Building Terms You Need to Know

These definitions will help you understand the cabin construction instructions better. They are specifically tailored to describe how these various parts items apply to this cabin design.

Birdsmouth: An angled notch near the bottom end of a rafter that nestles over the top edge of the wall.

Eaves: The bottom edge of the roof where rainwater runs off.

Extruded polystyrene foam: A smooth-textured, rigid foam insulation that’s typically blue or pink in colour. Unlike beady white expanded polystyrene foam, extruded poly resist the passage of airborne water vapour that can cause condensation during cold weather. Extruded polystyrene foam is used to insulate the roof and floor of this cabin.

Fascia: The vertical edges of the roof where they exist at the eaves and the gable ends. The eaves on this cabin are made with 2×10 lumber.

Feet: Abbreviated as a ‘ sign after a number. This cabin is 16’ wide x 25’ long.

Floor beams: Thick pieces of wood that support floor joists. In this cabin design the floor beams form the outer perimeter of the main floor and verandah floor.

Floor joist: Those wide boards installed on edge to support wood that forms the floor. To keep things simple, each floor joist is one length of 2×12 that spans the entire cabin width.

Footing: The area at the bottom of a foundation that supports the weight of the building on top. Footings are typically larger in size than the foundations on top of them, but the large size of the masonry piers used for this design probably require no special footing. Always check with local building authorities to make sure this detail is suitable for your soil conditions.

Gable wall: The triangular portion of wall that exists underneath a sloped roof. There’s a gable wall above the door in this cabin design, and another gable on the wall opposite this one.

Inches: Abbreviated as a “ sign after a number. The rough window frame openings on this cabin are 36” wide.

Lintel: A sandwich of lumber that strengthens the framework above window and door openings. Each lintel for this cabin are made of two 2x6s, with a spacer between them to form the 5 1/2” overall lintel thickness required.

Loft beams: Not typically found in conventional houses, loft beams form  the visible support structure that holds up the loft floor. In the case of this cabin, each loft beam measures 6×8 in cross section.

OSB: These letters stand for oriented strand board, which is a fancy name for waferboard. The only place you’ll find OSB in our cabin was on top of the floor and roof insulation. You could use OSB instead of plywood for the subfloor and wall sheathing, but plywood holds nails better.

Pressure treated wood: Construction lumber and plywood that’s been chemically treated to resist rot. Previous pressure treating chemicals included arsenic, but modern pressure treated wood is based on copper and is considered safe. Pressure treated wood is highly corrosive to metal, so only use stainless steel or hot-dipped galvanized fasteners to join it.

Rafter: The angled part of a roof frame that creates a sloped framework for supporting roof boards. In the case of this cabin, the rafters are 2x6s.

Roof sheathing: A layer of wood fastened to the top edge of the rafters to form the roof surface. This cabin design calls for 2×8 lumber as roof sheathing. This is thicker than usual, but offers several advantages.

Rough window and door frames: These oversized openings are 1” to 1 1/2” longer and wider than the windows and door that will fit in them. The extra space allows for leveling and adjustment during installation and is filled with spray foam to seal out air movement.

Ridge board: The 2×10 lumber that sits between the top ends of the rafters, forming the top point of the roof. In this cabin the ridge is made of two boards that join underneath one pair of rafters.

Skylight step flashing: L-shaped pieces of factory-finished sheet metal that get installed as shingles go down around a skylight. Flashing kits vary with different manufacturers, and are purchased to match the particular skylight you’re installing.

Spray foam: Like whipped cream from a can, except that it hardens. Spray foam is an excellent air sealant and insulation and comes in two forms. Hand-held cans deliver foam in small quantities for filling gaps around the windows and door, and larger spray foam kits are used fill wall cavities.

Structural screw: A specific type of wood screw with a threaded shank that’s large than a deck screw and a larger diameter head. Structural screws are relatively new, but very useful.

Subfloor: A layer of wood that rests on top of floor joists and remains hidden from view under the finished floor. The subfloor in this design is 3/4”-thick pressure treated plywood. Although it will remain sheltered from rain underneath cabin, pressure treated wood eliminates any risk from moisture migrating up from the ground.

Wall plates: These are the horizontal 2x6s that form the top and bottom of the wall frames. As is standard with wall framing, two 2x6s form the top plates, and one 2×6 forms the bottom.

Wall sheathing: A layer of wood fastened to the outside face of wall framing. In this case we used 5/8” sheathing-grade plywood to provide solid support for the staples holding the cedar shingles on.

Wall studs: Vertical 2x6s that form the main part of the walls. Full-size studs in this cabin measure 92 1/2” long, and combine with the top and bottom plates to form an overall wall height of 96”. Short studs define that area underneath and over top of windows and doors.