Insulation and Drywall

Insulation

Insulation completes the rough-in stage of the house. It and drywall mark the transition between focusing on the structure of the home to focusing on the details.

Spray foam in the ceiling

To ensure a tightly sealed home, we had foam sprayed into the places where ceiling joists could expose a gap to the exterior, e.g., the ends of ceiling joists that extrude outside and the center beam of the roof. Foam was also sprayed onto some of the foundation walls that protrude into the interior.

Insulation batts

Next the insulation batts went in. All of the batts are formaldehyde-free fiberglass. We insulated all of the interior walls with R-11 and R-13 for sound deadening (more on our soundproofing). This is enough insulation to stop some sound, but not enough for heat insulation. The external walls use R-21 insulation for better thermal control. Insulation was installed throughout the house, including under the floor in the crawlspace and the garage.

Drywall

Drywall starts the interior finishing stage. It covers up the bones of the house, and provides a blank canvas for the interior.

The drywall process is complex. The goal is to achieve flat, seamless surfaces for the walls and ceiling. The quality level of the drywall, from 0-5, specifies how flat and level it is. Level 3 is about the minimum you'd want inside a house, and level 4 is probably more normal for quality construction. Our house is getting level 5 drywall throughout, which allows us to avoid any texture on the wall. Instead, we have a smooth surface that will just be covered with paint. This increases light reflection, especially in windows up against the ceiling where the light may be coming in nearly parallel to the drywall surface. Wikipedia has more details about all the levels.

Getting this level of smoothness takes many steps:

1. 

   Floor markings indicating what's in the walls and ceilings

   Level the studs: The studs need to be level enough to avoid creating bows or bends in the drywall. In our case, at least one stud had to be removed and replaced because it was warped.

2. 

   Drywall, just hung.
   Notice the roughness of the corners and seams.

   Hang the sheetrock: Boards are cut and screwed in to the studs such that all of the walls and ceilings are covered by the sheetrock. Holes for lights, outlets, vents, and any other openings in the wall are cut at this stage. Since it is easy to lose items behind drywall, the installers marked everything out on the floor before any sheetrock went up.
   The sheetrock at this stage is pretty rough. Edges, especially corners, can be uneven. Screws are sunk a bit into the drywall, making small depressions. There are gaps between sheets and around cut-outs. It looks like a bunch of panels stuck on the walls. This makes the rooms feel a lot smaller than before.

3. 

   Tape and mud

   Seal the gaps: The next step is to seal up all the gaps and start evening the surface. This is done using mud, tape, and corner strips. Mud is put in-between the gaps in the sheetrock, and tape is embedded to provide some structural support. Particularly for inset corners, the tape helps to make a sharp right-angle. Mud is spread lightly over the screw holes to bring them up to level with the sheetrock. Corner strips are used for outset corners. These are a thin piece of metal at a right angle, with some tape over that. Putting these over outset corners and applying mud covers up the rough edges of the drywall, and provides a sharp, clean corner. At this point, the walls start to look more coherent, and the space opens up a bit.

4. 

   Corners and more mud

   More mud: Two more layers of mud are applied as-needed to level everything out, especially the corner strips and tape, which may have slight raised edges otherwise. The edges of openings, such as can lights, are covered and leveled with mud. Each layer of mud needs to dry, so the house is warmed up and let sit for a day or two.

5. 

   The smoothing layers

   Smoothing coats: The final step is to add two full coats of material to smooth and level the dry wall. This was done using Smooth-Wall, a spray-on self-leveling coating that brings the drywall up to level 5. It serves as a polyvinyl acetate (PVA), which provides a basic primer coat, and makes everything a uniform material. These coats are just a primer and leveler, so the walls aren't meant to look perfect. There is a slight variation in color due to the drywall, and a slight texture on the walls. Both of these will be cleaned up with a couple layers of paint.

At this point, the walls and ceilings become a single smooth, level piece. The rooms are well-defined, and the surface looks very close to its final state. The perspective of the rooms change a bit; the ceiling height on the main level is more apparent, as is the shape of the soffits, columns, and doorways. The walls are now ready for paint.