Post date: Oct 12, 2014 2:01:43 PM
Openings
The doors and windows connect the outer and inner walls. I’ll work on this detail tomorrow. Basically you build a box of OSB between the inner and outer stud walls, then add blocking to connect the window installation flanges and seal these against air infiltration.
If the door is set midway between the walls, then you must be certain that it can open without binding - meaning a block on the hinge side (at least).
Actually, all the hard work was published in Fine Homebuilding December 2012 as Windows in Double Stud Walls: In-Betweenies. The principal difference between my house and the drawing in Fine Homebuilding is that I will have stucco outside finish, rather than siding.
Stucco
When I looked up stucco finishes I found out that three-coat stucco will be 7/8” thick! I also found a good video that details the entire stucco process and a slide show that shows good and bad practices and the resulting problems - though it is laced with technical terms.
Lintels
Since traditional houses were made of adobe, they have a feature that is common to masonry houses - a lintel over the doors and windows. This lintel is a beam that supports the bricks above the opening, since there is no wall below to support them. The lintels are necessary, whether they are visible or not.
I kind of like to make necessary things visible, for visual consistency. There are a few hitches in this case:
Wood that is exposed to sun and rain tends to deteriorate. That nice weathered appearance means that the wood is losing some of its original, useful properties. That is why we paint wood siding and wooden windows, decade after decade, and they still rot. A lot of work for nothing. A nicely painted lintel might as well be made of steel or plastic or concrete!
Wood shrinks and expands with changes in moisture and can twist and warp as it dries. That makes it hard to seal out air, which is greatest source of heat loss in buildings. Not sure yet if we can compensate for this.
My architect’s house has exposed lintels. I’ll have to discuss this topic with him. The jury is still out.
Parapets
In the detailed drawings I had made for my homework I extended the outer stud wall straight up past the edge of the roof to form a parapet wall. The architect prefers something a bit fancier: a separate wall made to curve inward at the top. One of the houses here in Valverde Commons is built this way and it does look nice, if subtly.
The trade-off is construction complexity. The outer wall would be capped with a plate (2x4 across the tops of the studs). This is normal technique. The roof sheathing would lap over this plate. If the roof slopes, then the plate will have to slope, too. (If the roof were attached to a ledger board fastened to the inside of the outer wall studs, making the ledger slope would be very easy.)
Then the parapet wall is constructed somewhat like a boat, with ribs sawn from 2x10 in a curve, covered with 1/4" plywood that will bend to match the curve, these ribs are fastened to 2x10 sill, and mounted to the roof platform. Again, if the roof slopes, then the ribs will need to be of different sizes to make the top of the parapet horizontal. Not a trick for a boat builder, but not common for a framing carpenter.
Then, too, we must consider the construction of a continuous insulation and air barrier between the wall and the roof. The insulation will be interrupted by the 2x10 sill and ribs of the now-curved parapet. If this wall is air-sealed under the sill, and has good flashing at the top to keep out rain, how does the moisture that is trapped within the parapet escape? Moisture trapped within walls will generate mold in the insulation and rot the structure.
And the rigid insulation board that sheathes the exterior of the walls will not bend over the parapet, and making that transition seems hard to me.
... I await instruction from my architect.