Good-Looking, Long-Lasting Lap Siding
Clever details and flawless installation means this rainscreen wall assembly will weather the biggest storms.
I recently had the chance to watch and photograph the crew of J&J Custom Builders of Milford, Conn., install siding on an extensive remodel they’re working on in southeast Conn. Like a lot of modern custom home builders, J&J routinely installs lap siding over an airspace, often called a rainscreen. The gap allows any infiltrated water to drain and it allows the wall to dry when it gets wet from wind-driven rain.
The assembly starts out as a conventional 2×6 wall with Zip System sheathing with taped seams. On top is a 1-1/2-in.-thick layer of polyiso exterior insulation secured with 2-in. diameter Thermal-Grip washers. The foam also has taped seams for additional airtightness and water-shedding. Vertical furring strips are attached to the framing with structural screws and new prefinished fiber-cement siding is fastened to the furring with ring-shank stainless-steel nails. The top and bottom of the wall is vented with Cor-A-vent SV3, a corrugated plastic material that looks a lot like corrugated cardboard. The Cor-A-Vent allows air circulation to promote drying. SV3 at the tops and bottoms of windows ensures those areas can dry too.
At the top of the wall the vent material is hidden by the frieze board. The frieze is padded out 1 in. so that it laps over the siding for better water shedding. At the bottom of the wall, above the water table, there’s an aluminum drip cap. On top of that goes the first course of siding. The first course is spaced out to the wall with a piece of 1/4-in. PVC. The ends of the siding are cut so they land on a furring strip and the joint is flashed with Bear Skin, a flexible piece of flashing. J&J does really nice work, so watch the short video above that explains the assembly and then check out the full article, “Siding to Last a Lifetime” in FHB #276.