Welcome to ProTradeCraft’s Weatherization Nation. A show about building smart, from the start.
In this first season, we’ll follow MARK IV Builders as they construct a substantial addition to this 75-year old neo-federal house in Washington, DC. Washington is in climate zone 4, which is categorized as mixed humid and cold, so this climate zone can go either way and it’s prone to water problems.
Sketch Desk: addition design considerations
The superintendent for the project is Ray Williams, a specialist in air sealing strategies for remodeling old homes.
Ray: “Today we’re in the Greater Washington DC area starting a project on a brick exterior house with slate shingles up top.
We took down a one-story addition, we’re going to put up a two-story addition that’ll consist of a kitchen and some living space, master bedroom and en suite upstairs, we’re going to go back with Hardi Plank siding, and we should be adding just under 1,000 square feet."
The old addition was kind of a one-story addition with a two-story light scoop. It brought in tons of light and opened the living space, but there were some water problems due to—maybe more enthusiasm than science-based construction know-how.
One of the most basic scientific principles has to do with gravity. Water flows downhill, so sloping the ground toward the house causes problems at the very beginning.
Other problems began at the roof...
RAY: "There was a spot where they had little wings off the chimney, created a little wing-wall area. It went back into this wall over here.
And instead of putting step flashing like you see up by the chimney, they just rolled the shingles up. They tried to create a tw-inch dam with the shingles rolled up."
So that was doomed to fail, but there were several things. If you looked at these outside corners, nothing but water damage and rot. The OSB plywood —you could just take it with your hands and peel it off like cardboard."
This shouldn’t come as a surprise, because water is a professional. If you go to it’s LinkedIn page, you’ll see that its job description literally is to turn houses to mush.
git ‘er done: An overview of the whole process, every step of the way
The project allows us to explore tying in new construction to old, which is where a lot of problems can creep in.
- The second episode will look at demolition, digging, and foundation drainage solutions.
- Episode three will focus on a warm and dry crawlspace using Thermax foam insulation board, thick plastic, and smart details. The floor and walls are covered with plastic and then the walls are insulated with Thermax polyiso foam boards and Great Stuff.
- Episodes four and five will cover best practices in Tyvek installation, how to properly flash a window into a WRB, and then how to install the window.
- In episode six we’ll jump up on the roof and look at roof flashing details, and install some Protec synthetic roof underlayment.
- Back on the ground in episode seven, we’ll install DrainVent rainscreen, which allows the siding to dry on the backside, and keeps water from sneaking in from the outside.
- In the final episode, we will cover how to use a blower door to find the last air leaks before covering everything with drywall.
Next time: Demolition, digging, and drainage.
ProTradeCraft would like to Thank DuPont Tyvek for sponsoring this first season of Weatherization Nation and also for the technical assistance in getting the construction details and sequences correct.
