastened to the foundation.A sole plate holds the vertical studs in alignment and attaches them to the foundation. and Top PlateHorizontal 2x material at the top of a wall system that is fastened to the foundation. It holds the vertical studs in alignment and creates space for drop ceiling members or second floor joists to rest. connections which are both metal channels and use Metal Self Tapping ScrewsScrews with special tips that allow them to be screwed directly into metal without the need for pre-drilling.. The other components that make up the wall assembly are the same as wooden stud walls.

SIPs are prefabricated wall panel systems. SIPs are usually constructed by sandwiching EPS foam between sheets of plywood or oriented strand board (OSB). This exterior wall type is comprised of several components:

  • A double 2x sole plate is attached to the foundation or slab to which the SIP panel will be glued and nailed
  • 2x splines are installed in one side of the panel to create a male connection for the corresponding panel’s female pocket connection that allows the panels to be glued and nailed together to form a continuous wall system
  • A 2x top plate is installed at the top of the panel that the roof panel will tie into or the second floor subfloor will tie into (see detail).
  • The exterior side of the panel is either OSB or plywood
  • The interior cavity of the wall panel is EPS
  • The interior side of the panel is OSB or plywood to which gypsum board is attached

Metal SIP – This type of Structurally Insulated Panels (SIPs) has metal skin on both the exterior and interior faces of the panel with an EPS foam core. Instead of using a 2x sole plate and top plate, a metal track is used to connect the panels to the subfloor or foundation and the top of the panel is also capped with a metal track.

Our Application

Make It Right has used all of the exterior wall types above. In New Orleans, we currently are building all our homes with the OSB SIP wall type. Our standard OSB SIP wall widths are 4.5” and are R-17. In some cases, we use 6.5” wall widths, which are R-25.

If you would like to read more about R-Values see our Library page.

Lessons Learned

On our first homes in New Orleans, Make It Right used standard wooden stud exterior walls and advanced framing construction. We glued and nailed the exterior sheathing and used spray foam insulation in the interior wall cavity. We tested these walls for impact resistance and they performed much better than standard walls – an essential factor in area where winds reach 130 MPH.

Today we use OSB SIP exterior walls on all our homes. The SIP walls are delivered to our construction site in pre-fabricated panels with rough openings for doors and windows already cut out. OSB SIP walls are easy and fast to construct, well-insulated and stronger than standard wooden stud construction. The panels are lifted into place by a crane and assembled on the floor foundations by the site crew. Using this method, we reduced the time needed to construct the exterior of the home and dry-inThe stage of construction during which the roof, windows and doors are installed and all leaks are fixed. At this stage, subcontractors can begin interior finishing (floors, countertops, paint, etc)., which makes the home more affordable.